AQA AS 1-4 Short answer
what is the general formula for a monosaccaride?
(CH2O)n
How are erythrocytes specialised?
(Red blood cells) their biconcave shape provides a large surface area for gas exchange. They have no nucleus so there's more room for haemoglobin.
How are neutrophils specialised?
(White blood cell) their flexible shape allows them to engulf foreign particles or pathogens. The many lysosomes in their cytoplasm contain digestive enzymes to digest the engulfed particles.
how do you work out the length of a phase during meiosis?
(number of cells in phase/total number of cells) * time of cell cycle
Why will an enzyme only bind to one substrate molecule?
- Active site of enzyme has specific tertiary structure - Only that substrate molecule's shape is complementary to shape of active site on enzyme - So can only bind to form ESC with that enzyme
What are the advantages of the scanning electron microscope?
- Can build up 3D image - Specimen doesn't need to be thin - High resolution
What are the limitations of the electron microscope?
- Difficulty preparing specimen - High energy electron beam may destroy sample - Must he kept in a vacuum - Complex staining process - Images may contain artefacts
What are the roles of starch?
- Energy storage - Used to store sugar in plants as it's insoluble
What are the characteristics of triglycerides?why are they useful?
- High ratio of energy storing carbon to hydrogen bond(excellent energy source) - low mass to energy ratio (energy can be stored in large volumes) -large non-polar insoluble in water(storage doesn't effect osmosis or water potential) - High ratio of hydrogen to oxygen bonds (releases water)
What are the advantages of a transmission electron microscope?
- High resolution
Effect of substrate concentration on enzyme controlled reaction
- If the concentration of the enzyme is constant, the rate or reaction will increase as substrate concentration increases. - At low substrate concentrations the enzyme molecules have limited no. of substrate molecules to collide with.
what happens during expiration?
- Internal intercostal muscles contract, external muscles relax. - Diaphragm muscle relaxes and returns to dome shape. - Ribcage moves downwards and inwards. - Thorax volume decreases. - Pulmonary pressure is greater than atmospheric pressure and air forced out of the lungs.
Explain why an increase in temperature increases the rate of enzyme activity.
- Kinetic energy of molecules increases. - More successful ES collisions occur - More ESCs are formed - Rate of reaction increases - Rate reaches V-Max at optimum temperature
Draw and explain substrate concentration limiting factor graph.
- Large quantities of substrate molecules initially. - Both the substrate and enzymes are always in constant motion. - Substrate molecules collide with empty enzyme active sites to form ESCs. - All active sites become occupied with substrate molecules, so the product is rapidly broken down. - Substrate number decreases due to being broken down. - All substrate has been converted into product so no more ESCs form and rate stops. - Steep incline - Levels off/plateaus
What are the disadvantages of a light microscope?
- Light has a king wavelength meaning the light microscope has a low resolution
What is a disadvantages of the scanning electron microscope?
- Lower resolution compared to TEM - must be kept in vacuum
Explain how a very high temperature can stop an enzyme from working
- Molecules have more KE so vibrate more - Causing H bonds and Ionic bonds holding tertiary structure together to break - Tertiary structure altered, active site shape changes - Enzyme becomes denatured and cannot carry out its function - Fewer ESCs can form, rate or reaction decreases
Explain how extreme pH can affect the overall shape of an enzyme
- The enzyme denatures - H+ concentration alters charges around active site - Due to breaking of H and Ionic bonds - Active site shape changes - Substrate is no longer complementary in shape so cannot bind to active site - No ESCs can form
What happens to an enzyme's shape and function when it is denatured?
- The tertiary structure of the enzyme is altered - Due to breaking of H bonds and Ionic bonds - Enzyme and substrate shape is no longer complementary - Substrate can no longer bind - No ESCs can form
What is the purpose of glycoproteins in the membrane?
- act as recognition sites -help cells attach to one another to form proteins -allow cells to recognise one another eg lymphocytes
What is the purpose of the phospholipids in the cell membrane?
- allows lipid soluble substances to enter and leave cell - prevents water soluble substances from entering and leaving cell -makes the membrane flexible and self sealing
What are ethical issues with vaccination?
- animal testing - side effects - who is it tested on - vaccination large quantities - expensive, continue them when disease is almost eradicated?
Describe the process of the indirect ELISA test?
- antigen attached to test plate - sample added - desires (monoclonal) antibodies if present will attach to complementary antigen - test solution removed antibodies remain due to strong bond - second antibody added that is attached to an enzyme - binds specifically to the tested antibody - solution drained and enzyme substrate is added intense colour change indicates antibody is present
Why don't vaccine completely eradicate disease?
- doesn't work on certain individuals - some may develop disease after vaccination - antigenic variability(mutations) - variety of pathogen - pathogens hide from immune system - objection to vaccination
What makes a vaccination programme successful?
- economically available - few side effects - means of producing, transporting and storing - means for administering - herd immunity
What does courtship behaviour allow organisms to do?
- identify members of their own species - form a pair bond - synchronise mating - identify a suitable mate
What are the characteristics of lipids?
- insoluble in water - soluble in organic solvents
Why is starch suited for storage?
- it's large and insoluble therefore doesn't diffuse out of cells - compact - when hydrolysed forms glucose which is easily transported - branch form means enzymes can work simultaneously
What limitations does the tracheal system have?
- mostly relies on simple diffusion for exchange of gases between cells and environment - diffusion pathway needs to be short; limits the size insects can attain
How do respiratory gases move in and out of the tracheal system through ventilation?
- movement of muscles in insects - mass movements of air in and out of tracheae - further speeds up exchange of respiratory gases
What are some non specific immune responses?
- mucus - hair - stomach acid - phagocytes
How do respiratory gases move in and out of the tracheal system along a diffusion gradients?
- oxygen used up by cells - concentration towards ends of tracheoles falls - diffusion gradient so O2 diffuses from atmosphere through tracheae and tracheoles to cells - CO2 produced at cells during respiration - diffusion gradient going opposite way - CO2 diffuses along tracheoles and tracheae to atmosphere - diffusion in air more rapid than water so bases exchanged quickly
What is the four main things the immune system identifies?
- pathogens -cells from other organisms of the same species -abnormal body cells -toxins
What are the characteristics of a phospholipid? Why are they useful?
- polar molecules (in aqueous environments they form a bilayer forming a hydrophobic later surrounding cells) -contain phosphate(help hold cell surface membrane together) -phospholipid structure helps them form gylycolipids
What is the properties of an antibody?
- protein molecule able to make many shapes with different amino acid sequences -variable region complementary to antigens - able to bond to two antigens at once and clump them together - constant site that allows self recognition from cells
What are the characteristics of ATP? How does this aid short term storage?
- rapidly re forms, cells don't need to store large quantities -releases less energy than glucose, useful or reactions as its released in small manageable quantities
What two things must haemoglobin be able to do to be efficient at transporting oxygen?
- readily associate to oxygen at the gas exchange surfaces - readily dissociate from oxygen at tissues
Describe the process of the direct ELISA test
- specific monoclonal antibody attached to a test plate -test sample added to test for specific antigen - if antigen present it attaches to antibodies - binding of antigen can withstand drainage - second antibody added that is attached to a receptor enzyme - substrate added
How is water used in the metabolism?
- used to break down complex molecules by hydrolysis -reactions that take place in the aqueous medium -major raw material in photosynthesis
What do T cells respond to? (Cell mediated immunity)
- viral infected body cells -transplanted cells -cancer cells -antigen presenting phagocytes
How is the alveoli adapted?
-200 million of them to create a large surface area (70m2) -very thin walls providing a small diffusion pathway
what is the process of humoral response?
-B-cell find complementary pathogen in the bodily fluids -B cell produces antibodies that bind to the antigens -antigen enter b cell by endocytosis and is presented on the surface -T helper cell bind to antigen to stimulate the B cells to undergo clonal selection -plasma cells and memory cells are made
What are the advantages of a light microscope?
-Cheaper than an electron microscope - Image can be seen through microscope doesn't need to be projected on a screen - can view dead specimen
What are the disadvantages of the transmission electron microscope?
-Difficult to prepare specimen -High energy electron beam may destroy sample -Carried our in vacuum therefore living cells can't be viewed - Specimen must be thin
What is the secondary structure of proteins? What does it do?
-NH and -C=Oon either side of the peptide bond -NH has a positive charge and -C=O has a negative this forms a weak bond that causes protein structure to be twisted
how is an artery's structure related to it's function?
-Narrow lumen; High pressure -Highly elastic - expand and recoil -Thick muscular wall - to withstand force; more elastic fibres (recoil) -No valves (except aortic and pulmonary semi-lunar at the start) -Oxygenated blood from heart - except pulmonary artery to lungs -Pulsatile blood flow (expansion + recoil) Pulse can be felt - e.g. wrist
how is the structure of a vein related to it's function?
-Wide lumen; Low pressure -Thin wall - less elastic and less muscular -Valves (semi-lunar) - prevent backflow -Deoxygenated blood to heart from tissues -A except pulmonary vein from lungs -Non pulsatile - smooth flow of blood
what is the evidence for substances in the phloem?
-a solution containing organic molecules flows out of the phloem when it is in use -carbon 14 used a tracer shows the process of translocation -cutting away phloem creates bulging above due to build up of organic matter -the mouthpart of sap-sucking insects is in the phloem -metabolic inhibitors stop translocation
What are the advantages of multi-cellular organisms?
-able to move -able to hunt(likely to he in top if food chain) -able to adapt to environment -specialised body reigons -able to find a mate
What is the purpose of glycolipids in the cell membrane?
-act as recognition sites —helps maintain stability of membrane -helps cells attach to one another and form tissues
How is the ELISA test performed?
-apply the sample to the surface of the slide so the antigens can attach -wash the surface several times to remove any loose antigens -add the monoclonal antibodies specific to the antigen and leave to bind -wash the surface to remove excess antigen specific antibody -add a second antibody with an enzyme attach which will bind to the first antibody -add the colourless substrate to the enzyme which will change colour if the enzyme is present -the amount of antigen present can be analysed using the intensity of the colour
what is the process of cell mediated response?
-cell presents antigens -a T-helper cell binds to the antigens that have been presented (corresponding binding sites) -this causes replication of T-cells via mitosis -triggers B-cells to divide -stimulates phagocytosis -stimulates cytotoxic T-cells
what is the evidence for the cohesion-tension theory?
-diameter of tree trunks decrease during daylight hours due to the increased negative pressure in the xylem. -when a xylem vessel is broken, the column is broken -water does not leak out of a broken xylem vessel
What three ways is ATP synthesised?
-during photosynthesis -during respiration in cells -when phosphate is donated to ADP in cells
how do you carry out differential centrifugation?
-filter homogenate to remove cellular debris -spin sample at low speed -remove the sediment pellet from the bottom then spin the remaining supernatent again at a higher speed
Describe the mass flow hypothesis.
-hydrogen ions are actively transported from companion cell to cell walls while sucrose go through facilitated diffusion into companion cell -co-transport of hydrogen and sucrose into sieve tube elements -water moves from xylem to phloem due to a more negative water potential -high pressure forces sucrose down the phloem -cells in the sink store the sucrose while water re0enters the xylem
Why is glycogen suites for storage?
-insoluble - compact -highly branched (enzymes can work simultaneously)
How does the process of expiration work?
-inter coastal muscles contract moving ribcage down and inwards -diaphragm relaxes and moves up -volume in lungs increases causing a high air pressure forcing air out of the lungs
What is the process of inspiration?
-inter coastal muscles relax moving ribcage up and out -diaphragm contracts and moves downwards -volume in kings decreases causing a lower air pressure drawing in atmospheric air
how does HIV divide?
-invades a T helper cell -attachment proteins bind to CD4 recpetors of the T helper cells (these are complementary and specific) -the virus RNA and reverse transcriptase enter the cell -nuclear material from the RNA is converted to DNA using reverse transcriptase -the HIV DNA is integrated with the host's DNA -transcripted and translated to make new viral proteins -host cell bursts, killing the cell and releasing the viral proteins.
how does the structure of DNA link to its function?
-large and compact = holds a lot of info -double stranded = easy replication using template strand -base pairings = protein synthesis through mRNA -hydrogen bonds = strong in numbers but easy to break during replication
how is the structure of a capillary related to it's function?
-large number of endothelial cells- large surface area for exchange -Wall is one cell thick - short diffusion distance Endothelium is continuous throughout circulatory system
What does the body need energy for?
-movement -active transport -metabolic processes -maintaining body temperature -anabolism -repair and division of cells
what is the process of phagocytosis?
-pathogen and phagocyte are chemically attracted (chemiosmosis) -pathogen engulfed into a phagosome -lysosomes binds with phagosome -gets digested by the lysozyme enzyme -phagocyte displays the pathogens's antigens on its surface
What is the purpose of proteins in the cell membrane?
-provide structural support -acts as channels transporting molecules across the membrane -allows active transport -form cell surface receptors -help cells adhere together -act as receptors
What is the purpose of cholesterol in the cell membrane?
-reduces lateral movement of other molecules including phospholipids -make membrane less fluid at high temperatures -prevents leakage of water and dissolved ions from cells
how do insects limit water loss?
-small surface area to volume ratio -waterproof coverings -spiracles which can close
What are the characteristics of antibodies?
-soluble in blood and tissue fluid -specific to antigens - complementary to antigens
Why might vaccination not eliminate a disease?
-some people might get the disease before immunity is created from the vaccine -herd immunity cannot be reached due to individuals having ethical, medical or religious objections -vaccine cannot be produced due to there being multiple forms of one pathogen -immunodeficiency in individuals -pathogens hide form the body's defences -antigenic variability due to pathogen antigens mutating regularly
How is lipids used in the body?
-source of energy -waterproofing -insulation -protection
how is the structure of a phloem related to its function?
-stacked to make a column -pores in sieve plates allow substances through -companion cells mean that there are very few organelles in the sieve tube elements so things can pass through
Why is cellulose suited for support?
-strong hydrogen bonds between glucose chains -microfibrils form fibres providing more support
what re the features of a transport system?
-suitable medium to carry materials -materials transported on mas over a long distance -closed system -mechanism for moving the transport medium -mechanism for maintaining mass flow -mechanism for controlling rate of flow
What is the max resolution of an electron microscope?
0.5nm
What is the water potential of pure water?
0KPa
Describe how the insect is adapted to ensure minimal water loss and explain how these adaptations help minimise water loss. (4 marks)
1 Exoskeleton / cuticle / outer covering of insect; 2 is waterproof;3 Insect has a small surface area to volume ratio; 4. which reduces the area over which water can be lost;5 Spiracles can be closed; 6 to prevent water loss from the spiracles;
Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them. (5 marks)
1 Many alveoli/ alveoli walls folded provide a large surface area;2 Many capillaries provide a large surface area;3 (So) fast diffusion;4 Alveoli or capillary walls/ epithelium/ lining are thin/one cell thick/short distance between alveoli and blood; 5 Flattened/ squamous epithelium6(So) short diffusion distance/ pathway;7 (So) fast diffusion;8 Ventilation / circulation; 9 Maintains a diffusion / concentration gradient;
Describe how the MMR vaccine results in immunity (6 mark)
1 Three different viruses (in vaccine);2 With antigen (on each virus);3 Different for each (virus);4 Macrophage/phagocyte presents antigen;5 Binds to/activates (receptor protein on) T-cells;6 T-cells activate B-cell;7 Antigen binds to receptor on B-cell;8 B-cell divides/ clonal selection;9 Different clone/antibody against each virus;10 Plasma cells/B cells secrete antibody;11 Memory cells formed (B and/or T);12 Vaccine stimuates (primary immune) response;13 Memory cells give rapid response in future (preventing development of disease/giving immunity);
How is RNA different from DNA?
1) has ribose not deoxyribose 2) contains Uracil (U) instead of Thymine 3) usually single stranded
What did Darwin observe about the world around him?
1) organisms produces more offspring than survive 2) there's variation in the characteristics of members of the same species. 3) characteristics can be passed down from one generation to the next 4) individuals that are best adapted are more likely to survive.
Clonal Selection
1)B cell has an antibody which is complimentary to the pathogenic antigen 2)The antigen is absorbed by the B cell by endocytosis 3)Helper T cells bind to the antigen and stimulate the B cell to divide by mitosis to form a clone of identical cells 4)Each clone produces the same antibody
Process of inspiration
1)External intercostal muscles contract while internal intercostal muscles relax 2)Ribs are pulled upwards and outwards, increasing the volume of the thorax 3)Diaphragm muscles contract, causing it to flatten which also increases volume 4)Increased volume of thorax results in reduced pressure in the lungs 5)Atmospheric pressure is now greater than pulmonary pressure so air is forced into the lungs
Process of expiration
1)Internal intercostal muscles contract and external intercostal muscles relax 2)Ribs are pulled downwards and inwards, reducing the volume of the thorax 3)The diaphragm muscles relax also deceasing the volume 4)Decreased volume of the thorax means increased pressure in the lungs 5)Atmospheric pressure is now lower than pulmonary pressure so air is forced out of the lungs
How lymphocytes recognise cells belonging to the body
1)Lymphocytes collide with other self cells in the fetus 2)Some lymphocytes will have receptors that are complementary to body cells 3)These lymphocytes either die or are suppressed 4)This also happens with adults in the bone marrow
Phagocytosis
1)Pathogen is engulfed to form a phagosome 2)Lysosomes fuse with the vesicle 3)Lysozymes destroy the bacteria by hydrolysing its cell walls 4)The soluble products are absorbed into the cytoplasm
Process of the cell-mediated response
1)Phagocyte presents pathogenic antigens on it's cell membrane 2)Receptors on a specific helper T-Cell fit exactly onto these antigens 3)Attachment activates helper T-Cell to divide rapidly and from clones 4)The clones develop into memory cells, stimulate phagocytosis, stimulate B-Cells to divide and activate cytotoxic T-Cells
Why is the diffusion of gases between the alveoli and blood very rapid?
1)Red blood cells are slowed as they pass through capillaries, allowing more time for diffusion 2)Distance between alveolar air and red blood cells is reduced because they are flattened against capillary walls 3)Alveoli and capillaries have very thin walls 4)Alveoli and capillaries have a large total surface area 5)Lungs are constantly ventilated and the heart constantly circulates blood so there is a steep conc gradient
How do you preform a protein test?(copper)
1. Add equal volumes of test lipid solution and sodium hydroxide in a test tube 2. Add dilute a few drops Copper(II) sulphate 3. Mix gently 4. Purple colour indicates protein
When is the test for a non-reducing sugar?
1. Add solution being tested to test tube 2. Add equal amount of Benedict's solution 3. Place in water bath, if no precipitate forms no reducing sugars are present 4. Add test solution and hydrochloride acid together in a different test tube 5. Slowly add sodium hydrocarbonate solution, test with universal indicator 6. When solution is neutral redo Benedict's test
How do B cells provide an immune response?
1. Antigen enters B cell by endocytosis and is presented in the outside 2.T helper cell binds to processed antigen and stimulates B cell to divide through clinal selection 3. Some B cells formed secrete antibodies which attach to specific antigens on pathogen, these B cells are plasma cells 4. Other B cells form memory cells which provide immunity and a quicker immune response in the future
How are lipids broken down?
1. Bile produced by the liver breaks up large lipid droplets into smaller ones called micelles 2. Pancreas produces lipase to break down lipid droplets into fatty acids and glycerol 3. The fatty acids and glycerol diffuse through endoplasmic reticulum into epithelial cell to for triglycerides 4. Packed in Golgi as chylomicrons 5. Released through exocytosis
Describe how mRNA is produced in the nucleus of a cell. (6 marks)
1. Helicase; 2. Breaks hydrogen bonds; 3. Only one DNA strand acts as template; 4. RNA nucleotides attracted to exposed bases; 5. (Attraction) according to base pairing rule; 6. RNA polymerase joins (RNA) nucleotides together; 7. Pre-mRNA spliced to remove introns.
Describe the mass flow hypothesis for the mechanism of translocation in plants. (4/5 marks)
1. In source / leaf sugars actively transported into phloem; 2. By companion cells; 3. Lowers water potential of sieve cell / tube and water enters by osmosis; 4. Increase in pressure causes mass movement (towards sink / root); 5. Sugars used / converted in root for respiration for storage.
Describe the process of active transport
1. Molecule undergoing active transport binds to carrier protein 2. ATP bonds to carrier protein also, the ATP is hydrolysed to give a phosphate. 3. The phosphate provides energy changing the shape of the carrier protein to change and move the molecule to the other side 4. Removal of phosphate causes carrier to return to its original shape
Describe the process of a T lymphocyte destroying a pathogen?
1. Pathogen taken in by phagocyte, phagocyte presents antigen on cell surface 2. Receptors on T cell fit to the antigen 3. Attachment activates T cell causing it to divide by mitosis in clinal selection 4. Cloned T cells: -stimulate B cells to divide -stimulate phagocytosis -develop into memory cells to provide immunity and quick immune responses in future -develop into cytotoxic T cells
Describe the process of phagocytosis
1. Phagocyte is attracted to pathogen by its chemical products 2. Receptors on cell surface of the phagocyte recognise pathogen as foreign attach to chemicals on pathogen surface 3. Produce pseudopodia and engulf the pathogen to form a vesicles called the phagosome 4. Lysosomes move to phagosome and release lysosomes which hydrolyse pathogen and destroy it 5. Fragments of pathogen leave cell by endocytosis
How do you preform a lipids test?
1. Place 2cm3 of solution being tested in test tube 2. Add 5cm3 of ethanol and shake 3. Add 5cm3 of distilled water, shake 4. A cloudy white precipitate indicates lipid
Give three ways in which courtship behaviour increases the probability of successful mating. (4 marks)
1. Recognise / identify / attract same species;Ignore: references to letting them produce fertile offspring2. Stimulates / synchronises mating / production / release of gametes;3. Recognition / attraction of mate / opposite sex;4. Indication of (sexual) maturity / fertility / receptivity / readiness to mate;5. Formation of a pair bond / bond between two organisms (to have / raise young).
Describe how farming effects biodiversity of animals (4 marks)
1. Removal of plant/weeds/pests; 2. use of pesticides/ploughing2. few(er) habitats / niches;3. (So) lower diversity of insects / fewer insect species / fewer insect types;3. (So) fewer food sources / less variety of food.
How do you use a light microscope?
1. Select the lowest power objective lens 2. Use the coarse adjustment knob to bring the stage to just below the objective lens. 3. Move the stage down until it's roughly in focus. 4. Use the fine adjustment knob until you have a clear image.
Describe process of co-transport in a epithelial cell in the ileum
1. Sodium moves out of cell via the sodium potassium pump by active transport. Potassium replaces the sodium and moves into cell from bloodstream 2. Low concentration of sodium created in the epithelial cell 3. Sodium moves into the cell from the ileum by facilitated diffusion through a co transport protein 4. Sodium brings a glucose molecule through the protein into the epithelial cell 5. Glucose moves into blood stream from cell
Describe the process of cell fractionation
1. Tissue is cut into pieces and placed in a cold, buffered, isotonic solution 2. Tissue is homogenised 3. Homogenate is filtered 4. Centrifuged at different speeds
How do viruses reproduce?
1. Virus attaches to host cell by attachment proteins 2.virus injects nucleic acid into cell 3.injected nucleic acid provides instructions and cell produces viruses inside of cell 4. Viruses break out of cell
Name two features that helps to reduce water loss?
1. Waterproof covering (in insects this is a rigid outer skeleton with waterprof cuticles 2. Small surface area to volume ratio (minimise area of water loss)
What are the roles of lipids?
1. source of energy 2. waterproofing 3. insulation 4. protection
How is starch broken down throughout digestion?
1.Salivary amylase begins hydrolysing watch into maltose in the mouth.(mineral salts maintain optimum pH of amylase) 2. Stomach acid denatures amylase 3. Pancreatic juices mix with food in intestines amylase breaks down remaining starch.(alkaline salts maintain pH) 4.muscle in intestines move food along ileum, living of ileum produces maltase to hydrolyse maltose into glucose
How do you do Benedict's test?
1.pour solution being tested into a test tube 2.add an equal amount of Benedict's solution 3.heat test tube in water bath 4. Red precipitate indicates a sugar is present
Micrometer
1x10-6 m
Nanometer
1x10-9 m
How many divisions are there in meosis?
2
How many hydrogen bonds are there between cytosine and guanine?
2
What does a phospholipid molecule consist of?
2 fatty acids, a phosphate and glycerol
How many hydrogen bonds are between A and T?
2 hydrogen bonds
What is the maximum resolution of a light microscope?
200nm. This corresponds to a max magnification of around x1500
what is the composition of oxygen and carbon dioxide in te air?
21% oxygen, 0.04% carbon dioxide
How many hydrogen bonds are there between adenine and thymine?
3
What binds to mRNA codon?
3 complimentary bases
how many hydrogen bonds are between C and G?
3 hydrogen bonds
What is the tertiary structure of a protein?
3D structure with ionic, hydrogen and disulfide bonds
how many oxygen molecules can bind to a haemoglobin?
4 - 1st is hard to bind, 2nd and 3rd are easy to bind and 4th is hard to bind
What is the structure of haemoglobin?
4 polypeptide chains (2 alpha, 2 beta), each of which carry a haem group. The haem groups have Fe2+ on them that can bind to 1 oxygen
Why is DNA replication said to be semi conservative?
50% of the original strand of DNA remains meaning some of the original is conserved during replication.
What percentage of oxygen diffuses into blood from water?
80%
what is the structure and function of ribosomes?
80s found in eukaryotes and 70s found in prokaryotes and are made up of RNA and protein, site of protein synthesis
How is a chromosome formed?
A DNA molecule combines with the protein histone. The complex formed is cooled and folded into loops. The loops are condensed and packed together to form chromosome strands (chromatids)
Define monoclonal antibody
A antibody that is specific to only one antigen
How does a light microscope work?
A beam of light is condensed by a condenser lens the beam then travels over an object and through a projective lens produces an enlarged image
Normal distribution curve
A bell-shaped curve produced when a certain distribution is plotted on a graph
what is a biological catalyst?
A biological catalyst is a substance that speeds up the rate of a chemical reaction. Enzymes are proteins that act as a biological catalyst.
What is amylopectin?
A branched form of glucose. It is more compact which is ideal for starch as it's a store for glucose. Contains alpha 1-6 glycosidic bonds.
What is a buffered solution? Why is it needed?
A buffered solution is a solution that maintain the pH a change in pH denatures enzymes and alters shapes of other biological molecules and cells
Glycolipid
A carbohydrate covalently bonded with a lipid. They act as recognition sites, help maintain stability of the membrane and help cells attach to one another.
Prokaryote
A cell of an organism belonging to the kingdom Prokaryote that is characterized by lacking a nucleus and membrane-bound organelles. E.g. bacteria
Antigen-presenting cell
A cell that can display foreign antigens on it's surface e.g. phagocyte, invaded body cell
Define Haploid cell
A cell that contains half the normal number of chromosomes in a normal body cell
Define diploid cell
A cell that contains the same number of chromosomes as that of a normal body cell
Eukaryote
A cell that has a membrane-bound nucleus and chromosomes. The cell also possesses a variety of other membrane-bound organelles, such as mitochondria and endoplasmic reticulum.
what is an antigen presenting cell?
A cell with foreign antigens displayed on the surface
Chromosome mutation
A change that occurs in a chromosome. These changes are most often brought on by problems that occur during meiosis and can result in changes in the number of chromosomes in a cell or changes in the structure of a chromosome
Gene mutation
A change to one or more nucleotide bases in DNA that could result in a change in genotype which may be inherited
Autosome
A chromosome which is not a sex chromosome
Define exon
A coding segment in a eukaryotic gene
What does 3 bases produce?
A codon
What is a prosthetic group?
A cofactor that is permanently bound by covalent bonds to an enzyme molecule
Tissue
A collection of similar cells that perform a specific function.
Organ
A combination of different tissues that are coordinated to perform a variety of functions.
What is the nuclear envelope?
A double membrane surrounding nucleus controlling entry of substances into and out of nucleus
Trachea
A flexible airway that is supported by rings of cartilage which prevent it collapsing as the air pressure inside falls when breathing in. Its walls are made up of muscle, lined with ciliated epithelium and goblet cells.
The trachea
A flexible airway which is supported by rings of cartilage. Tracheal walls are lined with ciliated epithelium and globular cells
Index of diversity
A formula is used to quantify the biodiversity of a habitat. It takes into account the number of species present as well as the abundance of each species.
What is a change in one or more nucleotide called?
A gene mutation
What is a subsitution mutation?
A gene mutation has been replaced by a nucleotide eg. CTC replaced to form CTG
What does a oxygen dissociation graph show?
A graph that shows the relationship between saturation of haemoglobin with oxygen and the partial pressure of oxygen
Tumour
A group of abnormal cells which develops and constantly expands in size.
What is a tissue?
A group of cells that act together to perform a specific function.
What is a microfibril?
A group of cellulose strands
Haemoglobins
A group of chemically similar molecules found in a wide variety of organisms. Protein molecules with a quaternary structure that has evolved to make it efficient at loading oxygen under one set of conditions but unloading it under a different set of conditions. It has four polypeptide chains which are linked together to form a spherical molecule - each polypeptide is associated with a haem group which contains a ferrous (Fe2+) ion which can combine with an oxygen molecule (O2).
What is an organ?
A group of different tissues that work together to perform a certain function.
Cancer
A group of diseases caused by a growth disorder of cells as a result of damage to the genes that regulate mitosis and the cell cycle which results in uncontrolled growth and division of cells.
What is population?
A group of individuals of the same species that live in the same place and can be interbred
Population
A group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.
Define species
A group of organisms that can interbreed and produce fertile offspring
Species
A group of organisms that have a common ancestry and so share the same genes and are capable of breeding together to produce fertile offspring - are reproductively separated from other species.
What is an organ system?
A group of organs working together to perform a particular function
What is a species?
A group of similar organisms able to reproduce and give fertile offspring.
Retrovirus
A group of viruses which have the ability to make DNA from RNA because they have reverse transcriptase.
Pancreas
A large gland situated below the stomach. It produces a secretion called pancreatic juice, which contains proteases to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse starch.
Tracheae
A large internal network of tubes in insects with supported rings to prevent them collapsing.
Expiration
A largely passive process when external intercostal muscles relax, internal intercostal muscles contract, ribs move downwards and inwards and the diaphragm muscles relax, decreasing the volume of the thorax, which increases the pressure.
what is an organism?
A living thing
Ileum
A long muscular tube where food is further digested. Enzymes are produced by its walls and by glands that pour their secretions into it. Inner walls are folded into villi which gives them a large surface area. Where products of digestion are absorbed into the bloodstream.
Mutagen (mutagenic agent)
A material or other factor which increases the normal mutation rate eg high energy radiation, chemicals
What is Simpson's index of diversity?
A measure of diversity.
What is potency?
A measure of how many types of cells a stem cell can make. Eg Multipotent or pluripotent.
Standard deviation
A measure of how spread out about the mean your values are. The more spread out the data the higher it will be.
Bilayer
A membrane consisting of two layers of phospholipids.
Pathogen
A microorganism that causes disease
What is a pathogen?
A microorganism that causes disease
The outer walls of the epidermis cells contain what?
A mixture of lipid polymer and waxes that make a waterproof cuticle
What is a non competitive inhibitor?
A molecule that binds to the active site changing the shape of an enzyme
What are competitive inhibitors?
A molecule that blocks the active site meaning enzyme can't work effectively
Antigen
A molecule that triggers an immune response by lymphocytes.
Heart
A muscular organ that lies in the thoracic cavity behind the sternum. It operates continuously and tirelessly throughout the life of the organism. Made of four chambers - left and right atria and left and right ventricle.
Stomach
A muscular sac with an inner layer that produces enzymes. Its role is so store and digest food, especially proteins.
What is the structure of the mesophyll like?
A network of air spaces
What are alveoli covered with?
A network of blood capillaries
Define intron
A non coding segment of eukaryotic DNA
What happens in meiosis: telophase 1 and cytokinesis?
A nuclear envelope forms around each group of chromosomes. Then the cytoplasm splits and two haploid daughter cells are produced.
Homologous chromosomes
A pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features. They are not necessarily identical as may have different alleles. They are capable of pairing during meiosis.
What does homologous chromosomes mean?
A pair of chromosomes, one maternal and the other paternal, have the same gene loci so therefore determine the same features
What surrounds each stoma (singular stomata)?
A pair of guard cells
Lungs
A pair of lobe structures made up of a series of highly branched tubules called bronchioles, which end in tiny air sacs called alveoli.
The lungs
A pair of lobed structures which are made up of highly branched tubules which end in tin air sacs
Organelle
A part of a cell.
What is the difference between a triglyceride and a phospholipid?
A phospholipid has a phosphate group in place of a fatty acid.
Potometer
A piece of apparatus which enables the rate of water loss in a plant to be measured.
What is a xerophyte?
A plant that lives in hot conditions
Chiasmata
A point at which paired chromosomes remain in contact during the first metaphase of meiosis and at which crossing over and exchange of genetic material occur between the strands.
Polypeptide
A polymer consisting of a large chain of amino acids bonded together by peptide bonds.
What is cellulose?
A polysaccharide made from beta glucose that has to alternate every other unit in order to form glycosidic bonds. It is extremely strong and is prevented from spiralling by multiple hydrogen bonds.
Bacteria
A prokaryote.
What is a channel protein?
A protein channel that's allows specific water soluble molecules to pass through the membrane
Capsid
A protein coat which encloses the nucleic acid in a virus.
Carrier protein
A protein completely spanning the phospholipid bilayer which bind to ions or molecules then change shape in order to move these molecules across the membrane.
Protein channel
A protein completely spanning the phospholipid bilayer which form water-filled tubes to allow water-soluble ions to diffuse across the membrane.
Antigen
A protein on the cell surface membrane that is recognised as non-self by the immune system and triggers an immune response
what is an antibody?
A protein produced by lymphocytes in response to the presence of the appropriate antigen
Enzyme
A protein that acts as a catalyst and so lowers the activation energy needed for a reaction.
Describe haemoglobin
A protein with a quaternary structure adapted to transport oxygen around the body
Antibody
A protein with specific binding sites produced by B cells in response to the presence of appropriate antigen.
what is the structure of haemoglobin?
A quarternary structure with 4 polypeptide chains, each with a haem group that contains an iron ion, giving haemoglobin its red colour. globular - round, compact and soluable
What are terpenoids?
A range of essential oils that have antibacterial and anti-fungal properties. Eg menthols produced by mint plants
What is a condensation reaction?
A reaction in which two molecules combine to form a larger molecule, producing H2O as a by product
What is a retrovirus? What is an example?
A retrovirus is a virus that contains RNA not DNA An example is HIV
Translation: What does the mRNA attach to?
A ribosome
What is on top of each filament?
A row of lamellae
What is the countryside stewardship scheme?
A scheme to conserve wildlife and biodiversity and improve and extend wildlife habitats by promoting management techniques to land owners.
Define gene
A section of DNA that contains the base sequences for specific amino acids that together form a protein
Codon
A sequence of three adjacent nucleotides in mRNA that codes for one amino acid
Anticodon
A sequence of three adjacent nucleotides on a molecule of transfer RNA that is complementary to a particular codon on a messenger RNA molecule.
Triplet
A sequence of three bases in DNA.
Bronchioles
A series of branching subdivisions of the bronchi whose walls are made up of muscle (which constricts to control the flow of air in and out of the alveoli) lined with epithelial cells.
Graticule
A series of lines on a microscope which can be used to calculate the size of objects.
Diaphragm
A sheet of muscle that separates the thorax from the abdomen
Diaphragm
A sheet of muscle that separates the thorax from the abdomen.
Degenerate
A single amino acid may be coded for by more than one triplet code.
Define unicellular
A single celled organism
What are archaea?
A single celled organism that is prokaryotic, similar genes to eukaryotic cells, membranes contain fatty acid chain with ether linkages, no murein in cell walls
What kind of circulatory system do fish have?
A single circulatory system. The heart pumps blood to the gills to pick up oxygen and then on through the rest of the body in a single circuit.
What is a monosaccharide?
A single monomer of sugar
mRNA
A single stranded polynucleotide found in HIV.
What is an isotonic solution? Why is it needed?
A solution that maintains water potential to reduce osmosis which may cause cells to burst or shrivel
Isotonic
A solution which has the same water potential as the cell within it.
What is myoglobin?
A special type of haemoglobin found in muscles that has a high affinity for oxygen making it efficient for storage of oxygen.(acts as oxygen store for exercise)
What is an exchange surface?
A specialised area that is adapted to make it easier for molecules to cross from one side of the surface to another.
Courtship behaviour
A specialised behaviour that precedes the fertilisation of eggs by a male to ensure successful reproduction.
Define niche
A specific place that an organism occupies, including all relationships with other organisms
Atrial systole
A stage of the cardiac cycle when the atrial walls contract, forcing the remaining blood into the ventricles from the atria. Ventricle walls remain relaxed.
Ventricular systole
A stage of the cardiac cycle when the ventricle walls contract simultaneously (after a short delay to allow the ventricles to fill with blood) which increases the blood pressure and causes the atrioventricular valves to shut ('lub'). Ventricle pressure rises further and forces the semilunar valves open as pressure exceeds that in the aorta and the pulmonary artery, allowing blood to be pumped blood into these vessels.
Chylomicrons
A structure formed when triglycerides associate with cholesterol and lipoproteins, which are adapted for the transport of lipids. Start forming in the endoplasmic reticulum and continuing in the Golgi apparatus.
What is phylogeny?
A study of the evolutionary history of groups of organisms. The phylogenic tree shows how all organisms have evolved from a common ancestor.
Antibiotic
A substance produced by living organisms that can destroy or inhibit the growth of microorganisms
Lymphatic system
A system of vessels which begin in the tissues. Initially they resemble capillaries (except that they have dead ends), but they gradually merge into larger vessels that form a network throughout the body. These larger vessels then drain their contents back into the bloodstream via two ducts that join veins close to the heart. It is how the remainder of tissue fluid (which cannot return to the capillaries) is carried back.
Translation: What approaches the mRNA strand? What does it carry?
A tRNA molecule carries amino acids to the mRNA molecule
Transcription: What is one of the strands used for?
A template to make an RNA copy
Chromosome
A thread like structure made of protein and DNA by which hereditary information is physically passed from one generation to the next.
In an insect, a cell is never more than a short diffusion distance from what?
A tracheole
What is a malignant tumor?
A tumour that grows rapidly, that is less compact and more likely to be life threatening
What is a benign tumour?
A tumour that grows slowly, that's more compact and less likely to be life threatening
Natural immunity
A type of active immunity resulting from an individual becoming infected with a disease under normal circumstances.
Artificial immunity
A type of active immunity resulting from vaccination. It involves inducing an immune response in an individual without them suffering symptoms of the disease.
Mode
A type of average that is the number that occurs the most often.
Mean
A type of average where you add up all of the numbers then divide by how many numbers there are.
Median
A type of average where you place the numbers you are given in value order and find the middle number.
Transmission Electron Microscope (TEM)
A type of electron microscope which asses a beam of electrons through a very thin section of specimen (which often has been stained with heavy metals to show up the fine internal structures).
Scanning Electron Microscope (SEM)
A type of electron microscope which bounces beams of electrons off the surface of an object to develop a 3D image of the specimen (no need therefore for thin sections).
Light microscope
A type of microscope which has a condenser, objective lens and eyepiece lens and light is passed through the thin specimen an up through the objective and eyepiece lenses to the eye.
Dipeptidases
A type of protease which hydrolyse the bond between the two amino acids of a dipeptide. Dipeptidases are membrane-bound, being part of the cell-surface membrane of the epithelial cells lining the ileum.
Endopeptidases
A type of protease which hydrolyses the peptide bonds between amino acids in the central region of a protein molecule forming a series of peptide molecules.
Exopeptidases
A type of protease which hydrolyses the peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases. They progressively release dipeptides and single amino acids.
What did Linneaus develop?
A universal naming system called binomial system
Vena cava
A vein connected to the right atrium and brings deoxygenated blood back from the tissues of the body (except the lungs).
Pulmonary vein
A vein which is connected to the left atrium and brings oxygenated blood back from the lungs.
Phagosome
A vesicle formed as the bacterium is engulfed by the phagocyte. The lysosome release their lysozymes into the phagosome.
Tissue fluid
A watery liquid that contains glucose, amino acids, fatty acids, ions in solution and oxygen. It supplies all of these substances to the tissues and receives carbon dioxide and other waste materials from tissues. It is the means by which materials are exchanged between blood and cells and bathes the cells of the body. It is formed from blood plasma.
ATP + H2O --------->
ADP + Pi + energy
Draw a graph to show how activation energy changes in the presence of an enzyme
AE - For a reaction to occur the reactants must collide with sufficient energy to alter the arrangement of the atoms in the molecules Enzymes work by lowering the AE Reactions can take place at lower temperatures
What is the full equation for the synthesis of ATP?
ATP + H2O ----> ADP + Pi + energy
How does ATP release energy?
ATP hydrolase breaks the bond between the 2nd and 3rd phosphate group, releasing high amounts of energy, producing ADP
What is acellular?
Acellular particles are non living particles that don't contain cells
Virus
Acellular, non-living particles that are smaller than bacteria. They contain DNA or RNA but can only multiply inside living host cells.
How do you test for sugars?
Add 2cm of Benedicts solution to your solution. Heat for a few minutes. The darker red the precipitate, the more reducing sugars there are.
How do you test for proteins?
Add 2cm of bitter solution, and it will turn lilac if there are proteins present.
How do you test for lipids?
Add ethanol. Decant the liquid into a test tube of water, leaving any undissolved substances behind. If there are lipids dissolved in the ethanol, they will emulsify, forming a cloudy white emulsion.
How can you adapt the benedicts test to test for non reducing sugars?
Add hydrochloric acid. Heat for 3 minutes and then cook. Neutralise with NaH2CO3, then preform the test as normal. This will hydrolyse the disaccharide into its constituent monosaccharides.
How does it affect structure of an enzyme?
Affect the bonds (hydrogen, ionic, peptide) forming so therefore the tertiary structure is different - Different shape = different function
What is the two ways antibodies aid the immune system?
Agglutination- Binds to two antigens clumping then together making them easier to engulf Helping phagocytosis- Binds to pathogens, the constant part is recognised and phagocytes engulf marked pathogen
How are ecosystems linked to air + water?
Air and water is purified by a variety of organisms
Are all amino acids changed?
All amino acids after the deletion are changed?
What is a community?
All the different populations that live together in an area
What does breeding ensure?
Alleles are passed onto the next generation
What is genetic polymorphism?
Alleles of the same gene are found at the same point (a locus). Polymorphism describes a locus that has two or more alleles.
Benefits of clonal selection
Allows the body to respond rapidly to any vast number of organisms
Where are spiracles located?
Along the side of an insect's body
What is the tertiary structure of a protein?
Alpha helixes that are twisted and folded to form a complex structure
Alleles
Alternative forms of a particular gene with different base sequences, and therefore different codes
Where is the site of gas exchange in mammals?
Alveolar epithelium
Give an example of a specialised exchange surface that is thin.
Alveoli. Each alveolus is made from a single layer of thin, flat cells called alveolar epithelium. O2 diffuses out of the alveolar space into the blood and CO2 diffuses out of the alveoli in the opposite direction. This helps to decrease the diffusion distance to increase rate of diffusion.
Suggest why we calculate dry mass
Amount of water present will vary; This will affect fresh mass / will not affect dry mass;
What are the 4 main types of polysaccharides?
Amylose, amylopectin, cellulose and glycogen.
Inspiration
An active process when external intercostal muscles contract, internal intercostal muscles relax, ribs are pulled upwards and outwards and the diaphragm muscles contract causing it to flatten, increasing the volume of the thorax, which reduces the pressure.
What are the groups in a protein?
An amine group (NH2) and a carboxylic acid (COOH) and an R group that is variable.
What is a habitat?
An area inhabited by a species. It includes physical factors (soil & temperature) and biotic factors (availability of food and predators)
Pulmonary artery
An artery connected to the right ventricle which carries deoxygenated blood to the lungs where its oxygen is replenished and its carbon dioxide is removed.
Aorta
An artery which is connected to the left ventricle and carries oxygenated blood to all parts of the body except the lungs.
How does a vaccination work?
An attenuated version of the pathogen is injected into someone. A macrophage engulfs the pathogen to form a phagosome and digest it. The phagosome becomes an antigen presenting cell which triggers the immune response and memory cells are made.
What is adhesion?
An attraction between molecules of different substances
Reverse transcriptase
An enzyme in HIV which enables the production of DNA from RNA.
Membrane-bound disaccharidase
An enzyme which is not released into the lumen of the ileum but is part of the cell-surface membranes of the epithelial cells that line the ileum. E.g. maltase
Ringing
An experiment when a section of outer layers (protective layer and phloem) is removed around the complete circumference of a woody stem while it is still attached to the rest of the plant. This results in the region of the stem immediately above the missing ring of tissue swelling because the sugars of the phloem accumulate above the ring and it leads to tissues dying below the ring because of the interruption of flow of sugars to this region. It shows that the phloem is responsible for translocating sugars.
What is a photomicrograph?
An image produced by an electron microscope
Why the secondary response is quicker
An increased quantity of antibodies is secreted t a faster rate than the primary immune response which ensures that a new infection is destroyed before it can cause harm
What do insects have instead of using their body surface for gas exchanges?
An internal network of tubes called tracheae
What is an inorganic ion?
An ion which doesn't contain carbon
What is a spiracle?
An opening in the exoskeleton of an insect that connects to the tracheal system
Ribosome
An organelle consisting of rRNA and proteins found in large numbers in the cytoplasm and on the RER of living cells. They bind to mRNA and use tRNA to synthesise polypeptides.
What is a autotroph?
An organism that makes its own food
What are the two types of enzymes?
Anabolic and metabolic
What are the 3 survival adaptations?
Anatomical Physiological Behavioural
What are phenols?
Antibiotic/antifungals. Tannins inhibit attack by insects. they bind to salivary proteins and digestive enzymes to deactivate them. insects that ingest large volumes of tannins do not grow and will eventually, die thereby reducing transmission by pathogens
How does a monoclonal antibody help direct cancer treatment?
Antibodies bind to the antigens prevent growth hormones attaching allowing the cell to divide. This prevent growth and replication
Monoclonal antibodies
Antibodies produced by a single clone of cells.
How does antigenic variability affect the production of flu vaccines?
Antigens on flu virus change every year. Memory cells produced from vaccination for one strain will not recognise the new strain of the virus as they are IMMUNOLOGICALLY DISTINCT. Therefore a new vaccine has to be made every year.
Define gene mutation
Any change to one or more nucleotide bases or a change in the sequence of bases in DNA
Define pathogen
Any microorganism that causes infectious disease
Define antigen
Any substance capable of eliciting an adaptive immune response
Memory Cells (B-Cell clone)
Are responsable for the secondary immune response. Do not produce antibodies directly but circulate in the blood and tissue fluid.When they detect the same antigen at a later date they divide rapidly and develop into plasma cells and more memory cels.
What is a deletion mutation?
Arises when a nucleotide is lost from the normal DNA
Herd immunity
Arises when a sufficiently large proportion of the population has been vaccinated which makes it difficult for a pathogen to spread within that population.
What are the two principles of classification?
Artificial Phylogenetic
How do prokaryotes carry DNA?
As chromosomes but the DNA molecules are smaller and circular
What is positive cooperativity?
As soon as one oxygen molecule binds to a haem group, the haemoglobin molecule changes shape, making it easier for the next molecules to bind.
What happens to tissue fluid when the plasma lose water?
As the plasma loses water it has a lower water potential meaning water moves from tissue fluid into the plasma
Clonal selection
As the receptor on a helper T cell attaches to the antigen this activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells. These cloned T cells stimulate B cells to divide and form a clone of identical B cells all of which produce the antibody that is specific to the foreign antigen.
What are agglutinins?
As there are two binding sites of the variable region, it is able to cross link pathogens by binding an to two antigens.
What are the disadvantages of multi-cellular organisms?
As they get bigger diffusion is less efficient and specialised exchange surfaces are needed
How does gas exchange occur in insects?
As tracheoles carry oxygen to tissue oxygen is used up creating a low concentration of oxygen. This causes gaseous oxygen to be drawn into tracheoles diffusing into cells.carbon dioxide produces causes a concentration gradient in the opposite direction and CO2 travels along trachea into the atmosphere
How is a water gradient established in a leaf?
As water evaporates out of the stomata it's replaced by water. Vapour from mesophyll cells. Mesophyll cells then have lower water potentials hence take in water from neighbouring cells
Describe the structure of a mammalian gaseous exchange system.
As you breath in, air enters your trachea. The trachea splits into 2 bronchi. Each bronchus branches into small tubes called bronchioles which end in smaller air sacs called alveoli.
Describe how you would investigate the effect of antibacterial chemicals on the growth of E coli (6 marks)
Aseptic technique/sterile agar plate, flame neck of culture bottle; Spread plate/controlled volume of bacteria transferred to plate and spread equally across the surface; Controlled volume of antibacterial chemical on to filter paper disc; Disc plated on inoculated agar plate and incubated at 25 degrees C for 2 days; Diameter of the zone of inhibition measured; Repeat measurements and mean calculated; Student T test to investigate significance of any difference between means.
How does pH affect enzyme activity?
At a specific pH the shape of the active site best facilitates the formation of an enzyme-substrate complex Any deviation will disrupt ionic and hydrogen bonds, a further change will cause the enzyme to become denatured
Gill lamellae
At right angle to gill filaments, which increase the surface area of the gills.
Where will alleles that code for the same characteristic be found?
At teh same position (locus) on each chromosome in a homologous pair
Where are the alveoli?
At the end of branches of the bronchioles
Why does haemoglobin readily load oxygen at the gas exchange surface?
At the gas exchange surface carbon dioxide is constantly removed leading to a slightly higher pH meaning the haemoglobin molecules shape makes it easier to bind to oxygen
What hope s during relaxation of all chambers?
Atria fills with blood as pressure rises the atrioventricular valves open Atrioventricular valves open semi lunar valves close
What happens during ventricular systole?(ventricles contract)
Atrioventricular valves close as blood flows into atria shutting them close, semi lunar valves open ventricles contract
What occurs during the atrial systole (atria contract)?
Atrioventricular valves open, atria contract to push blood into ventricles, semi-lunar valves close
Translation: What does a second tRNA molecule then do?
Attach to the next codon
What is cohesion?
Attraction between molecules of the same substance
Cohesion
Attraction between molecules of the same type - how water molecules form hydrogen bonds between one another and hence tend to stick together.
Translation: Where does the polypeptide chain move to?
Away from ribosome
Name the lymphocyte present in the humoral response.
B Lymphocytes
What is a lymphocyte?
B cells make antibodies. T cells coordinate the immune response. Natural killer cells are able to kill cells of the body which are not displaying a signal not to kill them as they have been infected by a virus or have become cancerous.
What biochemical food test could you carry out to determine if an enzyme was present?
BIURET TEST: - Add Biuret solution to sample - Positive result = Pale blue ---> Lilac
What are the 3 domains?
Bacteria, Archaea, Eukarya
what are the 3 types of domain?
Bacteria, Archaea, Eukarya
What are exons? (1 mark)
Base sequences which code for amino acid sequence in polypeptides
What is the consequences of deletion?
Bases all shift to replace base meaning all triplets after deletion are changed, this may alter primary structure of protein producing a different protein
Electron microscope
Beams of electrons are used to visualize structures in a vacuum. Electrons have a smaller wavelength than light so electron microscopes have a higher resolution than light microscopes.
If the mutation is advantageous what does it cause the individual to become?
Better adapted= suited towards the environment/ competition so they can therefore grow rapidly and breed successfuly
Process by which a bacteria is replicated is called...
Binary fission
Positive cooperativity
Binding of the first molecule makes binding of the second easier and so on, so the gradient of the curve steepens.
Myocardial infarction
Blockage of these coronary arteries (for example by a blood clot) leads to this. Also known as a heart attack.
Double circulatory system
Blood is confined to vessels and passes twice through the heart for each complete circuit of the body (to the lungs and tissues).
Where are B lymphocytes produced?
Bone marrow
What is bone marrow?
Bones are in living organisms containing nerves and blood vessels. The main bones contain marrow in the centres. Here, adult stem cells divide and differentiate to replace worn out blood cells - erythrocytes and neutrophils
Why do species need to identify a mate capable of breeding?
Both partners need to be sexually mature, fertile
What is an advantage to in situ conservation?
Both the species and the habitat are conserved. Larger populations can be protected and there's less disruption than removing organisms from the habitat.
The bronchioles
Branching subdivisions of the bronchi. Muscle walls allow them to constrict so that they can control the flow of air in and out of the alveoli
What can members of the same species do?
Breed with each other to produce fertile offspring
Air passes to the bronchioles from the?
Bronchi
Air passes to the alveoli from the?
Bronchioles
What are the airways of the lungs called?
Bronchioles
Translation: How do the two amino acids join?
By a peptide bond + first tRNA molecule is moved away
How are spiracles opened and closed?
By a valve
How do fossil records provide evidence for evolution?
By arranging fossils in chronological order, gradual changes in organisms can be observed that provide evidence of evolution.
Muscle layer
Can contract and so control the flow of blood in arteries, arterioles and veins.
What is an issue with the cuticle of a leaf?
Can prevent gas exchange
what does saturated mean?
Can't take anymore hydrogens and only has single c-c single bonds
How does a monoclonal antibody help indirect cancer treatment?
Cancer drugs attached to monoclonal antibodies which deliver the drugs by attaching to antigens on cancer cells(magic bullets) Also can attach enzymes to antibodies which activate cancer cells in the body
What is a non-reducing sugar?
Cannot reduce blue copper sulphate in Benedict's Solution
Glycoprotein
Carbohydrate chains attached to a protein (often extrinsic) which are part of the cell surface membrane. They act as recognition sites, help cells to attach to one another and allows cells to recognise one another.
What elements are present in carbohydrates?
Carbon, hydrogen, oxygen.
How strong is a ionic bond in a protein?
Carboxyl and amino bonds are easily broken
What proteins does facilitated diffusion occur through?
Carrier and channel proteins
What is the role of the oesophagus?
Carries food from mouth to stomach
Arteries
Carry blood away from the heart and into arterioles. They have a thicker muscular layer, thicker elastic layer and overall thicker wall than veins. They also do not contain valves (apart from the aorta and pulmonary artery).
Veins
Carry blood from capillaries back to the heart. They have a thinner muscular layer, thinner elastic layer and overall thinner wall than arteries. They contain valves at intervals throughout to ensure that blood does not flow backwards.
What does DNA polymerase do?
Catalysed the formation of the phosphodiester bonds between adjacent nucleotides
Primary response
Caused by initial response to the antigen which involves the production of antibodies and memory cells.
Secondary response
Caused by second exposure to the antigen. Memory cells are responsible for this response - they divide rapidly and develop into plasma cells (which secrete many antibodies quickly) and more memory cells.
Define Cell fractionation
Cell fractionation is the process where cells are broken up and organelles are separated out
T cells are what type of immunity?
Cell mediated immunity
Diploid
Cell or nucleus containing pairs of homologous chromosomes (two sets of chromosomes)
Haploid
Cell or nucleus containing single, unpaired chromosomes (a single copy of each chromosome)
What happens in S?
Cell replicated it's DNA, ready to divide for mitosis.
What can you see using a scanning electron microscope?
Cell surfaces. They scan a beam of electrons across the surface, which knock the electrons from the specimen which are gathered into a cathode Ray. A 3D image is produced.
What does a plant cell consist of?
Cell wall Cell membrane Cytoplasm Vacuole Nucleus Chloroplasts Mitochondria
What does cancer treatment target?why?
Cells that are diving as cancer cells divide the fastest
What is the structure of the epidermis like?
Cells that fit closely together
What are diploid cells?
Cells that have two sets of chromosomes. Human body cells are diploid.
T cells
Cells which mature in the thymus and are associated with cell-mediated immunity.
How did species used to be named?
Certain features
Describe how you would calculate % change
Change / original x100
Homologous characteristics
Characteristics with similar evolutionary origins regardless of their functions in the adult of a species e.g. wing of a bird, arm of a human and front leg of a horse
Analogous characteristics
Characteristics with the same function not the same evolutionary origins. e.g. wings of butterflies and birds used for flight but originated in different ways.
Where are the lungs located?
Chest cavity
Which statistical test do you use if your data is categoric? (i.e. falls into separate categories like pink and white flowers)
Chi squared
What is a basophil?
Chiefly responsible for allergic and antigen response by releasing the chemical histamine causing inflammation.
What is the role of cholesterol in the membrane?
Cholesterol is a type of lipid. Molecules fit between the phospholipids. They bind to the hydrophobic tails, causing them to pack more closely together. This makes the membrane less fluid and more rigid.
What happens during the second division of meiosis?
Chromatids move apart to form four four daughter cells containing one chromatid from the original homologous chromosome pairs
What happens in crossing over?
Chromatids of each pair twist over each other Tensions are created and portions of chromatids break off Broken portions rejoin with chromatids of a homologous partner
What do the linear DNA molecules exist of?
Chromosomes
What happens in meiosis: metaphase 1?
Chromosomes alone in the cell equator, the spindle fibres attach to centromeres. Then independent assortment occurs. This is when the position of each bivalent is independent of the other Chromosomes. The maternal and paternal chromosomes can be either side of the equator.
What happens in anaphase 1?
Chromosomes are pulled to opposite poles Spindles attach to centromere of separate pairs of chromosomes Spindles Contract and shorten
What happens in prophase 1?
Chromosomes are visible as they condense
What happens in prophase during mitosis?
Chromosomes become visible Nuclear envelope breaks Chromosomes drawn to middle by centrioles Centrioles move to polar ends of cell and develop spindle fibres known as the spindle apparatus
What happens in prophase 2?
Chromosomes condense again
What happens in meiosis: prophase 1?
Chromosomes condenses, and the nuclear envelope disintegrates. Spindles fibres begins to form. Homologous chromosomes pair up forming bivalents, and crossing over occurs.
What happens in independant segregation?
Chromosomes line up alongside homologous partner Line up randomly When they separate the way the homologous pair goes into the daughter cell is random
What happens in metaphase 2?
Chromosomes line up at the equator
What happens during metaphase in mitosis?
Chromosomes line up on the equator of cell Spindle fibres from centrioles attach to centromeres
Describe the features which would help you to recognise when a cell is in i) metaphase of mitosis; ii) in anaphase of mitosis (4/6 marks) (i)
Chromosomes or chromatids on equator / in middle of cell; Of spindle (once); No nuclear membrane (once only). (ii) Chromatids moving towards poles / centrioles;of spindle (once);Two centromeres per chromosome/ centromeres are being pulled; No nuclear membrane (once only).
What happened during telophase during mitosis?
Chromosomes reach respective poles and nuclear envelope reforms Chromosomes become thinner and disappear leaving chromatin Cytokinesis
Define homologous chromosomes
Chromosomes that carry the same gene but the not the same allele
How are epithelial cells specialised?
Ciliated epithelial cells have cilia that beat harmful particles away from places like the lungs to places like the stomach where they can be dissolved by HCl. Squamous epithelium are very thin to allow for efficient diffusion of gases.
Describe the process of a prokaryotic cell undergoing mitosis?
Circular DNA replicates and both copies attach to polar sides of the cell Plasmids replicate Cell membrane begins to grow between between DNA New cell wall forms Original wall separates
Define double circulatory system
Circulatory system in which blood is pumped through the heart twice in a complete cycle
What is artifical classification?
Classifies animals by physical characteristics such as size/ number of legs
Are the spiracles opened or closed most of the time?
Closed to prevent water loss
As you move down the heirarchy organisms are more ....... related
Closely
How does the blood clot?
Clotting Factors are released. Platelets bind to the collagen and a temporary plug is formed. Inactive thrombokinase in the blood becomes active and the presence of this means prothrombin in the blood becomes active thrombin. this means soluble fibrinogen in the plasma becomes insoluble fibrin. Fibres attach to the platelets forming a plug and the blood clots.
How does blood clotting prevent disease?
Clotting temporarily seals wounds. Clotting factors activate an enzyme cascade that makes insoluble fibrin.
What is shape of tRNA?
Clover
Define start code
Code at the beginning of the gene beginning the process of protein synthesis
Define stop code
Code at the end of the gene that stops protein synthesis
Define degenerate code
Code for an amino acid that codes for more than one triplet
Explain cohesion and adhesion in water.
Cohesion and adhesion occur due to the strong attraction between water molecules, so they are attracted more to the water than the surface.
Nucleotides
Complex chemicals made up of an organic base, a sugar and a phosphate. They are the basic units of which the nucleic acids DNA and RNA are made.
What is the function of the cytoskeleton?
Complex system of microtubules that form a kind of road that motor proteins transport things along.
Transcription: What then occurs with the bases?
Complimentary base pairing occurs but T is replaced with U
Name the reaction when the components of a triglyceride join together.
Condensation reaction.
What type of reaction is this called? Why does it have this name?
Condensation reaction. A water molecule is formed.
How are triglycerides formed?
Condensation reactions The bonds that are formed are called ester bonds
What is the purpose of rolled leaves in limiting water loss?
Confine the lower epidermis and trap still air, area becomes saturated in water vapour so it has a high water potential. No water potential gradient between inside and outside of leaf
What is the lymphatic system?
Consists of lymph nodes and lymph vessels that carry lymph
Vaccines
Contain antigens of a weakened pathogen that allows your body to produce memory cells, without the pathogen causing any symptoms
Lysosome
Contain enzymes called lysozymes which they release into the phagosome which hydrolyse the bacterium.
TH cells (helper T cell)
Contain receptors which respond to a single antigen. Many different types of T cell, each one responds to a different antigen.
Circulatory system
Contains a pump (heart), vessels (arteries, capillaries and arteries) and a medium (blood) to transport substances around the body.
How is a palisade mesophyll cell specialised?
Contains many chloroplasts, so they can absorb lots of sunlight. The walls are thin so CO2 can easily diffuse.
What is Rough Endoplasmic Reticulum?
Contains most of the cells ribosomes which is the sites for protein synthesis and produce rough appearance.
Why should we reduce soil depletion?
Continuous Monoculture causes soil depletion because the nutrients required by the crops are used up. The economic costs of soil depletion include increased spending on fertilisers and reduced yield.
Internal intercostal muscles
Contraction leads to expiration
External intercostal muscles
Contraction leads to inspiration
Guard cells
Control the opening and closing of stomata.
What is the Rio CBD?
Convention on biological diversity. It aims to develop international strategies on the conservation of biodiversity and how to use plant and animal resources in a sustainable way.
What is CITES?
Convention on international trade in endangered species. An agreement designed to increase international cooperation in regulating trade in wild animals and plant specimens. The counties made it illegal to kill endangered species.
Which statistical test do you use you want to see if there is a significant correlation between two variables?
Correlation coefficient
Disadvantages of taking vaccine orally
Could be broken down by enzymes in the gut, or the molecules of the vaccine may be to large to be absorbed into the blood
What direction does blood flow in the fish's lamellae?
Counter-current to water
What is the purpose of the cell surface membrane?
Creates a boundary between cytoplasm and exterior environment Allows different conditions to be established inside and outside of the cell Controls movement inside and outside cell
Why are the cells non-identical? (Variation)
Crossing over Independant segregation Fusion of gamete
What is cytokinesis)
Cytoplasm dividing
Genetic diversity can be compared within, or between species by investigation of? (3 marks)
DNA Base sequences, amino acids sequences, immunological comparisons
Describe how new viruses are produced after HIV has infected a T cell. (4/6 marks)
DNA copy made (of viral RNA);Inserted into host DNA / chromosomes;(Uses viral DNA to) make viral proteins/particles;Makes viral RNA;(Host) cell makes new viruses;"Budding off" / wrapped in cell membrane;
Why is an mRNA copy of the gene used?
DNA double helix is too large to pass through nuclear pores
Describe semi-conservative replication
DNA double strand separate and act as templates, producing 2 identical copies of the DNA, each has half the original strand and half the new strand process
What is the enzyme used in unwinding DNA?
DNA gyrase
How is DNA structured?
DNA has a backbone that protects the reactive organic bases, the backbone also allows the molecule to twist in a helix shape Hydrogen bonds between bases forms bridges High CG base pairings to make molecule stable
Describe the process of transcription
DNA helicase breaks hydrogen bonds between two poly nucleotide chains of DNA Exposed nucleotides if one strand(template strand) join to complementary base pairs from the base pool in the nucleus RNA polymerase joins nucleotides together to form a strand of pre-mRNA
What is the enzyme used in unzipping DNA?
DNA helicase?
Describe the structure of chromosomes.
DNA is one long molecule. It wraps itself around a histone. This is called chromatin which super condenses to form chromosomes, which then replicate themselves. The replicated chromosomes are called sister chromatids and are held together by a centromere.
What happens in prophase of mitosis?
DNA is replicated Two copies of DNA remained joined at the middle called the centromere
How does DNA replicate?
DNA molecule unwinds and DNA helicase breaks the hydrogen bonds between bases. free nucleotides match up with the template strand DNA polymerase forms the phosphodiester bonds between the nucleotides
Transcription: What happens when the mRNA has been made?
DNA strands coil back and the hydrogen bonds reform
Describe the process of transcription
DNA unwinds and separates (H bond between bases broken) Template strands form due to exposed bases Free RNA nucleotides align with template strand through complimentary base pairing RNA polymerase bonds the nucleotides together, forming a molecule of mRNA complimentary to the DNA mRNA leaves nucleus via nuclear pores after splicing
Natural Selection
Darwin's theory to explain the mechanism of evolution. The process by which organisms better adapted to their environment survive and reproduce and pass on their advantageous alleles to the their offspring, whilst those less well adapted fail to do so.
Starting from the right ventricle where does blood go next? Include blood vessels and whether the blood is oxygenated or deoxygenated?
Deoxygenated blood pumped to lungs along the pulmonary artery. Oxygenated blood pumped from lungs to left atrium via pulmonary vein. Pumped into left ventricle out the aorta to body Deoxygenated blood comes from the body to the right atrium via vena cava
What does DNA stand for?
Deoxyribonucleic acid
Countercurrent flow
Describes how the flow of water over the fill lamellae and the flow of blood within them are in opposite directions. Allows a diffusion gradient to be maintained all the way across the gill lamellae.
what is the role of hydrogen ions?
Determine the pH of the solutions and therefore the functioning of enzymes
Variation
Differences between individuals. It can be interspecific (between different species) or intraspecific variation (between individuals of the same species).
What is variation?
Differences in the characteristics of individuals in a species
How do environmental factors cause variation?
Differences in the environment cause variation. Characteristics controlled by environmental factors change over an organisms life (eg accents)
What is an allele?
Different forms of a gene
Define allele
Different versions of the same gene
Facilitated diffusion
Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances (normally large, polar or charged molecules) across plasma membrane.
Diffusion
Diffusion is the net movement of molecules (or ions) from a region of high concentration to a region of low concentration. It is passive.
What is artificial classification?
Divides organisms according to physical appearances such as size or No. legs
Characteristics of passive immunity
Does not require exposure to antigen, short lived as antibodies are broken down, memory cells not produced, instant immunity
order of classification system
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Give the hierarchical order of taxa in our classification system (1 mark)
Domain, kingdom, phylum, class, order, family, genus, species
Prokaryotic cells _______ have a _______
Don't Nucleus
What type of circulatory system does most mammals have?
Double circulatory system
What is independent segregation?
During the first division maternal and paternal homologous chromosomes line up in random orders leading to a more varied population
Independent segregation
During the formation of gametes, each gamete receives just one gene copy, which is selected randomly. Each pair of alleles segregates independently of the other pairs and all possible combinations of alleles can occur in the resulting gametes.
How do we use monoclonal antibodies in medical diagnosis?
ELISA test
Why an electron microscope can be used to produce images [2]
EM gives high resolution due to short wavelength of electrons;
Non-overlapping
Each base appears in only one triplet - each base is only read once.
Define non overlapping
Each base sequence is only read once
What does non-overlapping mean?
Each base sequence is read in sequence, separate from the sequence before and after it
why is the middle of the S curve steep?
Each binding changes the shape of the haem group so it makes binding easier and faster.
Why is DNA replication called semi-conservative?
Each daughter DNA molecule is composed of one parental strand and one new strand
How does pH affect enzyme activity?
Each enzyme has an optimal pH at which it can perform at its maximum rate. Too high or too low of a pH, the H+ and OH- ions mess up the ionic bonds so the enzyme denatures
What are a fish's gills made up of?
Each gill has stacks of filaments
Taxon
Each group within a phylogenetic biological classification (pl. taxa)
Describe the structure of an enzyme, using your knowledge of protein structure.
Each individual enzyme has its own specific sequence of amino acids. Help in tertiary form by hydrogen bonds, disulphide bridges and ionic bonds. This 3-D structure gives the enzyme many of its properties.
Chromatid
Each of the two thread-like strands into which a chromosome divides that are joined together by a single centromere prior to cell division
Why do haemoglobins of different species have different affinities towards oxygen?
Each species produce haemoglobins with different amino acid sequences, resulting in varying affinities
Define universal
Each triplet codes for the same amino acid in other organisms
B cells
Each type of B cell produces a specific antibody that responds to one specific antigen.
What is an example of anatomical survival adaptations?
Ears+ fur in artic foxes
After the first oxygen bind it makes it _____ for other molecules of oxygen to bind
Easier
How does an electron microscope work?
Electron microscopes use beams of electrons that are focused by magnetic fields. The beam passes through the specimen, the specimen absorbs electrons, electrons that pass through are picked up and appear dark creating an image
What is the structure of the palisade mesophyll like?
Elongated cells with lots of chloroplasts
Name a test for lipids.
Emulsion test
what is the test for lipids known as?
Emulsion test
How do you test for lipids?
Emulsion test -Shake the test substance with ethanol until it dissolves -Pour the solution into water -If lipids are present they will precipitate out of the liquid as a milky emulsion
What are the roles of polysaccharides?
Energy stores and structural.
Valves
Ensure that blood does not flow backwards and that when body muscles contract, compressing veins, pressurising the blood within them, they ensure the blood flows in one direction only: towards the heart.
Why is synchronisation of mating important?
Ensures mating occurs when max prob of egg + sperm meeting
Why is recognising members of a same species important?
Ensures mating only occurs between members of same species
Why do species need to synchronise mating?
Ensures that mating occurs when there is the max probability of the sperm+ egg meeting
Define tissue fluid
Environment around cells in a multicellular organism
What is the rate of mitosis affected by?
Environment of cell Growth factors (hormones etc) Mutation in genes
What happens in stabilising selection?
Environmental conditions remain stable, individuals with phenotypes closest to the mean population are favoured Increase in frequency of alleles towards the mean
What is the limiting factor when increasing the substrate concentration?
Enzyme concentration because ALL the enzyme active sites are OCCUPIED AT ALL TIMES
ELISA
Enzyme linked immunosorbent assay which uses antibodies to detect the presence and quantity of a protein in a sample.
RNA Polymerase
Enzyme that joins together nucleotides to form messenger RNA during transcription
What is the definition of an enzyme?
Enzymes are 3D biological catalysts that speed up reactions without themselves being used up.
What does a high turnover mean?
Enzymes are very fast acting; they can convert many molecules of substrate per unit time e.g. catalase converts millions of hydrogen peroxide to oxygen and water per second.
How do enzymes work?
Enzymes have a specific shape the lock and key model suggests their specific shape fits into a substrate (molecule)
Describe the lock and key model of an enzyme.
Enzymes have a specific shaped active site which is complementary to the substrate molecule.
What is chemical digestion?
Enzymes hydrolyse large, insoluble molecules into smaller, soluble ones
what is chemical digestion?
Enzymes hydrolyse large, insoluble molecules into smaller, soluble ones
What is the outer layer of a leaf called?
Epidermis
What are methods of in situ conservation?
Establishing protected areas such as national parks (restricts urban development and farming), preventing the introduction of species that threaten local biodiversity, protecting habitats (controlling water levels and trimming trees), promoting particular species and giving legal protection to endangered animals.
Name the bonds formed between glycerol and fatty acids.
Ester bonds
What is the bond called between the glycerol and the fatty acids in a triglyceride?
Ester bonds.
____________ cells have protein ________ DNA
Eukaryotic Associated
Transcription: Where does it take place?
Eukaryotic : nucleus Prokaryotic: cytoplasm
What two factors lead to a high biodiversity?
Evenness is population Richness of species
How does DNA evidence support evolution?
Evolution is caused by gradual changes in the base sequence of an organisms DNA. Organisms that diverged away from each other more recently have more similar dna
What is phylogeny?
Evolutionary history of a species
What are Cristae?
Extensions formed by the double membrane in organelles folding over
How strong is a disulphide bond?
Fairly strong not easily broken
What are phospholipids?
Fats that contain a glycerol, two fatty acids and a phosphate group. They are amphipathic, so form micelles in water. Makes up 80% of membranes.
What does lymph contain?
Fats, salts, glucose and some proteins. Less O2 and more waste. No red blood cells or platlets but still clots. Contains WBCs and antibodies
Directional selection
Favours one extreme of the range of characteristics and the other extreme is selected against - shift in population curve
Stabilising selection
Favours the mean of the distribution because the extremes are at a selective disadvantage - frequency of mean phenotype increases
How is O2 able to bind to haemoglobins?
Fe in Haem group binds to 4 oxygen molecules. (8 atoms)
Fibrosis
Fibrosis is the formation of scar tissue in the lungs. Scar tissue is thicker and less elastic than normal tissue so means that the lungs are less able to expand. Tidal volume is reduced and so is FVC. There is a reduction in gaseous exchange and a faster ventilation rate.
Explain how two features of gills allow efficient gas exchange.
Filaments/lamellae provide large surface area; Thin/flattened epithelium/ one/two cell layers so short diffusion pathway (between water and blood); Countercurrent/blood flow maintains concentration/diffusion gradient;
Explain how two features of gills allow efficient gas exchange. (2)
Filaments/lamellae provide large surface area; Thin/flattened epithelium/ one/two cell layers so short diffusion pathway (between water and blood); Countercurrent/blood flow maintains concentration/diffusion gradient;
Ultrafiltration
Filtration under pressure at the arterial end, assisted by blood pressure (a hydrostatic pressure) which causes small molecules to be forced out of the capillaries, leaving all cells and proteins in the blood because they are too large to cross the membranes.
What is the binomial naming system?
First name is generic name = Genus (capital) Second name is specific name = species (lowercase_
Give an example of a specialised exchange surface that has a good supply.
Fish Gills. In the gills, CO2 and O2 are exchanged between the fish's blood and the surrounding water. They contain a large network of capillaries which keeps them supplied with blood. They are also well ventilated as fresh water constantly passes over them.
What is ram ventilation?
Fish maintains water flow over the gills by holding the mouth open
What is tissue fluid?
Fluid formed from blood plasma and other components of the blood from homeostatic systems
Villi
Folded finger-like projections of the ileum wall, about 1mm long, which are increase the surface area of the ileum and therefore accelerate the rate of absorption.
What is Villi?
Folds in the epithelial layer in the ileum creating a large surface area
Emphysema
Foreign particles become trapped din the alveoli. This causes inflammation which attracts phagocytes. The phagocytes produce an enzyme that breaks down elastin, so the alveoli can't recoil as well which means gaseous exchange decreases. Increased ventilation rate.
what is the role of phosphate ions?
Form a structural role in DNA molecules storing energy in ATP molecules component of DNA and RNA nucleotides
Transcription
Formation of messenger RNA molecules from the DNA that makes up a particular gene. It is the first stage of protein synthesis.
What is the purpose of a thick cuticle?
Forms a water proof barrier preventing water evaporating out of cells
Describe Keratin
Found in hair, nails, claws and horns. Provides mechanical protection. It's water proof and have very strong hydrogen bonds
Describe Elastin
Found where things need to stretch and adapt their shape. They help blood vessels stretch and help lungs inflate and deflate.
What are the consequences of addition of a base?
Frame shift to the right all base triplets after the addition are altered changing the primary structure of the protein formed
How is glucose transported around the plant?
From the source to the sink via the phloem
What does artificial classification describe?
Function not evolutionary origin
How do fungi cause infection in plants?
Fungi infect vascular tissue and extract nutrients by releasing extra cellular enzymes that digest surrounding tissues
What do the air spaces in the mesophyll allow?
Gases to move to and from cells by diffusion in gas phase
What is within a species?
Gene pool
What do species have thats similar?
Genes, physical and biochemical characteristics Similar development patterns and immunological features
Which grouping does the first name in an organism's binomial name give you? (1 mark)
Genus
What type of protein are enzymes?
Globular
Enzymes are made of what biological molecule?
Globular proteins which act as a biological catalyst.
What are the three components of a triglyceride?
Glycerol and three fatty acids.
How do animals store glucose?
Glycogen
What is glycogen?
Glycogen is a branched polysaccharide made from alpha glucose. It contains 1-4 and 1-6 glycosidic bonds. It's an energy store in humans.
What is glycogen?
Glycogen is a polysaccharide
Describe the process of HIV replication
Glycoproteins(gp120,gp41) bind to receptor (CD4) on T cell and fuses with cell surface membrane Reverse transcriptase catalysed the production of DNA from the viruses RNA creating two DNA strands DNA is integrated into cells DNA, protein synthesis occurs and a new virus is formed this new virus buds off the host cell
What are glycosidic bonds?
Glycosidic bond is a covalent bond that forms between two monosaccharides
What is the name of the bond formed when two monosaccharides join together?
Glycosidic bond.
How does the mucous membrane prevent disease?
Goblet cells in epithelial cells produce mucus to trap pathogens. Ciliated epithelium waft the mucus up the trachea to the top of the oesophagus. Pathogens in mucus swallowed into the digestive system
What is phylum?
Group of closely related classes
Polygenes
Group of genes that are responsible for controlling a characteristic.
Define population
Group of interbreeding organisms of a species
Hierarchy
Groups within larger groups; with no overlap between groups at each rank
What three things is mitosis needed for?
Growth Repair Reproduction
How do monoclonal antibodies work in pregnancy tests?
HCG I'm pregnant woman's urine attaches to the antibodies in a pregnancy test reaction zone The chemical in the test zone reacts with the complex and releases coloured dye
How does human population growth affect global biodiversity?
Habitat loss, over exploitation as there's a greater demand for resources, urbanisation can isolate species and pollution is killing species and habitats.
How is increased use of monoculture affecting global biodiversity?
Habitats are lost as land is cleared to make way for large fields (habitat diversity). Local and naturally occurring plants are seen as pests so are destroyed (species diversity). Heritage varieties of crops are lost because they are not planted.
If the oxygen dissociation curve is to the left that means....
Haemoglobin has a greater affinity for oxygen meaning it easily loads
If the oxygen dissociation curve is more to the right that means....
Haemoglobin has a lower affinity for oxygen and it dissociates easily
Low affinity
Haemoglobins with this for oxygen take up oxygen less easily, but release it more easily.
High affinity
Haemoglobins with this for oxygen take up oxygen more easily, but release it less easily.
What are haploid cells?
Haploid cells have only one copy of each chromosome. Gametes are haploid.
What is non-disjunction?
Happens when chromosomes mutate or chromosomes fail to separate
Describe how you would calculate dry mass
Heat at 100°C / heat to temp to evaporate water; Weigh and heat until no further change in mass;
What is an example of both a genetic and an environmental factor that varies?
Height - genes determine how tall you grow but as does diet.
Elastic layer
Helps to maintain blood pressure by stretching and recoiling (springing back) in arteries, arterioles and veins.
If the concentration of CO2 is low haemoglobin has a.....
Higher affinity for oxygen
What happen to oxygen in the lungs?
Higher partial pressure of oxygen means haemoglobin has higher affinity for oxygen so more association occurs so more oxyhemoglobin will be produced
Key things to remember
Higher partial pressure of oxygen means higher affinity Haemoglobin binds at the lungs and unloads at tissues
What are they wound around?
Histone proteins
Xylem vessels
Hollow thick-walled tubes which transport water through flowering plants.
What happens in metaphase 1?
Homologous chromosomes line up along the equator
What happens during the first division in meiosis?
Homologous chromosomes pair up and their chromatids wrap around each other (Equivalent proportions of these chromatids may be exchanged) Homologous pairs are separated with one chromosome from each pair going into one of the two daughter cells
Transpiration pull
How a column of water is pulled up the xylem as a result of transpiration.
Hydrolysis
How digestive enzymes function - the splitting up of molecules by adding water to the chemical bonds that hold them together.
What is magnification?
How much bigger the image is that the specimen
What is magnification?
How much bigger the image is that the specimen.
Permeability
How permeable a substance is depends on the size, polarity and charge of the molecule. If it is small, non-polar and fat soluble it is very permeable and can pass through the cell membrane.
What does a phylogenetic tree tell you? (1 mark)
How recently two species shared a common ancestor
What does HIV stand for?
Human Immunodeficiency Virus
HIV
Human immunodeficiency virus which causes the disease acquired immune deficiency syndrome (AIDS). It has a lipid envelope, attachment proteins, a capsid and two single strands or RNA and enzymes.
B cell are what type of immunity?
Humoral immunity
What elements make up lipids?
Hydrogen Oxygen Carbon
Cellulose is made up of parallel strands of β-glucose molecules Name the bond which holds these strands together.
Hydrogen bond.
What does dipeptidases do?
Hydrolyse bond between two amino acids of a dipeptide
What does carboghydrases break down?
Hydrolyse carbohydrates into monosaccharides
What does lipases break down?
Hydrolyse lipids into glycerol into fatty acid
What does endopeptidases do?
Hydrolyse peptide bond between amino acids in the central region of a protein molecule, forming a series of peptide molecules
What does exopeptidases do?
Hydrolyse peptide bond on terminal aminos acids of the peptide molecules formed by endopeptidases
What do proteases break down?
Hydrolyse proteins into amino acids
. What is the name of the reaction by which a disaccharide can be split into its constituent monosaccharides?
Hydrolysis reaction.
What do the terms hydrophilic and hydrophobic mean?
Hydrophilic - attracts water; hydrophobic - repels water
What is the movement of fluid based on?
Hydrostatic (caused by force of heart beat) and oncotic (dissolved solutes leading to osmotic/concentration gradients) pressure.
What causes tissue fluid components to move out of blood?
Hydrostatic pressure at the end of blood capillaries causes tissue fluid to move out of the plasma into tissue
What is the result of a loss of tissue fluid?
Hydrostatic pressure is reduced and the venous end of the capillaries is at a lower pressure causing tissue fluid or be forced back into capillaries
Substitution mutation
If a nucleotide is changed in the DNA sequence
Deletion mutation
If a nucleotide is lost from the DNA sequence, resulting in a 'frame shift' in translation
What does the Benedict's test determine?
If a precipitate forms a reducing sugar is present
Why are ecosystems interlinked?
If one area loses biodiversity the natural valance may be affected
What are the consequences of substitution?
If the base added alter the triplet and codes for a different amino acid the protein produced is different with a alternative function
Mis-sense mutation
If the base change results in a code for a different amino acid completely
Nonsense mutation
If the base change results in the formation of a stop codon
Silent mutation
If the base change still codes for the same amino acid as before (as code is degenerate)
What can you see using a laser scanning microscope?
Images at different depths. They use laser beams to scan a specimen usually tagged with a fluorescent light, which is focused through a pinhole. A detector is hooked up to a computer and a 3 D image is made.
What is artificial active immunity?
Immunity induced in the basis of vaccination Involve inducing an immune resilience in an individual without them having the symptoms
Humoral
Immunity involving antibodies in the body fluids (humour)
Cell-mediated
Immunity involving body cells- T-lymphoytes only respond to antigens presented on body cells rather than in body fluids
What is passive immunity?
Immunity produced by introduction of antibodies into individuals from an outside source without direct contact from the pathogen or antigen NO MEMORY CELLS
What is artificial passive immunity?
Immunity provided by an injection of antibodies made by another individual.
What is natural active immunity?
Immunity provided by antibodies made by the immune system from an infection
What is artificial active immunity?
Immunity provided by antibodies made in the immune system from vaccinations.
What is natural passive immunity?
Immunity provided by breast milk or via the placenta. This makes the baby immune to diseases that the mother is immune to.
Passive immunity
Immunity received by being given antibodies from another organism
What is natural active immunity?
Immunity resulting from becoming infected with a disease. Body naturally produces its own antibodies and memory cells and may continue to do so
what is the role of sodium ions?
Important in the co-transport of glucose and amino acids across plasma membranes
How do you add two glucose units.
In a condensation reaction. Water is a product. It produces a 1-4 glycosidic bond.
What is turgidity?
In a plant cell, the rigid strong cellulose wall will prevent bursting. The cell will swell up to a certain size when it's contents push against the cell wall, which will resist any further swelling.
What is a limiting factor?
In chemical processes: - a component that limits the number of products that can be formed - or limit rate of reaction when it is present in small quantities.
Where are stem cells found?
In early human embryos or the bone marrow of adults
What are meristems?
In plants, stem cells are found in meristems. In the root and stem, stem cells of the vascular cambium divide and differentiate to become xylem vessels or phloem sieve tubes.
What is in situ conservation?
In situ means on site conservation which involves protecting species in their natural habitat.
Transcription: How are the introns removed?
In splicing where the exons join together forming a mRNA strand
How are guard cells specialised?
In the light, they take up water and become turgid. Their thin outer walls and thickened inner walls force them to bend outwards, opening the stomata. This allows the Leaf to exchange gasses for photosynthesis
Where does the gaseous exchange in an insect take place?
In the muscle fibres, which tracheoles have penetrated into
How do bacteria cause disease?
In the right conditions, bacteria can reproduce every 20mins. Once in a host, they cause disease by damaging cells or by releasing waste products or toxins that are toxic to the cell
What is domain eucarya?
Includes all kingdoms composed of organisms made from eukaryotic cells mEMBRANE BOUND ORGANELLES
What reduces the effect of competitive inhibitors?
Increasing substrate concentration
What is the equation for the index of diversity?
Index of diversity= N(N-1) ÷ ∑n(n-1) N= total number of organisms of a species n= total of organisms in each species
How do genetic factors cause variation?
Individuals of the same species have the same gene but different alleles. These make up its genotype. You inherit your genes from your parents. (Eg blood type)
What is Darwin's theory of evolution by natural selection?
Individuals show variation in their phenotypes. Selection pressures create a struggle for survival. Those who are best adapted survive and pass on these adaptions to their offspring
What is the tunica intima?
Inner most part of the blood vessel. They reduce friction between the vessel walls and blood ; it is folded so that the vessel can stretch.
What is ring vaccination?
Inoculating the areas around and area with an outbreak so it can't spread past the circle.
How does the evolution of pesticide resistance affect humans?
Insects that are pesticide resistant can kill crops and carry and spread disease.
Where is lymph found?
Inside lymph vessels. The largest is called the thoracic duct. Lymph enters the left arteriography vena cava.
How do plants store sugar?
Insoluble starch
What occupies most of the cell cycle?
Interphase
What are the three main stages of the cell cycle?
Interphase Cell division Nuclear division
What are the steps of mitosis in order?
Interphase Prophase Metaphase Anaphase Telophase
Where do tracheoles penetrate?
Into muscle fibres
What are the types of variation?
Intraspecific - within a species Interspecific - between species
Define vaccination
Introduction of disease antigens to stimulate an immune response
What are genes that don't code for amino acids called?
Introns
what is used to test for starch?
Iodine
Translation: What does the tRNA then do?
It has an anticodon complimentary to the first codon on the mRNA so attaches itself
What is an unsaturated fatty acid?
It is a fatty acid that has at least one double bond in its molecule So this means that it is a liquid at room temperature
What is a saturated fatty acids?
It is a fatty acid that has no double bonds. It is carrying the maximum number of hydrogen atoms So this means that it remains solid at room temperature
How does callous help in a plant?
It is a large polysaccharide that is deposited in the sieve tubes at the end of the growing season. deposited around the sieve plates and blocks the flow in the sieve tube. this can prevent the pathogen spreading around the plant is also deposited between plasmodesmata.
Describe phospholipids
It is a lipid molecule made up of a phosphate group and two fatty acids. The phosphate group 'head' is hydrophilic and the fatty acid 'tail' is hydrophobic The phospholipids form the cell membrane by forming a phospholipid bilayer
Describe triglycerides
It is a molecule made up of a glycerol molecule and three fatty acids The fatty acids are hydrophobic 'tails' so this means that the 'tails' are insoluble in water All fatty acids have the same basic structure but the hydrophobic 'tail' varies
How is RNA different from DNA?
It is a single helix molecule Contains the organic base Uracil instead of Thymine Contains a ribose sugar not a ribose sugar
What is a disadvantage to in situ conservation?
It is difficult to control some factors such as poaching, predators, disease or climate change.
What is the function of the vacuole?
It is filled with cell sap to help support plants.
What is the function of the SER?
It is responsible for the synthesis of lipid and hormones.
What is the function of the RER?
It is responsible for the synthesis of proteins, as it is covered in ribosomes.
What is the function of the nucleus?
It is the control centre of the cell. It stores the genome and transmits genetic information that provides instructions for protein synthesis.
What is photophosphorylation?
It is the process of generating ATP from ADP and phosphate
What does cytochrome c show?
It is used in respiration, but is different in all organisms. If the sequences are the same, the two species are closely related. The more differences, the less closely related the two species are.
What is altitude acclimatisation?
It is when the body adjusts slowly to changes in altitudes
What is the function of the Golgi apparatus?
It is where proteins and packaged and modified.
What is ex situ conservation?
It means off site conservation. It involves protecting a species by removing part of the population from a threatened habitat.
Describe collagen
It's a strong fibrous protein used in cartilage, connective tissue and tendons. Found in artery walls to prevent bursting under high pressures.
What is haemoglobin affinity towards oxygen?
It's chemical attraction towards O2 molecules
What does water do for aquatic plants?
It's clear hence let's them photosynthesise as light can reach them
Is it difficult for the first oxygen molecule to bind for haemoglobin? Why?
It's difficult as the shape of haemoglobin makes it harder for the oxygen to bind hence the initial gradient on the graph is low
Why is diffusion in gas phase better?
It's faster than diffusion in liquid phase
TC cells (cytotoxic T cells)
Kill abnormal cells and body cells that are infected by pathogens by producing a protein called perforin which makes holes in the cell-surface membrane.
What are the units for water potential?
Kilo pascals KPa
7 Classification of organisms?
Kingdom Phylum Class Order Family Genus Speices
What are the taxonomy ranks?
Kingdom Phylum Class Order Family Genus Species
What is classification levels?
Kingdom Phylum Class Kinky Pete Came Over For Gentle Spooning Order Family Genus Species
What is the order of the taxonomic groups?
Kingdom, Phylum, Class, Order, Family, Genus, Species
What hydrolyses lactose unto glucose and galactose?
Lactase
Why does the water in the end of tracheoles have an effect on gas exchange?
Lactate produced by anaerobic respiration causes water potential in muscle cells to become lower. This means water in the end of tracheoles to move into muscle cells by osmosis. The loss of water in the tracheoles causes a low pressure which draws in more air
Glucose + galactose = _______
Lactose + water
Single felled organisms have a __________ surface area to volume ratio
Large
When collecting variation data how do we ensure it is reliable? (1 mark)
Large and random samples taken/ mean SD calculated
How is the capillary network adapted?
Large blood supply so lots of gas exchange can occur
What type of molecule uses facilitated diffusion to get through the membrane?
Large, polar ,charged water soluble molecule
What is the quaternary structure of a protein?
Larger proteins form complex molecules linked in numerous ways possibly to non protein groups
Domain
Largest taxon either bacteria, archaea and eukarya
Why do species need to form the pair bond?
Leads to successful mating + raising of offspring
Why is forming a pair bond important?
Leads to successful mating and raising offspring
What does it mean if the dissociation curve is towards the left or right?
Left = greater affinity to O2 so loads easily but unloads less so Right = Lower affinity to O2 so loads less easily
Intercostal muscles
Lie between the ribs. Two sets - internal whose contraction leads to expiration and external whose contraction leads to inspiration.
What factors effect transpiration rate? (4 marks)
Light intensity, temperature, humidity and wind speed.
Transcription: What does RNA polymerase do?
Line up the free RNA nulceotides in the nucleus to attach to the exposed bases > mRNA molecules
What type of DNA do eukaryotes have?
Liner DNA molecules
Binominal naming system
Linnaeus' system to name species. 1st: Generic name (genus). 2nd: Specific name (species) E.g. Felix tigris
Cholesterol
Lipid that is an important component of cell-surface membranes because it adds strength. Excess in the blood can lead to atheroma.
What are the characteristics of a memory cell?
Live a long time, do not produce antibodies but circulate in the blood. When they encounter the specific antigen again they divide rapidly to form plasma cells Provide long term immunity
What are the characteristics of archaea?
Lives in extremes of heat, pressure, saltiness and decay. Small loop of dna, no organelles, unique cell wall, 70S ribosomes.
Define biotic
Living components of an ecosystem
Oxygen + haemoglobin is known as....
Loading/associating
Gill
Located within the body of the fish, behind the head.
what is a locus?
Location of a gene on a chromosome
What are microtubules?
Long filament proteins that make up spindle fibres
What are polypeptides?
Long strands of amino acids.
Eukaryotic DNA is ________ than prokaryotic DNA
Longer
What causes guard cells to close their stoma?
Losing water, thus becoming less firm and changing shape
What does a loss of biodiversity lead to?
Loss of genetic variation
Where does the large surface area of lungs come from?
Lots of alveoli
If the concentration of CO2 is high haemoglobin has a....
Lower affinity for oxygen
How does CO2 cause the haemoglobin molecule to change shape?
Lowers PH and changes the shape of the protein.
Give 2 examples of animals which have adapted to have specialized hemoglobin molecules regarding O2 affinties
Lugworms - live in U-shape burrow, as tide goes out burrow not filled with as much water so they have high affinity to absorb as much O2 as possible Llamas - High altitudes with low atmospheric pressure and partial pressure of O2 so llama haemoglobin = high affinity
How do we breathe out?
Lungs recoil and external intercostal muscles relax
Lacteals
Lymphatic capillaries that are found in the centre of each villus, where chylomicrons pass into and then enter the bloodstream.
White blood cells involved in immune responses
Lymphocytes
What is the third sediment formed in cell fractionation?
Lysosomes
What is the specific immune response?
Macrophages will fight off the pathogen and from an antigen presenting cell. An opsonin attaches to the pathogen and monokines cause T cell differentiation (colonal selection). Then T helper cells signal to active B cells via interleukins.
How is the ribcage adapted?
Made from bone to protect thorax
Where is mRNA made?
Made in nucleus
what is the equation for magnification?
Magnification = size of image / size of object
What does blood contain?
Mainly plasma - a yellow fluid containing water, glucose, urea, plasma proteins and ions. There are also RBCs and WBCs and thrombocytes.
What is the purpose of sunken stomata/stomatal hair in limiting water loss?
Maintains humid air around stomata, trap moist air reducing water potential limiting water loss
Describe how you would use a colorimeter to work out an unknown concentration using a calibration curve
Make solutions of known/different concentrations; Use colorimeter to measure absorbency value of each solution and plot calibration curve/graph described; Treat the unknown sample in the same way (same volume of indicator etc); Find concentration of sample from calibration curve;
Gill filaments
Make up the gills of a fish - they are stacked up in a pile.
Glucose + glucose = ________
Maltose + water
What is two alpha glucose's joined together?
Maltose.
Conservation
Management of the Earth's natural resources in such a way that maximum use can be made of them in the future
Organ system
Many organs work together in an organ system to perform a particular function
Define Mass Flow
Mass flow is the bulk movement of liquids (and gases) due to a pressure difference.
Define vaccine
Material introduced in a vaccination
B-Lymphocytes
Mature in the bone marrow and associated with humoral immunity
T-Lymphocytes
Mature in the thymus glad and associated with cell-mediated immunity
What is the purpose of extensive roots in limiting water loss?
Maximises water uptake
what is oxygen saturation?
Measure of the percentage of haemoglobin binding sites in the bloodstream occupied by oxygen
Explain how you would calculate the volume of a sphere
Measure the radius ; Repeat and calculate a mean radius Use formula =4/3 πr^3
Phagocytosis
Mechanism by which phagocytes engulf particles to form a vesicle or a vacuole.
Plasma membrane
Membranes consisting of a phospholipid bilayer found around and within all cells. The cell-surface membrane is the plasma membrane that surrounds cells.
When does crossing over happen?
Meosis 1
What is the central tissue of a leaf called?
Mesophyll
A globular protein is ________ an example is ______
Metabolical Haemoglobin
What happens during anaphase in mitosis?
Metro meets divide to form two chromatids Chromatids are pulled by spindle fibres to opposite poles of cell Mitochondria provide energy
What are microvilli? What do they do?
Microvilli are ginger like projections on the epithelial cell membrane that increase the surface area of the ileum further providing a good rate of diffusion
What is tunica media.
Middle layer of blood vessel. Controls vasoconstriction and vasodilation.
What does the vacuole contain?
Mineral salts Sugars Amino acids Pigments Waste
The alveoli
Minute air-sacs at the end of each bronchiole. Elastic fibres allow the alveoli to stretch and then spring back when expelling CO2. The alveolar membrane is the gas exchange surface
Alveoli
Minute air-sacs with a diameter of between 100µm and 300µm at the end of the bronchioles. They are lined with epithelium. Between the alveoli there are some collagen and elastic fibres.
Stomata
Minute pores that occur mainly on the leaves, especially on the underside. They allow gaseous exchange (and water vapour to leave as well). They are opened and closed by guard cells.
What is the second sediment formed in cell fractionation?
Mitochondria
How is the alveoli membrane adapted?
Moist surface so gases dissolve easily
What do we use to classify organisms?
Molecular - similarities in protein and dna Embryological - early stages of development Anatomical - structure and function of body Behavioural - behaviour and social organisms
What are competitive inhibitors?
Molecules that bind to the active site of an enzyme and inhibit the ability of the substrate to bind. they are a similar shape to the substrate
Define active transport
Moment of molecules against the concentration gradient from and area with a low concentration to an area with a higher concentration using ATP
What is a macrophage?
Monocytes after they migrate from the blood stream and enter tissue.
More different alleles= ..... genetic diversity
More
DNA is ________ chemically stable compared to ___
More RNA
What is the structure of the spongy mesophyll like?
More air spaces and less chloroplasts than palisade mesophyll
What does greater divertsity mean for survival?
More likely individuals can survive any environmental change
What does the shape of an oxygen dissociation curve show?
More to the left: Haemoglobin has a higher affinity for oxygen at low partial pressures and so binds to it more readily More to the right: Haemoglobin has a lower affinity for oxygen at higher partial pressures and so dissociates more readily
How do fungi cause disease in animals?
Most common fungal infections are where the fungal hyphae form a mycelium under the surface of the skin. These can grow to release spores, which cause irritation and redness.
How is climate change affecting global biodiversity?
Most species need a specific climate to survive, so a change in climate can mean a habitat can become uninhabitable. This causes a change in the range of some species. Some species may be made to migrate to more suitable areas causing a change in species distribution. Is there's isn't somewhere to migrate to the species becomes extinct.
What are eukarya?
Mostly multi-celled organisms that have a nucleus, membrane bound organelles, membranes containiing fatty acid chains with ester linkages
Active transport
Movement of a substance from a region where it is in a low concentration to a region where it is in a high concentration. The process requires the expenditure of metabolic energy in the form of ATP.
Absorption
Movement of digested food molecules through the wall of the intestine into the blood or lymph
How does mass transport link to gas exchange in insects?
Muscles in the trachea contract and squeeze air through the trachea speeding up gas exchange
Intercostal muscles
Muscles which lie between the ribs
Oesophagus
Muscular tube which carries food from the mouth to the stomach
How are new alleles of a gene produced? (1 mark)
Mutation
How is cancer formed?
Mutations disrupt or change the normal cell cycle causing cells to divide in an uncontrollable way where the rate of cell growth is higher than that of cell death so has a higher mitotic index than regular cells
What is an alkaloid?
N containing compounds e.g. caffeine. it gives it a bitter taste to inhibit herbivore feeding and inhibit/activate enzyme action. helps reduce damage from pathogens that enter after grazing
What specialised cells do animals have?
Neutrophils, erythrocytes, epithelial cells and sperm cells.
Can the effect of a non competitive inhibitor be reduced?
No
Transcription: Are the introns needed?
No
Will extreme phenotypes survive?
No
Does it code for same amino acid?
No a different amino acid
Does the change always lead to a different amino acid being coded for?
No as DNA is degenerate so it may have no affect
Is the water potential of 25kPa possible?
No because all water potential values are lower than 0
Is the DNA wound around histones in prokaryotes?
No it condenses to fit by "supercoiling"
Correlation Coefficient Null Hypothesis
No significant correlation between X and Y
Is substitution always bad?
No the base added may not change the amino acid codes for meaning the protein produced stays the same
Define abiotic
Non living component in an ecosystem
What is the distribution like?
Normal distribution with large standard deviation before natural selection occurs
How strong is a hydrogen bond in a protein?
Not very strong easily broken
Foreign (non-self)
Not your own body's cells and molecules.
What is the first sediment formed in cell fractionation?
Nuclei
What does a animal cell consist of?
Nucleus mitochondria Endoplasmic reticulum Golgi apparatus Lysosomes Ribosomes Cell membrane Cytoplasm
Ventilation rate (min-1)
Number of breaths taken in one minute
How do you calculate mitotic index?
Number of cells undergoing mitosis ÷ total number of cells
Species diversity
Number of different species and number of individuals of each species within any one community
Define species diversity
Number of different species and the number of individuals of each species in a community
What do you need to calculate an index of diversity (1 mark)
Number of individuals of each species and total number of individuals of all species
How do you calculate the proportion of polymorphic gene loci?
Number of polymorphic gene loci / number of loci.
In a phylogenetic tree where are the oldest species compared to newer species?
Older species at base New species coming of branches
What are chromatids?
One o the two strands of a chromosome joined together by a centromere
Chromatid
One of the two strands of a chromosome that are joined together by a single centromere prior to cell division.
What is a centriole?
One of two small cylindrical structures, made from microtubules, found just outside the nucleus in animal cells, in a region known as the centrosome
What is a disadvantage to ex situ conservation?
Only a small number of individuals can be cared for, and it is disruptive to take them out of their natural habitat. Also species may catch diseases from humans and become dependant.
What protects a fish's gills from damage?
Operculum
Blood flows in the _______ direction to water in fish this is caked ___________
Opposite Counter current flow
Lysosome
Organelle formed when the vesicles produced by the Golgi apparatus contain enzymes. They are where unwanted materials & worn-out organelles are digested.
Ribosome
Organelle made of rRNA and protein where protein synthesis occurs.
Golgi
Organelle that contains a stack of membranes that make up flattened sacs (cisternae) where glycoproteins are synthesized, lipids are transported, modified and stores, proteins are packaged and lysosomes are formed.
Chloroplast
Organelle that is the site of photosynthesis
Mitochondria
Organelle where energy is released in aerobic respiration
Smooth endoplasmic reticulum (SER)
Organelle where lipids and carbohydrates are synthesized, stored and transported.
Vacuole
Organelle which contains a solution of mineral salts, sugars, amino acids, wastes and sometimes pigments such as anthocyanins. They support herbaceous plants by making cells turgid, may provide a temporary food store and if they contain pigments they may colour petals to attract pollinating insects.
Nucleus
Organelle which contains the hereditary material (DNA) which codes for she synthesis of proteins in cytoplasm.
Rough endoplasmic reticulum (RER)
Organelle which provides a large surface area for the synthesis of proteins and glycoproteins and where proteins are transported that are synthesised on ribosomes.
Cell wall
Organelle which provides mechanical strength to prevent the cell bursting under the pressure created by the osmotic entry of water, to give mechanical strength. Made of cellulose in plants and chitin in fungi.
What can you see using a transmission electron microscope?
Organelles. Electromagnets are used to focus a beam of electrons which is then transmitted through the specimen. Denser parts absorb more light so look darker on the image.
Classification
Organisation of living organisms into groups
What would happen if we lost species?
Organisms in an ecosystem are interdependent, so a loss of a species can disrupt the food chain and the nutrient cycles.
What is an example of physiological survival adaptations?
Oxidising fat rather than carbs in kangaroos
How is oxygen obtained in a single felled organism?
Oxygen is absorbed across body surface by diffusion carbon dioxide given off in a similar way
What happens in meosis 1?
P1 M1 A1 T1
What is the upper layer of the mesophyll called?
Palisade mesophyll
What specialised cells do plants have?
Palisade mesophyll cells, root hair cells and guard cells.
Flagellum
Part of a bacterial cell which helps the bacteria to move.
What could a change in environment result in?
Particular phenotypes being better suited so they will survive. Over time selection moves in the direction of these individual traits
What is indirect transmission?
Passing a pathogen from host to new host, via an intermediary. Such as air, water, food or a vector.
What is direct transmission?
Passing a pathogen from host to new host, with no intermediary. This can happen via droplet infection, sexual inter course or touching an infected oerson
Define transportation
Passive process that moves water without using metabolic energy
Describe how a microbe can be broken down by the process of Phagocytosis (4)
Pathogen is engulfed by the phagocyte. Forming a vesicle surrounding the pathogen (called a phagosome). Lysosomes fuse with this vesicle releasing digestive enzymes Lysosome enzymes hydrolyse the proteins and lipids in the pathogen. Waste materials are ejected from the cell or presented on cell surface memebrane.
Antigenic variability
Pathogen may mutate frequently so that its antigens change suddenly rather than gradually which means vaccines become ineffective because the new antigens on the pathogen are no longer recognized by the immune system.
How does the evolution of drug resistance affect humans?
Pathogens have evolved resistance to specific drugs so infections are harder to treat.
How can stem cells cure Parkinson's?
Patients suffer from tremors, as there is a loss of a particular type of nerve cell found in the brain, which produce the hormone dopamine (helps movement). Stem cells could help regenerate the dopamine producing cells.
How are proteins digested?
Peptidases are enzymes that break down polypeptides. 1. Endopeptidases hydrolyse peptide bonds within proteins. This happens in the stomach to make proteins into polypeptides. 2. Exopeptidases hydrolyse the peptide bonds to make polypeptides into dipeptides. This happens in the ileum. 3. Dipeptidases turn dipeptides into amino acids. They are in the microvilli cell walls - they are a carrier protein.
What is a prokaryotic cell wall made from?
Peptidoglycan.
White blood cells that ingest and destroy pathogens
Phagocytes
Why does the structure of ATP make it a good short term energy store
Phosphate bonds are unstable
How is ATP reformed from ADP?
Phosphate is added in a condensation reaction catalysed by the enzyme synthase
What is the name of the covalent bond formed between the sugar and the phosphate group on the DNA backbone?
Phosphodiester
What is the main component of the cell surface membrane?
Phospholipids
How does the structure of phospholipids relate to their function?
Phospholipids form the cell membrane by forming a phospholipid bilayer. The cell membrane controls what enters and leaves the cell With their hydrophilic 'heads' and hydrophobic 'tails', they form a double layer, with the hydrophilic 'heads' facing out towards the water and the hydrophobic 'tails' facing inward. So this will mean that the centre of the bilayer is hydrophobic, so water-soluble substances can't easily pass through the phospholipid bilayer
What is mechanical digestion?
Physical breakdown of large pieces of food into smaller pieces
What is a habitat?
Place where an organism lives
Xerophyte
Plants which have a restricted supply of water which have evolved a range of adaptations to limit water loss through transpiration.
What are the characteristics of a plasma cell? What do they do?
Plasma cells secrete antibodies in response to pathogens They only live a couple of days and male 2,000 antibodies every second Responsible for immediate immune defence
What is dynamic equilibrium?
Point in which rate of osmosis is equal and water potential doesn't change as both sides are equal
What allows carbon dioxide into a leaf?
Pores called stomata
Exon
Portions of DNA within a gene that codes for proteins. They are joined together during splicing.
Intron
Portions of DNA within a gene that do not code for a polypeptide. They are removed from pre-messenger RNA after transcription.
Describe the process of splicing
Pre-mRNA contains exons and introns, the enzyme splicisome removes the introns so on coding triplets are left in the mRNA
Define hydrostatic pressure
Pressure created by the pumping of the heart
What does chemo therapy do?
Prevents DNA replication Prevents metaphase interfering Prevents spindle formation
What are the levels of organization?
Primary, secondary, tertiary and quaternary.
Artificial classification
Process of classifying organisms based on differences useful at time e.g. colour, size, number of legs
Phylogenetic classification
Process of classifying organisms based upon evolutionary relationships between organisms and ancestors
What is an example of physiological adaptations?
Processes inside an organism that increases rate of survival. Eg, brown bears hibernate over winter to conserve energy.
How does a cytotoxic T cell destroy a pathogen?
Produce the protein perforin which breaks down cell membrane causing infected cells to become freely permeable leading to death of cell
Lactase
Produced by the epithelial lining and is a membrane-bound disaccharidase which breaks down lactose into the monosaccharides glucose and galactose.
Maltase
Produced by the epithelial lining and is a membrane-bound disaccharidase which breaks down maltose into glucose.
Sucrase
Produced by the epithelial lining and is a membrane-bound disaccharidase which breaks down sucrose into the monosaccharides glucose and fructose.
Bile salt
Produced by the liver and split up lipids into tiny droplets called micelles.
Pancreatic amylase
Produced by the pancreas and released into the small intestine where it continues the hydrolysis of starch to maltose.
Salivary amylase
Produced by the salivary glands and released into the mouth and starts hydrolysing starch in food to maltose.
Where is maltase? Where is it produced?
Produced in the lining of the ileum, breaks down maltose into a monosaccharide such as alpha glucose
Where is amylase produced? What does it do?
Produced in the salivary glands and pancreas. Breaks down starch into disaccharides such as maltose,lactose and sucrose
What are the 5 kingdoms?
Prokaryotae, protoctista, fungi, plantae, animalia
What is the purpose of the capsule?
Protects the bacterium from other cells and helps them stuck together for further protection
Why does an enzyme have a globular shape?
Protein chain is folded back on itself in a spherical or globular shape with hydrophilic R groups on the outside of the molecule
What is an antibody?
Protein molecule works quaternary structure
Perforin
Protein secreted by cytotoxic T-Cells that makes holes in the cell surface membrane, making it permeable to all substances and killing the cell
When are introns removed
Protein synthesis so don't affect amino acid order
What makes up the cell surface membrane?
Proteins Glycoproteins Glycolipids Phospholipids Cholesterol
Histones
Proteins, which together with DNA, make up the chromosomes of eukaryotic cells.
What does the rough endoplasmic reticulum do?
Provides a large surface area for protein synthesis Provides a pathway for materials (especially proteins)
Transcription: What is the first step? What attactches to what?
RNA polymerase attaches to DNA at beginning of gene
Tracer
Radioactive isotopes can be used to trace the movement of substances in plants. 14CO2 is used so plants incorporate this isotope into the sugars produced during photosynthesis. These radioactive sugars can then be traced as they move within the plant using autoradiography. This shows that sugars are found where phloem tissue is in the stem.
Ecosystem diversity
Range of different habitats within a particular area
Specific response
Reaction to a specific antigen by lymphocytes
What 4 things ensures reproduction is successful ?
Recognise members of same species Identify mate capable of breeding Form pair bond Synchronised breeding
What are the 4 things it allows individuals to do?
Recognise memebers of same species Identify a mate Form a pair bond Syncronise mating
What is the advantage of a leaf having hairs?
Reduce air movement and trap water
define ecosystem diversity
Refers to the range of different habitats from a small local habitat to the whole earth
What are some examples of methods of ex situ conservation?
Relocating organisms to a safer area, breeding organisms in captivity and reintroducing them into the wild, botanic gardens and seeds banks.
How can you tell if two organisms belong to the same species grouping? (1 mark)
Reproduce and produce fertile offspring
Gamete
Reproductive (sex) cell that fuses with another gamete during fertilisation
Transport system
Required to take materials from cells to exchange surfaces and from exchange surfaces to cells. They must have a suitable medium to carry materials, a form of mass transport in which the transport medium is moved around in bulk over large distance, a closed system of tubular vessels and a mechanism for moving the transport medium within vessels.
Characteristics of active immunity
Requires exposure to antigen, long lasting as memory cells circulate in the blood, memory cells produced, takes time for immunity to be produced
Active immunity
Resistance to disease resulting from the activities of an individual's own immune system whereby an antigen induces plasma cells to produce antibodies.
Passive immunity
Resistance to disease that is acquired from the introduction of antibodies from another individual, rather than an individual's own immune system e.g. across the placenta or in the mother's milk. It is usually short lived.
Tough fibrous outer layer
Resists pressure changes from both within and outside arteries, arterioles and veins.
What is the magnification and resolution of a transmission electron microscope?
Resolution = 0.2 nm Magnification = 1,000,000
What is the resolution and magnification of a light microscope?
Resolution = 200nm Magnification = 1500
What is the magnification and resolution of a scanning electron microscope?
Resolution = 2nm Magnification = 100,000
Define resolution
Resolution is the minimum distance apart two objects can be to appear as two separate objects
How does respiration affect oxygen dissociation?
Respiration produces: increase incarbon oxide levels Higher temperatures Effect: If the carbon dioxide levels increase more dissolved in blood plasma reducing carbonic acid which lowers the blood pH If temperature increases more heat is produced Response: then the haemoglobin shape changes and so more haemoglobin dissociates oxygen meaning more is available for respiration
What enzyme is contained in HIV? What does it do?
Reverse transcriptase catalysed the production of DNA from RNA
What doe RNA stand for?
Ribonucleic acid
Translation: Where does it occur?
Ribosomes
Where does mRNA travel to?
Ribosomes
What is the difference in ribosomes in eukaryotic and prokaryotic cells?
Ribosomes are smaller in prokaryotic cells (70s) in eukaryotic cells they contain larger ones (80s)
Name the main chambers and valves within the heart
Right Atrium, Right Ventricle, Left atrium, Left Ventricle, Atrioventricular valves, Semi-lunar valves.
Give the names of experiments which support mass flow hypothesis
Ringing, radioactive tracers
How is the trachea adapted?
Rings of cartilage to support the trachea stop it from collapsing
Give an example of a specialised exchange surface with s large surface area.
Root hair cells. The cells on plant roots grow into long hairs which stick out. Each branch of root will be covered in millions of these microscopic hairs which increase surface area. This increases rate of absorption of water.
What do all members of the same species have that's the same? What is different?
Same gene but different alleles
In homologous chromosomes describe the chromosomes
Same size+ same genes
What does universal mean?
Same specific base triplet code for the same amino acids in all living things
Random sampling
Sampling a population to eliminate bias e.g. grid square and co-ordinates
What are problems with species richness?
Seasonal Expensive + time-consuming
Kingdom
Second largest taxon of classification. Eukarya domain divides into Protoctista, Fungi, Plantae and Animalia.
Plasma Cells (B-Cell clone)
Secrete antibodies into the blood plasma, antibodies lead to the destruction of the antigen and are the immediate defence of the body against infection
Gene
Section of DNA on a chromosome that controls a feature by coding for formation of one or more specific polypeptides or a functional RNA (including rRNA and tRNA).
What is directional selection? (1 mark)
Selection for ONE extreme/mean shifts over time
Define ecosystem
Self contained self supporting combination of abiotic and biotic organism
What is the role of membranes within cells.
Separates the organelles contents from the cytoplasm. In some organelles, metabolic processes occur on membranes.
What is the function of gene?
Sequence of amino acids Functional RNA
Explain how a change in the primary structure of a globular protein may result in a different three-dimensional structure. [3]
Sequence of amino acids changes; tertiary structure changes/folds in a different way; bonds form in different places (not peptide);
What is the primary structure of protein? What does it determine?
Sequence of amino acids formed through polymerisation, this sequence is determined by DNA and determines the proteins structure and function
Insects are small hence have a ________ diffusion pathway
Short
What is needed for species to be able to breed with each other?
Similar genes Behaviour is similar otherwise they will not recognise others
What does tissue fluid contain?
Similar to blood plasma, but less oxygen, amino acids and glucose. Also contains a few WBCs."
Compare DNA Vs RNA (6/ 10marks)
Similarities: Contain phosphate Made up of nucleotides Contains organic bases (A, C and G) (not T as it is replaced by U in RNA) Pentose sugar (3 max) Differences RNA single stranded RNA has non-coding strands (introns) removed Ribose sugar in RNA deoxyribose in DNA U in ribose replaces the T 3 types of RNA, only one DNA Smaller than DNA (3 max)
Companion cell
Since the sieve tube element lacks organelles, the companion cell with its nucleus, mitochondria, ribosomes, enzymes etc., controls the movement of solutes and provides ATP for active transport in the sieve tube element. Strands of cytoplasm called plasmodesmata connect the sieve tube element and companion cell.
What is the bacteria domain?
Singel celled prokaryotes No membrane bound organelles Cluster together Small ribsomes Cell wall= meurin
What is the archaea domain?
Single celled prokaryotes Genes and protein synthesis more simialr to eukaryotes (Extreme Bacteria)
what is the function of chloroplasts?
Site of photosynthesis
Define source
Sites of photosynthesis that produce glucose
Salivary glands
Situated near the mouth. They pass their secretions via a duct into the mouth which contain salivary amylase which hydrolyses starch into maltose.
How do you calculate magnification?
Size of image ÷ size of object
What organelles do prokaryotic cells have that eukaryotic cells don't?
Slime capsule Plasmid Flagellum NO MEMBRANE BOUND ORGANELLES
Fish have a ______ surface area to volume ratio, which means?
Small SA:V ration meaning the body cannot supply and remove realities gases easily
How is haemoglobin adapted to animals?
Small animals have a larger surface area to volume ratio and so they lose heat more easily they therefore have a higher metabolic rate to produce more heat to counter act the loss. They therefore require a higher oxygen concentration and so haemoglobin is adapted to have a lower affinity for oxygen at any given partial pressure allowing dissociation to occur more readily
Plasmid
Small circular loops of DNA which contain genes that bacteria can have.
What are defensins?
Small cysteine rich proteins with broad antimicrobial action. they act on molecules in the plasma membrane of pathogens
What are the characteristics of bacteria?
Small loop of dna, no organelles, peptidoglycan cell wall, 70S ribsosomes. Some tolerate heat or decay conditions.
What are coenzymes?
Small organic non protein molecules that bind temporarily to the active site of the enzyme molecules. They are chemically changed during the reaction.
What are nuclear pores?
Small pores in the nucleus allowing large molecules entry and exit
How is water loss limited in insects?
Small surface area to volume ratio- to maximise the area over which water is lost Waterproof covering Spiracles- can open or close
What type of molecules can pass through the membrane by simple diffusion?
Small, non-polar and uncharged lipid soluble particles
What are the properties of monosaccharides?
Small, sweet, soluable. Energy sources.
Arterioles
Smaller arteries that control blood flow from arteries to capillaries. Their muscular layer is relatively thicker than in arteries and elastic layer is relatively thinner than in arteries.
What is the purpose of low stomata denisity in limiting water loss?
Smaller surface area for diffusion of air ,less places for evaporation to occur
What is the purpose of small surface area in limiting water loss?
Smaller surface area for evaporation
What are arterioles?
Smaller than arteries. They have a layer of smooth muscle but have less elastic tissue.
What do the tracheae divide into?
Smaller tubes called tracheoles
What is a capillary?
Smallest type of blood vessels. Substances like glucose and oxygen are exchanged between cells and capillaries
Memory B cells
Some B cells develop into memory cells which can respond to future infections by the same pathogen by dividing rapidly and developing into plasma cells that produce antibodies as part of the secondary response.
What are antitoxins?
Some antibodies attach to molecules released by pathogenic cells. These molecules may be toxic and in such renders the toxin harmless.
Why do you stain samples?
Some objects may be transparent so you can stain them. Some parts of the object take up more of the dye than others so the contrast makes different parts show up.
What is the role of proteins in a membrane?
Some proteins form channels in the membranes. These allow small or charged particles through. Other proteins transport molecules across the membrane by active transport and facilitated diffusion. Thy also act as receptors for molecules in cell signalling.
How does inflammation prevent disease?
Specialised cells release cell signalling histamine which causes vasodilation, capillaries become more permeable to white blood cells which enter tissue fluid and cause swelling.
What does biodiversity consider?
Species diversity Genetic diversity Ecosystem diversity
How do you measure biodiversity?
Species richness
What happens in anaphase 2?
Spindle fibres attach to centromere Chromatids are pulled apart
What happens in telophase 1?
Spindle fibres dissolve 2 cells form
What happens in telophase 2?
Spindle fibres dissolve 4 haploid non-identical cells form
What is a spiracle what does it do?
Spiracles are tiny pores in the trachea in which gases enter and exit. Spiracles May open or close though the use of valves
What is the lower layer of the mesophyll called?
Spongy mesophyll
Diastole
Stage of the cardiac cycle when the atria and ventricles are relaxed. Blood returns to the atria of the heart. Atrial pressure increases as they fill with blood, causing the atrioventricular valves to open, which allows blood to flow into the ventricles. The semi-lunar valves are closed ('dub') because the pressure in the ventricles is lower than that in the aorta and the pulmonary artery.
What is graph of distribution after selection like?
Standard deviation is less then upper curve Mode shifted to right TOWARDS EXTREMES
Show two ways in which the structure of cellulose is different from the structure of starch. [2]
Starch 1,4 and 1,6 bonds / branching Cellulose 1,4 bonds / no 1,6 bonds / straight; starch All glucoses /monomers same way up cellulose Alternate glucoses upside down; starch Helix / coiled/compact cellulose Straight; Starch monomer Alpha glucose Cellulose monomer Beta glucose
What is starch? How is it formed?
Starch is a polysaccharide formed as glucose is joined together in a long chain during a condensation reaction
Is it worse to have deletion at the start or end of a molecule?
Start as more amino acids have the potential to change forming a completely different protein
Define sinks
Storage places of glucose
Why do bases attach in a 3' 5' direction?
Strands are antiparallel Nucleotides arranged differently Enzymes are specific to substrates Must bind in opposite directions due to lock and key
How are the tracheae supported?
Strengthened rings (chitin) to prevent it from collapsing
A fibrous protein is ______ an example is ______
Structural Collagen
What is an example of anatomical adaptions?
Structural features the increase chances of survival. Eg, otters are streamlined so they can glide through the water and whales have a layer of blubber to keep them warm.
What are analogous features?
Structures of different species having similar functions but not from the same ancestor
Which statistical test do you use you want to compare two mean values to see if they are significantly different from each other or not?
Student's T test
What does courtship behaviour ensure?
Successful reproduction
What hydrolyses sucrose into glucose and fructose?
Sucrase
Glucose + fructose = _______
Sucrose + water
Describe mass flow of sucrose through sieve elements
Sucrose actively transported into sieve tube Sieve tunes have a low water potential, water moves from xylem which has a high water potential Sieve element has a higher hydrostatic pressure As sinks use up sucrose they have high water potential leading to them losing water gaining a low hydrostatic pressure Sucrose moves from a high pressure to a low one
Describe the movement of sucrose into sieve elements
Sucrose is produced in the source Sucrose diffuses down a concentration gradient unit companion cells Hydrogen ions are actively transported from companion cell into spaces between cells Hydrogen ions diffuse along concentration gradient into sieve tube elements Co-transport occurs and hydrogen ions transport sucrose into sieve element
How do expulsive reflexes prevent disease?
Sudden expulsion of air carried away irritation micro organisms
The primary function of gas exchange in animals is?
Supplying oxygen for respiration
What is the function of the vacuole?
Support the plants Provide short term food supply
What factors effect diffusion?
Surface area Temperature Concentration gradient Diffusion pathway
Exchange surface
Surfaces across which substances could be transferred. To allow exchange to be efficient, surfaces will often have a large surface area:volume ratio, be very thin and selectively permeable. There will also often be movement of the environmental medium and a transport system to ensure the movement of the internal medium.
Where is tissue fluid found?
Surrounding the cells in tissues.
What does the smooth endoplasmic reticulum do?
Synthesises, stores and transports lipids Synthesises, stores and transports carbohydrates
What is the bionomial naming system?
System of naming organisms in which they have a general name eg tiger and a specific scientific name
Name the lymphocyte present in the Cell-mediated response.
T lymphocytes
How does a fish push water through its gills?
Takes it in through its mouth, pushes it back through the gills and out past the operculum
What is physical breakdown?
Teeth break down large molecules of food into smaller molecules of food providing a larger surface area for break down of molecules
What effects enzyme action?
Temperature pH Concentration of substrate Concentration of enzyme
what does affinity mean?
Tendency to combine with oxygen
Define biodiversity
Term used to describe the whole variety of life on earth
What does the fluid mosaic model propose?
That the fabric of the membrane consisted of a phospholipid booster with proteins floating in it making up a mosaic pattern. The lipid molecules can change places with each other and some of the proteins may move, giving fluidity.
Why is the structure of the gills?
The Gill is broken up into smaller sections called gill filaments which are stacked up in a pile at a right angle top of each other called the gill lamella which increases SA
What does the Golgi apparatus do?
The Golgi apparatus Adds carbohydrates to proteins to form glycoproteins Produced secretory enzymes such as pancreatic enzymes Transports, modifies an stores lipids Form lysosomes
What is the difference between alpha glucose and beta glucose?
The OH group is above carbon one in beta glucose.
What is the difference between an α-glucose and a β-glucose molecule?
The OH group on carbon 1 is 'down' in α-glucose and 'up' in β-glucose.
How do disulphide bonds form?
The R group of the amino acid cysteine contains sulphur. Disulphide bridges are formed between the R groups of two cysteines.
Define immunity
The ability of an organism to resist infection by a disease causing microorganism involving recognition of antigens
What is resolution?
The ability to clearly distinguish the individual parts of an object.
What is classification?
The act of arranging organisms into groups based on their similarities and differences.
What is the induced fit hypothesis?
The active site is not a rigid fixed structure, and can change to fit the substrate.
Independent assortment
The alleles of two (or more) different genes get sorted into gametes independently of one another. The allele a gamete receives for one gene does not influence the allele received for another gene. This is because homologous chromosomes line up in random orientations at the middle of the cell at metaphase as they prepare to separate, meaning that the same parent cell can produce different combinations of chromosomes in the daughter cells.
Partial pressure
The amount of a gas that is present in a mixture of gases is measured by the pressure it contributes to the total pressure of the gas mixture.
Define activation energy
The amount of energy required for a reaction to begin to take place
Fluid mosaic model
The arrangement of the various molecules of the cell-surface membrane. Fluid because the individual phospholipid molecules can move relative to one another and mosaic because the proteins vary in shape, size and pattern.
Coronary artery
The blood vessels which branch off the aorta and supply the heart muscle with oxygenated blood.
what is the immune system?
The body's defence against disease causing organisms.
Self
The body's own cells and molecules.
What is atherosclerosis?
The build-up of fats, cholesterol, and other substances in and on the artery walls.
Mass-flow theory
The bulk movement of a substance through a given channel or area in a specified time. Sucrose is transferred into sieve elements from photosynthesising tissue and there can be mass flow of sucrose solution down a hydrostatic gradient in sieve tubes (caused by active transport of sucrose into sieve tubes at the source and out of sieve tubes at the sink, and osmosis - movement of water into sieve tubes near source and out of sieve tubes near sink).
Attachment protein
The capsid can have these which are essential to allow the virus to identify and attach to a host cell.
Lumen
The cavity of the intestines
What happens in G1?
The cell grows and new organelles and proteins are made. at the G1 check point, the cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering S.
What happens during G2?
The cell keeps growing and proteins needed for division are made. There is another check point where the cell checks whether all the DNA has been replicated without any damage. If it had, the cell will enter mitosis.
How does the skin prevent disease?
The cells at the surface cells dry out and the cytoplasm is replaced by keratin known as keratinisation. The dead cells act as a barrier.
Daughter cell
The cells that are produced by cell division.
Lumen
The central cavity of the blood vessel through which the blood flows.
What happens during anaphase?
The centromeres divide, separating each pair of sister chromatids. The spindles contract, pulling chromatids to opposite ends of the cell, centromere first.
What happens during telophase?
The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They are now called chromosomes again. A nuclear envelope forms around each group of chromosomes so there are 2 new nuclei
What happens during prophase?
The chromosomes condense, getting shorter and fatter. Centrioles start moving to opposite ends of the cell, forming a network of protein fibres called the spindle. The nuclear envelope breaks down and the chromosomes lie free in the cytoplasm.
What happens in metaphase?
The chromosomes line up along the middle of the cell and become attached to the spindle at their centromere. At the metaphase checkpoint, the cell checks that all the chromosomes are attached to the spindle before mitosis can continue.
Define community
The combination of all interacting populations within a habitat
Human genome
The complete set of genes in a cell, including those in mitochondria and/or chloroplasts
Genome
The complete set of genetic material present in a cell or an organism.
What happens during cytokinesis?
The cytoplasm divides. In animal cells, a cleavage furrow forms to divide the cell membrane. There are now two genetically identical daughter cells.
How do we breathe in?
The diaphragm contracts and flattens and rib cage lifts
Concentration gradient
The difference between the concentration of a gas or substance inside and outside of the cell. The steeper the concentration gradient, the faster the rate of diffusion.
AIDS
The disease caused by HIV.
What is a double helix?
The double coiled shape of DNA, two sugar phosphate strands that run antiparallel
What is the systole phase?
The emptying phase. The ventricles contract, pumping blood out of the arteries. The semi lunar valves are open and the av valves are shut.
what is a genome?
The entire set of genetic material in an organism
What is a host body?
The environment in which the pathogens live. They live by taking nutrition from the host and cause damage in the process
What is phylogenetic classification based on?
The evolutionary relationships between organisms and their ancestors
Non-disjunction
The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.
What is the diastole phase?
The filling phase. The atria and ventricles are relaxed. Blood flows into the right and left atria. The valves are open and allow blood to flow into the ventricles. The sumi lunar valves are shut
Rectum
The final section of the intestines where the faeces is stored before being egested by the anus.
What is binomial system?
The first name is the Genus (Uppercase) The second name is the species (lowercase)
Homogenation
The first stage of cell fractionation when cells are broken up by a homogeniser (blender) and organelles are released from the cell.
Prophase
The first stage of mitosis when the chromosomes become visible and when spindle fibres develop. The nucleolus disappears and the nuclear envelope breaks down.
How is fetal haemoglobin adapted?
The foetus gets oxygen form the mother through the placenta. Feral haemoglobin is adapted to have a higher affinity for oxygen than the mother and this allows the fetal haemoglobin to bind to oxygen at lower oxygen partial pressures
Telophase
The fourth stage of mitosis when chromosomes reach their respective poles and become longer and thinner, finally disappearing altogether, leaving only widely spread chromatin. The spindle fibres disintegrate and the nuclear envelope and nucleolus re-form.
What does normal directional selection graph represent?
The frequency of phenotypes in a population
Proteome
The full range of proteins produced by the genome. This is sometimes called the complete proteome, in which case the term proteome refers to the proteins produced by a given type of cell under a certain set of conditions.
what is a proteome?
The full range of proteins that a cell is able to produce
Universal
The genetic code is the same in all organisms - this is indirect evidence for evolution.
Oxygen dissociation curve
The graph of the relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen. Shows how at low oxygen concentrations little oxygen binds to haemoglobin (shallow gradient initially). After the first oxygen molecule binding the quaternary structure of the haemoglobin molecule changes, making it easier for the other subunits to bind an oxygen molecule, therefore it takes a smaller increase in the partial pressure of oxygen to bind the second molecule and third molecule so the gradient steepens. After the binding of the third molecule, it is less likely that a single oxygen molecule will find an empty site to bind to so the gradient of the curve reduces and the graph flattens off.
Bohr shift
The greater the concentration of carbon dioxide the more readily the haemoglobin releases its oxygen because the more carbon dioxide there is, the lower the pH, the greater the haemoglobin shape change, the more readily oxygen is unloaded, the more oxygen is available for respiration.
Genetic Diversity
The greater the number of different alleles that all members of a species possess, the greater the genetic diversity of that species.
What is the relationship between oxygen affinity and carbon dioxide?
The greater the partial pressure of carbon dioxide the greater the reduction of affinity of haemoglobin and oxygen and so the greater the dissociation
Why is a phospholipid molecule said to be polar?
The head of the molecule is hydrophilic and said to be attracted to water The tail of the molecule is hydrophobic and does not mix wit water
What happens during tertiary organisation?
The helix/pleat folds into a 3D globular or fibrous shape. It has disulphide bonds, ionic and hydrogen bonds as well as hydrophobic and hydrophilic bonds.
Describe the movement of water around the stomata
The humid air around the stomata is not humid than exterior air creating a water potential gradient causing water vapour to diffuse out of the stomata
Transcription: What happens to the DNA strand?
The hydrogen bonds are broken between the two strands exposing the bases
Surface area: volume ratio
The important relationship between the surface area of a biological unit such as a cell or a whole animal, and its overall volume, which affects many aspects of its biochemistry. As the size of the unit increases, its surface area grows relatively more slowly than its volume.
What is activation energy?
The initial energy needed for a reaction to start.
Non-Specific response
The initial response by phagocytes
How is a chloroplast's membrane specialised?
The inner membrane, called thylakoid membranes, house chlorophyll. On these membranes some of the reactions for photosynthesis occur.
Vaccination
The introduction of a vaccine containing appropriate disease antigens into the body, by injection or mouth, in order to induce artificial immunity.
Translation
The latter part of protein synthesis when the mRNA is used as template to which complementary tRNA molecules attach and the amino acids link to form a polypeptide.
what is the compensation point?
The level of light intensity at which the rate of photosynthesis exactly matches the rate of respiration.
What is chromatin?
The loosely coiled form of chromosomes during interphase of the cell cycle; chromatin is made of DNA and proteins.
what is transpiration?
The loss of water vapour through the stomata of leaves.
Ventricles
The lower chambers of the heart which have a much thicker muscular wall as it has to contract strongly to pump blood some distance, the left side to the rest of the body (and therefore has a thicker muscular wall) and the right side to the lungs.
Cohesion-tension theory
The main factor that is responsible for the movement of water up the xylem, from the roots to the leaves. Transpiration pull puts the xylem under tension (there is negative pressure within the xylem) and because of the cohesive nature of water (due to hydrogen bonds between water molecules) there is a continuous stream of water being pulled across the mesophyll cells and up the xylem.
Transpiration
The main force that pulls water through the xylem vessels in the stem of a plant is the evaporation of water from leaves through stomata.
What is biomass?
The mass of living material
Chromatin
The material that makes up chromosomes. It consists of DNA and the protein histone.
Forced Expiratory Volume
The max amount of air that can be breathed out in one second
Forced Vital Capacity
The maximum amount of air it is possible to forcefully expel from the lungs after a deep breath in
How does enzyme concentration affect enzyme activity?
The more enzyme molecules there are, the more likely there are to be collisions between enzyme and substrate molecules, forming more enzyme-substrate complexes
What is facilitated diffusion?
The movement of large of polar molecules through the phospholipid bilayer using channel proteins and carrier proteins.
What is active transport?
The movement of molecules against the concentration gradient, from low to high, using atp and carrier proteins.
what is translocation?
The movement of sugars through a plant in phloem from source to sink
What is the transpiration stream?
The movement of water from the roots through the xylem and out of the leaves
Define diffusion
The net movement of molecules or ions from an area of high concentration to an are of low concentration until molecules are evenly spread out
What is the nucleolus?
The nucleolus is the middle of the nucleus, in the nucleoplasm, where the assembly of ribosomes begins. (RNA is manufactured)
What is species diversity?
The number of different species and the abundance of each species in an area.
Species richness
The number of different species represented in an ecological community. It does not take account the abundances of species or their relative abundance distributions.
Sampling size
The number of observations in a sample.
How do alleles code for slightly different versions of the same gene?
The order of bases in each allele is slightly different
Community
The organisms of all species that live in the same area
Exocytosis
The outward bulk transport of materials through the cell surface membrane. How chylomicrons move out of the epithelial cells by this process.
Osmosis
The passage of water from a region where there is a higher water potential to a region where there is a lower water potential through a partially permeable membrane.
What is facilitated diffusion?
The passive movement of a particle across a cell membrane via a channel protein.
What is diffusion?
The passive net movement of particles from an area of high concentration to an area of low concentration until evenly distributed
what is the cardiac cycle?
The period from the end of one ventricular contraction to the end of the next ventricular contraction. one complete cycle
Interphase
The period of the cell cycle when the cell is not dividing.
Habitat
The place where an organism normally lives
Centromere
The place where the two copies of DNA after replication are joined together.
Taxonomy
The practice of biological classification
Intercropping
The practice of growing two or more crops in close proximity usually to produce a greater yield on a piece of land.
What is water potential?
The pressure created by water molecules
Water potential
The pressure created by water molecules. It is the measure of the extent to which a solution gives out water. The greater the number of water molecules present, the higher (less negative) the water potential. Pure water has a water potential of zero.
What is water potential?
The pressure created by water molecules. pure water = 0 so water with more solute becomes more negative
What is hydrostatic pressure?
The pressure that the fluid exerts on the walls of its container.
Write a paragraph using the terms probability and chance if the different or association from stats results at P 0.001 has a calculated value greater than the criterial value.
The probability of the difference or association being due to chance is less than 0.1% ; Therefore there is a significant difference or association between the two means/variables
Write a paragraph using the terms probability and chance if the different or association from stats results at P 0.05 has a calculated value greater than the criterial value.
The probability of the difference or association being due to chance is less than 5% ; Therefore there is a significant difference or association between the two means/variables
Splicing
The process by which base sequences corresponding to the introns are removed and the functional exons are joined together.
Binary fission
The process by which cell division occurs in prokaryotic cells.
Oxygen loading
The process by which haemoglobin binds with oxygen is called loading or associating. In humans this takes place in the lungs.
Oxygen unloading
The process by which haemoglobin releases its oxygen is called unloading or dissociating. In humans this takes place in the tissues.
Emulsification
The process by which lipids are split up into tiny droplets called micelles by bile salts, which are produced by the liver. It increases the surface area of the lipids so that the action of lipases is sped up.
Translocation
The process by which organic molecules and some mineral ions are transported from one part of a plant to another.
Protein synthesis
The process by which the genetic code codes for proteins in the cell. The template strand of DNA codes for mRNA in transcription, which is then translated into an amino acid sequence at the ribosomes.
Ventilation
The process in which air is constantly moved in and out of the lungs to maintain diffusion of gases across the alveolar epithelium. Also known as breathing.
Define cell specialisation
The process in which cells with identical genetic information express different genes allowing them to become specifically adapted to a function
What is classification?
The process of grouping things based on their similarities
What is transcription?
The process of making pre-mRNA from DNA
Ventilation
The process of moving gases in and out of the lungs
Polyploidy
The process of the genome doubling that gives rise to organisms with multiple sets of chromosomes.
Cell fractionation
The process where cells are broken up and the different organelles they contain are separated out.
Crossing over
The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that their alleles are exchanged
Translation: When does the process stop?
The process will continue producing a polypeptide chain until their is a "stop" signal
What is asexual reproduction?
The production of genetically identical offspring from a single parent
How do you make and secrete a protein?
The protein is transcribed in the nucleus then translated in the RER. Vesicles are pinched off and moved to the Golgi where they are modified. Vesicles are pinched off and then fuse with the plasma membrane and are released.
Biodiversity
The range and variety of genes, species and habitats within a particular region. Made up of three components: genetic diversity, species diversity and ecosystem diversity.
Heart rate
The rate at which the heart beats in beats per minute.
How does substrate concentration affect enzyme activity?
The rate increase initially and then levels off because all enzymes are constantly occupied and adding more substrate will not make a difference.
Recombination
The rearrangement of genetic material, especially by crossing over in chromosomes.
What does the oxygen dissociation curve illustrate?
The relationship between partial pressure of oxygen and saturation of haemglobin with O2
Why is genetic code universal?
The same specific base triplets code for the same amino acids in all living things
What is taxonomy?
The scientific study of how living things are classified
Ultracentrifugation
The second stage of cell fractionation when the fragments in filtered homogenate are separated in a machine called a centrifuge.
Metaphase
The second stage of mitosis when the chromosomes arrange themselves across the equator of the cell.
Genetic code
The sequence of triplets of nucleotides (codons) in DNA which determines the sequence of amino acids in an organism's proteins. It is degenerate; non-overlapping; universal ; has start and stop codons
What happens when haemoglobin bond to carbon dioxide
The shape of the haemoglobin molecules changes meaning it binds loosely to oxygen making dissociation easier
How does molecular evidence support evolution?
The similarities in other molecules provide evidence. You can compare sequence of amino acids in proteins and compare antibodies. The more similar, the more closely related they are.
First barrier of entry to pathogens
The skin
Locus
The specific linear position of a particular gene on a certain chromosome
Template strand
The strand of DNA which is used during transcription to make mRNA. It runs in a 3' to 5' direction so the mRNA is built in a 5' to 3' direction.
Describe the induced fit hypothesis of an enzyme.
The substrate collides and binds with the active site. The active site shape changes to allow a substrate molecule to fit more closely around substrate molecule. This puts a strain on the substrate molecule and distorts particular bonds (H and Ionic) This lowers activation energy needed to break the bond.
What happens during ringing experiment where the phloem is removed?
The sugars gather above the place of removal causing swelling, the lower half dies as it has no sucrose
Anaphase
The third stage of mitosis when the centromeres divide into two and the spindle fibres pull the individual chromatids making up the chromosome apart to their respective, opposite poles of the cell.
Phloem
The tissue which transports biological molecules in flowering plants. It is made up of sieve tube elements, long thin structures arranged end to end. Their end walls are perforated to form sieve plates. Associated with the sieve tube elements are cells called companion cells.
Biomass
The total mass of living material, normally measured in a specific area over a given period of time
what is genetic diversity?
The total number of different alleles in a population
Co-transport
The transport of one substance coupled with the transport of another substance across a plasma membrane in the same direction through the same protein carrier.
What happens in meiosis 2?
The two daughter cells undergo the stages again, similar to mitosis, making 4 genetically different haploid daughter cells.
tRNA
The type of RNA made of around 80 nucleotides and has an anticodon, which is complementary to a section of mRNA. Each molecule is specific to one amino acid.
mRNA
The type of RNA that is a long strand arranged in a single helix and its base sequence is determined by the sequence of bases on a length of DNA
Mitosis
The type of nuclear division in which the daughter cells have the same number of chromosomes as the parent cell.
Meiosis
The type of nuclear division in which the number of chromosomes is halved.
Cell-mediated immunity
The type of response when T lymphocytes respond to antigens that are presented on a body cell.
Humoral immunity
The type of response which involves B lymphocytes and antibodies.
Which side of a leaf are most stomata on?
The under-surface
Atria
The upper chambers of the heart which are thin-walled and elastic and stretches as it collects blood.
Atrioventricular valves
The valves found between the atrium and ventricle which prevent the backflow of blood into the atria when the ventricles contract and the ventricular pressure exceeds atrial pressure. The left is also known as the bicuspid and the right is also known as the tricuspid.
Semilunar valves
The valves found in the aorta and pulmonary artery which prevent the backflow of blood into the ventricles when the pressure in these vessels exceeds that in the ventricles.
What is genetic diversity?
The variation of alleles within a species. Eg the variation of alleles within the dog species gives rise to different breeds.
What is biodiversity?
The variety of living organisms in an area?
Cardiac output
The volume of blood pumped by one ventricle of the heart in one minute. It is usually measured in dm3min-1.
Stroke volume
The volume of blood pumped out at each beat measured in dm3.
What does degenerate mean?
There are more possible combinations of amino acids, some amino acids are coded for by more than one base triplet
What is a degenerate?
There are more than one possible combination of triplets then amino acids
What does the term "saturated" mean in the context of triglycerides?
There are no carbon-carbon double bonds in the fatty acid chain.
What happens to oxygen in the respiring tissues?
There is a high partial pressure of carbon dioxide so inversely the partial pressure of oxygen will be low therefore haemoglobin will have a lower affinity for oxygen some more dissociation occur
What is the structure of a DNA nucleotide?
There is a phosphate group, a deoxyribose sugar and a nitrogenous base.
What are the bonds between bases?
There is double bond between A and T and a triple bond between C and G
Chi squared test Null Hypothesis
There will be no significant difference between observed and expected
Why is a deletion mutation more likely to have a larger effect than substitution?
There's a frame shift so all amino acid sequence changes
Students T Test Null Hypothesis
There's no significant difference in the means
What are the roles of subcutaneous fat/blubber? (5)
Thermal protection, buoyancy, protection around the kidneys, energy storage in the fats in adipose cells and they make membranes and sex hormones.
Sieve tube element
These are living, tubular cells that are connected end to end. The end cell walls have perforations in them to make sieve plates. The cytoplasm is present but in small amounts and in a layer next to the cell wall. It lacks a nucleus and most organelles so there is more space for solutes to move. The cell walls are made of cellulose so solutes can move laterally as well as vertically. Next to each sieve tube element is a companion cell.
Spindle fibres
These form the spindle apparatus which are responsible for pulling the chromatids to separate ends of the cell.
How is the bronchioles adapted?
These structures branch into smaller and smaller sections
Tracheoles
These tubes extend from the tracheae and extend throughout all the body tissues of the insect to allow atmospheric air to be brought directly to respiring tissues.
How viruses cause infection
They Invade cells and take over the genetic machinery and organelles of the cell. The viruses make copies of themselves until the cell bursts and releases the virus to infect other cells.
What are phospholipids?
They are a lipid that is similar to triglycerides but one of the fatty acids it replaced with a phosphate group
Describe the structure of an enzyme.
They are all tertiary proteins with a globular shape which has a specific 3D shape called an active site where reactions take place.
How are the two stands of DNA arranged?
They are anti parallel, so one is 3-5 and the other is 5-3
What is a purine?
They are double ringed nitrogenous bases,so are bigger bases. They are A and G
What is the function of lysosomes?
They are filled with hydrolytic enzymes that ingest and digest broken or unused parts of the cell.
what is the role of iron ions?
They are found in haemoglobin where they transport oxygen. lack of these = anaemia
What is the function of elastic fibres in the gaseous exchange system.
They are in the walls of the trachea, bronchi and bronchioles and alveoli. They help the process of breathing out. On breathing in, the lungs inflate and the elastic fibres are stretched. Then the fibres recoil to help push air out.
Describe fibrous proteins
They are long and narrow that have structural functions. They are generally insoluble in water and have repetitive amino acid sequences.
What are polypeptides? What do they do?
They are primary structures that are composed of protein molecules that form peptide bonds
Why are the volumes of gas exchanged in mammals so large?
They are relatively large organisms with a large volume of living cells They have to maintain a high body temperature which is related to them having high metabolic and respiratory rates
Describe globular proteins
They are rounded/spherical that are catalytic and used in transport. They are generally soluble in water. It's very sensitive to changes in heat and pH.
What is the function of chloroplasts?
They are the site of photosynthesis in plants.
What are opsonins?
They bind to antigens. Phagocytes can bind to the constant region of the antibody and phagocytosis can occur.
How is water loss through spiracles prevented?
They can be opened and closed using valves, and there are tiny hairs around them
Why is biodiversity important for large scale ecosystems?
They can function and self-regulate
How is haemoglobin adapted at lows oxygen partial pressure environments?
They can have haemoglobin with a high affinity for oxygen so more oxygen binds to haemoglobin and some more is available for respiring cells or they can have haemoglobin with a lower affinity for oxygen so it will dissociate oxygen more readily They may also have more haemoglobin so have have a higher carrying capacity and so more oxygen binds to haemoglobin however blood becomes thicker and so blood pressure increases to pump the thicker blood
What does the features reducing water loss mean for gas exchange?
They cannot use their body surface to diffuse respiratory gases
What are arteries?
They carry blood away from the heart to the rest of the body. Their walls are thick and muscular and have elastic tissue to stretch and recoil as the heart beats to help maintain the high pressure.
How do protoctista cause disease?
They cause harm by entering the host cells and feeding on the contents as they grow.
How do larger insects push more air into their tracheoles?
They close their spiracles, and their muscles pull the skeletal plates of the abdominal segments together, pumping air in the air sacs into the tracheoles
What is a neutrophil?
They deal with defence against bacterial infections and other very small inflammatory processes and are usually first to respond. Their activity and death in large numbers form pus.
How is a sperm cell specialised?
They have a flagellum so they can swim to the egg. They also have lots of mitochondria to provide the energy to swim. They acrosome contains digestive enzymes to enable the sperm to penetrate the surface of the egg.
How are root hair cells specialised?
They have a large surface area for absorption and a thin permeable walls, for entry of water and ions. They cytoplasm contains extra mitochondria to provide the energy needed for active transport.
Why can small organisms rely on simple diffusion?
They have a large surface area to volume ratio.
Lipids are non-polar molecules. What does this mean?
They have an even distribution of charge across the molecule.
What are the characteristics of viruses?
They have attachment proteins on the lipid envelope They contain a capsid containing RNA and enzymes
What is an unsaturated fat?
They have double bonds, which form a kink. Found in seeds and oily fish. Liquid at room temp.
How is a mitochondria's membrane specialised?
They have folded inner membranes called cristae, which give a large surface area for some of the reactions of aerobic respiration and localise some of the enzymes needed for respiration to occur.
What keeps tracheae air passages open?
They have rigid rings in their walls
What are venules and what do they do?
They have very thin walls that can contain some muscle cells.
What effect do enzymes have on activation energy?
They lower it
Why is low genetic diversity bad?
They might not be able to adapt to changes so the whole population can be wiped out in a single event. Populations may include isolated populations such as those in captivity.
What is the function of Cillia?
They move bacterial cells away from danger and towards food.
What is an eosinophil?
They primarily deal with parasitic infections and an increase in them indicate such.
What is the role of membranes at the surface of cells? (Plasma membrane)
They separate the cells components from its external environment, regulates transport on materials into and out of the cell, and contains receptors for cell communication.
What is a monocyte?
They share the "vacuum cleaner" function or neutrophils but are much longer lived as they have an additional role: they present pieces of pathogens to T cells so that the pathogens may be killed.
What is the role of glycolipids and glycoproteins?
They stabilise the membrane by forming hydrogen bonds with surrounding water molecules. They are a site where drugs, hormones and antibodies bind. They act as receptors for cell signalling and are also antigens.
What are veins?
They take blood back to the heat under low pressure. They have a wider lumen with very little elastic muscle tissue. Veins contain valves to stop backflow.
What is the function of the rings of cartilage in the gaseous exchange system
They're in the walls of the trachea and bronchi. They provide support as its strong but flexible. It stops the trachea and bronchi collapsing when you breath in and pressure drops.
What is the function of smooth muscle in the gaseous exchange system
They're in the walls of the trachea, bronchi and bronchioles. Allows their diameter to be controlled. During exercise the smooth muscle relaxes, making the tubes wider. This means there's less resistance to air flow and air can move in and out of the lungs more easily.
What are some adaptations of xerophytes?
Thick cuticles, small/needle-shaped leaves, few stomata, stomata in pits, hairs
How is the structure of the aterioles different from that of the arteries? Why?
Thicker muscle layer to allow constricted blood flow as blood moves from arteries to capillaries
Endothelium
Thin inner lining which is smooth to reduce friction in all vessels.
What is the structure of a capillary like? Why?
Thin linen and thin wall- makes the diffusion pathway shorter Highly branched- increase surface area for diffusion Spaces between lining- allow white blood cells to deal with infections within tissues
What is the structure of a vein like? Why?
Thin muscle layer- construction and dilation not required Thin elastic layer- blood travels at a low pressure not requiring recoil and stretching Thin wall- thick wall not required as blood flows at a low pressure Valves- prevent back flow due to low blood pressure
What are filaments?
Thin plates
How does tylose formation help a plant?
This is balloon like swelling that fills the xylem vessels so that it can no longer carry water. this prevents the spreading through the vessel. the tylose also contains a high concentration of chemicals toxic to pathogens
What is exocytosis?
This is how large molecules are moved out of a cell. They don't pass through the cell, but instead a vesicle containing them is moved towards and fused with the plasma membrane. ATP is needed.
What is endocytosis?
This is how large particles are brought into the cell. A segment of the membrane surrounds and encloses the particle and brings it into the cell enclosed in a vesicle.
What happens during quaternary organisation?
This is similar to tertiary organisation but is very rare. It is where there is more than one type of polypeptide chain.
What happens during primary organisation.
This is the formation of the polypeptide chain. Contains peptide bonds
What is cytolysis?
This is when the cells split. This is due to there being a less negative water potential outside the cell than inside, so water enters the cell via osmosis.
What is a saturated fat?
This is where there are no double bonds, so all the carbons have maximum hydrogen attached. Found in meats and dairy. Solid at room temp.
What does a triglyceride consist of?
Three fatty acids and a glycerol Every fatty acid forms an water bond a glycerol in a condensation
Where are T lymphocytes produced?
Thymus gland
Microvilli
Tiny finger-like projections from the cell-surface membrane of some animal cells.
What are organelles?
Tiny organs. They work together for the cell to function.
Where do gases enter and leave tracheae?
Tiny pores called spiracles on body surface
Spiracles
Tiny pores that allow gases to enter and leave the tracheae (and water vapour to leave as well). They are opened and closed by a valve.
Stomata
Tiny pores which guard cells control the opening and closing of. If the stomata are open, water vapour molecules diffused out of the air spaces into the surrounding air.
Micelles
Tiny structures (4-7nm in diameter) formed when monoglycerides and fatty acids remain in association with the bile salts that initially emulsified the lipid droplets. They break down as they come into contact with the epithelial cells lining the villi of the ileum and release the monoglycerides and fatty acids which diffuse across the cell membrane into the epithelial cells.
What do microtubules do?
Tiny tubes made of a protein called tublin and found in most eukaryotic cells. Help with cell support and determining cell shape, transport within cell and movement (spindles and cilia)
Capillaries
Tiny vessels that link arterioles to veins. Their walls consist mostly of the lining layer making them extremely thin, they are numerous and highly branched, they have a narrow diameter and narrow lumen and there are spaces between the lining (endothelial) cells.
Spongy mesophyll
Tissue in the leaf, which has large air spaces so gases can readily come into contact with mesophyll cells and large surface area of mesophyll cells for rapid diffusion.
Justification of the Students T Test
To compare 2 means
Justification of the Chi Squared Test
To compare frequencies/number
what does pulmonary mean?
To do with the lungs
Why do species need to recognise a member of the same species?
To ensure mating only occurs between members of same species Only members of same species produce fertile offspring
Why are booster vaccines given?
To ensure memory cells have been produced
Justification of Correlation Coefficient
To identify a correlation between two variables
What is the purpose of a nasal cavity?
To keep air warm and control moisture levels. Nasal hairs trap dust and microorganisms.
Why is air constantly moved in and out of the lungs?
To maintain diffusion of gases across the alveolar epithelium
Why is the solution cold in cell fractionation?
To reduce enzyme activity
Pulmonary ventilation rate (dm3min-1)
Total volume of air that is moved into the lungs in one minute
What is the structure of an artery like? Why?
Tough outer layer- resists the high pressure of blood slow Muscle layer- contract and control blood flow for homeostasis Elastic layer- helps maintain blood flow by stretching and recoiling to smooth out best of heart Thin inner lining- reduces friction and allows efficient diffusion of oxygen
Air passes to the bronchi from the?
Trachea (windpipe)
Where do the tracheoles go? What does this mean?
Tracheoles extend throughout all body tissue of insect so atmospheric air (with O2) is brought directly to respiring tissues
What is the process in which a piece of RNA is made from DNA?
Transcription
What process forms a protein from RNA?
Translation
Define co-transport
Transport of substances using a concentration gradient already set up by direct active transport of ions
What is a channel protein?
Transport protein that provides a tube-like opening in the plasma membrane through which particles can diffuse
What is bulk transport?
Transporting molecules that are too large to diffuse through the plasma membrane. They do this through bulk transport, using ATP. This involves enclosing substances to be moved in their own small globes of membrane, which can then fuse with the membrane.
what is the function of haemoglobin?
Transports oxygen around the body: - Loads oxygen in lungs - Unloads oxygen in respiring tissue
Phospholipid
Triglyceride in which one of the three fatty acid molecules is replaced by a phosphate molecule. Phospholipids are important in the structure an functioning of plasma membranes.
Name a type of lipid
Triglycerides
What are the types of lipids?
Triglycerides (saturated and unsaturated), phospholipids and cholesterol.
How does the structure of triglycerides relate to their function?
Triglycerides are mainly used as energy storage molecules. This is due to: The long hydrocarbon 'tails' of the fatty acid contain lots of chemical energy and release a load of energy when broken down They are insoluble so they doesn't affect water potential of a cell (so water won't diffuse into the cell by osmosis). In water the triglycerides clump together as insoluble droplets, with the hydrophobic 'tails' facing inward and the hydrophilic 'head' facing outwards into the water
Give four features of the genetic code (4 marks)
Triplet, universal, non-overlapping and degenerate
What are tracheae?
Tubes in the insect respiratory system that carry air
How many bronchi does the trachea branch into?
Two
What are homologous chromosomes?
Two chromosomes with the same set of genes, in the same sequence, sometimes with different alleles. paternal and maternal chromosomes
Bronchi
Two divisions of the trachea each leading to one lung. Amount of cartilage reduces as they get smaller. Also produce mucus to trap dirt particles and cilia that move this towards the throat.
The bronchi
Two divisions of the trachea, each leading to a lung. They produce mucus to trap dirt particles and have cilia which move mucus towards the throat
What is the structure of an antibody?
Two heavy peptide chains and two light peptide chains joined by disulphide bonds
What is convergent evolution?
Two totally different species developing similar traits. Eg porcupine & cactus
Carbhohydrases
Type of digestive enzyme which hydrolyse carbohydrates, ultimately to monosaccharides.
Lipases
Type of digestive enzyme which hydrolyse lipids (fats and oils) into glycerol and fatty acids.
Proteases
Type of digestive enzyme which hydrolyse proteins, ultimately into amino acids.
Lymphocyte
Type of white blood cell responsible for the immune response. They become activated in the presence of antigens. There are two types: B lymphocytes and T lymphocytes.
Phagocyte
Type of white blood cell which carries out a non-specific immune response and ingests and breaks down pathogens by phagocytosis.
What is amylose?
Unbranched alpha glucose polymers found in the the mouth and the stomach. It spirals to make it smaller and is held together by hydrogen bonds.
Explain the dipole covalent bonds found in water.
Unequal electron association results in a charge seperation, so H is slightly positive and O is slightly negative.
Name 3 features of DNA?
Universal Degenerate Non-overlapping
Haemoglobin > oxygen is know as....
Unloading/dissociating
what does unsaturated mean?
Unsaturated compounds have at least one double or triple bond in their carbon chain.
How do saturated and unsaturated fatty acids differ in appearance at the molecular level?
Unsaturated fatty acids have a kink where the double bond(s) are present. Saturated fatty acids are straight.
What base is specific to RNA? What does it pair with?
Uracil pairs with adenine
What are the 3 regions of an antibodies and what do they do?
Variable region has a specific shape that is complimentary to the antigens. The constant region is the same in all antibodies, it has an easy binding site for phagocytic cells. The hinge region makes it more flexible.
What do differences in DNA cause?
Variation
Define genetic diversity
Variety of genes passed by the individual that make up a population of species
Genetic diversity
Variety of genes possessed by individuals that make up any one species
Tidal volume (dm3)
Volume of air normally taken in at each breath when the body is at rest
How does counter current exchange work?
Water and blood flow in opposite directions, water has a high concentration oxygen compared to blood meaning oxygen would diffuse into the blood. As both constantly flow blood doesn't lose oxygen as concentration of oxygen is always higher in water
What does xylem transport?
Water and mineral ions
What problem is associated with spiracles being open?
Water can be lost from the insect
What is a problem with spiracles?
Water can escape
What is the advantage of a thick cuticle and no stomata on the exposed side of a leaf?
Water can't escape
How does water enable organisms to cool down?
Water evaporates from organisms skin eg sweat is secreted and evaporates taking heat energy with it
As water evaporates from the stomata what happens in the leaf?
Water is drawn up through the xylem column and more water vapour diffuses out of the spongy mesophyll
How does water support a hydrostatic skeleton?
Water isn't easily compressed hence can withstand great pressure
Why does water in the xylem form a "column"?
Water molecules form hydrogen bonds between molecules leading to them being able to stick together(good cohesion) This forms a column
Why is the specific heat capacity if water so high?
Water molecules stick well together and are very cohesive making them harder to separate
Define osmosis
Water moves from an area with a high water potential to an area with a lower water potential through a selectively permeable membrane
Why is water a good solvent?
Water readily dissolves: -gases such as oxygen and carbon -wastes such as ammonia and urea -inorganic ions and small hydrophillic (eg monosaccharides , amino acids) -enzymes
What is oxygen taken from in gas exchange in fish?
Water taken in through the mouth
What is the advantage of a leaf rolling up?
Water vapour is trapped and kept near stomata
who discovered DNA?
Watson and Crick
Why should we maintain genetic resources?
We need them for: food, mainly from plants and animals; clothing, a lot of fibres are made from plants and animals; drugs, many are made from plant compounds; fuels, we use many micro organisms to produce fuel; and other industrial materials such as wood, paper, adhesives etc.
Why do we classify things?
We want to identify the variety of organisms out there in a specific way.
Glycogen is a branched molecule.
What type of bond allows this? 1,6 glycosidic bond.
Natural passive immunity
When a baby becomes immune due to antibodies it was given by the mother e.g. in breast milk
What is substitution of bases?
When a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base
What is addition of bases?
When a nucleotide is added to the normal DNA sequence
What is deletion of bases?
When a nucleotide is lost from a normal DNA sequence
Sampling bias
When a sample is collected in such a way that some members of the intended population are more or less likely to be included than others. The data you collect may therefore not be accurate or represent the group.
When is air forced into the lungs (air pressure)?
When air pressure in the atmosphere is greater than air pressure in the lungs
Asthma
When airways become inflamed and irritated, usually due to an allergen. During an attack, smooth muscle lining the bronchioles contracts and a large amount of mucus is produced. FEV is severely reduced.
Antigen-presentation
When an antigen-presenting cell e.g. phagocyte displays foreign antigens on their own cell-surface membrane.
TB
When an individual is infected with TB bacteria, the immune system builds a wall around the bacteria in the lungs. This forms tubercles. Infected tissue within the tubercles dies and this damages the gas exchange surface, decreasing tidal volume. Ventilation rate is increased.
What is an adaption?
When an organism has features that increases its chances of survival and reproduction.
What is an example of a behavioural adaption?
When an organisms changes how it acts to increase chances of survival. Eg, Possums 'play dead' when there's a predator.
What is meant by the 'saturation point' in an enzyme-controlled reaction?
When enzyme active sites are all 'saturated' with substrate molecules and no more can bind.
How do hydrogen bonds form?
When hydrogen with a slight positive charge is attracted to an atom with a slight negative charge.
Artificial active immunity
When immunity is induced by a vaccine
Transcription:When does RNA polymerase stop making mRNA?
When it reaches a "stop" signal of the DNA molecule
What is crossing over?
When maternal and paternal chromatids wrap around each and break off equal segments that rejoin to form a chromatid with two different genetic groups
Plasma B cells
When the B cell is activated to divide by mitosis it gives a clone of plasma cells which produce and secrete the specific antibody that exactly fits the antigen on the pathogen's surface.
Antigenic variation
When the antigen on a cell changes due to changes in the genes of the cell
what is double circulation?
When the blood passes through the heart twice during one circuit around the body.
What is crenation?
When the cell shrivels. This is due to there being a more negative water potential outside the cell than inside so water leaves the the cell via osmosis
Cytokinesis
When the cytoplasm divides.
What is plasmolysis?
When the cytoplasm of the plant cell shrinks and the membrane pulls away from the cellulose cell wall. The cells are described as plasmolysed
Active immunity
When the immune system makes its own antibodies after being stimulated by an antigen
What is herd immunity?
When the majority of the population has been vaccinated, which provides protection for those who haven't been vaccinated as the pathogen cannot spread.
Herd Immunity
When those vaccinated are less likely to get a disease, so those who cannot be vaccinated are less vulnerable as the pathogen cannot spread as rapidly in the population
What is a polysaccharide?
When three or more monosacchraides are joined together
Artificial passive immunity
When you become immune after being injected with antibodies from another organism e.g. a transplant
Natural active immunity
When you become immune after catching a disease
Define habitat
Where a community or organism lives
Equator
Where the chromosomes arrange themselves during metaphase.
Centrioles
Where the spindle fibres develop from in animal cells.
Large intestine
Where water is absorbed.
What are phagocytes?
White blood cells that ingest pathogens like bacteria (phagocytosis)
How do you join two proteins together?
With a condensation reaction, where water is removed and a peptide bond is formed (CONH)
What are plants that live in dry environments called?
Xerophytes
Plasma
Yellow liquid inside blood vessels, which carries red blood cells, platelets, white blood cells and also dissolved substances such as proteins, water, glucose, amino acids and hormones. Composition is controlled by various homeostatic systems.
Can there be mutations in gene pool?
Yes
Transcription: Are both introns and extrons copied into mRNA?
Yes
Are these mutations harmful?
Yes but also some are advantageous
What happens during inhalation?
You breath in. Then the external intercostal muscles contract so ribs move upwards and outwards. The diaphragm contracts and flattens is the thoracic cavity volume increases. The lungs expand so air pressure in the lungs decrease. Finally, the difference in air pressure caused air to rush into the lungs.
What happens during exhalation?
You breath out. The diaphragm expands and relaxes. Volume in the thoracic cavity decreases. The lungs compress so air pressure in the lungs increased. Finally, the difference in air pressure caused air to rush out of the lungs.
What is an advantage of ex situ conservation?
You can control the environment. Things like predation and hunting can be managed.
Explain high specific heat capacity in water.
You need lots of energy to increase the temperature of 1kg by 1^c as they bonds are strong.
How are carbohydrates digested?
a carbohydrase beaks down a carbohydrate into a dissacharide and then a dissacharidase breaks this down into monosaccharides. the products are absorbed by the ileum
Explain the sodium potassium pump
a carrier protein that pumps the sodium and potassium molecules in/out of the cell against the concentration gradient using ATP. needed to allow the sodium ions involved in co-transport to be transported by facilitated diffusion
How is phosphate arranged in ATP?
a chain of three phosphate groups
what is a phosphodiester bond?
a chemical bond of the kind joining successive nucleotides in a polynucleotide.
What is lymph?
a colourless fluid containing white blood cells, that bathes the tissues and drains through the lymphatic system into the bloodstream.
What is polyploidy?
a condition in which an organism has more than two complete sets of chromosomes
What is the Bohr effect?
a decrease in the amount of oxygen associated with hemoglobin and other respiratory compounds in response to a higher partial pressure of co2 and so the curve shifts to the right
What is a potometer?
a device that can measure the rate of water uptake as a leafy stem transpires
what is the structure and function of the nuclear envelope?
a double membrane that surrounds the nucleus, controls the exit and entry of materials
What is a species?
a group of living organisms consisting of similar individuals capable of producing living and fertile offspring
What is a phospholipid?
a lipid containing a phosphate group in its molecule
What is a triglyceride?
a lipid made of one glycerol and three fatty acids
What is a monomer?
a molecule that can be bonded to other identical molecules to form a polymer.
What is adenine?
a nitrogen containing organic base
how does benedict's test work?
a reducing sugar will reduce the benedict's reagent changing the colour where as a non- reducing sugar will not result in a colour change
What is a keystone species?
a species on which other species largely depend on. They are often predators keeping the prey in check or modifiers (eg beavers) or hosts that provide a particular environment (eg palm trees)
What is a cofactor?
a substance (other than the substrate) whose presence is essential for the activity of an enzyme.
what is a metabolite and why is water one?
a substance formed in or necessary for metabolism. water is used in hydrolysis reactions, reactions take place in aqueous mediums and is a raw material in photosynthesis
What is a buffer?
a substance that minimises changes in pH or temperature (water buffers temperature)
What is the bottleneck effect?
a sudden reduction in population size due to a change in the environment which rarely represents the genetic makeup of the initial population
What is ribose?
a sugar molecule with a 5 carbon ring structure (pentose sugar) that acts as a back bone to other molecules
What is a reducing sugar?
a sugar that can reduce another chemical
what is a codon?
a three-nucleotide sequence that codes for an amino acid
What is a virus?
a tiny, nonliving, particle that enters and reproduces inside a living cell. symptoms are felt by the damaging of body cells
What is an antigen?
a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.
What is a carrier protein?
a transport molecule that changes shape to allow the molecule to pass across the membrane
What is a carrier protein?
a transport molecule, change shape to allow the molecule to pass across the membrane
what is the structure and function of a lysosome?
a vesicle containing digestive enzymes, used in phagocytosis, release enzymes to the outside of cells (exocytosis), break down cells after they have died (autolysis)
what is the positive result?
a white emmulision
How does temperature affect enzyme activity?
a. as temperature increases, so does the rate of reaction because the molecules are moving faster and have a higher chance of hitting each other. At extremely high temperatures, the enzyme is denatured due to a change in the tertiary structure. At lower temperatures the substrate molecules do not have enough kinetic energy for the reaction to take place even in the presence of the enzyme
what is the structure of viruses?
acellular (non-living particles), smaller than bacteria (20-300nm), can only multiply in host cells, DNA in the protein layer, gylcoprotein layer envelopes the virus. they have attachment proteins on the surface to allow it identify and attach to host cells
what is the test for proteins and what is the result?
add biuret solution to a sample in a test tube. purple colouration indicates the presence of peptide bonds and hence, a protein
what is the role of cholesterol in the bilayer?
add strength, prevents loss of water due to being hydrophobic and prevents cell movement
what is ATP?
adenosine triphosphate, made up of adenine, ribose and 3 phosphate groups
what is the tracheal system in insects?
air passses in through spiricls, then through trachea, then through trachioles and into the cells
what are some examples of reducing sugars?
all monosaccharides and some disaccharides
What is a gene pool?
all the alleles in a population
Gene pool
all the different alleles of all the genes of all the individuals in a population at any one time
why does differential centrifugation work?
all the organelles have different densities so they separate according to the speed of the centrifuge
Explain why we collect a large number of results
allows anomalies to be identified / increases reliability (of means / averages / results); allows use of statistical test; effect of variation in data to be minimised;
what are the benefits to water having strong cohesion?
allows it to be pulled through a xylem
What are the two isomers of glucose?
alpha glucose and beta glucose
What are proteins made of?
amino acids
what is heart rate?
amount of cardiac cycles in a minute
what are the two components of starch?
amylose (spiral structure, unbranched) and amylopectin (branched and made up of a-glucose)
What is the binomial system?
an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species
what are the 3 types of adaptions?
anatomical, behavioural and physicological
what is an example of directional selection?
antibiotic resistance in bacteria
What is active immunity?
antibodies are stimulated due to direct contact with the antigens. immunity takes time to develop but is long lasting due to the production of memory cells
What is passive immunity?
antibodies enter the body form an outside source means no direct contact with the antigen is required. immunity is acquired immediately but is lost once the antibodies are gone due to the lack of memory cells
why does your body not attack itself when you are born?
any lymphocyte that attack an antigen is not longer produced via mitosis (apoptosis) so any lymphocytes that attack body cells will no longer be produced by the time you are born
what are the vessels called that transport blood between the heart and the body?
aorta and vena cava
What are ribosomes?
are made of protein and ribosomal RNA and consist of two subunits. It is the site where mRNA is translated into polypeptide with the help of tRNA.
what is the structure and function of nuclear pores?
around 3000 pores of the nucleus, allow the passage of molecules such as mRNA
What are coronary arteries?
arteries that supply the heart muscle with blood
Describe how the structure of an artery wall differs from that of a capillary wall in relation to the functions of the two blood vessels. (3 marks)
artery has muscle artery has elastic tissue to withstand pressure / capillary only one cell thick with pores for exchange
what are the two types of classification?
artificial and phylogenetic
How does temperature affect enzyme activity?
as temperature increases, so does the rate of reaction because the molecules have more kinetic energy and have a higher chance of hitting each other. at extremely high temperatures, the enzyme is denatured due to the breaking of ionic bonds on the active site lower temperatures the substrate molecules do not have enough kinetic energy for the reaction to take place even in the presence of the enzyme
What is it called when O2 binds with haemoglobin? Where does this take place?
associating - Takes place in the lungs
What is atrial systole?
atria contract forcing blood into the ventricles
What is a micelle?
ball of phospholipids
What three things do all nucleotides contain?
base sugar phosphate group
what is phylogenetic classification?
based on evolutionary relationships. classifies baced on how closely related different species are and form homologous features
How do bacteria reproduce?
binary fission (asexual reproduction) to produce genetically identical daughter cells
What are non-competitive inhibitors?
bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective
What are the similarities between mRNA and tRNA?
both single chains, pentose sugar is ribose, manafactured in the nucleus, have uracil instead of thymine
What is inspiration?
breathing in, active process
What is expiration?
breathing out, passive process
What is ventilation?
breathing- moves air in and out of the lungs
why is ATP a useful carrier?
can be easily reformed and goes in a cycle
what is a semi qualitative test?
can be used to estimate an exact value when compared to other results
why is it good that water has a high surface tension?
can support organisms
what effect does high partial pressure of CO2 have on haemoglobin?
carbonic acid reduces the pH so the haemoglobin changes shape, and has a lower affinity for oxygen
what is a fatty acid?
carboxylic acid consists of hydrocarbon chain and terminal carboxyl groups
how do the carrier proteins act as pumps?
carry specific molecules one way across the membrane, opposite to the conc gradient uses ATP which causes the protein to change shape after binding carry molecules at a faster rate molecules can be accumulated either inside cells or organelles, or outside cells
What molecules form the cell wall in plant cells?
cellulose
what is a lumen?
central blood-filled space of a vessel
What is the function of centrioles?
centrioles are involved in spindle formation during mitosis.
what is the secondary structure of a protein?
chain folded, alpha helix or beta pleated sheet, hydrogen bonds
what is the positive result for a non-reducing sugar?
changes colour of benedict's second time round
what are the two types of chromosome mutation?
changes in whole sets of chromosomes and changes in the number of individual number of chromosomes
What are inhibitors?
chemicals that selectively inhibit the action of specific enzymes
what happens during prophase?
chromosomes condense and become visible nuclear membrane breaks down centrioles move to each side of the cell and produce spindle fibres
what is the process of binary fission?
circular DNA replicates and attaches to the membrane plasmids replicate cell membrane begins to grow between the DNA and pinches dividing the two cells new cell wall forms creating two daughter cells with variable plasmids
what do the branches mean on a phylogenetic tree?
closer the branch, the closer related
what do antibodies do?
clump the antigens together (agglutination), mark for destruction
How is glucose absorbed?
co-transport with sodium ions from the ileum to the blood capillaries.
What are exons?
coding regions
what is mean by non-overlapping?
codons are read individually and in sequence
what is meant by universal?
codons code for the same amino acid regardless of the organism
what is the positive result of the test for starch?
colour change to blue-black
what is blood?
complex fluid that circulates in blood vessels
Haemoglobin is described as a quaternary protein, what is meant by this?
composed of four polypeptide chains, each containing a haem group.
What are isomers?
compounds with the same molecular formula but different structures and properties
what are the three factors effecting the rate of diffusion across the membrane?
concentration gradient, temperature and thickness of membrane
What reaction forms nucleotides?
condensation reaction
what reaction bonds amino acids?
condensation reaction
how are the bonds made in a nucleotide of DNA?
condensation reactions
what are the properties of all lipids?
contain hydrogen, carbon and oxygen insoluble in water soluble in ethanol
What is the function of the nucleus?
contains genetic material and manufactures RNA and ribosomes
what is the role of DNA?
contains instructions on how to make proteins
what is the structure and function of the matrix?
contains proteins, lipids, ribosomes and DNA, allows the organelle to produce proteins
What is the function of the cell membrane?
control the movement of substances in and out of the bilayer. to allow lipid soluble substances to pass through and prevent water soluble products to pass through
Suggest how the proportion of dividing cells in a thin section could be determined.(3 marks)
count cells using microscope; count number of cells in cell division/where chromosomes visible; and then the total number of cells in field of view;
What is the process of homogenisation?
cut the tissue put in cold isotonic buffer solution put in homogeniser homogenate is filtered
what happens during cytokinesis?
cytoplasm divides to form two identical daughter cells
What base pairs with guanine?
cytosine
What bases have single ring structures? What are these bases called?
cytosine uracil thymine called pyrimidines
what is the structure of a xylem vessel?
dead tissues with no cytoplasm or end walls form a hollow tube and with maturity, the vessels gets strengthened with lignin
What is the fluid mosaic model?
describes the arrangement of the molecules that make up a cell membrane as the individual molecules can move (fluid) and the embedded molecules are different sizes and shapes (mosaic)
How do amino acids differ from each other?
different R groups (residual group)
why do different organisms have different haemoglobin?
different organism sneed their Hb to have different affinities for oxygen
what are the two types of selection?
directional and stabilising
What is a pathogen?
disease causing organism
What is it called when O2 is released from haemoglobin? Where does it take place in humans?
dissociation - in humans this takes place in respiring tissues `
Describe how B-lymphocytes respond when they are stimulated by antigens.(4 marks)
divide by mitosis / form clones; produce plasma cells; (plasma cells) make antibodies; (plasma cells) produce memory cells;
what is the process of virus replication?
do not under go cell division as they aren't alive attach to the host cell using attachment proteins inject their nucleic acid into the cell genetic material in the acid then give instruction tot eh host cell to produce viral components instead
How can cancer be treated?
drugs that prevent DNA from replicating or inhibit the metaphase stage b interfering with spindle fibre formation
what type of organism used simple circulation?
e.g. fish, animals with no need to maintain body temperature, low respiration rate
what type of organism uses double circulation?
e.g. mammals, animals that maintain body temperature through high respiration rates
What is directional selection?
environment changes to favour a certain phenotype that varies from the mean so the mean shifts towards the favoured phenotype.
What is stabilising selection?
environment remains stable, favouring the mean, so the phenotypes at the extremes are eliminated.
What is ELISA and what is it used for?
enzyme-linked immunosorbent assay, used for drug testing, allergen testing, antibody and antigen presence testing and diagnosis of diseases such as HIV
what are the type of bond in lipids?
ester bonds
what do you add to the sample before testing?
ethanol, to dissolve the lipids
what is the structure and function of the cristea?
extensions of the inner membrane, provides a large surface area for the attachment of proteins
what is a lipid?
fats and oils
what is needed for a successful vaccination program?
few side effects can be administered at the right time able to vaccinate the majority ways to produce, transport and store economically available for all
What is ultrafiltration?
filtering of the blood at a molecular level
what is plasma?
fluid component of blood
what is the structure and function of stroma?
fluid filled matrix, second stage of photosynthesis
what is the structure and function of vacuoles
fluid filled sacs, makes cells turgid, stores sugars and amino acids, add pigment to petals
where is starch found and what is it's function?
found in plants and is a source of energy
What is interphase (s-phase)?
full preparation for mitosis, cell makes new organelles (cell synthesis), DNA replicates so two copies remain attached to the centromere, chromosomes not visible and exist as chromatin
What is a reduction reaction?
gain of electrons
What are gills made up of?
gill filaments with gill lamelea on them, increasing the surface area.
what is a quantitative test?
gives an exact value
what is a qualitative test?
gives information of the presence but not the quantity of a substance
What are the 3 monosaccharides?
glucose, fructose, galactose
what is the role of glycoproteins and glycolipids in the bilayer?
glycolipid - carb part extends out of the cell, attach to form tissues glycoproteins - act as receptors for chemicals and allow cells to recognise them
What bases have double ring structures? What are these bases known as?
guanine adenine called purines
what are the 5 things leading to a loss in biodiversity
habitat loss, invasive species, climate change, over harvesting and pollution
what is the structure and function of the rough endoplasmic reticulum?
has ribosomes on the outer surface, provides a large surface area for protein synthesis and provides a pathway for transporting material
what is the structure and function of the lower epidermis?
has stomata and guard cells, for gas exchange
What is the circulatory system made up of?
heart and blood vessels
What is diastole?
heart muscles relax and it fills with blood
what are the conservation techniques?
hedgerow plantations, pond maintenance, reductions in pestiside use, crop rotaions and medows
in the lungs, what is the Hb affinity for oxygen?
high
why is water a good habitat for organisms
high latent heat capacity so a lot of energy is needed to heat it up.
why do plants need transport systems?
high metabolic demands, small surface area to volume ratio
How is tissue fluid formed?
high water potential on the arteriole side so plasma is forced out the capillaries and becomes tissue fluid, moving down a water potential and pressure gradient
What is cell fractionation?
homogenisation followed by differential centrifugation
What does an oxygen dissociation curve show?
how saturated the haemoglobin is with oxygen at any given partial pressure
what is an example of stabilising selection?
human birth weight
what are the physical barriers in the body?
hydrochloric acid (kills bacteria), epithelial mucus and the skin
What bond occurs between base pairs?
hydrogen bond
Why is water cohesive?
hydrogen bonding means water sticks together really well
why does water have strong cohesion?
hydrogen bonds can form between molecules
what are the 4 examples of inorganic ions in the body?
hydrogen, iron, sodium and phosphate
why is haemoglobin soluble?
hydrophobic side chains face inwards and the hydrophilic side chains face outwards
why is the bilayer formed?
hydrophobic tails face inwards are they are non-polar and do not interact with water and the hydrophilic heads face out, towards the cytoplasm and fluid outside of cells
how do phospholipids create a bilayer?
hydrophobic tails on the inside and hydrophilic heads create a protective layer
What are the names of the enzymes for the following molecules and name the products: i) Lactose ii) Sucrose iii) Maltose (iv) Amylose
i) Lactose + Lactase ----> Glucose + Galactose ii) Sucrose + Sucrase ----> Glucose and Fructose iii) Maltose + Maltase ----> Glucose + Glucose iv) Amylose + Amylase ----> a-glucose + a-glucose
what condition must the sample must be in before homogenisation?
ice cold - to stop lytic enzyme activity pH buffered - to prevent damage to organelles isotonic - to prevent osmotic lysis (bursting cells)
Why is ice less dense than water?
ice has a regular structure and there is less mass in a given volume
Explain why specific base pairing is important in DNA replication. (4 marks)
identical/exact copies made; same base sequence as original DNA; both strands act as template/complementary base pairing occurs on both strands;
where do inorganic ions occur in the cells?
in solution in the cytoplasm and bodily fluids
how is dna stored in a bacterium?
in the dna loop and plasmids, circular dna
what are the two ways that meiosis prodices genetic variation?
independent assortment/segregation and crossing over
What is a vaccine?
injection of a weakened or mild form of a pathogen to stimulate an immune response and produce memory cells
What is an ecosystem?
interaction of the biotic and abiotic factors
What are the stages of the cell cycle?
interphase, mitosis, cytokinesis
what is the structure and function of the spongy mesophyll?
irregular shaped cells with large gaps, to allow gases through and to increase the surface area
Why is water known as the universal solvent?
it dissolves the greatest number of substances (hydrophilic, polar substances). dissolves gasses, waste products, inorganic ions and enzymes
What does a chloroplast look like?
it has 2 membranes and contains flattened sacs known as thylakoids stacked on top of each other.
what is the structure of the HIV virus?
it is a complex enveloped retro virus. it has a core made of 2 copies of RNA associated with reverse transcriptase, surrounded by a capsid made of proteins. a matrix surrounds this and then a lipid capsule surrounds the core. Embedded in the capsule are attachment proteins.
What does the cell surface membrane do?
it is partially permeable and controls the exchange of materials between the cell and its environment.
What is the structure of a mitochondria like?
it is surrounded by a double layer and has a matrix that contains 70s ribosomes and circular DNA.
What is resolution?
it is the minimum distance between which two points can be separated.
What is magnification?
it is the number of times larger an image is compared to the real size of the object.
What is Smooth Endoplasmic Reticulum?
it is the site for lipid synthesis and chemical modification of protein. it also destroy toxic substances.
What is the nuclear envelope?
it surround the nucleus with 2 membranes that contains gaps called pore which allow mRNA to move out of the nucleus and allow nutrients and enzyme to enter.
What does the golgi apparatus do?
it transports and chemically modifies the materials contained within it. it is also involved in formation of lysosome
why does HIV reduce the immune system and lead to AIDS?
it uses T helper cells as it's host cell, killing it in the process of replicating then moving on to infest a new cell. the reduced the amount of T helper cells in the body leads to aids as the immune system is now heavily compromised
what is the structure and function of the smooth endoplasmic reticulum?
lack of ribosomes and more tubular in apperence, synthesis and transport of lipids
what effect does the ends of the tracheas containing fluid have?
lactate poduced during anaerobic respiration dissolves and lowers the water potential in cells. water therefore moves into the cells via osmosis and decreases the amount that is in the ends of the tracheoles, drawing more air into them. this speeds up diffusion as the final diffusion pathway is in a gas state rather than a liquid one.
what are the features of specialised exchage surfaces?
large sruface area relative to the volume of the organisn, short diffusion pathway, slectively permiable membranes, movement of environmental medium and movement of internal medium.
what is the benefits of the lipid droplets?
large surface area meaning quicker hydrolysis to fatty acids and glycerols
what effect does deforestation have on biodiversity?
loss of habitats means a reduction in biodiversity
what are the adaptions in guard cells?
lots of chloroplasts, thick inner layer, thin outer layer
in the respiring tissues, what is the Hb affinity for oxygen?
low
what is the partial pressures of O2 and CO2 in the lungs?
low CO2, high O2
why does most plasma move back into the blood?
low water potential at the venule side so most plasma moves back into the blood vessel, moving up the pressure and water potential gradient
Which type of RNA is less stable?
mRNA Individual molecules broken down in cells
Describe the process of translation
mRNA codons are read at a ribosome. tRNA molecules with anticodons and an amino acid bound to them attatch to the codons on the mRNA moleule. The amino acids are strung together to create proteins.
why is splicing not needed in prokaryotic cells?
mRNA is produced rather than pre-mRNA so has no introns to remove
Starting with mRNA in the nucleus of a cell, describe how a molecule of protein is synthesised. (6/8 marks)
mRNA leaves (nucleus) through nuclear pore; 2. To ribosome; 3. tRNA molecules bring amino acids (to ribosome); 4. Specific tRNA molecule for specific amino acid; 5. Anticodon of tRNA corresponds / complementary to codon on mRNA; 6. Peptide bonds form between amino acids; 7. tRNA detaches and collects another amino acid; 8. Ribosome moves along mRNA;
Describe the process of translation
mRNA leaves through the nuclear pore and goes to the ribosomes in the cytoplasm Each triplet(codon) is read and paired to anticodons found on tRNA molecules, tRNA molecules also contain amino acids Amino acid pair to complementary code of the specific codon and are joined together using ATP and an enzyme As the codes is read amino acids continue to bond until stop code us reached resulting in a protein
What is translation?
mRNA to protein
Define multicellular
made of many cells
what is the structure of a phospholipid?
made up of 2 hydrophobic tails for each hydrophilic head. Structure is flexible and changes shape easily due to fluidity and moves more easily with increased kinetic energy. Structure is strong due to attraction between hydrophobic tails
give the structure of cellulose
made up of B-glucose and has hydrogen bonds between chains
what is the structure and function of the golgi apparatus?
made up of flattened sacs called cisternae and vesicles, makes glycoproteins, produces secretory enzymes, secretes carbohydrates, transports and modifies lipids and forms lysosomes
what is the structure and function of the cell wall?
made up of microfibrils of cellulose, provides mechanical strength
What is function of rRNA?
makes up ribosomes
What is inbreeding?
mating between closely related individuals
What are T lymphocytes?
mature in the thymus cell mediated response - react to phagocytes displaying engulfed pathogen's antigens, virus infected body cells, transplanted cells and tumour cells
What are B lymphocytes?
matured in the bone marrow humoral response - bodily fluids such as blood
What can monoclonal antibodies be used for?
medical diagnosis (cancer, pregnancy, HIV, chlamydia, hepatitis, influenza) targeting medication to specific cells - (direct and indirect MCA therapy)
What does mRNA stand for?
messenger RNA
What is mRNA?
messenger RNA, long strand, act as templates during protein synthesis
What are the properties of water?
metabolite, universal solvent, high specific heat capacity, high latent heat of vaporisation, strong cohesion, high surface tension, less dense in solid form, colourless
how are the products of lipid digestion absorbed?
micelles are formed through the combination of glycerols and fatty acids with bile salts. the micelle transports these into the epithelium cell triglycerides are formed then they associate with cholesterol and proteins to form chylomicron. they exit the epithelial cells and enter the lymphatic system
What is an example of behavioural adaptation?
migration
what is resolution?
minimum distance two points can be apart and still be distinguished as two separate points
what happens during anaphase?
mitochondria gather around the spindle fibres centrioles pull the individual chromatids apart chromatids move to poles of the cell and are now referred to a chromosomes
Name 3 types of carbohydrates.
monosaccharides, disaccharides, polysaccharides.
what is menat by degenerate?
more than one codon can code for the same amino acid
What is breathing?
movement of air into and out of the lungs
what happens to the fluid that doesn't move back into the blood vessels?
moves into the lymph vessels and become lymph. it is moved around the body when muscles contract
what effect does increasing the temperature have on the graph?
moves to the right, more temp = more respirtaion = more CO2. also the O2 is needed for respiration so needs to be given up easier
Are introns in prokaryotes?
nO
list the sequence of structures air passes through to the lungs
nasal cavity, trachea, bronchi, bronchioles, alveoli
what are the two types of active immunity?
natural (infected with pathogen) or artificial (due to a vaccine)
What are introns?
non-coding regions
what are the 3 features of DNA?
non-overlapping, degenerate and universal
what is phosphorylated nucleotide?
nucleotide with phosphate groups attached
what happens during metaphase?
nucleus no longer exists chromosomes line up along the equator spindle fibres attach to the centromere
in what order will the organelles be removed in a centrifuge?
nucleus, mitocondria and chloroplasts, ER and golgi, ribosomes
What is species diversity?
number of species and individuals in a community
how can diversity be investigated?
observable characteristics, dna base sequenes, rna base sequences and amino acid sequuences
why is water a unique substance?
on substance that naturally occurs as a solid liquid and a gas
where do antigens exists?
on the cell membrane
where are the proteins in the bilayer?
on the surface - give support and act as receptors spanning the bilayer - channel proteins to allow water soluble products through and carrier proteins to allow ions through and active transport
What genes cause cancer?
oncogenes (tells cell to move onto next stage) and tumour suppressing genes (stops the cell cycle)
what are the structural adaptions in the alveolis?
one cell thick - short diffusion pathway elastic tissue - stretch and recoil to allow max amount of oxygen in close together - no air gaps
What is a nucleotide?
organic base, sugar (ribose or deoxyribose) and phosphate group
What does phloem transport?
organic substances
what type of animals have a high affinity for oxygen and why?
organism sin a low O2 environment e.g. fish. graph moves to the left
What is a hetrotroph?
organism that must consume another organism in order to survive; consumers
what type of animals have a low affinity for oxygen and why?
organisms with a high metabolic rate due to needing more O2 for respiration. graph moves to right
What is tunica externa?
outermost layer of the blood vessel. Protects, reinforces and anchors the vessel to surrounding structures.
What is herd immunity?
over 95% of the population are vaccinated and this stops the spread
How are lipids digested?
pancreatic lipase and intestinal lipase
Define locus
particular position on homologous chromosomes of a gene
What is the bond between amino acids called?
peptide bond
what is the cell wall in a prokayrotic cell made out of?
peptidoglycan / murein
What do cytotoxic T cells do?
perforate (put holes in) the cell and kills it
What are the two main uses of water
photosynthesis hydrolysis reactions
what is non-specific immunity?
physical barriers and phagocytosis
what is the sink?
place where the organic substances are stored or exit the plant
what are the 4 types of eukarya kingdoms?
plantae, fungi, animalia, protoclista
What are xerophytes?
plants adapted to sreas of low water supply
what is in blood?
plasma containing red blood cells, white blood cells, platelets, dissolved respiratory gases, products of digestion, metabolic waste, hormones and antibodies
What is a dipole?
polar molecule
What is a polynucleotide?
polymer of nucleotides
give 3 features of all polysaccarides
polymers made through condensation reactions insoluable
What molecules form the cell wall in prokaryote cells?
polysaccharides called peptidoglycans
What does abundant mean?
present in large amounts; plentiful
What is apoptosis?
process of programmed cell death
What is the function of the mitochondria?
produce ATP.
what is the significance of meiosis?
produces haploid gametes and produces genetic variation
What are the differences between prokaryotic and eukaryotic cells?
prokaryotic cells do not have a nucleus or any membrane bound organelles. They have 70s ribosomes (smaller) and the dna is naked, not wound round a histone protein.
what are the 4 stages to mitosis?
prophase, metaphase, anaphase, telophase
what are the semi-lunar valves?
pulmonary and aortic valves, lead out of the heart (out of ventricles)
what are the vessels to do with the lugs called?
pulmonary vein and artery
what is the process of natural selection?
random mutations in an individual creates variation in a gene pool. individuals with desirable charcteristics have an advantage and survive and reproduce due to competition. Their offspring then inherit these genes and the allel frequency of them increase leading to adaptions in the species.
What is independent assortment?
random separation of homologous chromosomes. the chromosomes can line up along the equator in any order
what are the benefits of courtship behaviours?
recognition of species, identification if a mate is in season, forms a bond and syncronising mating
what effect does ariculture have on biodiversity?
reduces biodiversity through monocultures, hedgerow removal, pestisides and herbisides
what are the features and limitations of a scanning electron microscope?
relatively high magnification and resolution (100,000x and 10nm), no complex staining techniques and specimen doesn't have to be thin, 3D image very expensive, specimen must be dead inna vacuum
What is splicing?
removal of introns and joining of exons
what are the vessels called to do with the kidneys?
renal vein and artery
What does rRNA stand for?
riBOSOMAL RNA
What is the lock and key model?
rigid active site. Substrate fits inside the rigid active site like a key
What is a gene?
segment of DNA that codes for a protein
what are plasma membranes made of?
selectively permeably bilayers of phospholipids
DNA replication is ____________ conservative
semi
Where does meiosis occur?
sex cells
what is the structure and function of the epithelial tissue?
sheets of thin flat cells lining the surface of organs they protect and secrete
what is the structure of glycogen?
short, highly branched chains of a-glucose
What are homologous features?
similar features that originated in a shared ancestor
What is a monosaccharide?
simple sugar unit
What is a pyrimidine?
single-ringed nitrogenous base, so they are smaller. They are C and T and U
What is the function of the mitochondria?
site of aerobic respiration, production of ATP
What are spiracles?
small pores in the exoskeleton of an insect
what is the structure and function of the nucleolus?
small spherical region in the nucleoplasm, manufactures ribosomal RNA and assembles ribosomes
What can pass through the cell membrane?
small, nonpolar and uncharged molecules
What are aterioles?
smaller arteries that control blood flow from arteries to capillaries.
why are gametes formed during meiosis?
so the baby can have the diploid number of chromosomes
why is it important that the formation of oxyhaemoglobin is a reversible reaction?
so the haemoglobin can release the oxygen
why must plant cells be in water potentials less negative than that inside the cell?
so water can enter the cell causing it to become turgid. this is possible due to the cell wall
explain the co-transport of glucose with sodium ions
sodium ions diffuse into the cell due to the sodium potassium pump maintaining the concentration gradient through a carrier protein they carry with them a glucose molecule with them this molecule then diffuses into the blood plasma via facilitated diffusion
What are globular proteins?
soluble proteins with a specific 3D shape e.g. enzymes, hormones, antibodies, haemoglobin. form colloids in water, folded into spherical shape
what are courtship behaviours?
species develop behaviours related to mating to allow them to be successful
what is the structure and function of carrier proteins?
specific molecules bind and cause them to change shape, the opens one side and closes the other
What is the primary structure of a protein?
specific sequence of amino acids in a polypeptide chain
what are the features and limitations of light microscope?
specimen can be viewed live, relatively cheap low magnification (1,500x), low resolution (200nm)
what happens during telophase?
spindle fibres disintergraets two nuclear envelopes start to reform nucleolus forms chromosomes unwind and become non visible again and called chromatin
what is the structure of the phloem?
stacked, living cells (sieve tube elements) with sieve plates and companion cells
what is the structure and function of the grana?
stacks of around 100 thylakoids containing chlorophyll, first stage if photosynthesis
Describe the process of DNA replication
stage 1- enzyme helicase breaks helix structure and unwinds DNA. hydrogen bonds between bases break stage 2- DNA polymerase adds nucleotides in a 5' and 3' direction, DNA nucleotides added to the newly exposed bases on both the 3' and 5' strand stage 3- leading strand is continuously synthesised whereas the lagging strand is synthesised in stages with primers stage 4- fragments sealed with bases with enzyme ligase
What are fibrous proteins?
strong/insoluble/inflexible material e.g. collagen and keratin. long parallel polypeptide chains linked by crosslinks to form fibres
what is the function of cellulose?
structural molecule in the call walls of plants
what are the two types of DNA mutation?
substitutaion and deletion
give three examples of disaccharides
sucrose, maltose, lactose
How is ATP synthesised?
synthesis of ATP is a reversible reaction, it is synthesised by the enzyme of ATPase in a hydrolysis reaction
what are the 4 factors that effect the rate of enzyme action?
temperature, pH, concentration of enzyme, concentration of substrate
what is energy?
the ability to do work
What is the induced fit model?
the active site moulds around the substrate to form the enzyme-substrate complex.
what is the respiritory membrane?
the alveolar epithelium and the capillary endothelium
Rib cage
the bony frame formed by the ribs round the chest
What is hydrolysis?
the chemical breakdown of a compound due to reaction with water.
why do cancer patients loose hair?
the drugs also attack normal cells but are the most effective on fast dividing cells, such as cancer cells and hair cells
Adenosine triphosphate (ATP)
the energy molecule used by cells. its is made up of 3 phosphate groups, a nitrogenous base and a ribose sugar. it is produced in the chloroplast and mitochondria
What is crossing over?
the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring.
what is non-disjunction?
the failure for chromosomes to separate completely during meiosis resulting in gametes having either one more of one less chromosome
what can cause a low genetic diveristy?
the founder effect, the bottle neck effect and inbreeding
what is simple circulation?
the heart is passed once during a full cycle
How does substrate concentration affect enzyme activity?
the high the substrate concentration the higher the rate of reaction as the re are more substrates to collide with but eventually these will be in excess and the rate will remain constant.
what is the importance of the index of diversity?
the higher the value, the higher the species diversity
why do organ doners need to be a good match?
the lymphocytes will treat it as foreign and attack the cells
What is the tonoplast?
the membrane of the large permanent vacuole present in plant cells.
Resolution
the minimum distance needed to differentiate between 2 adjacent objects
what is the DNA like in eukaryotic cells?
the molecules are longer and linear, associated with proteins and form chromosomes
What is the DNA like in prokaryotic cells?
the molecules are shorter, form circle and are not associated with proteins
How does enzyme concentration affect enzyme activity?
the more enzymes the higher the rate of reaction as they can be reused but they will eventually be the limiting factors
what is osmosis?
the movement of water molecules from a region of higher water potential to an area of lower water potential through a selectively permeable membrane.
What is habitat diversity?
the number of different habitats in an area.
What is species richness(1 mark)
the number of different species in a community
What is species richness?
the number of species in a community
What is allele frequency?
the number of times an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene
Allele frequency
the number of times an allele occurs within the gene pool in a population, relative to all others at same locus
Magnification
the number of times bigger the image/drawing is compared to the object/real size
why does the graph move to the right when the partial pressure of CO2 increases
the oxygen will only bind with he haemoglobin at high concentrations due to the changed shape of the Hb molecule
What is an enzyme-substrate complex?
the physical interaction between enzyme and substrate
what is partial pressure?
the pressure exerted by a particular gas in a mixture of gases
What happens during secondary organisation?
the protein chain folds into either a beta pleat or an alpha helix. They are held together with hydrogen bonds.
What is the founder effect?
the reduced genetic diversity that results when a new population is established by a small number of individuals form a larger population
What is the nucleolus?
the region of nucleus which contains large amounts of DNA and RNA and its function is to make ribosomes
What happens in meiosis: anaphase 1?
the spindle fibres contract, separating the homologous pairs - one chromosome goes to each end of the cell.
What is biodiversity?
the variety of life in the world or in a particular habitat or ecosystem.
what is countercurrent flow and why is it good?
the water and blood flow are in opposite directions. this means equalibrium can never be reached and there is always a concentration gradient
what is the vascular bundle in a leaf?
the xylem and phloem cells
Why do large organisms need a circulatory system?
their surface are to volume ratio is to small to rely of diffusion and they have a high metabolic rate so need specialised transport systems to carry materials around their bodies
what are the structure and function of protein channels
they are hydrophilic and are filled with water so only allow specific water soluble molecules to pass through due to them binding snd changing the shape of the cannel and opening it
why does the phloem contain little reducing sugars?
they are too reactive
What job do lysosomes carry out?
they contains digestive (hydrolytic) enzymes and has a variety of destructive functions, such as the removal of old cell organelles.
why can unicelular oganisms rely on diffusion for gas exchange?
they have a surface area large enough, compared to their volume, to allow efficient exchage across their body
why do introns have to be removed?
they prevent protein synthesis
why can enzymes catalyse a reaction?
they reduce the activation energy of the reaction
what adaptions do xerophytes have?
thick waxy cuticles, small surface area of leaves, low stomata density, rolled leaves, extensive roots
what is the structure and function of the upper epidermis?
thin layer of cells with a waxy cuticle, allows light in and prevents water loss
what are the adaptions for diffusion in the lungs?
thin, partially permeable walls, good blood flow and ventillation maintains concentration gradient, large surface area to volume ratio in the alveolis
what are plasmodesmata?
this is a gap in the cell wall which runs through the walls of two adjacent cells. it allows for the transport of larger substances between cells.
how are polymers made?
through polymerisationn
What base pairs with adenine?
thymine
Calculation for pulmonary ventilation rate
tidal volume (dm3) x breathing rate (min-1) = pulmonary ventilation rate (dm3min-1)
what is the structure and function of the palisade mesophyll?
tightly packed cylinder cells with lots of chloroplasts, photosynthesis
why is water added?
to disperse the lipid in the water and form an emmulsion
why do we test with benedict's first when testing for non reducing sugars?
to ensure no reducing sugars are present
why is hydrochloric acid then added?
to hydrolyse the glycosidic bond in the solution
why is sodium hydrogen carbonate added?
to neutralise the solution
how and why does foetal haemoglobin differ from adult haemoglobin?
to the left of adult Hb on the graph due to needing a high affinity for oxygen as the mothers oxygen intake has to supply herself and the foetus.
how does cholesterol effect the risk of CVD?
too many LDLs increases formation of atheroma.
What are the two stages of protein synthesis?
transcription and translation
What does tRNA stand for?
transfer RNA
What is tRNA?
transfer RNA, folded into a clover leaf shape,bind to amino acids
What does tRNA do?
transports amino acids to the ribosome
what are the two types of lipid?
triglycerides and phospholipids
What type of molecule is ATP?
triphosphate
what is the structure of an antibody?
two heavy chains, two light chains the top of which have variable region. two antibody binding sites. has disulfide bonds between chains
What is a disaccharide?
two monosaccharides joined together
What is the quartenary structure of a protein?
two or more polypeptide chains clustered and folded into a specific shape
what are memory cells?
type of B lymphocyte that do not produce antibody but can stimulate the production o plasma cells in the presence of an antigen. part of the secondary immune response as they create long term immunity
What are plasma cells?
type of B lymphocyte that produces around 2000 antibodies a second. part of the primary immune response as they only live for a few days in the body
What is a prokaryote?
unicellular organism that lacks a nucleus
What are bacteria?
unicellular prokaryotic (no nucleus) organisms, no membrane boud organelles, cell walls made of murein
what are the ethical issues surrounding vaccinations?
unknown health risks animals used in testing side effects to some individuals tests on humans expensive
What are stem cells?
unspecialised cells from which differentiated cells develop. all genes are on
What are stem cells?
unspecialized cells from which differentiated cells develop
what is artificial classification?
uses observable, analogous features such as appearance to sort organisms into groups
what are the atria-ventricular valves?
valves separating the atrium and ventricles. on the right side this is the tricuspid valve and on the left this is the bicuspid
What is ecosystem diversity?
variety of habitats, ecosystems, communities
what is ventricular systole?
ventricles contract, opening the semilunar valves and blood moves out
what are the features and limitation sto the transmission electron microscope? (TEM)
very high magnification (500,00X), very high resolution (0.2nm) specimen must be in a vacuum and very thin, very expensive, artefacts
What is the cohesion-tension theory?
water evaporates from leaves, lowering the water potential. water is drawn out of the xylem creating tension/negative pressure in the xylem. cohesive forces between water molecules cause it to form a column and is pulled up the xylem through the transpiration pull
What does hydrophobic mean?
water hating, non-polar substance that cannot dissolve in water
what does hydrophilic mean?
water loving, polar substance that can dissolve in water
why must animal cells be in isotonic conditions?
water will diffuse in if the water potential is higher outside of the cell causing the cell membranes to burst. this means water diffuses in and out of the cells at a constant rate
What is a source?
where organic substances are made e.g. the leaves
what is parallel flow and why is it bad?
where the water and blood flow are in the same direction. this means that equalibrium may be reached so diffusion cannot take place after this point
what is the structure and function of a flagellum?
whip-like structure which produces rotational movement to allow the bacteria to be motile
what are the 4 things that affect rate if transpiration and how do they affect it?
windspeed - higher the wind speed, higher the rate of transpiration temperature - higher the temperature, higher the rate of transpiration light intensity- more light, higher the rate of transpiration (limiting due to only a specific amount of stomata that can open) humidity - higher the humidity, lower the rate of transpiration
Are DNA molecules wound or straight?
wound
what is the structure of the stem?
xylem and phloem (vascular tissue) are surrounded by the endodermis and is then surrounded by the cortex
what happens during inspiration?
• External intercostals lift ribcage upward (internal intercostals pull ribcage in) • Diaphragm flattens, pulls lungs downward • Causes reduction in pressure in the lungs
Describe a chemical test you could carry out to show that a piece of coconut contains lipids. [3]
(Crush in) ethanol / alcohol; Add (to) water (Order of adding is critical for this point); Emulsion / white colour
Explain why the rate of reaction of an enzyme is low away from its optimum pH. [3]
(change in pH) leads to breaking of bonds holding tertiary structure/ changes charge on amino acids; enzyme/protein/active site loses shape/denatured; substrate will not bind with/fit active site; fewer/no ES complexes formed;
Describe how you would use a biochemical test to show that a solution contained a non-reducing sugar, such as sucrose. [3]
,first reducing sugars test; boil with dilute HCl acid then Neutralise with NaHCǑ, add benedict and heat to 95 degrees C brick red ppt forms if reducing sugar is present
Explain why the diameter of the trunk is smallest at midday. (6 marks)
. Diameter of trunk minimal at warmest / brightest time of day / midday = warmest / brightest; 2. Stomata open in light → more water loss; 3. Water evaporates more when warm / more heat energy for water evaporation; 4. Hydrogen-bonding between water molecules / cohesion ( / described) between water molecules; 5. Adhesion (described) between water molecules and walls of xylem vessels; 6. (Xylem) pulled inwards by faster flow of water / pulled in by tension;
What type of variation is shown by human height? (1 mark)
Continuous variation - range of values/not discrete categories/ many categories/no gaps;
Give two possible causes of this variation that result from meiosis during gamete formation.(2 marks)
Crossing over / chiasmata; Random segregation / independent assortment; In meiosis I and meiosis II;
An enzyme catalyses only one reaction. Explain why [2]
(Enzyme has) active site; Only substrate fits (the active site);
During exercise the oxygen-haemoglobin dissociation curve moves to the right, describe the advantage of this change
(Haemoglobin) releases more oxygen; For respiration; The tissues of a mouse have a higher rate of oxygen consumption per gram of body tissue than an elephant.
How is the cardiac cycle controlled? (6marks)
(SAN) myogenic; Electrical Impulse (spreads over atria and) produces atrial contraction; Delay at AVN; Electrical impulse is prevented from passing to the ventricles by non-conducting tissue Allowing atria to empty before ventricles contract; Impulse to base of ventricles; Contraction of ventricles from base up
What is genetic diversity? (1 mark)
All the different alleles of all genes in a population
Name the reaction which occurs when starch is broken down into maltose. [1]
Hydrolysis
Explain how the small intestine is adapted to its function in the absorption of the products of digestion. (6/9 marks) 1.
Large surface area provided by villi / microvilli;2. long / folds increase surface area / time for absorption;3. thin epithelium;4. short diffusion pathway;5. capillary network absorbs amino acids / sugars;6. lacteal for absorption of digested fats;7. Maintains a steep concentration gradient;8. mitochondria supply ATP / energy for active transport;9. carrier proteins (in membranes);
How do you calculate magnification? [1]
M= I (Image)/ A (actual size)
Describe how the MMR vaccine results in immunity (8 mark)
1 Three different viruses (in vaccine);2 With antigen (on each virus);3 Different for each (virus);4 Macrophage/phagocyte presents antigen;5 Binds to/activates (receptor protein on) T-cells;6 T-cells activate B-cell;7 Antigen binds to receptor on B-cell;8 B-cell divides/ clonal selection;9 Different clone/antibody against each virus;10 Plasma cells/B cells secrete antibody;11 Memory cells formed (B and/or T);12 Vaccine stimuates (primary immune) response;13 Memory cells give rapid response in future (preventing development of disease/giving immunity);
Describe the events in the cardiac cycle (6marks)
1) Blood enters atrium - Blood volume increases pressure in atrium- Pressure in atrium greater than in ventricl- atrioventricular valve opens. - Atrium muscles contract- Further increases pressure- Remaining blood forced into ventricles2) Blood enters ventricle- increase in volume of blood increases the pressure in the ventricles- Pressure in ventricle greater than in atrium- atrioventricular valve closes. 3) Ventricle muscles contract- increasing pressure further in ventricle until greater than in aorta/ pulmonary artery- Semi Lunar valve opens.- Blood enters aorta/ pulmonary artery- Blood is pumped to body (left) or lungs (right)4) Ventricle muscles relax- Pressure in ventricle is less than in aorta/ pulmonary artery- Semi lunar valves close
The thickness of the aorta wall changes all the time during each cardiac cycle. Explain why. (5 marks)
1. (Aorta wall) stretches; 2. Because ventricle/heart contracts / systole / pressure increases; 3. (Aorta wall) recoils; 4. Because ventricle relaxes / heart relaxes /diastole / pressure falls; 5. Maintain smooth flow / pressure
Explain how tissue fluid is formed and how it may be returned to the circulatory system. [5]
1. (hydrostatic) pressure of blood high at arterial end;2. fluid/water/soluble molecules pass out (reject plasma);3. proteins/large molecules remain;4. this lowers the water potential / water potential becomes more negative (inside the capillary);5. water moves back into venous end of capillary (reject tissue fluid);6. by osmosis;7. lymph system collects any excess tissue fluid;8. (lymph) returns to blood / circulatory system / link with vena cava/ returns tissue fluid to vein;
Describe the role of the enzymes of the digestive system in the complete breakdown of starch. (6 marks)
1. Amylase;2. (Starch) to maltose:3. Maltase;4. Maltose to glucose;5. Hydrolysis;6. (Of) glycosidic bond;
Describe what happens to chromosomes in meiosis. (6 marks)
1. Chromosomes shorten / thicken / condense; 2. Chromosomes associate in homologous / (described) pairs / formation of bivalents / tetrads; 3. Crossing-over / chiasma formation; 4. Join to spindle (fibres) / moved by spindle;(*) 5. (At) equator / middle of cell;(*) 6. (join via) centromere / kinetochore;(*) 7. (Homologous) chromosomes move to opposite poles / chromosomes separate / move apart; (ALLOW 'are pulled apart') 8. (Pairs of) chromatids separated in 2nd division; (*) OR " independent assortment"
Describe and explain the mechanism that causes forced expiration. (4 marks)
1. Contraction of internal intercostal muscles 2. Relaxation of diaphragm muscles/Relaxation of external intercostal muscles; 3. Causes decrease in volume of chest/thoracic cavity; 4. Air pushed down pressure gradient;
Meiosis results in genetic variation in the gametes which leads to variation in the offspring formed by sexual reproduction. Describe how meiosis causes this variation and explain the advantage of variation to the species. (6/8 marks)
1. Crossing-over; [IGNORE any wrong ref. to timing] 2. Independent / random assortment / orientation / segregation of (homologous) chromosomes in meiosis I; 3. Independent / random assortment / orientation / segregation of chromatids in meiosis II; + Any three from: 4. Different adaptations / some better adapted; 5. Some survive / example described; 6. To reproduce; 7. Pass on gene / allele; 8. Allows for changing environment / different environment / example described;
The events that take place during interphase and mitosis lead to the production of two genetically identical cells. Explain how. (4 marks)
1. DNA replicated; Reject: DNA replication in the wrong stage 2. (Involving) specific / accurate / complementary base-pairing; Accept: semi conservative replication 3. (Ref to) two identical / sister chromatids; 4. Each chromatid / moves / is separated to (opposite) poles / ends of cell. Note: sister chromatids move to opposite poles / ends = 2 marks for mp 3 and mp 4 Reject: meiosis / homologous chromosomes / crossing over or events in wrong stage
Mitosis is important in the life of an organism. Give reasons why. (4 marks)
1. Growth / increase in cell number; 2. Replace cells / repair tissue / organs /body; 3. Genetically identical cells; 4. Asexual reproduction /cloning;
Describe the part played by cell surface membranes in regulating the movement of substances into and out of cells.(6/10 marks)
1. Non-polar/lipid soluble molecules move through phospholipid layer/bilayer;2. Small molecules/water/gases move through phospholipid layer/bilayer;3. Ions/water soluble substances move through channels in proteins;4. Some proteins are gated;5. Reference to diffusion;6.Carriers identified as proteins;7. Carriers associated with facilitated diffusion;8. Carriers associated with active transport/transport with ATP/pumps;9. Different cells have different proteins;10. Correct reference to cytosis;
Explain how a concentration gradient occurs and how this ensures efficient gas exchange in insects (3 marks)
1. Respiring cells use up oxygen; 2. Oxygen concentration decreases towards the end of the tracheoles; 3. So oxygen diffuses down a concentration gradient from the tracheae along the tracheoles to the respiring cells.
Describe how the structure of DNA is related to its function (4/7marks)
1. Sugar-phosphate backbone: provides stability & protects bases 2. Double stranded: replication can occur semi-conservatively where each strand can act as template making replication more accurate 3. Complementary base pairing (A-T and G-C) makes replication more accurate 4. Individual hydrogen bonds are weak: easily unzip DNA for replication 5. Many hydrogen bonds in the DNA molecule: stable 6. Long molecule: can store lots of information7. Helix/coiled: compact;
Describe how haemoglobin is involved in absorbing oxygen in the lungs and transporting it to respiring tissues. (6 marks )
1. diffusion of oxygen into haemoglobin in red blood cells; 2. high affinity of haemoglobin in high partial pressure of oxygen 3. loads / becomes saturated in lungs / at high ppÓ oxygen; 4. oxyhaemoglobin formed; 5. unloads / low affinity in low partial pressure of oxygen; 6. respiration in tissues gives high CÓ concentration / high temperature/ high H+ concentration / low pH 7. dissociation curve shifts to right / 8. oxyhaemoglobin dissociation at higher partial pressure of carbon dioxide.
Describe and explain the role active transport in the absorption of digested food by the ileum.(4/6 marks)
1. movement against concentration gradient;2. energy / ATP required;3. reference to carrier proteins;4. monosaccharides or named / amino acids moved into epithelial cells;5. reference to co-diffusion e.g. glucose and NaCl;6. monosaccharides or named / amino acids move into blood
Describe and explain the role of diffusion in the absorption of digested food by the ileum. (4 marks)
1. movement along / down concentration gradient;2. monoglycerides / micelles/fatty acids move into epithelial cells;3. monoglycerides move from epithelium into blood;4. chylomicrons move into lacteals / lymph;
Describe and explain the role of facilitated diffusion in the absorption of digested food by the ileum. (3 marks)
1. movement along / down concentration gradient;2. reference to carrier / channel proteins;3. monosaccharides or named / amino acids move into epithelial cells;
Describe and explain four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue
1.Permeable capillary wall/membrane;2. Single cell thick/thin walls, reduces diffusion distance;3. Flattened (endothelial) cells, reduces diffusion distance;4. Fenestrations, allows some larger molecules through; 5. Small diameter/ narrow, gives a large surface area to volume/ short diffusion distance;6. Narrow lumen, reduces flow rate giving more time for diffusion;7. Red blood cells in contact with wall/ pass in single file, gives short diffusion distance / more time for diffusion;
If an organism has a diploid chromosome number of 28 (2n = 28) how many chromosomes will its gametes contain? (1 mark)
14
A protein molecule contains 150 amino acids. What is the total number of peptide bonds in this molecule? [1]
149
Calculate the possible number of different combinations of chromosomes following meiosis (without crossing over) if parent cell contains 22 chromosomes (1 mark)
211 = 2048 formula 2n
What is a monoclonal antibody?
A hybrid cell from tumour/cancer and B-lymphocyte form a hybridoma; Antibodies produced are all the same / from one type of plasma cell; specific to / complementary to / fits only one antigen;
Describe the induced fit model of enzyme action. [2]
Active site / enzyme not complementary; Active site changes (shape) / is flexible; (Change in enzyme allows) substrate to fit / E-S complex to form;
Describe one way that the lock and key model is different from the induced fit model. [1]
Active site does not change (shape) / is fixed (shape) / is rigid / does not wrap around substrate / (already) fits the substrate / is complementary (before binding);
Explain the advantages and limitations of using a transmission electron microscope [5]
Advantages: Small objects can be seen; TEM has high resolution as wavelength of electrons shorter; Limitations: Cannot look at living cells as cells must be in a vacuum; must cut section / thin specimen; Preparation may create artefact; Does not produce 3D or colored image;
Describe the structure of cellulose and explain how its structure is related to its function. [3]
Alternate β-glucose rotated 180o, long straight chains, Many hydrogen bonds join (polysaccharide) chains/molecules to each other / makes microfibrils / gives tensile strength;
Define the term antigen
An antigen is a molecule (usually protein) that stimulates an immune response resulting in the production of specific antibodies.
Describe how you would use a biochemical test to show that a solution contained protein. [2]
Biuret / alkali + copper sulphate; Lilac/purple/mauve/violet;
Why do mammals have a double circulatory system?
Blood passes twice through the heart for each complete circuit of the body. When blood passes through the lungs the pressure is reduced. Blood returns to the heart to increase the pressure before being circulated to the rest of the body.
Sketch the oxygen dissociation curve for both animals and explain the advantage of the position of the mouse curve.
Both curves drawn as sigmoidal curves with the mouse to the right. (at the tissues at low pp oxygen) the mouse haemoglobin is less saturated with oxygen / has reduced affinity; oxyhaemoglobin dissociates more readily / haemoglobin releases oxygen more readily / more oxygen released; allowing greater demand /respiration rate;
Which elements are found in proteins? [1]
Carbon, hydrogen, oxygen, nitrogen (sometimes sulphur)
Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells. [5]
Cell homogenisation to break open cells; 1. Accept suitable method of breaking open cells. Filter to remove (large) debris / whole cells; 2. Reject removes cell walls. Use isotonic solution to prevent damage to mitochondria / organelles; Keep cold to prevent / reduce damage by enzymes / use buffer to prevent protein / enzyme denaturation; Centrifuge (at lower speed / 1000 g) to separate nuclei / cell fragments / heavy organelles; Re-spin (supernatant / after nuclei / pellet removed) at higher speed to get mitochondria in pellet / at bottom.
Give three difference between prokaryotic DNA and eukaryotic DNA (3 marks)
DNA of prokaryotes, is short, circular and not associated with protein.
What is non-disjunction? (1 mark)
Failure of chromosomes to separate properly resulting in daughter cells with wrong number of chromosomes
Describe the structure of starch and explain how its structure is related to its function. [3]
Formed from α glucose; Joined by condensation/ by the removal of a water molecule/ glycosidic bonds; Between (carbons) 1 and 4 (and 1 and 6); Coiled chain; compact; (Allows) storage of large amount in a small space; Insoluble so has no effect on osmosis/water potential; Branches; (Allows) rapid breakdown/release of glucose / hydrolysis;
Describe how β-glucose molecule differs from a molecule of α-glucose. [1]
H at top right end (instead of OH) / OH at bottom (carbon 1)
Explain the importance of meiosis in the life cycle of a sexually reproducing organism. (4 marks)
Meiosis halves the number of chromosomes; Restoration of diploid number at fertilisation; Introduces variation;Correct reference to natural selection / survival;
Explain what is meant by a polymer. [1]
Molecule) made up of many identical/similar molecules/monomers/ subunits;
Explain how antibiotic resistant strains of bacteria are produced? (3 marks)
Mutation occurs producing resistance allele, bacteria with this allele survive and reproduce, passing on this allele. Frequency of allele increases over time.
Name two structures present in eukaryotic cells that are not present in the cells of prokaryotes. [2]
Nucleus; mitochondria; chloroplast, Golgi, RER; SER; centrioles
Describe how a microbe can be broken down by the process of Phagocytosis
Pathogen is engulfed by the phagocyte. Forming a vesicle surrounding the pathogen (called a phagosome). Lysosomes fuse with this vesicle releasing digestive enzymes Lysosome enzymes hydrolyse the proteins and lipids in the pathogen. Waste materials are ejected from the cell or presented on cell surface memebrane.
Describe the fluid-mosaic structure of a cell surface membrane.(5/8 marks)
Phospholipids and proteins; Phospholipid bilayer; Arrangement of phospholipid molecules 'Tails to tails';'Floating'(protein) molecules / molecules can move in membrane;Intrinsic proteins extend through bilayer; Extrinsic proteins in outer layer only;(Ref. to intrinsic and extrinsic, unqualified, gains 1 mark);Detail of channel proteins / protein shapes / glycoproteins;Presence of cholesterol between phospholipids.
How could you measure water uptake in mm3 per minute by a plant? (3 marks)
Potometer, as water moves up plant, an air bubble is moved along scale, need to measure distance, diameter of capillary tube and time.
Describe the ways in which prokaryotic cells and eukaryotic cells differ. [3]
Prokaryotic cells do not have a nucleus / have genetic material in cytoplasm; DNA in loop / ring; Not associated with proteins / do not have chromosomes /chromatin / do not divide by mitosis; Smaller ribosomes; No membrane-bound organelles; Such as mitochondria / lysosomes / endoplasmic reticulum / Golgi / chloroplasts; Prokaryotic cells may have mesosomes; Prokaryotic cells smaller; May be enclosed by capsule;
When comparing variation in size between two groups of organisms, it is often considered more useful to compare standard deviations rather than ranges. Explain why.(2 marks)
Range influenced by single 'outlier' (accept anomaly) / converse for S.D.; S.D. shows dispersion/spread about mean; Range only shows highest and lowest values/extremes; S.D. allows statistical use; Tests whether or not differences are significant;
Describe and explain how an increase in temperature affects the rate of an enzyme controlled reaction. [5]
Rate of reaction increases; Increasing temperature increases rate of movement of molecules/ kinetic energy; Collide more often/substrate enters active site more often/more enzyme-substrate complexes formed; Up to optimum; Rate of reaction decreases; High temperatures cause denaturation/loss of tertiary structure/3D structure; By breaking specified bonds (not peptide bond); Active site altered/substrate cannot bind/fit/
What is an unsaturated fatty acid? [1]
Some / two carbons with only one hydrogen / (double bonds) between carbon atoms / not saturated with hydrogen;
Explain how inhibitors affect the rate of enzyme-controlled reactions. [6]
Statement about two types, competitive and non-competitive; Competitive: Similar shape to substrate;Inhibitor can enter/bind with active site (of enzyme);Non-competitive: Affect/bind to enzyme other than at active site; Distorts shape of active site; Inhibitors: Prevent entry of/binding of substrate to active site; Therefore fewer/no enzyme-substrate complexes formed;
Describe how a high pressure is produced in the phloem near photosynthesising leaves (3 marks)
Sucrose AT into sieve tube, water potential becomes lower , water enters phloem by osmosis from xylem and increased volume increases pressure
Which bonds are found in a)Primary structure [1]b)Secondary structure [1] c)Tertiary structure [2]
a)Peptide b) Hydrogen (and peptide) c)Ionic, disulphide bridges, hydrophobic interactions (hydrogen and peptide)
What is the function of: a)Ribosome b)Smooth ER c)Golgi apparatus d) Chloroplast e)Mitochondria [5]
a)Protein synthesis b)Lipid synthesis and transport c)Processing and packaging proteins for secretion d)Photosynthesis e)Aerobic respiration to produce ATP
Describe what happens to the chromosomes during each of the following stages of mitosis. Prophase, Metaphase, Anaphase, Telophase (4 marks)
prophase - coil up/spiralise/condense; (allow shorter/contract/become visible) metaphase - move to equator or centre of cell / attach to spindle; (reject if reference to pairing) anaphase - chromatids separate/centromeres divide; (reject chromosomes move to poles without further explanation) telophase - uncoil; (allow lengthen/becomes less visible) 4
Describe how the structure of haemoglobin makes it effective in the transport of oxygen. (4 marks)
quaternary structure, haem groups bind oxygen, four polypeptide chains so four haem groups ,one haemoglobin molecule can bind 4 oxygen molecules / 8 oxygen atoms ,Bohr effect / oxygen release in the presence of carbon dioxide/acidic pH
Describe how the structure of tRNA differs from mRNA (2 marks)
tRNA has amino acid binding site, complementary base pairing holding folds and it is shorter Messenger RNA (mRNA) is used during translation to form polypeptides.
The structure of a phospholipid molecule is different from that of a triglyceride. Describe how. [2]
triglyceride has three fatty acids and phospholipid has two; no phosphate group present in triglyceride but present in phospholipid.
Explain how viruses cause damage to cells. [3]
uses / breaks up / digests host nuclear / genetic material (allow references made to DNA /RNA instead of nuclear /genetic); virus DNA / genetic material inserted into hosts DNA / chromosome / genetic material; host cells amino acids are used to synthesize viral proteins; cell lysis; by enzyme (produced by expressing a virus gene); toxin production;
