Bio Short Answer

Use the information in Fig. 5.1 to explain how sucrose: • moves into the companion cell • moves from the companion cell into the sieve tube element.

(at Y) protons, pumped out (of companion cell) / moved out by active transport / move out through proton pump ; A protons are moved out against concentration gradient 2 creates a, proton gradient / electrochemical gradient ; 3 protons go into the, cell wall / apoplast ; R mesophyll cell 4 (at X) protons enter cell by facilitated diffusion ; 5 (X is) cotransporter / cotransport protein ; 6 sucrose transported into (companion) cell together with protons ; 7 (sucrose enters) against concentration gradient ; 8 sucrose concentration, increases / maintained, in companion cell ; 9 sucrose diffuses into sieve tube (element) ; 10 through plasmodesmata ; 11 AVP ; e.g. ref. to, secondary / indirect, active transport

Explain the significance of the catalysis of the formation of carbonic acid in the transport of carbon dioxide.

(catalyses very) fast / AW, reaction ; (carbon dioxide as) hydrogen carbonate ions / bicarbonate ions ; diffuse / move / leaves, out of the (red blood) cell ; in(to) the plasma ; R 'into blood' (so that) blood can transport more than could be transported as carbon dioxide (in solution) / 80 - 90% CO2 transported this way ; idea that reaction maintains concentration gradient for CO2 from, tissues / tissue fluid, to blood ; if carbon dioxide transported then pH would decrease ; (therefore) maintains pH / prevents pH decreasing / acts as a buffer ;

Vaccination was used in the eradication of smallpox. Explain, in terms of antigens, why it has not been possible to do the same for malaria.

(malarial) parasite / pathogen / Plasmodium, (is eukaryotic) has many genes ; A has greater genetic complexity cf smallpox / AW 2 different (malarial) parasite, species / strains / AW, have different antigens ; R 'strands' 3 (malarial) parasite has different antigens in different stages of its life cycle ; 4 (malarial) parasite / Plasmodium, switches antigens / idea of antigens changing during infection / different genes coding for antigens switching on / AW ; R 'active sites' of antigens changing R 'antigens mutate' 5 parasite / antigen / stages of the life cycle, inside (host / liver / red blood) cells ;

A tissue is a collection of one or more types of cell, specialised to carry out a particular function. An organ can be considered a structural unit within an organism that: • consists of more than one type of tissue • performs a particular function. The aorta is the main artery of the body. Explain, with reference to its structure and function, whether the aorta may be described as a tissue or an organ.

(organ because more than one tissue type) three named tissue types ; ; ; endothelium A squamous epithelium A endothelial cells A epithelial cells smooth muscle A smooth muscle cells connective tissue elastic tissue A elastic fibres R elastin / elastic muscle fibrous tissue A collagen A collagen fibres nervous tissue A nerve cells blood A blood cells only in context of vasa vasorum general function transports / carries / AW, blood ; A delivers R pumps blood I provides detail ; e.g. to tissues / to body cells / to body / away from heart / AW R to lungs (blood) is oxygenated / contains oxygen

Describe the structure of a cellulose molecule and explain how cellulose is a suitable material for the cell walls of plants.

(polymer / polysaccharide of) β-glucose ; allow glucose if β given for bond 2 (1-4, β) glycosidic, bonds / linkages ; A glucosidic R if 1-6 also given 3 ref. to (β) glucose units, linked at 180° to each other / alternately orientated / AW ; 4 many -OH groups projecting out (in different directions) ; 5 unbranched (polymer) / straight chain / linear ; 6 many hydrogen bonds between molecules ; 7 (straight chain allows) molecules lie parallel to each other ; 8 (form) microfibrils ; 9 many microfibrils form (cellulose) fibres ; 10 ref. to fibres at angles / criss-cross / AW ; 11 (cellulose) cell wall is permeable ; A idea of many gaps, in wall / between fibres, allowing passage of water / (named) substances 12 ref. to strength to, prevent cell bursting / withstanding (turgor) pressure / AW ;

Describe and explain how water moves from inside the leaf at point Q on Fig. 3.1 to the atmosphere outside the leaf during transpiration.

(water) moves out of, cell / Q, by osmosis / down a water potential gradient ; 2 through the, cell (surface) / plasma, membrane ; 3 to, surface / cell wall of, the spongy mesophyll cell, cell Q ; 4 evaporates into (sub-stomatal) air space ; A water changes to water vapour 5 water vapour diffuses out through (open) stomata ; A moves out down a, water potential / water vapour concentration, gradient

Unlike malaria, TB is found across the whole world. Explain why malaria shows the distribution pattern shown in Fig. 4.1, but TB is found everywhere.

1 Anopheles / mosquito / vector, survives / breeds / lives, within the tropics / in hot and humid areas ; ora 2 Plasmodium / pathogen / parasite, needs to reproduce within the mosquito (at temperatures above 20°C) ; 3 eradicated in some countries outside the tropics ; 4 ref. to LEDCs and, poor / non-existent, mosquito control programmes ; 5 mosquitoes resistant to, DDT / insecticides / pesticides ; 6 Plasmodium resistant to, drugs / chloroquine / other named drug ; 7 TB is transmitted, by, droplets / coughing / sneezing ; A in the air 8 no vector / no mosquito / no requirement for hot or humid conditions ; 9 ref. to, HIV infection / lower immunity / immunocompromised ;

Vaccinations are used to control infectious diseases. They were used as part of the programme to eradicate smallpox and as part of the continuing programmes against diseases such as polio and measles. Smallpox was eradicated from the world in the 1970s. Polio is likely to be the next infectious disease to be eradicated. TB and malaria continue to be important diseases. Explain how vaccination provides immunity as an important part of programmes to control and eradicate infectious diseases.

1 active immunity ; 2 vaccine contains, antigen(s) / pathogen / microorganism / named type ; 3 (primary) immune response ; 4 B lymphocytes / B cells / plasma cells, synthesise / produce / secrete / release, antibodies ; 5 ref. to T helper cells (enhancing humoral response) ; 6 clonal selection / described ; 7 specific, (T / B) lymphocytes / antibodies ; A 'particular' / AW 8 memory cells, remain (in circulation) / give long-term immunity / give immunological memory / AW ; 9 fast(er) second(ary) response ; 10 ref. to boosters / AW ; 11 immunised person cannot spread disease to others ; 12 herd immunity / unimmunised people are safe(r) ; 13 surveillance of population for signs of disease / when there is an outbreak ; 14 ref. to ring immunity / AW ;

Describe the events that occur during the stage of the cell cycle named for cell A (PROPHASE).

1 chromatin / chromosomes / chromatids, condense / become visible ; A described e.g. coiling, supercoiling, shorten, thicken 2 each chromosome is two (sister) chromatids joined together (at a centromere) ; R 'two chromatids, join together / pair up' 3 nucleolus disappears ; 4 nuclear envelope, disassembles / breaks down / AW ; 5 centrioles / centrosomes, move to poles ; A MTOC / microtubule organising centre R 'ends' / 'sides' 6 ref to spindle ; e.g. spindle (fibres) start to form centrioles organise microtubules (to form spindle fibres) microtubules assemble

tRNA molecules are synthesised inside the nucleus of eukaryotic cells. Outline the process by which tRNA molecules are synthesised in the nucleus.

1 gene for each tRNA (molecule) is transcribed ; 2 hydrogen bonds in DNA are broken ; I unwinding /unzipping 3 one strand of DNA is the template ; 4 RNA polymerase ; 5 (free RNA) nucleotides joined together/ formation of phosphodiester bonds ; I complementary base pairing 6 AVP ; e.g. correct ref. to helicase in breaking hydrogen bonds [max 3]

6 Agrobacterium tumefaciens is a bacterium that can enter plants through wounds and cause a disease known as crown gall disease. The bacterium attaches to the surface of cells and inserts a small circular DNA molecule, known as a plasmid, into the cell. Some of the genes on the plasmid code for proteins that cause changes in the plant cell and result in the formation of a plant tumour, or gall. (a) Outline the changes that occur during tumour formation

6 (a) 1 proteins produced (for growth) ; 2 DNA replication ; 3 organelles / named organelles synthesised ; A more organelles 4 uncontrolled mitosis /AW or continuous cell cycle or cell cycle checkpoints not controlled ; 5 (new cells) do not differentiate ; A do not become specialised 6 loss of function (of tissue) ; A changed function/ new cells do not function as tissue of origin 7 (abnormal) mass of cells formed ; 8 AVP ; e.g. no programmed cell death/ apoptosis / cells immortal / cells grow independently of normal programming/ no contact inhibition

Describe and explain how water and nitrate ions are transported in the xylem from roots to leaves.

I descriptions across the root, e.g. symplastic and apoplastic route I ref. to hydrostatic pressure 1 nitrates dissolved in water ; 2 in an apoplastic / a non-cytoplasmic route (in xylem) ; 3 passive (transport)/ does not require energy ; describe 4 transpiration pull/ idea of column of water pulled up ; 5 movement of water out of xylem creates tension ; A negative pressure 6 cohesion of water molecules / explanation in terms of hydrogen bonding ; explain 7 adhesion of water molecules to cellulose/ lining ; I lignin 8 AVP ; e.g. water potential gradient root to leaf mass flow caused by evaporation

The stages shown in Fig. 4.1 are listed below. Draw a circle around the stage in the cell cycle that is cytokinesis and describe what happens in this stage in the root tip meristematic cell.

I details of telophase leading to cytokinesis cell plate forms (across equator of cell) 2 or cell wall / cellulose, laid down ; A cell wall forms (between the two) 3 (so) cytoplasm divided (into two) ; R cytoplasm constricts / pinches in / cleavage furrow forms / cleavage forms (i.e. referring to animal cell) 4 AVP ; detail of cell plate formation e.g. ref. to vesicles transported to equator / involvement of cytoskeletal structures idea that organelles shared out

Suggest how enzymes with the induced fit mechanism can be less affected by competitive inhibitors than those which use the lock-and-key mechanism.

Inhibitors have similar shape to substrate Has different chemical make up and does not stimulate shape change of active site. Less likely to bind to active site successfully as it is not entirely complementary. Inhibitor can fit perfectly in lock and key mechanism as it does not involve a shape change.

Describe how malaria is passed from an infected person to an uninfected person.

R virus or bacteria once in the answer female, Anopheles (mosquito) ; takes blood (meal) from an (infected) person, feeds on an (uninfected) person ; R 'bite' unless qualified with blood Plasmodium / parasite, transmitted in (mosquito's) saliva ; Plasmodium / parasite, blood transfusion / shared needles / across placenta / at birth ;

Some alveolar cells produce a surfactant that helps to prevent the collapse of alveoli on exhalation. Too much surfactant decreases the efficiency of gas exchange in the alveoli. A glycoprotein known as GM-CSF is released by some cells of the immune system when there is too much surfactant in the alveoli. Excess surfactant is then broken down by alveolar macrophages. Receptors for GM-CSF are on the cell surface membranes of alveolar macrophages. Explain how maintaining the correct quantity of surfactant in the alveoli is the result of a cell signalling mechanism.

accept (the) glycoprotein for GM-CSF throughout 1 (excess surfactant) stimulates immune system cells ; 2 release / secretion, of, GM-CSF ; I produce 3 GM-CSF is a signal or GM-CSF is a signalling, molecule / protein / glycoprotein ; A messaging molecule 4 binds to / combines with / AW, (cell surface membrane) receptors (on alveolar macrophages) ; 5 ref. to specificity ; A described as GM-CSF receptor complementary shape for GM-CSF 6 leads to / sets off / triggers / AW, response (in the cell) / removal of surfactant ; in context of macrophage A stimulates 7 detail ; e.g. triggers secondary messenger activates enzymes / enzyme cascade signal transduction phosphorylation events

Describe the structure of the chromosome in late prophase.

accept from labelled diagram two chromatids ; identical/ sister, chromatids ; joined by a centromere ; A kinetochore one from (reach chromatid) DNA complexed with protein histone proteins / histones ; telomeres at end of chromatid

The enzyme that catalyses the replication of DNA checks for errors in the process and corrects them. This makes sure that the cells produced in mitosis are genetically identical. Explain why checking for errors and correcting them is necessary

accept ora (errors are) mutations / named type of mutation ; ora if corrected there are no mutations (may lead to) production of altered proteins, so, impaired / loss, of function ; A altered amino acid in, protein / primary structure (may lead to) different antigens, so cells are rejected (by immune system) ; idea that cells cannot function together / impaired coordination ; ref. to cancerous cells / cancer(s) / tumours / sickle cell anaemia or other named monogenic condition ; further detail ; e.g. uncontrolled, division / mitosis / cell replication / cell growth e.g. lack of contact inhibition / no apoptosis or described / (proto)oncogene(s)

One of the functions of a plant hormone known as cytokinin is to act as a cell signalling molecule and promote cytokinesis. Suggest how cytokinin acts as a cell signalling molecule.

acts at target cell ; binds to receptor ; R receptor cells allow ecf for other mps R trapped/ caught ref. specificity ; A receptor complementary (shape) for cytokinin A cytokinin fits into receptor this is also mp2 A recognition of cytokinin by receptor receptor (located) in, cell surface/ plasma, membrane ; A cell membrane A phospholipid bilayer A transmembrane receptor sets off/AW, response in the cell/ described response(s) ; e.g. triggers secondary messenger activates enzyme(s) I signals / causes / stimulates, cell to divide/ cytokinesis (acts) extracellularly / extracellular signal or (acts) intracellularly / intracellular signal ; must be in context of candidate's answer

Outline how monoclonal antibodies are produced.

antigen, introduced / AW, into, (small) mammal ; A named small mammal 2 B-lymphocytes / B cells / plasma cells / splenocytes / antibody-producing lymphocytes, are taken / are isolated (from the spleen / lymph nodes) ; 3 (these) cells are fused / AW, with, myeloma / cancer, cells ; 4 hybridoma cells / hybridomas, formed ; R hybridised cells / hybrid cells 5 hybridoma cell, is cloned / AW ; 6 screening / testing, for hybridoma that produces desired antibody ; 7 ref. to scaling up / large-scale production / grow in a fermenter ; 8 AVP ; e.g. fusion using, fusogen / polyethylene glycol / PEG / electric current (electrofusion) / (Sendai) virus HAT medium, for, hybridoma growth / inhibiting myeloma growth humanisation of monoclonal antibody

The students repeated their investigation on enzyme A with a competitive inhibitor. They used the same concentrations of substrate as before, but added a competitive inhibitor to each reaction mixture. They used the same concentration of the inhibitor in each reaction mixture. The students found that Vmax was the same as before, but Km was higher than 0.3 mmol dm-3. Explain how the addition of the competitive inhibitor results in the same value for Vmax but a higher value for Km.

competitive inhibitor, occupies / competes with substrate for / AW, active site (of the enzyme) ; 2 reduces frequency of collisions (with substrate) / fewer ESCs form ; R no ESCs form 3 reduces reaction rate at low substrate concentrations ; 4 idea that curve with inhibitor is to the right of the curve without inhibitor ; 5 at high substrate concentration / with increasing substrate concentration, the inhibitor has, no / less, effect ; A idea that substrate outcompetes inhibitor at high substrate concentration 6 therefore Vmax is the same as it is determined by the enzyme concentration / AW ; A explanation in terms of active sites, saturated / fully occupied 7 idea of intercept to curve gives a higher value for Km ;

Explain briefly how sucrose is moved, or translocated, through sieve tubes.

dissolved in, water / sap ; A in solution mass flow ; down (hydrostatic) pressure gradient / moves from high(er) to low(er) pressure (potential) ; A symbol - ψp AVP ; e.g. from source to sink loading by, companion / transfer cells, requires ATP / is active ; I ATP required for mass flow

Use the information in Table 3.1 to explain why the blood pressure in the pulmonary artery is the same as the pressure in the right ventricle during systole, but higher during diastole.

during systole semi-lunar valve is open ; during diastole semi-lunar valve is closed ; proximity/AW pulmonary artery to (right) ventricle (so no pressure lost) ; elastic recoil of pulmonary artery maintains blood pressure/AW ; no/little blood in (right) ventricle, after contraction/during diastole ; fills with blood at low pressure ;

With reference to Fig. 5.1, explain why the researchers decided to use the form of the parasite which is injected by mosquitoes and not the form which leaves the liver.

first form of, pathogen / parasite, free / exposed, in plasma ; A not inside cells 2 second form of, pathogen / parasite, concealed / hidden, in liver / red blood cells ; for either mp 2 or 3 3 ref. to degree of exposure to antibodies / lymphocytes idea that 4 fewest number of parasites to destroy / earlier defence always more effective ; 5 vaccination against form leaving liver would, not protect against liver invasion / still cause liver damage ; 6 AVP ; e.g. suggestion that first form of parasite is easier to harvest

Meristematic cells have a similar role to stem cells found in animals. Suggest the role of a meristematic cell and explain the features that help it to carry out its role.

form cells that can, differentiate / become specialised ; A can develop into other cell types / totipotent A named examples 2 for, cell replacement / tissue repair / growth ; R for cell growth I found in growing region 3 divides to give continuous supply of, meristematic / stem, cells ; A divides to forms more, meristematic / stem, cells feature 4 (stem cells are) undifferentiated ; A not specialised / unspecialised 5 able to divide ; must be in context of mitosis A able to undergo mitosis A can replicate I reproduce R uncontrolled division 6 idea that genes not switched off ; ora

Suggest how the binding of monoclonal antibody to the diseased cells causes their destruction by cells of the person's immune system.

four from 1 ref. to monoclonal antibody, is recognised as, non-self /foreign ; or diseased cell (now) recognised as non-self /foreign ; 2 stimulates an immune response ; max three suggestions from 3 recognition and binding by / activation of / AW, T-lymphocytes / B-lymphocytes / AW ; A clonal selection A T- / B-, cell 4 ref. to specificity so healthy cells not destroyed ; 5 clonal expansion /mitosis ; 6 plasma cells (formed that) secrete antibody ; A B-lymphocyte 7 consequence ; e.g. antibody binds monoclonal antibody to lead to cell destruction 8 T-helper lymphocyte secretes cytokine, to activate macrophages / B-lymphocyte response / T-killer response ; AW e.g. stimulates humoral response 9 T-killer/T-cytotoxic, releases, perforin to, punch holes in (cell) membrane / cause death of cell ; AW 10 detail of involvement of phagocytes /macrophages ; e.g. receptor recognition of (monoclonal) antibody engulf the diseased cells with monoclonal antibody attached /AW A diseased cell (with monoclonal antibody) destroyed by phagocytosis [

State what is meant by a sink

growing / storage, area / region / correct named part of plant ; examples of part of plant that stores / growing root / shoot tip / bud / flower / maturing leaf / tuber / fruit / seed

The magnification used in Fig. 3.1 can also be obtained using a light microscope. Suggest why an electron microscope was used to obtain this image instead of a light microscope.

higher / better / AW, resolution / resolving power ; 2 0.5nm (A 0.2-1nm) compared to, 200nm 0.2µm (A range 100-300nm) or electrons have shorter wavelength ; R electron microscope has a shorter wavelength or idea that cell structures too small to interfere with light waves ora 3 better able to distinguish between two points ; A as a definition if mp 1 achieved 4 (can see) more detail ; treat 'clearer' as neutral 5 able to make thinner sections / able to see inside (oocyst) ; 6 can continue to obtain higher magnifications and see more detail ;

People with long-term chronic obstructive pulmonary disease (COPD) usually have blood which is poorly oxygenated during its passage through the lungs. This leads to a constriction of blood vessels in the lungs. Suggest the likely effect of this on the heart.

increase in power of contraction ; AW increase in (systolic) blood pressure ; strain on right ventricle/right ventricle does not function efficiently ; growth of muscle in/right ventricle increases in thickness ; insufficient oxygen to, heart/cardiac, muscle ; heart failure/heart attack ;

Outline the role of antibiotics in the treatment of infectious diseases.

kill bacteria / bactericidal ; A cause bacteria to, lyse / burst A destroy 2 (or) bacteriostatic / prevents bacterial growth / prevents bacterial replication; A ref. to preventing protein synthesis / inhibiting metabolic reactions 3 ref. to preventing spread (of bacteria) within body ; A prevents reservoir for re-infection 4 do not affect, human cells / human tissue / not toxic (to humans) ; 5 prevents death / consequences may be fatal if no antibiotic treatment / AW ; A ref. to, alleviating symptoms / faster recovery A restores good health / person feels well again / person cured 6 ref. to role in preventing, transmission / spread, of disease ; do not confuse with mp 3 ref. to (antibiotic) treatment of TB ; e.g. one of isoniazid, rifampicin (rifampin), pyrazinamide, ethambutol, streptomycin one of 6-12 months (latent), longer for active disease, two years or more for drug-resistant forms need combination treatment if active disease ref. to, MDR-TB / multidrug- resistant TB or XDR-TB / extensively drug-resistant TB 8 part of DOTS regimen / described ; (directly observed therapy short-course / direct observation treatment short course)

State the advantages of light microscopy, rather than electron microscopy, for studies of the cell cycle.

living cells can be viewed (with light microscope) ; 2 can watch the cell cycle happen (in real time / time lapse) / AW ; 3 all chromosomes can be seen (at once) ; 4 can see, whole chromosomes / all the stages of mitosis or cell cycle ; 5 do not need take sections to see mitosis ; 6 dyes / stains, can be used ; I ref. to natural colours of specimens A ref. to fluorescence microscopy

Tobacco smoke is known to cause increased production of macrophage elastase. MMP12 is the gene coding for macrophage elastase. Copies of this gene are produced as messenger RNA (mRNA). Describe how this mRNA is used in translation to produce macrophage elastase.

mRNA, binds /AW, to ribosome ; A ribosomal RNA I rRNA A mRNA moves to ribosome 2 tRNA with amino acid (to/at, ribosome) ; A aminoacyl/ charged, tRNA 3 tRNA/ anticodon, specific to an amino acid ; A specific tRNA/ anticodon for the amino acid 4 ref. to start codon; A AUG(met) / first codon is AUG/ initiator tRNA ; 5 (complementary) base pairing/ binding, between anticodon and codon ; 6 first and second tRNAs bind/ two tRNAs bound (at a time) or (tRNAs bring) amino acids, side by side/ close ; 7 peptide bond formation ; 8 ribosome moves along, one codon/AW ; 9 next (aminoacyl) tRNA arrives /amino acids added one at a time ; 10 elastase/polypeptide, released when STOP codon reached ; A process continues until a STOP codon reached 11 AVP ; e.g. ref. to, aminoacyl/A, site, and, peptidyl/P, site small subunit (of ribosome) attaches to mRNA aminoacyl tRNA synthetase binds amino acid to tRNA ATP required for tRNA-amino acid binding peptidyl transferase for peptide bond formation ref. to, exit /E, site, on ribosome ribosome moves 5' to 3'

Some transcription factors may prevent transcription. Suggest how.

may prevent breaking of hydrogen bonds between, base pairs / bases /nucleotides, (and access of RNA polymerase) ; attachment of, RNA polymerase (to DNA) ; progress / functioning, of RNA polymerase (along gene) ; synthesis / elongation of (pre) mRNA ; AVP ; e.g. interfere with action of helicase

Explain why the growth of roots, such as those of A. cepa, involves mitosis and not meiosis. EXTRA ATTENTION EXTRA ATTENTION EXTRA ATTENTION EXTRA ATTENTION

mitosis needs number of chromosomes to remain constant/diploid ; needs all daughter cells to be genetically identical/have no genetic variation ; A clones needs genetic stability ; meiosis halves the number of chromosomes/diploid → haploid ; A undergoes a reduction division daughter cells are all genetically different ; accept once only produces genetic variation ; accept once only involved in sexual reproduction (in flowering plants) not growth ; A production of gametes idea that cells that are genetically different will not function together in tissues ; ora

Suggest the advantages of using monoclonal antibodies in diagnosis of disease.

monoclonal antibodies used all have the same specificity ; R 'are specific' unqualified 2 detect only one, antigen / epitope ; 3 can distinguish between different, pathogens / strains of, pathogens ; A types of cancer cells 4 can be, labelled / tagged / marked / AW ; e.g. with fluorescent label 5 monoclonal antibodies can detect location of, tissues expressing antigen / cancer cells / blood clots ; A idea of locating areas of infection 6 fast(er) (diagnosis) ; 7 can detect antibody levels (e.g. HIV) ; 8 AVP ; e.g. some pathogens cannot be cultured I ref. to cost

The distribution of Anopheles shown in Fig. 5.2 includes over forty different species that are vectors of malaria. The areas with the highest number of cases of malaria are also the areas where Anopheles gambiae occurs. A. gambiae is responsible for most of the transmission of the disease in these areas. Suggest why A. gambiae is responsible for most of the transmission of Plasmodium. SKIP THIS ONE-REQUIRES DIAGRAM

not all countries with Anopheles have malaria/ example using Fig. 5.2 ; e.g. (although, Anopheles / vector, shown as present), no / few, cases (of malaria) in, North America/Europe (although, Anopheles / vector, occurs elsewhere) malaria, only / mainly, in subtropical and tropical areas ; explanations: Plasmodium/ parasite/ pathogen, not present in all areas where Anopheles is located/AW ; conditions (where Anopheles located) not always suitable for life cycle of, Plasmodium/ parasite/ pathogen ; some, areas / countries, have eradicated the disease (but still have the vector) ; AVP ; e.g. some countries have better prevention methods against malaria AVP ; some countries have effective treatment for malaria I vaccination

Describe how a mutated version of the EPAS1 gene can cause a change in the transcription factor protein produced?

nucleotide/base, sequence of, DNA/ gene, changed/AW ; A new allele (formed) ref. to altered mRNA/AW ; this may be in context of a named type of mutation consequence on tRNA tRNA/ anticodon, with different amino acid (to ribosome) ; A tRNA with different anticodon change in amino acid(s)/ different amino acid sequence/ change in primary structure ; affects, secondary structure/ tertiary structure/ 3D shape/ function, of protein ; ref. to one type of mutation ; e.g. base substitution means deletion/ insertion, leads to frameshift ref. to premature stop codon

Explain why existing vaccines may no longer be effective against bacteria with changing antigens.

ref. specificity ; in context of the immune response qualified ; e.g. existing , (B / T) lymphocytes / B-cells / T-cells, no longer activated / no recognition ora R if T lymphocytes produce antibodies existing plasma cells do not produce new antibody ora existing memory cells no longer activated / AW ora different / new, immune response required ora

Explain why the parasites were killed using radioactivity and not by using high temperatures.

ref. vaccines contain antigens ; 2 antigens are (mostly), proteins / glycoproteins ; 3 antigens, denatured by heat / not denatured by radioactivity ; A proteins denatured in context of antigenic proteins R parasite is denatured 4 detail e.g. loss of tertiary structure / bonds break ; 5 shape to be maintained for specificity of immune response / AW ; 6 AVP ; e.g. ref. to production of memory cells (for immunity)

Health authorities recommend that antibiotics, such as tetracycline, are only to be used for treating people with severe cases of cholera. Explain why it is recommended that antibiotics should not be given to people with mild cases of cholera or to protect people from cholera.

rehydration therapy, is effective / can treat cholera / reduces death rate ; 2 any detail ; e.g. solution of glucose and salts 3 antibiotic is a selection pressure / described ; 4 ref. to, antibiotic / tetracycline, resistance ; 5 ref. to, vertical transmission / horizontal transmission, of resistance ; A described, A transfer for transmission 6 antibiotics will become, ineffective / less effective / AW ; 7 keep antibiotics for use 'as last resort' ; AW 8 ref. to cost ; 9 antibiotics kill gut bacteria ; 10 idea that disrupts functions of digestive system ; 11 AVP ; e.g. antibiotics going into the environment / food chain antibiotics can cause mutation decreases need to develop new drugs prevents development of active immunity idea of transmission between bacterial species plasmids with resistance genes

Vaccination helps to prevent the spread of infectious diseases by stimulating an immune response in individuals against specific pathogens, such as Morbillivirus, the virus that causes measles. (i) Suggest two reasons why measles vaccination programmes may fail to prevent epidemics.

required percentage cover not reached/ high percentage cover required/ not enough people vaccinated ; 2 some do not respond successfully to vaccine ; 3 poor diet/ lack of vitamin A ; 4 poor storage of non-thermostable vaccine ; 5 vaccine not cost-free to population ; 6 inaccessible vaccination stations for some of the population ; 7 ref.to difficulty in giving boosters ; 8 ref.to reluctance to have children vaccinated ; 9 lack of advertising/ campaigns /education to encourage vaccination ; 10 different strain (to the one used in vaccine)/ antigens changing; R ref.to resistance

The World Health Organization (WHO) declared the world to be free of smallpox in 1980. (d) Outline some of the factors that led to the successful eradication of smallpox from the world population.

smallpox virus was stable/did not mutate ; 2 same vaccine was used for whole programme/vaccine did not need to be changed ; 3 vaccine was live/gave a strong immune response ; A effective 4 one dose was enough to give life-long immunity/no boosters required ; 5 heat stable/freeze dried vaccine ; 6 suitable for hot countries/isolated areas/rural areas ; 7 bifurcated/steel, needle, could be re-used/easier delivery/AW ; 8 herd/mass, vaccination/immunity ; A (many countries) mandatory vaccination 9 ring vaccination/ref. to contact tracing ; 10 few/no symptomless carriers ; 11 no animal reservoir/only in humans ; 12 infected people easy to identify ; 13 isolation of cases to prevent spread ; 14 AVP ; e.g. comparatively low cost, qualified; many volunteers became vaccinators/AW

Enzymes are globular proteins. State what is meant by the term globular

spherical / ball-shaped / AW ; has a tertiary structure ; ignore quaternary hydrophilic / polar, groups on outside ; water soluble ; ignore 'more than one polypeptide'

The stages shown in Fig. 4.1 are listed below. Draw a circle around the stage in the cell cycle in which the semi-conservative replication of DNA occurs and state what is meant by semi-conservative replication.

synthesis of two identical DNA, molecules / double helices (from one) ; each new molecule consists of one, original / parental, strand, and one, new / newly synthesised, strand ; AW A daughter for newly synthesised

DNA codes for polypeptides in cells. Transfer RNA (tRNA) is involved in this process. Describe the role of tRNA in the production of polypeptides in cells.

tRNA carries amino acid to ribosome ; 2 ref to specificity of amino acid carried ; 3 anti-codon on tRNA complementary to codon on mRNA ; A example for complementary, e.g. AUG and UAC 4 ref to two sites / P(eptidyl) and A(mino-acyl) sites, of ribosome ; 5 peptide bond is formed between amino acids ; R 'polypeptide bond' 6 tRNA, can be re-used / collects another amino acid ;

The leaf of C. sinensis, shown in Fig. 3.1, has developed in a sunny position. State three features of the leaf, visible in Fig. 3.1, which show that it has developed in a sunny position

thick (waxy) cuticle ; large / big / thick, upper epidermis / upper epidermal cells ; many / two / three, layers of palisade cells ; thick leaf ; densely packed with spongy mesophyll / many spongy mesophyll cells ; fewer / small, air spaces ; no, stomata / guard cells, on upper surface ; ora only on lower surface many chloroplasts (within spongy mesophyll cells) ; R xeromorphic features NOT visible, e.g. sunken stomata

Describe the function of ribosomes in protein synthesis.

translation / construction of polypeptide(s) ; 2 provide binding site for mRNA / mRNA attaches to ribosome / AW ; A entering ribosome 3 provides binding sites for (two) tRNA molecules ; A entering ribosome 4 two amino acids are held close together ; 5 formation of peptide bond(s) ; R dipeptide / polypeptide, bond 6 (allows) assembly of amino acids into, sequence / primary structure ; 7 AVP ; e.g. P and A site (and E site) bond between amino acids catalysed by peptidyl transferase

At the surface labelled S, movement of glucose molecules out of the intestinal epithelial cell occurs by facilitated diffusion. Outline the features of facilitated diffusion of glucose molecules.

transport/ transporter/ carrier, protein ; R pump protein specific protein ; glucose, binding site / AW ; I glucose binds R glucose receptor specific binding site (in protein) = 2 marks (glucose binding causes) conformational change ; AW, e.g. changes shape passive / no energy required/ no ATP required ; movement is, down the concentration gradient/ from high to low concentration ; must be in context of through the membrane protei