Biology
Describe the three proposed models of DNA replication.
- Conservative model: Proposed that two new daughter strands form to create a new double helix, and the original strands re-form into the parent molecule - Semi-conservative model: Proposed that each new DNA molecule contains one strand of the original DNA and one newly synthesized strand - Dispersive Model: Proposed that the parental DNA is broken into segments. Therefore, the daughter DNA contains a mix of parental and newly synthesized DNA.
List three differences between DNA and RNA
- DNA is the genetic material that controls protein synthesis, whereas RNA helps DNA and is involved in protein synthesis - DNA has the sugar called deoxyribose where as RNA has the sugar called ribose. - The bases in DNA are adenine, thymine, cytosine and guanine, and the bases of RNA include adenine, cytosine, guanine and uracil
The noncyclic, bu not the cyclic, pathway.
- Does not generate 3PG - Does not Generate chlorophyll - Does not generate ATP - Does not generate NADPH
What occurs during the light dependent reactions of plants?
- Electron Transport Chain - Chemiosmosis - Splitting of Water
Which processes are needed for the completion of oxidation of glucose?
- Glycolysis - Pyruvate Oxidation - The Krebs Cycle
List and describe the three stages of transcription
- Initiation: Transcriptional machinery is assembled on the sense strand. RNA polymerase binds to the promoter region of the sense strand - Elongation: RNA polymerase synthesizes a strand of mRNA that is complementary to the sense strand of DNA - Termination: RNA polymerase detaches from the DNA strand when it reaches a stop signal. The mRNA strand is released and the DNA double helix reforms
What is Rubisco?
- It catalyzes the carboxylation of CO2 to ribulose, 1-5 bisphosphate
Light that is absorbed by a leaf is?
- Not reflected - Captured by a photosystem - Used to increase the energy of an electron - Composed of most colours, other than green and yellow
State two major reasons why photosynthesis is not the reverse of cellular respiration.
- Photosynthesis transforms sunlight into chemical energy. Much of the glucose produced by plants gets converted into cellulose which is the main component of the cell wall. The term photosynthesis refers to the reactions that capture light energy (photo) and the reactions that produce carbohydrates (synthesis) - Cellular respiration includes the catabolic pathway that breaks down energy rich compounds (glucose) to produce ATP. - Photosynthesis is not the reverse of cellular respiration because it's adding energy to the system to keep it going in the form of sunlight. That energy then gets used in the form of chemical energy in cells. It doesn't go back to the sun.
Both carotenoids and chlorophylls are what?
- Pigments - Absorb photons of all energy ranges - And contain porphyrin rings
Condensation reactions are know for?
- Producing water and attaching two amino acids
Chemiosmosis depends on?
- Protein complexes in the thylakoid membrane - A difference in the H+ concentration between the thylakoid space and the stroma
Although scientist in the early 1900's had not yet identified the chemical composition of genetic material, what criteria did scientist know the genetic material had to meet?
- Scientist knew that the genetic material had to contain information that controls the production of enzymes and proteins. - It also had to have the ability to replicate itself with great accuracy in order to maintain continuity from one generation to the next - As well as allow occasional mutations as the means to introduce variation within species.
The NADPH produced during the light-dependent reactions are necessary for what?
- The carbon fixation phase which incorporates carbon dioxide into an organic molecule of the Calvin Cycle - The reduction phase which produces carbohydrates in the Calvin Cycle
What is the advantage, for a cell, of using a two-stage process (DNA —> RNA followed by RNA —> Cytoplasm) to transfer genetic information from the nucleus to cytoplasm?
- The cell saves the energy that would be required to transport an entire chromosome to the cytoplasm - The cell protects the hereditary material from risk of damage in the cytoplasm - The cell can produce multiple copies of a DNA molecule to speed up the protein production - There are several opportunities to regulate gene expression
List and summarize the three basic phases of DNA replication
1. Initiation: Helicase enzyme unwinds DNA to separate it into two strands. A replication bubble is formed when single-strand binding proteins stabilize the separate strands. 2. Elongation: New DNA strands are synthesized by joining free nucleotides together. This is catalyzed by DNA polymerase, which synthesizes the new strands that are complementary to the parental strand 3. Termination: The two new DNA molecules separate form one another
To reduce six molecules of carbon dioxide to glucose via photosynthesis, how many molecules of NADPH and ATP and required?
12 NADPH and 12 ATP
What is the net production of ATP molecules from two molecules of glucose undergoing glycolysis?
2
Production of one molecule of 3-phosphoglyceraldehyde requires how many turns of the Calvin Cycle?
3
If a DNA molecule contains 20 percent of A, approximately what percentage of G is present?
30 percent
What is the DNA template for the RNA sequence 5' - AACGGAGCCUAAUC - 3'?
5' - GATTAGGCTCCGTTA - 3'
By convention, the sequence of bases in a nucleic acid is usually expressed during replication in which direction?
5' to 3'
In a double stranded DNA molecule, the complimentary strand to 5'- AAACGCTT- 3' is?
5'- UUUGCGAA - 3'
What are proteins?
A biological macromolecule composed of amino acid monomers linked by covalent bonds
What are lipids?
A biological macromolecule composed of carbon, hydrogen, and oxygen atoms with a high proportion of non-polar carbon-hydrogen bonds
What is an enzyme?
A biological macromolecule that catalyzes, or speeds up, chemical reactions in biological systems
What is a monosaccharide?
A carbohydrate composed of between 3 to 7 carbon atoms
What is a disaccharide?
A carbohydrate composed of two monosaccharides joined by a covalent bond
What is a polysaccharide?
A carbohydrate polymer composed of many monosaccharides joined by covalent bonds between particular atoms
How many covalent bonds can a carbon atom make?
A carbon atom can make a maximum of four covalent bonds
What is an organic molecule?
A carbon containing molecule in which carbon atoms are nearly always bonded to each other and to hydrogen
Briefly describe how an enzyme is able to speed up a chemical reaction.
A catalyst is a substrate that speeds up chemical reactions but it doesn't get used up in the reaction. It can be recovered unchanged when the reaction is complete. Enzymes are able to speed up chemical reactions through a highly specific manner through interactions between the enzyme and the reactants for the reaction. - contains amino acid group R that end up close to certain chemical bonds in the substrate, causing these bonds to stretch or bend, which makes the bonds weaker and easier to break - Bring two substrates together in the correct position for reaction to occur - Transfer electrons to or from the substrate, destabilizing it and making it more likely to react - Adding or removing hydrogen ions to or from the substrate, destabilizing it and making it more likely to react
Define ribosome
A cell structure composed of proteins and rRNA that provides the site where protein synthesis occurs
What is fermentation?
A cellular respiration pathway that transfers electrons from NADH to an organic acceptor molecule
What is a neutralization reaction?
A chemical between am acid and a base producing water and salt
What is a hydrolysis reaction?
A chemical reaction that results in cleavage of a covalent bond with the addition of a water molecule
What is a condensation reaction?
A chemical reaction that results in the formation of a covalent bond between two molecules with the production of a water molecule
What is an operon?
A cluster of genes grouped together under the control of one promoter; occurs in prokaryotic genomes
What is mean by the term "universality", in reference to the genetic code?
A codon triplet codes for the same amino acid in all species of organisms
Differentiate between coenzymes and cofactors, and explain their role in biological systems.
A coenzyme is an organic molecule other than the substrate that is required for an enzyme catalyst reaction. These molecules assist enzymes in performing the reactions they catalyze. Without them, enzymes could not work. Many enzymes require one or more coenzymes or cofactors for their activity
What is the endoplasmic reticulum?
A complex system of channels and sacs composed of membranes enclosing a lumen, made of of two parts, the rough endoplasmic reticulum and the smooth ER
What is a pigment?
A compound that absorbs certain wavelengths of visible light while reflecting others
What is a peptide bond?
A covalent bond formed between two amino acids during protein synthesis
What is a concentration gradient?
A difference in concentration between one side of a membrane and the other
What is a nuclear envelope?
A double membrane surrounding the nucleus
What is constitutive gene?
A gene that is constantly being expressed; it does not undergo regulation of expression
In both the mitochondria and chloroplast, energy for the phosphorylation of ADP comes from the hydrogen ion gradient. Why is a gradient formed with ions more effective than a gradient of neutral molecules?
A gradient formed with ions more effective than one formed with neutral molecules, as both the concentration gradient and a charge gradient across the membrane contributes to the stored energy. So both a concentration gradient and voltage across the membrane build up. Both of these contribute to push a changed solute (ion) back across the membrane through the ATP synthase.
Define Helicase
A group of enzymes that aid in the unwinding of DNA (Found in the initiation phase)
What is the nuclear pore complex?
A group of proteins forming opening the nuclear envelope
What are fatty acids?
A hydrocarbon chain ending in a carboxyl group
What is a polymer?
A large molecule of repeating units of smaller molecules (monomers)
What is a macromolecule?
A large, complex molecule, usually composed of repeating units of smaller molecules covalently linked together
What is a vacuole?
A large, membrane-bound sac in plant cells and some other cells that stores water, ions, macromolecules, sugars and amino acids
What are phospholipids?
A lipid composed of a glycerol molecule bonded to two fatty acids and a phosphate group with an R group
What are steroid?
A lipid composed of four attached carbon-based rings
What are triglyceride?
A lipid molecule composed of a glycerol molecule and three fatty acids linked by ester bonds
What is DNA (deoxyribonucleic acid)?
A macromolecule composed of nucleotides containing the sugar deoxyribose
What is RNA (Ribonucleic Acid)?
A macromolecule composed of nucleotides containing the sugar ribose
What are carbohydrates?
A macromolecule that contains carbon, hydrogen and oxygen in a 1:2:1 ratio
What is entropy?
A measure of disorder
Define Mismatch Repair
A mechanism for repairing errors made during DNA replication, whereby a group of proteins recognize a mispaired nucleotide on the newly synthesized strand and replace it with a correctly paired nucleotide (found in the termination phase)
Define Histone
A member of the family of proteins that associate with DNA in Eukaryotic cells, which acts to help compact the DNA
What is a peroxisome?
A membrane bound sac containing oxidative enzymes that break down excess fatty acids, and hydrogen peroxide, and participates in the synthesis of bile acids and cholesterol
What is a lysosome?
A membrane bound vesicle containing enzymes that catalyze hydrolysis reactions, breaking down molecules
What is a vesicle?
A membrane enclosed sac used for transport and storage
What are carrier proteins?
A membrane protein that binds to and transports one or more particles of a substrate from one side of the membrane to the other along the concentration gradient for that substance
What is a channel protein?
A membrane protein that forms a channel across the cell membrane which allows specific ions or molecules to cross the membrane along the concentration their gradients
Describe how the structure of a chloroplast is ideally suited for photosynthesis.
A membrane system within the chloroplast forms interconnected disks called thylakoids that look like flattened sacs. They are often stacked to form structures called grana. Thylakoids are central to photosynthesis because the molecules that absorb the solar energy are embedded in the thylakoid membranes. Surrounding the grand in the chloroplast in the chloroplasts is a fluid-filled interior called the stroma. The stroma contains the enzymes that catalyze the conversion of the carbon dioxide and water into carbohydrates.
What is anaerobic respiration?
A metabolic pathway in which an inorganic molecule other than oxygen is used as the final electron acceptor during the chemiosmotic synthesis of ATP
What is glycolysis?
A metabolic pathway that breaks glucose down to pyruvate
What is a 5' cap?
A modified form of a G nucleotide; added to the 5' end of an mRNA
What are nucleotides?
A molecule compose of a sugar bonded to a phosphate group and a nitrogen containing base
Does a molecule have more energy in its oxidized or reduced form? Explain
A molecule has more energy in its reduced form than when oxidized. As covalent bonds are broken (shared pairs of electrons are separated) energy is released
Explain how the following terms are related? Macromolecule, polymer and monomer
A monomer is the basic building block of a larger polymer, typically a long molecule that may be composed of many hundreds or even thousands of monomeric units joined together. The truly large polymers belong in a class of giant molecules known collectively as macromolecules. Examples include: most proteins, large polysaccharides like starch, glycogen and cellulose, and many larger nucleic acids such as DNA
What is passive transport?
A movement of ions or molecules across a cell membrane form a region of higher concentration to a region of lower concentration, without the input of energy
What is frameshift mutation?
A mutation caused by the addition or deletion of a number of nucleotides not divisible by three, resulting in a change in the reading frame
What is point mutation?
A mutation involving a single base pair substitution, insertion or deletion
What is missense mutation?
A mutation that changes the amino acid sequence of a protein
What is a silent mutation?
A mutation that does not change the amino acid sequence of a protein
What is chromosome mutation?
A mutation that involved many changes in chromosomes, and may involve many genes
What is single gene mutation?
A mutation that involves changes in the nucleotide sequence of one gene
What is a nonsense mutation?
A mutation that shortens a protein by introducing a stop codon
Compared to retinal, chlorophyll can be described as a pigment that has what?
A narrow absorption range but high efficiency
What is a cytoskeleton?
A network of protein fibres that extends throughout the cytosol, providing structure, shape, support and motility
What is a nucleolus?
A non-membrane bound structure in the nucleus, which contains RNA and proteins
What is a pH scale?
A numerical scale ranging from 0 to 14 that is used to classify aqueous solutions as acidic, basic or neutral
What is DNA made up of?
A phosphate Group, an organic base and a sugar
What are the basic components of a single nucleotide in a DNA molecule?
A phosphate group, a deoxyribose sugar, and a nitrogen-containing base
What is meant by the dual character of a phospholipid molecule, and how is this essential to its function in living systems?
A phospholipid molecule has a dual character in the that part of the molecule — it's "head" group is polar and this hydrophilic, but it's "tail" portion is non-polar and thus hydrophobic. This structure is essential to its function in that it forces the molecules to orient their head groups toward water and their tails towards each other. This arrangement forms the familiar phospholipid bilayer that is the basic structure of the membranes in all cells.
Explain how a polar covalent bond is different from an ionic bond
A polar covalent bond involves the unequal sharing of a pair of electrons between two atoms, where one atom is more electronegative than the other. A polar bond results in one of the atoms having a partial negative charge (the more electronegative atom) and the other atom having a partial positive charge. In an ionic bond, two oppositely charged ions are attracted to one another, one ion has a full negative charge (as a result of it's extra electron) and the other has a full positive charge (as a result of having lost an electron). The full charge results from one of the atoms being so much more electronegative than the other that is able to fully acquire an electron from the more weakly electronegative atom. The transfer of the electron results in ion formation
What is a polypeptide?
A polymer composed of many amino acids linked together by covalent bonds
Describe the structure and function of a polyribosome
A polyribosome is a complex composed of multiple ribosomes along a strand of mRNA. It can produce many copies of a protein at the same time
Light that is visible to humans occupies what part of the electromagnetic spectrum?
A portion in the middle
What is endocytosis?
A process by which the cell membrane engulfs extracellular material to bring it inside the cell
What is reduction?
A process involving the gain of electrons
What is oxidation?
A process involving the loss of electron
What is C3 photosynthesis?
A process of converting carbon dioxide to glyceraldehyde-3-phosphate using only the calvin cycle, it involves production of a three carbon intermediate
What is oxidative phosphorylation?
A process that couples the oxidation of NADH and FADH2 by the electron transport chain with the synthesis of ATP by phosphorylation of ADP
What is chemiosmosis?
A process that uses energy in a hydrogen ion gradient across the inner membrane to drive phosphorylation of ADP to form ATP
What is One gene/One polypeptide hypothesis?
A proposal that one gene codes for one polypeptide or protein
What is the triplet hypothesis?
A proposal that the genetic code is read three nucleotide bases at a time
What is an activator?
A protein that binds to a particular DNA sequence to regular transcription, it increases the rate of transcription of a gene or genes
What is a repressor?
A protein that binds to a particular DNA sequence to regulate transcription; inhibits the transcription of a gene or genes
What is a substrate?
A reactant that interacts with the enzyme is an enzyme catalyzed reaction
What is photorespiration?
A reaction of oxygen with ribulose-1-5-bisphosphate in a process that reverses carbon fixation and reduces the efficiency go photosynthesis
Explain why a redox reaction must involve changes to two molecules simultaneously.
A redox reaction involves the transfer of electrons from one molecule to another, therefore, both the molecule being oxidized and the molecule being reduced are charged at the same time
What is a nucleoid?
A region in the cytoplasm of bacterial cells where DNA is found
Define Telomere
A repetitive section of DNA, near each end of a chromosome, the presence of this sequence helps to protect from loss of important genetic information during replication of the linear DNA in eukaryotic cells
What is an operator?
A repressor protein that binds to a DNA sequence element; it regulates transcription
What is a cell wall?
A rigid layer surrounding plant, algae, fungal, bacterial and some archaea cells, composed of proteins and/or carbohydrates, gives the cell its shape and structural support
Define Regulatory Sequence
A sequence of DNA that regulates the activity of a gene
What is the promoter region?
A sequence of nucleotides in DNA that indicates where the RNA polymerase complex should bind to initiate transcription
Define metabolic pathway
A sequential series of chemical reactions in living cells, each reaction is catalyzed by an enzyme
What is a 3' poly-A-tail?
A series of A nucleotides added to the 3' end of mRNA
What is the electron transport chain?
A series of electron carriers and protein complexes embedded in the inner mitochondrial membrane that accept and donate electrons in a sequential series, resulting in oxidative phosphorylation
What is the genetic code?
A set of rules for determining how genetic information in the form of a nucleotide sequence is converted to an amino acid sequence of a protein, a code specifying the relationship between a nucleotide and an amino acid
What is a transposon?
A short segment of DNA capable of moving within the genome of an organisms, also called a jumping gene
Which type of mutation would be least harmful to an organism: silent, missense, or nonsense? Explain your answer
A silent mutation has no effect on the amino acids of a protein, and therefore would be the least harmful to an organism. Missense mutations cause alterations in the amino acid of a protein and nonsense mutations result in a shortened protein due to a premature stop codon
What is the Golgi Apparatus?
A stack of curved membrane sacs that packages, processes and distributes proteins, lipids and other substances within the cell, acts like a "post office" for the cell
What is a ribosome?
A structure composed of RNA and proteins and responsible for synthesis of polypeptides in the cytosol and on the surface of the rough endoplasmic reticulum
What is a polyribosome?
A structure composed of multiple ribosomes along a strand of mRNA
Define Nucleoid
A structure in bacteria that contains the chromosomal DNA
What is a lipid bilayer?
A structure with hydrophilic "heads" of phospholipids directed towards the aqueous environment and a hydrophobic "tail" directed towards the centre, interacting with each other
What is a molecule?
A substance composed of two or more non0metal atoms that are covalently bonded together
What is a buffer?
A substance that minimizes changes in pH by donating or accepting hydrogen ions as needed
What is an acid?
A substance that produces hydrogen ions, H+, when dissolved in water.
What is a base?
A substance that produces hydroxide ions, OH-, when dissolved in water
What is a catalyst?
A substance that speeds up the rate of chemical reaction by lowering the activation energy for the reaction, is not consumed in the reaction
What is membrane assisted transport?
A transport method used to move materials that are too large to cross the cell membrane thorough a channel or carrier protein
A triglyceride is a form of what? And what is it composed of?
A triglyceride is a form of lipid composed of fatty acids and glycerol
What is an anticodon loop?
A triplet bases positioned at one end of a tRNA that recognizes and base pairs with a codon on mRNA during protein synthesis
What is a start codon?
A triplet of three bases that specifies the first amino acid of a protein
Use a water molecule to describe the relationships among all the following: Polar and non-polar molecules Intramolecular and intermolecular forces Hydrophilic and hydrophobic interactions
A water molecule's intramolecular forces make it a polar molecule. As such, it's intermolecular interactions are dominated by attraction to other polar molecules (hydrophilic molecules since they are attracted to water) and it's inability to attract non-polar molecules (hydrophobic molecules, since they are not attracted to water)
What are hydrogen bonds?
A weak association between an atom with partial negative charge and a hydrogen atom with partial positive charge
In the absence of sunlight, plants cannot use the Calvin Cycle due to a lack of what?
ATP and NADPH
What is substrate level phosphorylation?
ATP formation from transferring a phosphate group to ADP
What is the genetic sequence for the start codon in the genetic code?
AUG
Which compound enters the Krebs Cycle for further breakdown?
Acetyl-CoA
Which processes may be involved in post transcriptional control in eukaryotic cells?
Adding a poly-A-tail to pre-mRNA molecules and adding a 5' cap to pre-mRNA
Which of the following types of DNA of nitrogen bases are present in a DNA molecule?
Adenine, Thymine, Guanine and Cytosine
Describe the similarities and differences between starch, glycogen and cellulose
All three are polysaccharides composed of many monosaccharides linked together, they are composed of many individual glucose monomers linked together covalently, and are macromolecules. They differ in that starch and cellulose are plant products, whereas glycogen is an animal product. Another difference is that the glucose monomers in cellulose are joined in by different glycosidic linkages than those found in starch or glycogen. The molecules also differ in function: cellulose is involved in structural support, but starch and glycogen are energy storage molecules
Describe the basic structure of an amino acid
An amino acid molecule is composed of a central carbon atom, bonded to an amino group, a carboxyl group, and a hydrogen atom. Each amino acid also has an R group bonded to the central carbon atom, providing the amino acid with it's unique identity
What is a functional group?
An atom or group of atoms attached to a molecule that gives the molecule particular chemical and physical properties
What is an ion?
An atom or group that has gained or lost one or more electrons, giving it a positive or negative charge
What is Aminoacyl-tRNA synthetase?
An enzyme responsible for attaching an amino acid to a tRNA
Define DNA Polymerase III
An enzyme that adds nucleotides to the 3' end of the growing polynucleotide strand (found in the elongation phase)
Define DNA ligase
An enzyme that catalyses the joining of Okazaki fragments (Found in elongation phase, synthesized lagging strand)
Define DNA polymerase II
An enzyme that proofreads newly synthesized DNA (Found in the Termination phase)
Define DNA Polymerase I
An enzyme that removes RNA primer and fills the gaps between the Okazaki fragments on the lagging strand with DNA nucleotides, proofreads newly synthesized DNA (Found in the elongation phase, synthesized lagging strand)
What is a mutagen?
An event or substance that increases the rate of changes to the DNA sequence of an organism's genome
What is the mitochondrion?
An organelle in eukaryotic cells in which high energy organic molecules are oxidized to obtain energy
What is a chloroplast?
An organelle in the cells of photosynthetic organisms in which light energy from the sun is captured and stored in the form of high energy organic molecules such as glucose.
What are amino acids?
An organic molecule composed of a central carbon atom bonded to a hydrogen atom, an amino group, a carboxyl group and a variable R group
What are radioisotopes?
An unstable isotope that decays over time by emitting radiation
A DNA sequence and it's complement are comparable to a codon and its?
Anti-codon
What is an isotope?
Atoms of the same element that have different numbers of neutrons
What were the results of the experiments on s.pneomoniae done by Avery, MacLeod and McCarty?
Avery, MacLeod and McCarty conducted a series of experiments and discovered that: - When they treated heat-killed pathogenic bacteria with a protein-destroying enzyme, transformation still occurred - When they treated heat-killed pathogenic bacteria with a DNA-destroying enzyme, transformation did not occur. These results provided strong evidence for DNA's role in transformation
If protein were the hereditary material, what would Hershey and Chase have seen in the results of their experiments?
Bacterial cells that are infected by viruses with P-labelled DNA would not be radioactive. Bacterial cells infected with S-labelled capsid proteins would be radioactive
When making bread, bakers add warm water to the yeast before mixing it with the flour. Why is this a good idea?
Bakers use yeast to help the dough rise when baking bread. The reason as to why bakers add warm water to yeast before mixing it with the flour is because yeast is temperature sensitive. The primary function of yeast is to produce CO2 gas through fermentation. Fermentation is a cellular respiration pathway that transfers electrons from NADH back to organic acceptors (NAD+), this will activate energy release
When does oxidative phosphorylation occur?
- At the end of the respiratory chain - In and between cytochromes - Using a H+ concentration gradient
The chemical elements that are most common in living organism are?
- Carbon - Hydrogen - Oxygen - Nitrogen - Phosphorus
Which factors do not impact enzyme activity?
- Changes in temperature - Changes in substance concentration - Changes in pH - Changes in ionic concentrations
DNA replication is called semi-conservative why?
Because half of the original duplex appears in the duplex formed during replication
Why is water necessary for photosynthesis?
Because it provides the electrons to replace the lost electrons in photosystem 2
Explain why proteins are more structurally and functionally diverse than carbohydrate and lipids.
Because proteins can be built from many different monomers (there are 20 common amino acids) the many different properties of the amino acids (polar, non-polar, acidic or basic, and the reactivity of those specific functional groups found as part of their R groups), and the many different linear sequences of amino acids that are responsible.
Why is the one gene/one polypeptide hypothesis inconsistent with the existence of tRNA?
Because the genes that code for tRNA produce tRNA molecules, which are not translated into proteins
"Hydrogen bonding in water gives it some unique properties" Comment on this statement.
Because the intramolecular force between the water molecules are weak, water has a very low melting point, boiling point, surface tension and heat of vaporization compared to others common solvents. In addition, the unique networkings of the Hydrogen bonds in water give it more unique properties including: the ability of water molecules to surround ions and diminish the attraction of opposite charges for each other, solid state has less density than liquid state and thus has a negative volume of melting.
Why are glucose, fructose, and galactose isomers?
Because they have the same molecular formula (C6H12O6) but different three dimensional structures
In what ways are lipids similar to and different from carbohydrates?
Both are organic molecules and are used for storing energy in cells. Lipids, however, have a greater proportion of carbon and hydrogen atoms and fewer oxygen atoms and, in general, are hydrophobic. Carbohydrates are polar, hydrophilic molecules
What property of waxes is common in both plants and animals? Give an example and it's significance in a specific plant and a specific animal
Both are solids at room temperature. In plants such as trees, waxes coat leaves, preventing water loss and offering protection from insects In animals such as ducks, a waxy layer on feathers prevents them from getting wet, which would add weight and make it difficult to fly.
An example of a condensation reaction would be?
Building lipids from fatty acids
How is ATP produced in glycolysis and the Krebs Cycle?
By substrate level phosphorylation
How is a polymer formed from multiple monomers?
By the removal of an -OH and a hydrogen atom
Which organisms have the greatest problem with photorespiration?
C3 plants
What is the photosynthetic process used by some plants to survive in a hot dry climate, like the dessert?
C4 photosynthesis
What is the general or summary equation that describes cellular respiration, and must it be a summary of this process, rather than an ordinary chemical equation?
C6H12O6 + O2 = CO2 + H2O + energy. The chemical equation represents the combustion of sugar, a one step reaction. Since cellular respiration takes more than two dozen reactions, this must represent a summary of those processes `
What is the summary equation for photosynthesis?
CO2 + H2O + sunlight —> C6H12O6 + O2
The dark reaction in photosynthesis is limited by?
CO2, temperature and light
What do glycoproteins and glycolipids have in common?
Carbohydrates are covalently bonded to them
What is the source of the carbon in sugar produced during photosynthesis?
Carbon Dioxide
Which molecules are directly shared between the calvin cycle and the Krebs Cycle?
Carbon Dioxide
Explain, with reference to subatomic particles and stability, the difference between carbon-12 and carbon-14.
Carbon-12 has an atomic mass of 12 and has 6 neutrons whereas carbon-14 has 8 neutrons and an atomic mass of 14. Carbon-12 is very stake (and thus very common) compared to carbon-14 which is unstable and radioactive
What is aerobic respiration?
Catabolic pathways that require oxygen
Differentiate between cellular respiration and aerobic respiration
Cellular respiration includes the catabolic pathways that break down energy rich compounds to produce ATP while aerobic respiration refers to those pathways that require oxygen in order to proceed
What makes starch different from cellulose?
Cellulose forms long filaments, while starch is highly branched
Chef's often place salad greens in water to make the vegetables crispy. What organelle is principally responsible for the increase in plant cell rigidity?
Central Vacuole
Define Chargaff's rule. How did Chargaff's findings overturn earlier beliefs about DNA?
Chargaff's rule states that in the DNA nucleotides, the amount of adenine will be more or less equal to than the amount of thymine, and the amount of guanine will be more or less equal to then the amount of cytosine. The number of A-T nucleotides will not necessarily equal the number of C-G nucleotides. This overturned Levene's earlier hypothesis that the nucleotides occurred in equal amounts and were present in a constant repeated sequence.
The light reaction in photosynthesis does not include?
Charge Seperation
What is exergonic?
Chemical reaction that releases energy
What is endergonic?
Chemical reaction that requires energy
The generation of ATP by the movement of hydrogen ions down their concentration gradient across a membrane occurs because of a process called what?
Chemiosmosis
During photosynthesis, photons raise electrons to higher energy levels. These excited electrons belong to what compound?
Chlorophyll
Identify two examples of steroids, and explain their significance.
Cholesterol is an important component of animal cell membranes and it's the precursor used for making many other steroids. Estrogen is an important determinant of sexual function in females and helps regulate the storage of fat.
What is a reading frame?
Collectively the codons of mRNA that are read to produce an amino acid sequence, it is set by the start codon
There are four major types of chemical reactions that break apart and build biological molecules. For each type, write a sentence that summarizes a key defining feature that distinguishes it from the others.
Condensation reactions — which build molecules and release a molecule of water that is used to donate H- atom and an OH-group that are removed from the combining molecules Hydrolysis Reaction — Breaks apart molecules and consume a molecule of water that is used to donate an H-atom and an OH-group to the products Oxidations — Remove electrons from molecules, generally by breaking apart covalent bonds and forming a simpler, less complex product or products Reductions — Always accompany oxidations. They add electrons to molecules, typically building them up into larger, more complex molecules
What are constitutive genes and why are they important for cell survival?
Constitutive genes code for proteins that are needed for cell survival. Therefore, they are always active and are expressed at constant levels
Three important characteristics of the genetic code are continuity, redundancy, and universality. Explain what is meant by each of these terms
Continuity - The genetic code is read without commas, punctuations or spaces. It's read three genes at a time Redundancy: The genetic code can code for more than one amino acid Universality: The genetic code is universal for almost all organisms, therefore, a fruitfully will have the same genetic code as humans
The leading strand of DNA is synthesized in which direction?
Continuously in a 5' to 3' direction
Hydrogen Cyanide is a deadly poison. Explain how hydrogen cyanide inhibits aerobic respiration.
Cyanide act as an inhibitor of ETC (electron tranport chain) which ultimately inhibits the production of ATP (adenosine triphosphate), it disrupts the cellular respiration, quickly inhibiting the cytochrome C oxydase. So in result there is no Glycolysis or Krebs cycle and it results in death
According to Chargaff's rule, the following proportion exists in DNA
Cytosine = Guanine
How can the four bases that are found in DNA account for all the diversity on Earth?
DNA is the blueprint for all living organisms. DNA has only four nitrogenous bases (adenine, thymine, guanine and cytosine). These bases line up in a specific order and code for all 20 amino acids. The term is called universality because there has not been any other code or system found on any living organism on Earth.
Since the first nucleotides cannot be linked in a newly synthesized strand in DNA replication, what enzyme is required?
DNA polymerase
Describe one way that errors in replication are corrected
DNA polymerase have a proofreading function, where they excise incorrect bases and add the correct base.
Why is DNA replication important for cell reproduction?
DNA replication occurs during the S-phase of interphase, and prior to the cell division. Therefore, DNA replication is important since each new daughter cell must have the same genetic information as the parent cell.
Why does DNA replication require numerous enzymes?
DNA replication requires the use of many enzymes that have specific roles. The presence of numerous specialized enzymes may reflect the importance of having accurate DNA replication, since mutations in DNA can change the genetic makeup of an organism.
Dessert plants use CAM carbon fixation, in which carbon dioxide uptake occurs during the night. The carbon is then fixed for use in the daylight hours, when photosynthesis occurs. Hypothesize why desert plants take in carbon dioxide during the night.
Dessert plants take in carbon dioxide at night because the opening of stomata in CAM plants are opposite from most plants. The stomata are opened at night and closed in the daytime. When the carbon dioxide is removed from the four carbon compound malate in the daytime, it cannot leave the cell because the stomata are closed. In cool climates, CAM plants are very inefficient because they use energy to drive the reactions that store carbon dioxide
Oxygen enters a cell by which process?
Diffusion
What is common to both mitochondria and chloroplast?
Double Membrane
What is the second law of thermodynamics?
During any process, the universe tends toward disorder
Where does the membrane of a vesicle become part of the cell membrane?
During exocytosis
Differentiate between a hydrolysis reaction and a condensation reaction.
During hydrolysis, water us consumed (used as a reactant) by the reaction. During a condensation reaction, water is produced (released)
How do cells synthesize multiples strands of mRNA from one gene simultaneously? Why is this advantageous?
During the elongation phase of transcription, a second RNA polymerase complex can bing to the promoter region immediately after the previous RNA polymerase complex starts moving along the DNA. Therefore, multiple strands of mRNA can be synthesized from one gene at a time. This is advantageous for the cell since increased amounts of mRNA leads to more protein that can be produced in a given amount of time
During what stage of photosynthesis are ATP and NADPH converted to ADP + Pi and NADP+?
During the light independent reactions
While observing plant cells, a student noticed that chloroplasts appeared each of the cells. Before the observation she had expected to see the chloroplasts at the periphery of the cell near the cell wall. How can the students observation be explained?
During the preparation the cells may have been exposed to a hypertonic solution that resulted in plasmolysis
Explain why for each molecule of glucose that enters glycolysis there is more than one turn of the Krebs Cycle?
Each molecule of glucose produces two molecules of pyruvate. Each pyruvate goes through the Krebs cycle independently
Why is it important for newly replicated daughter strands of DNA to have the same information as the parent strand?
Each new cell that is produced must have an exact copy of parental DNA. The daughter strands of DNA are part of a DNA molecule that will be in the daughter cells. This ensures that newly born cells are similar to parents and maintain their genetic material.
Why do phospholipids placed in water form bilayers?
Each of the molecules has a polar and non-polar region
What is the advantage of plant leaves having a variety of photosynthetic pigments, rather than just chlorophyll?
Each pigment has an ideal wavelength of light that it absorbs, meaning that a wider variety (range) of wavelengths can be absorbed
Aerobic respiration ceases without oxygen because oxygen is a reactant in which pathway?
Electron Transport Chain
Which process would yield the greatest amount of energy in animal cell respiration?
Electron Transport Chain
What is the relationship between elements and atoms?
Elements are pure substances that cannot be broken down into simpler components by normal means. Atoms are the smallest units of elements that have all of an elements properties
What is pinocytosis?
Endocytosis involving liquid particles
What is phagocytosis?
Endocytosis involving solid particles
What is the first law of thermodynamics?
Energy cannot be created or destroyed, but it can be transferred from one type into another snd transferred from one object to another
What is free energy?
Energy from a chemical reaction that is available for doing work
Identify two functions of carbohydrates in living systems
Energy source and structural support
Regarding enzymes what is not true?
Enzyme reaction rate decreases as the concentration of substrate increases
Why would an enzyme be unable to catalyze many different types of reactions?
Enzymes are unable to catalyze many different types of reactions because the shape of an active site is usually very substrate specific. This specificity limits the ability of an enzyme to perform different types of reactions on different molecules
Outline and describe the ways in which an enzyme can prepare a substrate for a reaction.
Enzymes can prepare substrates for a reaction by altering the substrate, it's environment, or both. Substrate changes can involve the alteration of bond lengths or bond angles, the addition or removal of electrons, and or the addition or removal of H-ions or functional groups. Environmental changes may involve providing an acidic or basic environment at the active site and/or holding substrates together snd in the best orientation relative to one another
Would errors in transcription be more or less damaging than errors in DNA replication? Explain.
Erros in transcription would be less damaging than errors in DNA replication. An error in transcription would result in an error in one protein molecule, while an un-repaired error in DNA replication would cause a change in the genetic makeup of an organism
Why are enzymes important to biological systems if the reactions they facilitate will occur naturally with or without the presence of enzymes?
Even though many important biological reactions can occur naturally without an enzyme, their rates are often too low to support the needs of the cell or organism. Enzymes are important to biological systems because they help speed up these reactions to up the rate required to sustain life.
In the light dependent reactions, when light strikes the pigments (P700 and P680) what is the immediate result?
Excited electrons are passed to electron receptors
What transport mechanism exports materials from a cell without using a transport protein or the movement of the material directly through the lipid bilayer?
Exocytosis
True or False. During semiconservative replication, the original double helix remains intact and a new double helix forms.
False
True or False. Light driven electron transport in the chloroplast pumps H+ into the inter membrane space between the outer and inner membranes.
False
How many carbon atoms are in a molecule of RuBP?
Five
Some scientist do not use the lock - key analogy to describe the enzyme-substrate complex, because of the rigid structure that it seems to imply. Describe this analogy, and explain why it is not completely accurate.
For every lock there is key that just fits, for every enzyme there is a substrate that just fits. However, the enzyme actually recognizes the incoming substrate and binds perfectly to the substrate. This analogy only explains how an enzyme works at a basic level.
How many G3P's must be produced in order to make one glucose molecule? What is the function of the other G3P molecules?
For every twelve G3P molecule made in the Calvin cycle, two are used to make glucose. The other ten G3P are used to generate six RuBP
How did the work of Franklin and Pauling contribute to the Watson and Crick model of the DNA?
Franklin used X-ray photography to analyze the structure of DNA. Her observations provided evidence that DNA has a helical structure with two regularly repeating patterns. She also concluded that the nitrogenous bases were located on the inside of the helical structure and the sugar-phosphate backbone was located on the outside, facing toward the watery nucleus of the cell. Pauling's method of assembling three dimensional models of compounds led to the discovery that many proteins had a helical structure. Watson and Crick also used this information to propose that DNA had a helix shape.
Which scientist first isolated nuclein?
Freidrich Miescher
The final product of the Calvin Cycle is?
G3P
What product of the Calvin Cycle is used in a variety of additional reactions?
G3P is used in a variety of additional reactions
How did Garrod's findings demonstrate a link between genes and proteins?
Garrod's studies on alcaptonuria showed that having the black urine phenotype was due to a recessive inheritance factor that caused that production of a defective enzyme
An important function of the electron transport chain is to?
Generate a hydrogen ion gradient
Explain, using at least four functional examples, why proteins represent a diverse type of macromolecule?
Given the many different ways there are of ordering the 20 common amino acids, proteins exhibit tremendous diversity in structure and function. The protein fibres that lend structural support to tendons, transport proteins such as hemoglobin that carry oxygen in blood, enzymes that catalyze specific biological reactions, and antibody proteins that fight infections
ATP supplies the energy that drives most cellular activities. What is ultimate source contained in ATP?
Glucose
What energy rich organic compound is produced as a result of the Calvin cycle?
Glucose
What are the reactants in the equation for the metabolism of glucose by aerobic respiration?
Glucose + oxygen
Quickly summarize the function of the Krebs Cycle
Glucose is oxidized to carbon dioxide and water to produce usable energy in the form of ATP Acetyl CoA molecules donate two carbons to oxoloacetate and in the process of oxidizing twi carbon atoms, one turn of the cycle produces four NADH molecules, one FADH2 molecule and phosphorylates one ADP
Which pathway is common to both aerobic and anaerobic respiration?
Glycolysis
What is glycolysis, and what are it's starting materials and products?
Glycolysis is the metabolic pathway that breaks down glucose into two pyruvate molecules (ATP)
Describe the overall process of metabolizing glucose
Glycolysis, Pyruvate Oxidation, Krebs Cycle, Electron Transport Chain, Oxidative Phosphorylation
What are the five steps that metabolizes glucose?
Glycolysis, Pyruvate Oxidation, Krebs Cycle, Electron transport chain, oxidative phosphorylation
What are the stages of energy transfer from to ATP in a general overview of aerobic respiration, and in what parts of the mitochondrion do they occur?
Glycolysis-cytosol, pyruvate oxidation, and Krebs Cycle and oxidative phosphorylation
Plants are green, but a plant with only wavelength's of light will barely survive. Explain why?
Green pigments (like chlorophyll) reflect green light. The other colour wavelength's are absorbed by the plant for photosynthesis
How did Griffith test for the existence of a transforming principle?
Griffith used two types of the s.pnemoniae bacteria on mice, one of them (S-strain) was highly pathogenic but could be made non-pathogenic when heated. The other form was the (R-strain) and was non-pathegenic, he discovered that mice after being injected with a mixture of the heat killed S-strain and living R-strain, he concluded the the S-strain had passed on it's deadly properties to the live, non-pathogenic R-strain, he called this the transformation principle
The earliest photosynthesizers probably used what as a source of hydrogen?
H2O
Explain why it is advantageous for cells to synthesize an mRNA messenger.
Having RNA as an intermediate that can transport from the nucleus to the cytoplasm is preferred over DNA having to continually transport itself, which could increase the likelihood of damage to the DNA. Multiple steps in gene expression provide many opportunities for regulation. This allows the cell to have increased control over protein synthesis
In replication of DNA, the helix is opened and untwisted by which enzyme?
Helicase
Define Primer
In DNA replication, a short segment of RNA that is complimentary to a part of the 3' to 5' DNA template strand and serves as a starting point for addition of nucleotides (Found in the elongation phase, synthesis of the lagging strand)
Define Complementary Base Pairing
In DNA, the interaction of bases of nucleotides on opposite strands through the formation of hydrogen bonds
Define Chargaff's rule
In DNA, the percent composition of adenine is the same as thymine, and the percent composition of cytosine is the same as guanine
Describe the composition of a buffer. Briefly explain how a buffer works to maintain a constant pH.
In order to maintain optimum ranges of pH, organisms rely on buffers. Buffers are substances that resist changes in pH by releasing hydrogen ions when a fluid is too basic and taking up hydrogen ions when a fluid is too acidic. Most buffers exists as specific pairs of acids and bases. For example, one of the most important buffer systems in human blood involves the pairing of carbonic acid, H2CO3, and hydrogen carbonate ions, HCO3-.
(Using the diagram of a methane molecule) In which part of the molecule is the stored energy that is most important in chemical reactions?
In the covalent bonds
What is the location of the enzymes that catalyze the Krebs Cycle reactions?
In the mitochondrial matrix
What is the location of the enzymes that catalyze the krebs cycle reactions?
In the mitochondrial matrix
In which phase of DNA replication is the replication bubble created?
Initiation
Briefly describe the three stages of DNA replication. Name the enzymes that are involved and their roles in each stage of the process. (Note: The same process can be used to amplify or make copies of DNA in the lab: provided that you are adding all enzymes in the test tube or the media used to bring about DNA replication) do not get confused if this question is asked in a different way)
Initiation: Helicase enzymes cleave the hydrogen bonds that link the complementary base pairs between strands together. Once the double helix has been opened it is stabilized by single strand binding proteins. Topoisomerase II enzyme helps to relieve the strain on the double helix, and a replication bubble forms. Elongation: The elongation phase synthesizes the new DNA strands by joining individual nucleotides together. DNA polymerase III is the enzyme that catalyzes the addition of new nucleotides, it attaches the new nucleotides to the free 3' hydroxyl end of the pre-existing chain of nucleotides. Synthesis of the lagging strand requires DNA polymerase to move away from the replication fork. Synthesis of the lagging strand is done in short segments called Okazaki fragments. The short fragments of nucleotide sequences that are used to start or "prime" replication of the lagging strand are strands of RNA primers (RNA primase).For the synthesis of the lagging strand, several primers are used as the replication proceeds. DNA polymerase I, removes the RNA primer and fills in the space by extending the neighbouring DNA fragments. The Okazaki fragments are are joined together by DNA ligase. Termination: As soon as the newly formed strands are complete, the DNA rewinds automatically into their chemically stable double helix. DNA polymerase I along with DNA polymerase II proofread the newly replicated DNA to check for error, if error is found it is replaced with the correct one.
Lactate fermentation occurs in muscle cells when?
Insufficient oxygen is available
How does the reaction centre pigment differ from the other pigment molecules of the light harvesting complex?
It differs because the reaction centre pigment transfers excited electrons to other molecules
A point mutation in a polypeptide changes the codon 5'-UCA-3' to 5'- UUA -3'. How does this mutation affect the polypeptide?
It has no effect on the polypeptide
What role does ribulose-1,5-bisphosphate play in the calvin cycle?
It is a 5C compound that CO2 immediately binds to. It is unstable and breaks apart into two 3C compounds. This creates the cyclic nature of the calvin cycle
What is a mutation?
It is a permanent change in the nucleotide sequence of a cell's DNA
Light is required for the light dependent reactions because?
It is the source for electrons
What happens to the pyruvate generated in glycolysis before it enters the Krebs Cycle?
It looses a carbon in the form of CO2, and it's oxidized by NAD resulting in NADH. The remaining two carbons are attached to a coenzyme called CoA
Where does the Calvin Cycle take place?
It occurs in the Mitochondria
What did the identification of the transforming principle prove?
It proved that genetic information is contained in DNA
Which idea does the "universality" of the genetic code provide evidence for?
It proves that all living things likely evolved from one common ancestor
What does a splicesome do?
It removes introns from a pre-mRNA molecule to create the final m-RNA
Why is the balanced chemical equation for photosynthesis referred to as an overall equation?
It represents the overall sum of many reactions. It is an oversimplification because water and carbon dioxide don't simply join together to make glucose
What did the Hershey-Chase experiment show?
It showed that the virus protein wasn't responsible for directing the production of new viruses, and that DNA was the hereditary material.
What does the first law of thermodynamics state?
It states that energy cannot be created or destroyed, energy can be transformed from one to another, energy in the universe is constant and energy can be transferred from one object to another
What would a toxin that makes holes in the inner membrane of the mitochondria do?
It would stop ATP synthesis
In nucleic acids, what is the phosphate group attached to?
It's attached to the 5' end of the carbon sugar
What is intramolecular?
It's occurring between atoms within a molecule
What happens in the initiation phase of DNA replication?
It's the point where separation of the DNA occurs
How did Jacob and colleagues show that RNA acts as a "genetic messenger"?
Jacob and colleagues saw that bacteria infected with a virus had a newly synthesized virus-specific RNA molecule. This RNA molecule associated with bacterial ribosomes, which are the sites of protein production. Therefore, the RNA molecule carried the genetic information for the production of a viral protein
What is the energy of motion?
Kinetic Energy
The energy of motion is?
Kinetic energy
What process causes your leg muscles to feel sore after an intense workout?
Lactate fermentation
If anaerobic conditions continue in animal tissue following glycolysis, which substance will be produced?
Lactic Acid
Which situation would result in plasmolysis?
Leaving a plant cell in a hypertonic solution
Compare the light dependent and light independent reactions of photosynthesis
Light Dependent Only: Use light to make ATP and NADPH. Also uses water Light Dependent and Light Independent Reactions: Both occur in the chloroplast Light Independent Only: Uses ATP and NADPH to create glucose
What is wax?
Lipids composed of long carbon based chains that are solids at room temperature
Explain why lipids are efficient energy storage molecules
Lipids have many energy rich C-H bonds in their long hydrocarbon chains
Which wavelengths are absorbed by chlorophyll a?
Long wavelength light (such as red) Short wavelength light (such as blue)
Which organelle uses enzyme catalyzed hydrolysis to break down macromolecules into simpler molecules?
Lysosomes
What are nucleic acids?
Macromolecules composed of nucleotide monomers
Photosynthesis and cellular respiration both?
Make use of an electron transport chain
What are the immediate products of C3 and C4?
Malic acid and Glucose
Explain why control at the level of transcription saves considerable cellular energy for bacteria?
Many genes in bacteria are clustered together in operons and are therefore under transcriptional control of a single promoter. This type of transcriptional control is energy efficient since these genes are transcribed together into a single polycistronic mRNA, rather than individual mRNA molecules. Individual proteins are then synthesized from the polycistronic mRNA.
Why is it important that cells are able to replicate DNA quickly and accurately?
Many tissues and organs require continuous regeneration of new cells. Therefore, DNA replication must be quick and accurate since new daughter cells must receive exact copies of DNA from the parent cell.
In the fluid mosaic model of membranes, what does the term "mosaic" tell us about membranes?
Membranes are composed of a mixture of substances
What did Meselson and Stahl conclude from their experiment?
Meselson and Stahl concluded that DNA replication is semi-conservative. After one round of replication, DNA appeared as a single band, midway between the expected positions of 15N-labelled DNA and 14N-labelled DNA. After the second round of replication, DNA appeared as two bands, with one band corresponding to 14N-labelled DNA and other band in the position of hybrid DNA (half 14N and half 15N). In additional rounds of replication, the same two bands were observed, therefore supporting the semi-conservative model.
Which amino acid is coded for by only one codon sequence?
Methionine
How is it possible that some, but not all, mutations get passed from one generation to the next?
Mutations that occur in reproductive cells can be passed onto future generations. Mutations which occur in somatic cells do not get passed on to future generations
During glycolysis high energy electrons released from the intermediate compounds are first accepted by what?
NAD+
Explain what NADH is and how it is produced
NAD+ is reduced to form NADH, an energy-rich electron carrier that allows for the production of ATP
Coenzymes are an important part of your diet. Briefly describe the role of one coenzyme in cellular respiration.
NAD+ is used in cellular respiration to carry electrons from one enzyme controlled reaction to another. NAD+ reduced to NADH which carry energy-rich electrons to the ETC for the production of ATP.
In the Krebs Cycle, the oxidation of energy-rich compounds produces the reducing power of what?
NADH and FADH2
Which compounds are the electron donors in the electron transport chain?
NADH and FADH2
The largest single source of energy resulting in oxidation of one molecule of glucose comes from?
NADH produced in the Krebs Cycle
What is the final destination of the electrons released from water in photophosphorylation?
NADPH
The electron flow that occurs in the photosystem 1 during noncyclic photophosphorylation produce what?
NADPH and ATP
Why did Meselson and Stahl use two different isotopes of nitrogen in their experiment?
Nitrogen is a component of DNA and is incorporated into newly synthesized daughter strands. Having a "light" form of (14N) allowed the separation of different DNA strands based on the amount of isotope present in the newly synthesized DNA. DNA with more (15N) would be denser than DNA with 14N, and therefore could be separated by centrifugation
Many manufactures claim that their personal care products are "pH balanced". What might this term mean? Do consumers need to know that these products are pH balanced?
No, consumers don't need to know that the products are pH balanced because it doesn't make a difference to their skin. Companies say their products are pH balanced so that consumers think that it's better for their skin. The acidic conditions of the skin are caused by normal secretions from sweat glands and the breakdown of fatty acids on the skin by good bacteria that live on our skin. Together these secretions create the "acid mantle," a natural covering which protects the skin.
Would a frameshift mutation occur if six nucleotides were deleted in a sequence of DNA? Explain your answer
No, since the deletion of nucleotides is divisible by three.
Distinguish between cyclic and noncyclic phosphorylation
Non-cyclic photophosphorylation produces ATP, NADH and oxygen gas. The electron flow is unidirectional form water to NADP. Cyclic phosphorylation only produces ATP. Electrons cycle and, therefore, no source of electrons (water) or sink for electrons (NAD) is requires. Excited electrons leave photosystem 1 and are passed to an electron acceptor. From the electron acceptor, they pass to be b6-F complicate back to the photosystem 1. The proton gradient is generated in the same manner as in non-cyclic photophosphorylation, and ATP synthesis by chemiosmosis occurs
In the early model of DNA tested by Watson and Crick, the sugar phosphate handrails were on the inside of the helix and the nitrogenous bases were protruded outward. How is this model inconsistent with experimental evidence about the structure of DNA?
Nucleic acids are soluble in water. Therefore, the nitrogenous bases, which are somewhat hydrophobic, most be positioned away from the water found in the nucleoplasm, and the polar phosphate group (which are hydrophilic must be on the outside of the molecule, interacting with water.
What is the same of each unit of nucleic acid consisting of a sugar, attached phosphate group and is a base?
Nucleotide
How do nucleotides in DNA differ from nucleotides in RNA?
Nucleotides in DNA have a deoxyribose sugar, while nucleotides in RNA have a ribose sugar with a hydroxyl group at carbon 2. In addition to the sugar group each nucleotide is attached to a phosphate group and a base. The bases are adenine, cytosine, guanine, thymine in the case of DNA and adenine, cytosine, guanine, and uracil in the case of RNA
The calvin cycle requires each of the following inputs except? a) ATP b) NADPH c) O2 d) CO2
O2
Anaerobic respiration or fermentation does NOT:
Occur in the presence of oxygen
What is intermolecular?
Occurring between atoms of different molecules
Briefly describe the reason for the formation of Okazaki fragments
Okazaki fragments are formed so that the lagging strand of DNA can be replicated. For the synthesis of the lagging strand DNA polymerase III has to move away from the replication fork, for this it need the assistance of several primers to be used as the replication proceeds. Once each primer is added, a new DNA fragment is generated from the end of each primer. These fragments are called Okazaki fragments that each begin with a section of RNA. DNA polymerase I then removes the RNA primer and joins the Okazaki fragments
How would DNA replication be affected if there were a mutation in the gene that codes for DNA ligase?
Okazaki fragments would be be joined
Explain why the leading and lagging strands of a DNA molecule are replicated.
On the leading strand, DNA synthesis takes place along the DNA molecule in the same direction as the movement of the replication fork. The lagging strand is synthesized in short segments called Okazaki fragments.
What happens in the semiconservative theory?
Once DNA has been replicated it results in two identical daughter molecules each consisting of one old (parent) strand and one newly synthesized strand.
Given the current understanding of aa-RNA formation, how many different activating enzymes must a cell posses?
One for each type of t-RNA molecule
What is a transcription factor?
One of a set of proteins required for initiation of transcription, it is required for the RNA polymerase complex to bind to the promoter
What is a thylakoid?
One of many interconnected sac-like membranous disks within the chloroplast, containing the molecules that absorb energy form the sun
What is an isomer?
One of two or more molecules with the same number and type of atoms, but different structural arrangements
What is a photosystem?
One of two protein-based complexes composed of clusters of pigments that absorb light energy
Which is the main difference between cyclic and non-cyclic photophosphorylation?
Only photosystem 1 is used during the cyclic process
Which molecule links glucose oxidation, fatty acid metabolism, and the catabolism of some amino acids to the Krebs Cycle?
Oxaloacetic Acid
What is oxidative phosphorylation and when does it generate ATP?
Oxidative phosphorylation is the formation of ATP using energy obtained from redox reactions in the electron transport chain. In the process, the enzyme ATP synthase adds Pi to ADP molecules to make ATP after the krebs cycle is complete
Which compounds of the light-dependent reactions participates in both cyclic and noncyclic photophosphorylation?
P680
What processes occur during the reduction of phase of the calvin cycle?
PGA is energized by ATP through phosphorylation and reduced by NADPH to produce G3P
What do peaks and the trough mean?
Peaks represent greater light absorption. Troughs indicate that more reflection of light (less absorption) has occurred
A polypeptide chain is held together by what?
Peptide bonds
Which organelle is involved in the synthesis of bile acids and redox reactions that break down toxic substances?
Peroxisomes
Which scientist is credited with determine the chemical nature of DNA?
Pheobus Levine
Describe the relationship between photosynthesis and cellular respiration
Photosynthesis uses solar energy to convert inorganic's to energy rich organics, cellular respiration breaks down energy-rich organics to synthesize ATP
Distinguish among the following terms: - Photosynthesis - Photo system - Photosynthetic unit - Photolysis
Photosynthesis — is a process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can be later released to fuel the organisms' activities. Photosystem — One of two protein-based complexes composed of clusters of pigments that absorb light energy Photosynthetic unit — s a complex of pigments and proteins coupled to a reaction center where the initial light-driven charge separation of photosynthetic reactions takes place. Photolysis — or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule. Photodissociation is not limited to visible light
List four major differences between Photosystem 680 and Photosystem 700
Photosystem (700) - located at the outer surface of the grana thylakoid membrane - Pigments absorb longer wavelengths of light - It participates in cyclic and non cyclic photophosphorylation - It is not associated with the photolysis of water. Main function is ATP synthesis Photosystem 680 - Located at the inner membrane of the grand thylakoid membrane - Pigments absorb shorter wavelengths of light - Only participates in non-cyclic photophosphorylation - Main functions are ATP synthesis and hydrolysis of water
What is affected by errors in transcription?
Polypeptides formed during translation
A roller coaster has ascended the first hill and is ready for the first drop. As it rolls downhill, what kind of transformation energy has occurred?
Potential energy has been transformed to kinetic energy
Which cellular process directly uses the energy of ATP hydrolysis to move molecules against their concentration gradient across a membrane?
Primary Active Transport
Summarize the four levels of organization in protein structure.
Primary: the linear sequence of amino acids Secondary: Regions of repetitive structure seen in many different proteins Tertiary: The overall three dimensional shape of the protein Quaternary: The association of more than one polypeptide to form an intact protein
Identify the products of a neutralization reaction, and explain how the reactions changes the properties of the reacting acid and base
Products are a salt (an ionic compound) and water. The reaction neutralizes both the acid and the base and the loses its acidic properties and the base loses its basic properties
How does RNA differ from DNA?
RNA contains ribose and DNA contains deoxyribose
Why does transcription proceed much more quickly than DNA replication?
RNA polymerase doesn't proofread the growing RNA molecule
Colours of light most useful in photosynthesis are?
Red, Violet, and Blue
What is hydrophobic?
Refers to non-polar molecules that do not have attractive interactions with water molecules
What is hydrophilic?
Refers to polar molecules that have attractive interaction with water molecules
Allosteric sites are responsible for what?
Regulating enzyme activity
In prokaryotic genomes, which regions determine when certain genes and the associated cell functions are activated?
Regulatory sequences
Why does elongation take place in a slightly different way on each DNA strand?
Replication takes place in a slightly different way on each DNA strand because DNA polymerase can only catalyze elongation in the 5' to 3' direction. In order for both strands to be synthesized simultaneously, the method of replication must differ.
What pigment is used in human vision?
Retinal
Which carbohydrate would you find as part of a molecule of RNA?
Ribose
The majority of the G3P produced during the reduction and carbohydrate production phase is used to produce what?
RuBP to continue the cycle
Carbon fixation is catalyzed by what enzyme?
Rubisco
During the first phase of the Calvin Cycle, carbon dioxide is incorporated into ribulose bisphosphate to form what?
Rubisco
The following table gives the amount of each base, as percent, found in DNA collected from four samples of animal of the same species? Sample: A T G C 1 34 33 17 16 2 33 34 16 17 3 21 21 29 29 4 39 37 10 14
Samples 1 and 2
Explain why people once believed that the main hereditary factors were proteins rather than nucleic acids.
Scientist knew that the hereditary material had to have the ability to control the production of some enzymes and proteins, replicate itself with great accuracy and allow occasional mutations to introduce variety between species. Proteins were known to be composed of 20 amino acids which meant that proteins could produce millions of different proteins, while nucleic acids were composed of only four bases and could only make limited potential combinations, this led scientist to believe that proteins were the hereditary material.
What is a goal for scientist who are attempting to to mimic certain natural processes in the laboratory?
Scientist want to mimic the splitting of water by photosystem II because hydrogen is a clean source of energy.
The results of the Meselson-Stahl experiment supported which model of the DNA replication?
Semi-conservative model
Rosalind Franklin contributed to Watson and Cricks discovery of the structure of DNA. What field did Franklin conduct her research?
She conducted her research in X-Ray Crystallography
Define Okazaki Fragments
Short DNA fragments that are generated during the synthesis of the lagging strand in DNA replication (found in the elongation phase).
What is the difference between gene mutations and chromosomal mutation?
Single gene mutations involve changes to a the nucleotide sequence of one gene. Chromosomal mutations involve changes in chromosomes, and therefore may effect many genes
What are two cellular processes that can cause mutations?
Spontaneous mutations may arise during DNA replication if there is incorrect base pairing by DNA polymerase. DNA transposition can also cause mutations by the movement of specific DNA sequences (transposons or jumping genes) moving within and between chromosomes
Where is starch stored?
Starch is stored in the roots of plants where it's produced from glyceraldehyde-3-phosphate and transported from the chloroplasts
What is potential energy?
Stored energy
What are nucleosomes?
Structural units of DNA that consist of about 200 bases wrapped around a group of histones
Identify at least three structural and functional characteristics of carbohydrates
Structurally carbohydrates are organic molecules with many hydroxyl groups, that often contain carbonyl groups, and that generally have the molecular formula (CH2O). Functionally carbohydrates are used as an energy source for cells (e.g glucose) for energy storage (starch and glycogen) and to provide structural support (e.g cellulose)
The primary form of sugar transported from the site of photosynthesis to the rest of the plant is?
Sucrose
List at least three different compounds other than glucose that are made from G3P.
Sucrose, Starch, Cellulose and RuBP
Which is not a produce of the light dependent reaction?
Sugar
Temperature and pH effect enzyme activity, but they cannot be described as inhibitors. Briefly explain why.
Temperature and pH effect enzyme activity because if there is any change in temperature condition or pH level it alters the enzyme's three dimensional shape. When temperature becomes too low, the bonds that determine the enzyme shape are not flexible enough to enable substrate molecules to fit properly, and at higher temperature the bonds are too weak to maintain the enzyme's shape. However they cannot be described as inhibitors because they don't physically interact with the enzyme and reduce the activity of the enzyme. There are two types of mechanisms: Competitive Inhibition: Interacts with the active site of the enzyme Non-Competitive Inhibition: binds to an allosteric site on the enzyme
(Using the diagram of a methane molecule) Which term best describes the structure of the molecule?
Tetrahedral
What did Rosalind Franklin's X-ray diffraction images reveal about the structure of DNA?
That DNA has a helical structure
Which process is explained by the triplet hypothesis?
That a possible grouping of nucleotides code for one amino acid during protein synthesis
What is an acceptor stem?
The 3' end of a tRNA molecule that is the site of attachment for a particular amino acid, based on the anticodon
In chemiosmosis, the diffusion of hydrogen ions across a membrane in the organelle occurs through passageways created by?
The ATP synthase
Define Origin of Replication
The DNA sequence where replication begins
Which part of an amino acid has the greatest influence on the overall structure of a protein?
The R group
What is the significance of an R group?
The R group of an amino acid may be polar, non-polar, acidic or basic, which determines many of its properties. When amino acids are part of a protein, the many R groups of those amino acids will largely determine the secondary and tertiary structure of the protein. This structure, in turn, helps to determine the proteins function
Define Messenger RNA (mRNA)
The RNA that contains the genetic information of a gene and carries it to the protein synthesis machinery, and provides the information that determines the amino acid sequence of a protein
What is a ribosomal RNA (rRNA)?
The RNA that is associated with proteins in the ribosomes
How does Watson and Crick's model of DNA account for the diversity of life on Earth and the accurate replication if hereditary material?
The Watson-Crick model of DNA accounts to: - The known size and shape of the DNA molecule - From the x-ray crystallography of Rosalind Franklin they gathered the known rations of the different nucleotides - The chemical structure of nucleotides - The Watson-Crick model of DNA also allows it to be faithfully replicated, it shows that the two strands can be separated and then each can be used a template to synthesize the new daughter strands - It allows for DNA information to be translated to RNA by synthesizing a complementary RNA molecule - RNA is then used to determine the structure of proteins - The chemical nature of DNA also results in rare random mutations which provide variation within species, that is the basis of evolution
Explain how Watson and Cricks model of the DNA molecule accounts for the ability of a cell to make identical copies of its DNA.
The Watson-Crick model of DNA allows it to be faithfully replicated by showing that the two strands can be separated and then each can be used a template to synthesize the new daughter strands
What is the fluid mosaic model?
The accepted model of the cell membrane, which is the basic framework of a semi-fluid phospholipid bilayer with a mosaic of proteins, carbohydrates may be attached to lipids or proteins
Explain the meaning and significance of activation energy as it relates to chemical reactions.
The activation energy of a reaction is the initial input of energy needed to start the reaction. Its value is significant because reactions with high activation energies occur more slowly than reactions with low activation energies. Anything that lowers the activation energy of a reaction (such as a catalyst) will speed up the rate of the reaction. Many of the chemical reactions that occur in cells have high activation energies and only proceed at the rates needed for life because cells have enzymes that catalyze those reactions
Bond energy refers to what?
The amount of energy needed to break a chemical bond
Streptomycin is an antibiotic that works by inhabiting the attachment of tRNA that carries a modified form of methionine. Explain what effect this antibiotic must have on bacteria?
The anticodon would prevent the initiation of translation of bacterial proteins. Therefore, the bacterial cells would not survive.
Describe the basic structure of a triglyceride, and explain how the presence of double bonds affect its properties
The basic structure of a triglyceride is a glycerol molecule with three fatty acid chains linked to it covalently. The fatty acid chains may be all saturated (no carbon-carbon double bonds) or all unsaturated (one or more carbon-carbon double bonds) or a mixture of saturated and unsaturated chains. The unsaturated chains may be monounsaturated or polyunsaturated. The presence of carbon-carbon double bonds in the fatty acid chains makes the chains bent (or kindle) so that they do not pack together as well. Molecules with unsaturated fatty acid chains tend to be liquids at room temperature whereas those with saturated fatty acyl chains (that are quite straight and pack together well) tend to be solids at room temperature.
Define Gene
The basic unit of heredity that determines, in whole or part, a genetic trait, a specific sequence of DNA that encodes for proteins and RNA molecules, and can contain sequences that influence production of these molecules
Define energy
The capacity to do work
What is an enzyme-substrate complex?
The combined structure of an enzyme with a substrate that is bound to the enzyme's active site
Define Genome
The complete genetic makeup of an organism, an organisms total DNA sequence
Define Chromatin
The condensed form of genetic material that predominates for most of the eukaryotic cell cycle, consists of a complex of DNA and protein
Define Nucleosome
The condensed structure formed when double stranded DNA wraps around an octamer of histone proteins
What is the conservative theory of DNA replication?
The conservative theory is that the replicated DNA contains two new strands of DNA and the original (template) pair reforms into the parent molecule
What is gene regulation?
The control and change to gene expression in response to different conditions in the cell or environment
What is the Krebs Cycle?
The cyclic pathway that acquires acetyl-CoA and oxidizes it to carbon dioxide while regenerating the compound that picks up more acetyl-CoA, converts released energy to ATP, NADH and FADH2
Define Antiparallel
The directionality of the two strands in a DNA molecule, the strands run in opposite directions, with each end of a DNA molecule containing the 3' end of one strand and the 5' end of the other
The energy to phosphorylate ADP during oxidative phosphorylation is derived from where?
The energy is released from a reaction when converting a substrate to a product in glycolysis
What is kinetic energy?
The energy of motion
What is bond energy?
The energy required to break or form a chemical bond
What is activation energy?
The energy required to initiate a chemical reaction
How do peroxisomes protect themselves from the reactive hydrogen peroxide they produce?
The enzyme catalase breaks down hydrogen peroxide within peroxisomes
What evidence supported the idea that RNA acts as an intermediate molecule between DNA and proteins?
The evidence that supported RNA as an intermediate molecule included the following: - RNA is found in the nucleus and cytoplasm - The concentration of RNA in the cytoplasm is correlated with protein production Therefore, RNA is synthesized in the nucleus and transported to the cytoplasm
Which reaction would result in the production of water?
The formation of a peptide bond
Define DNA supercoiling
The formation of additional coils in the structure of DNA due to twisting forces on the molecule
Which process is considered a redox step?
The formation of rubisco
What is the function of the Clavin Cycle?
The function of the calvin cycle is to fix atmospheric carbon and create a three-carbon sugar called G3P
In the Watson-Crick model of DNA, what are the "handrails"?
The handrails are sugar-phospate molecules
Identify the dependent and independent variables in Hershey and Chase's experiments. What are some controls?
The independent variable in the experiment was the type of radioactive isotope to use to tag the virus. The dependent variable in the experiment was the presence of radioactivity inside the infected bacterial cell. Some of the controls include: the usage of the same type of virus in both experiments and the usage of the same protocol for infecting bacterial cells in both experiments
(Using the diagram from the review) What type of inhibitor is shown? Explain your answer. How could you reduce the action of this inhibitor?
The inhibitor shown in the diagram is a competitive inhibitor. These are structurally similar to the substrate of the enzyme and bind to the active site. This means that when a competitive inhibitor binds to the active site of an enzyme, it prevents the substrate from binding to the active site. Only once the inhibitor has been released from the active site can the substrate bind. The inhibitor is called a competitive inhibitor as it competes with the substrate for the active site. The effects of a competitive inhibitor can be reduced by increasing the substrate concentration. More substrate would successfully bind to the active site than inhibitor and therefore reducing the effect of the inhibition.
In the mitochondria, the electron transport chain is associated with what?
The inner membrane
What is the Krebs Cycle, and what is it significance in the process of aerobic respiration?
The krebs cycle is the cyclic metabolic pathway that acquires acetyl-coA and ultimately oxidizes it to carbon dioxide while regenerating the compound that picks up more acetyl-coA, it converts released energy to ATP, NADH and FADH2. It's importance is in the production of of large quantities of NADH and FADH2, which generate more ATP than would be formed if substrate level phosphorylation had occurred instead of oxidative phosphorylation
During what stage of photosynthesis is O2 produced?
The light-dependent reaction involving photosystems 1 and 2
What is RNA polymerase?
The main enzyme that catalyzes the formation of RNA from a DNA template
List and explain the major components of the translation machinery
The major components of the translation machinery are: - mRNA — it contains the genetic information that determines the amino acid sequence of a protein tRNA — contains an anticodon that base-pairs with a codon on the mRNA and has the corresponding amino acid attached to it according to the genetic code Ribosome — are composed of rRNA and proteins and are involved in the process of protein synthesis Translation Factors — are proteins that act as accessory factors, they needed at each stage of translation
What was the major finding of the Hershey-Chase experiment?
The majority of radioactive phosphorus was transferred into the bacterial cells, proving that DNA was the hereditary material.
In cellular respiration, the energy released by the electron transport chain pumps hydrogen ions across the membrane from where?
The matrix to the inter-membrane space
Define Semi-Conservative
The mechanism of DNA replication in which each newly synthesized DNA molecule is composed of one strand from the original and one new strand
Which event requires a net input of energy?
The movement of an ion out of a cell against its electrochemical gradient
What two events are linked in chemiosmosis?
The movement of hydrogen ions is linked to the synthesis (creation) of ATP by chemiosmosis
What is osmosis?
The movement of water from an area of higher concentration to an area of lower concentration, across a semi-permeable membrane
What is diffusion?
The net movements of ions or molecules from an area of higher concentration to an area of lower concentration
Explain how the three dimensional structure of a protein can be changed (in the absence of a gene mutation) and why this can be harmful to an organism.
The overall three dimensional structure of a protein can be changed by a variety of environmental variables and chemical or physical treatments. Anything that could alter the intramolecular and or intermolecular interactions that occur in a protein may alter its structure and thus its function as well. For example, a change in temperature (too hot or too cold), in pH, or ionic environment (would result in changes I'm salt concentration). All of these changes could denature a protein either partly or completely. Since all cells depends on the many different functions performed by these proteins, a change in the structure of one or more proteins can be harmful to an organism.
The oxygen that is released as O2 comes from what molecule?
The oxygen that is released as O2 during photosynthesis came form water molecules
What is substrate-level phosphorylation and when does it generate ATP?
The process in which two molecules of ADP are covered into two molecules of ATP for every molecule of glucose entering glycolysis is called substrate level phosphorylation, This is reaction 7 in the process of glycolysis
What is catabolism?
The process of breaking down compounds into smaller molecules to release energy
Define DNA replication
The process of producing two identical DNA molecules from an original, parent DNA molecule
What is anabolism?
The process of using energy to build large molecules from smaller ones
Give an example of an anabolic pathway
The production of glucose in plants
What is light independent reaction?
The reaction that assimilates carbon dioxide to produce an organic molecule that can be used to produce biologically important molecules such as carbohydrates
What is light-depedent reaction?
The reaction that traps solar energy and uses it to generate ATP and NADH
How is cell specialization possible when all go the cells in an organism contain the same genetic information?
The regulation of genes allow for cell specialization. Gene expression is controlled so that only certain genes are active at certain amount and at certain times in each cell type. Therefore, each cell type can have its own set of proteins
Define nucleotide
The repeating unit od nucleic acids, composed of a sugar group, a phosphate group, and a nitrogenous base
What were the results of the experiments performed by Beadle and Tatum on Neurospora Crassa. What was the significance of their result?
The results of the Beadle and Tatum experiment showed that a single gene produces one enzyme (one gene/one polypeptide hypothesis). This was later modified to one gene/one polypeptide hypothesis since not all proteins are enzymes
What is thermodynamic?
The science that studies the transfer and transformation of thermal energy (heat)
What does the second law of thermodynamics apply to?
The second law of thermodynamics applies to closed systems
What is the semi-conservative theory of DNA replication?
The semi-conservative theory is that the replicated DNA contains one new strand of DNA and the complementary parent strand
What is an active site?
The site on an enzyme where the substrate binds, where the chemical reaction is catalyzed by the enzyme that takes place
What is a monomer?
The smallest reaping unit of a polymer
What is the NaK pump and how does it work?
The sodium potassium pump is a primary active transporter that hydrolyzes one molecule of ATP for every three sodium ions it pumps out of the cell and every two potassium ions it pumps in. Both ions are moved across their concentration gradient The pump works by undergoing a series of shape changes powered initially by ATP hydrolysis and then later by the binding or release of the ions and a phosphate group that is transiently bound to pump during the pumping cycle. During the pumping cycle the E1 conformation of the protein releases K+, bind Na+, and hydrolysis ATP. In E2 conformation, the protein is transiently phosphorylate on its cytoplasmic side, released Na+ and binds K+.
Water vapours exits and CO2 enters a leaf through?
The stromata
What is biochemistry?
The study of the activity and properties of biologically important molecules
Define metabolism
The sum of all chemical reactions that occur in the cell
What is transcription?
The synthesis of RNA from a DNA template
What is translation?
The synthesis of protein from an mRNA template
What is the endomembrane system?
The system within the cell that acts to synthesize, modify, and transport proteins and other cell products, it includes the Endoplasmic reticulum, golgi complex, vesicles, and the cell membrane, among other structures
What is the hydrophobic effect?
The tendency of non-polar molecules or non-polar portions of molecules to stay away from water. The hydrophobic effect is very important in determining the tertiary structure of proteins and in the structure of many other biological molecules
What is gene expression?
The transfer of genetic information from DNA to RNA to protein
What was the transforming principle in the Griffith's experiments on s.pneumonia?
The transforming principle was DNA
What is active transport?
The transport of a solute across a membrane against its concentration gradient
What is facilitated diffusion?
The transport of ions or molecules across a membrane by means of a membrane protein along the concentration gradient for that ion or molecule
Why did Hershey and Chase use two different radioactive isotopes in their experiments?
The two different radioisotopes were used to trace each type of molecule. One sample of T2 virus was tagged with radioactive phosphorus since phosphorus is present in DNA and not protein. And the other sample of T2 virus was tagged with radioactive sulfur since sulfur is only found in the protein coat of the capsid.
What is photophosphorylation?
The use of photons of light to drive the phosphorylation of ADP to produce ATP via chemiosmosis
What is the main objective of DNA replication?
Then main objective of DNA replication is to produce two more identical DNA molecules from a parent DNA molecule
Explain why a cell typically contains only 30 to 45 different kinds of tRNA molecules, rather than the expected 61? In your explanation consider the wobble effect in the genetic code.
There are 61 sense codons that code for the 20 amino acids commonly found in proteins. A nucleotide at the third position of a codon pairs with a nucleotide in the first position of the anticodon. Unlike the other nucleotide positions involved in the codon-anticodon pairing, this pairing is often weak or "wobbles," and nonstandard pairings can occur. Since many synonymous codons differ at only the third nucleotide position, it is likely that in these codons the "wobble" and nonstandard base-pairing with the anticodons will result in the correct amino acid being inserted in the protein even if a nonstandard pairing occurs.
During cellular respiration, the process that follow glycolysis depend on whether or not oxygen is present. Explain briefly.
There are two types of cellular respiration, there aerobic which is a catabolic pathway that requires energy and then theres anaerobic which is a metabolic pathway which uses other inorganic molecules other than oxygen as the final electron acceptor. Aerobic organisms, like us humans,need to breathe oxygen to maintain the hydrogen concentration gradient and to keep ATP synthetase working.
The shape and charge distribution of a protein are important because?
These properties govern the function for each protein
What happens to the electrons carried by NADH and FADH2?
They are moved between proteins in the inner membrane of the mitochondrion
What do high energy photons have?
They have short wavelengths
Compare and contrast the thylakoid membrane in plant cells to the cristae found in the mitochondria
Thylakoid Only: - Found in the chloroplast - Contains chlorophyll and photosystems - Home of electron transport carriers that pump protons across the membrane - Results in the production of O2, NADPH and ATP Thylakoid and Cristae: - Double membrane - Electron transport chains - ATP synthase - Increase surface area - Result in the production of ATP Cristae Only: - Found in mitochondria - Home of electron transport carriers that pump protons across the membrane - Result in the production of ATP, NAD ad H2O
The pigment molecules responsible for photosynthesis are located in the?
Thylakoid membrane of the chloroplast
Photosynthesis takes place i the membranes of small sacs called?
Thylakoids
What are thylakoids and why are they important to photosynthesis?
Thylakoids are one of many interconnected sac-like membranous disks within the chloroplast. They contain the molecules that absorb energy from the sun to power photosynthesis.
What is the function of the TATA box in a sequence of DNA
To act as a promoter site for RNA polymerase and to determine the point of termination of the growing polypeptide chain
What is the function of DNA ligase in DNA replication?
To anneal (splice) smaller fragments of DNA to create one continuous strand
What is the function of DNA primase in DNA replication?
To create an RNA primer to initiate DNA replication
What is the function of RuBP in the Calvin Cycle?
To generate ATP
What is an important factor of the electron transport chain?
To generate a hydrogen ion gradient
What is the function of DNA polymerase in DNA replication?
To insert new bases during elongation, using the parental strand as a template
What is the function of the splitting of water in the light dependent reactions?
To supply electrons and hydrogens for (ultimately) the production of ATP and NADPH
Go over the process of protein synthesis. (transcription and translation)
Transcription: Initiation— transcriptional machinery is assembled on the sense strand. RNA polymerase polymerase binds to the sense strand. Elongation — RNA polymerase synthesizes a strand of mRNA that is complementary to the sense strand of DNA Termination — RNA polymerase detaches from the DNA strand when it reaches a stop signal. The mRNA strand is released and the DNA double helix reforms Translation: Initiation — all the translation components come together. Proteins called initiation factors assemble the small ribosomal sub-units, mRNA, initiator tRNA and the large ribosomal sub-unit for the start of protein synthesis Elongation — Protein synthesis occurs. The polypeptide becomes longer one amino acid at a time. In addition to tRNA's, elongation requires elongation factors, which enable tRNA anticodons to bind to mRNA codons. Termination — When a stop codon on the mRNA is reached, the polypeptide and all the components of the translation machinery are separated.
Explain why translation is an energy-consuming process, and which organelle provides energy for this process?
Translation consumes large amounts of energy since many molecules (i.e proteins and nucleic acid components) must be synthesized and assembled. Energy is also needed to from peptide bonds that exist between the amino acids in proteins. This energy is provided by the mitochondria, which supply the cell with most of it's energy.
How is translation initiated and terminated?
Translation is initiated when initiation factors assemble the translation components. The small ribosomal subunit attaches to the mRNA near the start codon (AUG). The initiator tRNA (with anticodon UAC) binds to the start codon. The large ribosomal subunit then joins to form the complete ribosome. Translation is terminated when a stop codon on the mRNA is reached. This causes the polypeptide and the translation machinery separate. The polypeptide is then cleaved from the last tRNA by a release factor
What is exocytosis?
Transport method in which a vacuole fuses the cell membrane and releases its contents outside the cell
A DNA molecule has the same amount of adenine and thymine, is this true or false?
True
DNA polymerase catalyzes the elongation of a DNA strand in the 5' - 3' direction, is this true of false?
True
True or False, CO2 fixation occurs within the stroma
True
True or False. For every CO2 molecule fixed by photosynthesis, one molecule of O2 is produced.
True
True or False. If you know the absorption spectrum of a pigment, you can predict the pigments colour
True
True or False. The elongation of Okazaki fragments during DNA synthesis progresses away from the replication fork.
True
What is the composition of a typical active ribosome?
Two sub units with binding sites for three tRNA molecules and mRNA
Which codon serves as a stop signal during translation?
UAG
Use as an example to explain the difference between a specific and non-specific DNA repair mechanism.
UV radiation can lead to a mutation by covalently linking thymines to form a thymine dimer. A specific mechanism for repairing thymine dimers is photorepair, where an enzyme specifically recognizes and cleaves thymine dimers. A non-specific mechanism for repairing UV damages is excision repair, where a group of enzymes identify and correct many different types of DNA damage
Which of the following is not primarily composed of protein? a) hair b) urine c) nails d) enzymes e) collagen
Urine
The O2 given off by photosynthesis comes from?
Water
The oxygen produced in photosynthesis comes from what molecule?
Water
What is the sequence for the movement of electrons during the light-dependent reactions of plants?
Water, P680, P700 and NADP+
How does the model that was proposed by Watson and Crick account for the observations made by Franklin in her X-ray crystallography studies of DNA?
Watson and Cricks model of the DNA accounts for the observations made by Franklin because it had a helical structure, with the nitrogenous bases facing inward and the sugar-phosphate backbone facing the outward. They showed that the distance between the sugar-phosphate backbone remained constant throughout the entire molecule.
What happens to the electrons that are lost by a compound that is undergoing an oxidation reaction?
When a compound is oxidized, its electrons are donated to another molecule (which we say becomes reduced)
Write one or two sentences to explain the meaning of the term enzyme-substrate complex. Also explained the following additional terms: active site, substrate, catalyst
When an enzyme catalyzes a biological reaction, it needs to bind the substrate at its active site to form an enzyme substrate complex. The enzyme destabilizes the substrate as it binds to the active site, lowering the activation energy of the reaction and allowing covalent bonds to be broken and new bonds to form
When do C3 plants encounter a problem?
When the temperature of the air rises above 28C and the stomata close to conserve water, which prevents carbon dioxide from entering the air spaces in the leaf
What is the wobble position?
Wobble position refers to the last codon, it's said to be in the wobble position because it's weakly bonded as the first two codons
Can cellular respiration occur without oxygen?
Yes, but it requires an alternative to oxygen as the final electron acceptor
What is redox reaction?
a chemical reaction that involves the transfer of electrons from one substance to another, also called oxidation reduction reaction
Which statement is false? a) Glycolysis occurs in the mitochondrial matrix b) glycolysis breaks down glucose into two three carbon compounds c) glycolysis used two ATP molecules and coverts them into ADP d) Glycolysis reduces two molecules of NAD+ into NADH
a) Glycolysis occurs in the mitochondrial matrix
Which of the following statements about DNA replication in prokaryotes and eukaryotes are true? a) Prokaryotes have a single origin of replication, while eukaryotes have multiple origins of replication b) In prokaryotes, elongation occurs in a 3' to 5' direction. In eukaryotes, elongation occurs in a 5' to 3' direction c) The rate of DNA replication in prokaryotes and eukaryotes are similar d)Prokaryotes and Eukaryotes both have telomeres at the ends of their linear chromosomes e) Prokaryotes have a continous synthesis of both leading and lagging strands, while eukaryotes have discontinuous synthesis on both leading and lagging strands
a) Prokaryotes have a single origin of replication, while eukaryotes have multiple origins of replication
Define transfer RNA (tRNA)
an RNA molecule that links the codons on mRNA to the corresponding amino acid for protein synthesis
Which pathway is aerobic? a) Fermentation b) Electron Transport Chain c) Lactic acid formation d) glycolysis
b) Electron Transport Chain
Which of the following statements about the inner mitochondrial membrane is false? a) It is permeable to positively charged ions b) It is impermeable to NADH c)The only way hydrogen ions can move into the matrix is through the ATP synthase
b) It is impermeable to NADH
Which of the following occurs in the stroma of the chloroplast? a) Light dependent reactions b) Electron Transport Chain c) Calvin Cycle d) Photolysis
c) Calvin Cycle
Which of the following is false regarding light-dependent reactions? a) Produce ATP through chemiosmosis b) Produces NADPH c) Requires carbon dioxide as an electron source d) provides H+ needed to synthesize G3P e) none of the above
c) Requires carbon dioxide as an electron source
Which of the following statements about photosynthesis is true? a) the light dependent reactions can occur only in the light, the light independent reactions only in the dark b) Photorespiration is more efficient at producing glucose than is photosynthesis c) The light dependent reactions produce the energy rich compounds that are used to run the light independent reactions
c) The light dependent reactions produce the energy rich compounds that are used to run the light independent reactions
Which of the following is true about C4 plants? a) They close their stomata during the day and open them at Night b) They do not use the calvin cycle for synthesizing carbohydrates c) They increase the concentration of carbon dioxide to bundle-sheath cells by carrying it into these cells in the form of malate d) Malate leaves bundle-sheath cells to pick up more carbon dioxide
c) They increase the concentration of carbon dioxide to bundle-sheath cells by carrying it into these cells in the form of malate
A reaction produces water as a product. Which statement regarding the reaction is false? a) A condensation reaction may have occurred b) A dehydration reaction may have occurred c) A neutralization reaction may have occurred d) A hydrolysis reaction may have occurred e) All of the above are true
d) A hydrolysis reaction may have occurred
Which of the following does not belong? a) methane b) cyclohexane c) propanol d) sodium chloride e) water
d) sodium chloride
Which of the following provides the most accurate information about the shape of a molecule? a) Electron model b) Structural model c) molecular formula d) space-filling model e) compound formula
d) space-filling model
Which of the following statements are false? a) energy cannot be created or destroyed b) energy can transformed from one type to another c) the universe tends toward disorder d) the energy of the universe is constant e) energy cannot be transferred from one object to another
e) energy cannot be transferred from one object to another
Define splicing
in mRNA, splicing is a process of excising out the introns and combining in the exons
How is RNA involved in protein synthesis?
mRNA is the template for translation, while tRNA and rRNA are involved in the translation of mRNA
What is a precursor mRNA (pre-mRNA)?
mRNA that has not undergone processing
What is a mature mRNA?
mRNA that has undergone processing
Predict where mRNA is transported in the cell after transcription is finished
mRNA would be transported from the nucleus to they cytoplasm for translation
(Using the diagram of a methane molecule) The methane molecule is best described as?
non-polar
Cholesterol is a precursor for what?
testosterone
What is carbon dioxide fixation?
the reaction of carbon dioxide with ribulose bisphosphate to produce two identical three-carbon molecules, 3-phosphoglycerate
What is the calvin cycle?
the reactions that convert carbon dioxide to the three carbon organic molecule glyceraldehyde-3-Phosphate (G3P), can occur in the absence or presence of light, also called the dark reactions and the Calvin-Benson cycle