CH 6
STUDY QUESTIONS
63. Which of the following is true of ATP?
a. The hydrolysis of ATP is exergonic.
b. ATP consists of adenine bonded to deoxyribose.
c. ATP releases a relatively small amount of energy when hydrolyzed.
d. An active cell requires a hundred or so molecules of ATP per second.
e. On average, ATP is consumed within a second of its formation.
Answer: e
62. How does the second law of thermodynamics apply to organisms?
a. As energy transformations occur, free energy increases and unusable energy decreases.
b. To maintain order, life requires a constant input of energy.
c. The potential energy of ATP is converted to kinetic energy such as muscle contractions.
d. Reactions occur only with an input of energy.
e. It doesn’t; the complexity of organisms is in disagreement with the second law.
Answer: b
57. The maximum possible rate of an enzyme reaction influenced by a competitive inhibitor depends on the
concentration of
a. inhibitor.
b. substrate.
c. product.
d. enzyme.
e. free energy.
Answer: b
56. What can never be created or destroyed?
a. Entropy
b. Energy
c. Free energy
d. Thermal energy
e. Potential energy
Answer: b
55. The process that involves an end product acting as an inhibitor of an earlier step in a metabolic pathway is called
a. feedback activation.
b. feedback inhibition.
c. positive feedback.
d. concerted activation.
e. competitive inhibition.
Answer: b
53. The catalysis mechanism used by lysozyme is
a. acid-base catalysis.
b. covalent catalysis.
c. metal cofactor redox catalysis.
d. induced strain.
e. unknown.
Answer: d
54. The ability of an enzyme’s active site to sometimes bind inhibitors that are larger than the substrate is called
a. induced fit.
b. enzyme flex.
c. the lock and key paradox.
d. substrate-induced active site shaping.
e. enzyme retrofit.
Answer: a
52 A type of enzyme inhibitor that binds within the enzyme’s active site is termed
a. allosteric.
b. noncompetitive.
c. competitive.
d. extracompetitive.
e. None of the above
Answer: c
51. When organisms move from one environment to another, they sometimes synthesize variations of existing enzymes,
which are called
a. coenzymes.
b. abzymes.
c. isozymes.
d. effectors.
e. activators.
Answer: c
49. Factors that can either activate or inhibit allosteric enzymes are called
a. proteins.
b. coenzymes.
c. sites.
d. effectors.
e. competitors.
Answer: d
48. Once a spontaneous reaction is initiated, the speed with which it reaches equilibrium without a catalyst is influenced
by
a. the equilibrium constant.
b. a change in free energy.
c. a change in entropy.
d. activation energy.
e. standard free energy change.
Answer: b
10. The first law of thermodynamics states that the total energy in the universe is
a. decreasing.
b. increasing.
c. constant.
d. being converted to free energy.
e. being converted to matter.
Answer: c
15. In a chemical reaction, transition-state species have free energies
a. lower than either the reactants or the products.
b. higher than either the reactants or the products.
c. lower than the reactants, but higher than the products.
d. higher than the reactants, but lower than the products.
e. lower than the reactants, but the same as the products.
Answer: b
17. The enzyme α-amylase increases the rate at which starch is broken down into smaller oligosaccharides. It does this
by
a. decreasing the equilibrium constant of the reaction.
b. increasing the change in free energy of the reaction.
c. decreasing the change in free energy of the reaction.
d. increasing the change in entropy of the reaction.
e. lowering the activation energy of the reaction.
Answer: e
33. The presence in a system of energy that is unusable for the purpose of doing work is related to the system’s
a. temperature.
b. entropy.
c. work.
d. thermodynamics.
e. equilibrium.
Answer: b
38. An active site is
a. the part of the substrate that binds with an enzyme.
b. the part of the enzyme that binds with a substrate.
c. the site where energy is added to an enzyme catalyst.
d. the site where enzymes are found in cells.
e. None of the above
Answer: b
39. Enzymatic reactions can become saturated as substrate concentration increases because
a. enzymes have the maximum possible number of hydrogen atoms attached to them.
b. the concentration of substrate cannot increase any higher.
c. substrates are inhibitors of enzymes.
d. the activation energy of the reaction cannot be further lowered.
e. there are a limited number of the enzyme molecules present.
Answer: e
20. In the presence of alcohol dehydrogenase, the rate of reduction of acetaldehyde to ethanol increases as you increase
the concentration of acetaldehyde. Eventually, the rate of the reaction reaches a maximum, at which point further
increases in the concentration of acetaldehyde have no effect. Why?
a. All of the alcohol dehydrogenase molecules are bound to acetaldehyde molecules.
b. At high concentrations of acetaldehyde, the activation energy of the reaction increases.
c. At high concentrations of acetaldehyde, the activation energy of the reaction decreases.
d. The enzyme is no longer specific for acetaldehyde.
e. At high concentrations of acetaldehyde, the change in free energy of the reaction decreases.
Answer: a
21. When an enzyme catalyzes both an exergonic reaction and an endergonic reaction, the two reactions are said to be
a. substrates.
b. endergonic.
c. kinetic.
d. activated.
e. coupled.
Answer: e
22. In glycolysis, the exergonic reaction 1,3-diphosphoglycerate → 3-phosphoglycerate is coupled to the reaction ADP +
Pi → ATP. Which of the following is most likely to be true about the reaction ADP + Pi →ATP?
a. The reaction never reaches equilibrium.
b. The reaction is spontaneous.
c. There is a large decrease in free energy.
d. The reaction is endergonic.
e. Temperature will not affect the rate constant of the reaction.
Answer: d
26. How does a noncompetitive inhibitor inhibit binding of a substrate to an enzyme?
a. It binds to the substrate.
b. It binds to the active site.
c. It lowers the activation energy.
d. It increases the ∆G of the reaction.
e. It changes the shape of the active site.
Answer: e
27. Which type of inhibitor can be overcome completely by the addition of more substrate?
a. Irreversible
b. Noncompetitive
c. Competitive
d. Prosthetic
e. Isotonic
Answer: c
28. Binding of substrate to the active site of an enzyme is
a. reversible.
b. irreversible.
c. noncompetitive.
d. coupled.
e. allosteric.
Answer: a
32. An RNA molecule that has enzyme activity is called
a. RNAse.
b. ribonuclease.
c. an allosteric enzyme.
d. a regulatory enzyme.
e. a ribozyme.
Answer: e
36. The rate of a chemical reaction in a cell is the measure of how
a. often the reaction occurs.
b. quickly the reaction reaches equilibrium.
c. much energy must be added to have the reaction occur.
d. much activation energy is required to have the reaction occur.
e. easily the reaction is inhibited.
Answer: b
40. Competitive inhibitors of enzymes work by
a. fitting into the active site.
b. fitting into a site other than the active site.
c. altering the shape of the enzyme.
d. changing the enzyme into an inactive form.
e. increasing the activation energy of the enzyme-catalyzed reaction.
Answer: a
41. Allosteric inhibitors act by
a. decreasing the amount of enzyme molecules.
b. increasing the amount of enzyme molecules.
c. decreasing the amount of the inactive form of the enzyme.
d. decreasing the amount of the active form of the enzyme.
e. increasing the amounts of substrate.
Answer: d
42. Negative feedback in a sequence of chemical reactions involves a chemical that appears
a. late in the sequence and inhibits an earlier reaction.
b. early in the sequence and inhibits a later reaction.
c. early in the sequence and activates a later reaction.
d. late in the sequence and activates an earlier reaction.
e. late in the sequence and inhibits a later reaction.
Answer: a
43. Denatured enzymes are the same as
a. ribozymes.
b. abzymes.
c. isozymes.
d. destroyed enzymes.
e. coenzymes.
Answer: d
44. The inhibition of enzyme activity by noncompetitive inhibitors can be reduced
a. by decreasing the concentration of allosteric enzymes.
b. by decreasing the concentration of substrate.
c. by increasing the concentration a competitive inhibitor.
d. by increasing the concentration of substrate.
e. only when they become unbound.
Answer: e
45. The concentration of a substrate in a reaction at equilibrium depends most strongly on the concentration(s) of
a. enzyme.
b. the active form of the enzyme.
c. the activator.
d. the other substrates and products.
e. the products.
Answer: e
46. An allosteric site of an enzyme is the place where a(n) _______ may bind.
a. competitive inhibitor
b. substrate
c. prosthetic group
d. activator
e. coenzyme
Answer: d
47. In some cases, a substrate–enzyme complex is stabilized by
a. hydrogen bonds.
b. covalent bonds.
c. ionic attractions.
d. hydrophobic interactions.
e. All of the above
Answer: e
ONLINE QUIZ QUESTIONS
1.The overall reaction: glucose + O2 + CO2 + H2O + energy
a.can occur in biological systems without enzymes.
b.is endergonic.
c.is exergonic.
d.occurs in a single step in cells.
e.transforms glucose molecules to a higher energy state.
Answer: c
2.Which statement about thermodynamics is not true?
a.Free energy is given off in an exergonic reaction.
b.Free energy can be used to do work.
c.A spontaneous reaction is exergonic.
d.Free energy tends always to a minimum.
e.Entropy tends always to a minimum.
Answer: e
3.Which of the following statements about energy is true?
a.All molecules have the same energy content.
b.ADP has more energy than ATP.
c.Oxidized compounds have more free energy than reduced compounds.
d.Reduced compounds have more free energy than oxidized compounds.
e.Substances capable of oxidation require ATP hydrolysis.
Answer: d
4.Which statement about kinetic energy is true?
a.It is stored energy.
b.It is the energy of movement.
c.It does not alter the state or motion of matter.
d.Water stored behind a dam is an example.
e.It can be stored in chemical bonds.
Answer: b
5.Which of the following is not part of the second law of thermodynamics?
a.When energy is converted from one form to another, some of that energy becomes unavailable to do work.
b.Not all energy can be used.
c.If needed free energy is not available, the reaction does not occur.
d.As a result of energy conversions, disorder tends to increase.
e.The total energy before the transformation equals the total energy after the transformation.
Answer: e
6.Which of the following is a characteristic of a coenzyme?
a.Coenzymes contain inorganic ions.
b.Coenzymes are usually larger than the enzyme to which they bind.
c.Coenzymes are permanently bound to the enzyme.
d.Coenzymes must collide with the enzyme to bind to its active site.
e.Coenzymes include the heme group that is attached to the oxygen-carrying protein in hemoglobin.
Answer: d
7.The rate of an enzyme-catalyzed reaction
a.is constant under all conditions.
b.decreases as substrate concentration increases.
c.cannot be measured.
d.can be affected by the pH of the environment.
e.can be increased by inhibitors.
Answer: d
8.Which statement about ATP is not true?
a.ATP gains and transfers free energy needed by the cell to do work.
b.ATP can be converted into a building block for DNA and RNA.
c.The hydrolysis of ATP is endergonic and yields ADP.
d.ATP can phosphorylate.
e.ATP consists of adenine bonded to ribose, which is attached to three phosphate groups.
Answer: c
9.Which statement about irreversible inhibition of enzymes is true?
a.The inhibitor can bind non-covalently to the enzyme’s active site.
b.Inhibitors are classified as either competitive or non-competitive.
c.The inhibitor can create a covalent bond and permanently inactivate the enzyme.
d.The inhibitor and substrate compete since only one can bind to the active site.
e.The inhibitor may bind to a site away from the active site and change the enzyme’s shape.
Answer: c
10.Which statement about pH effects on enzyme activity is not true?
a.Decreasing or increasing pH from optimum may reduce the activity of an enzyme.
b.Most biochemical reactions have an optimum pH range.
c.If a pH change occurs, the enzyme may no longer have the correct shape to bind to its substrate.
d.In neutral or acidic solutions, carboxyl groups release H+ and become negatively charged carboxylate groups.
e.In neutral or acidic solutions, amino groups accept H+ and become positively charged ammonium groups.
Answer: d
11.Enzymes are
a. biological catalysts that bind specific reactant molecules.
b. a type of protein.
c. catalysts that lower the activation energy of a reaction.
d. All of the above.
e. None of the above.
Answer: d
12.Which of the following statements concerning enzymes is true?
a. Molecular structure does not determine enzyme function.
b. Binding at the active site allows the enzyme to always retain its shape.
c. Enzymes function on their own; they never need cofactors or any sort of regulation.
d. Some enzymes change shape when substrate binds to them.
e. Non-competitive inhibitors compete for the active site.
Answer: d
13.Which of the following statements concerning enzymes is false?
a. In the absence of an enzyme, the two types of substrate molecules react very slowly.
b. Enzymes speed up the rate of a chemical reaction.
c. The active site of an enzyme holds the substrate molecules in the correct orientation, which increases the opportunity
to form products.
d. Non-competitive inhibitors increase the rate of an enzyme-catalyzed reaction.
e. A competitive inhibitor binds at the active site.
Answer: d
14.The optimal temperature of all enzymes in a single organism falls within a small range.
a. true
b. false
Answer: a
CH 7
STUDY QUESTIONS
TEST FILE QUESTIONS
Fill in the Blank
1. Oxidation and _______ occur together.
Answer: reduction
2. Due to its ability to carry electrons and free energy, _______ is the most common electron carrier in cells.
Answer: NAD
3. Pyruvate is _______ to form acetate.
Answer: oxidized
4. The chemiosmotic formation of ATP during the operation of the respiratory chain is called _______.
Answer: oxidative phosphorylation
5. The loss of an electron by a ferrous ion (Fe2+) to yield a ferric ion (Fe3+) is called _______.
Answer: oxidation
6. In a redox reaction, the reactant that becomes oxidized is called a _______.
Answer: reducing agent
7. A chemical reaction resulting in the transfer of electrons or hydrogen atoms is called a _______ reaction.
Answer: redox
8. The pathway for the oxidation of glucose to pyruvate is called _______.
Answer: glycolysis
9. The conversion of glucose to lactic acid is a form of _______.
Answer: fermentation
10. Fatty acids must be converted to _______ before they can be used for respiratory ATP production.
Answer: acetyl CoA
11. During alcoholic fermentation, NAD+ is regenerated by the reduction of acetaldehyde to _______.
Answer: ethanol
12. NAD is an abbreviation for _______.
Answer: nicotinamide adenine dinucleotide
13. An enzyme that transfers a phosphate group from ATP to another protein is called a _______.
Answer: kinase
CH8
STUDY QUESTIONS
STUDY GUIDE QUESTIONS
Knowledge and Synthesis Questions
1. Which of the following cellular metabolic processes can occur in the presence or the absence of oxygen?
a. The citric acid cycle
b. Electron transport
c. Glycolysis
d. Fermentation
2. Which of the following statements regarding glycolysis is true?
a. A 6-C sugar is broken down to two 3-C molecules.
b. Two ATP molecules are consumed.
c. A net sum of two ATP molecules is generated.
d. All of the above
3. During which process is most ATP generated in the cell?
a. Glycolysis
b. The citric acid cycle
c. Electron transport coupled with chemiosmosis
d. Fermentation
4. One purpose of the electron transport chain is to
a. cycle NADH + H+ back to NAD+.
b. use the intermediates from the citric acid cycle.
c. break down pyruvate.
d. All of the above
5. Cellular respiration is allosterically controlled. Which of the following act as inhibitors at the various control points?
a. ATP
b. NADH + H+
c. Both a and b
d. None of the above
6. Which of the following describes the role of the mitochondrial membrane?
a. The membrane acts as an anchor for the membrane-associated enzymes of cellular respiration.
b. The membrane allows for the establishment of a proton-motive force.
c. Both a and b
d. None of the above
7. In a redox reaction between G3P and NAD+ yielding BPG and NADH + H+, __________ is oxidized and __________ is
reduced.
a. G3P; NAD+
b. BPG; NADH + H+
c. G3P; NADH + H+
d. NAD+; NADH + H+
8. Which of the following is true regarding redox reactions?
a. Oxidizing agents accept electrons.
b. A molecule that accepts electrons is said to be reduced.
c. Redox reactions involve electron transfers.
d. All of the above
9. Cyanide poisoning inhibits aerobic respiration at cytochrome c oxidase. Which of the following are results of cyanide
poisoning at the cellular level?
a. Oxygen is not reduced to water.
b. ATP cannot be synthesized in the mitochondria because electron transport is never completed.
c. Cells (with the exception of brain cells) must switch to anaerobic respiration.
d. All of the above
10. Not all cells can switch between aerobic and anaerobic respiration. If a cell cannot switch to anaerobic respiration in
the absence of oxygen, what happens?
a. The cell concentrates oxygen to continue aerobic respiration.
b. The cell dies.
c. The cell uses fermentation.
d. None of the above
11. The main purpose of cellular respiration is to
a. convert energy stored in the chemical bonds of glucose to an energy form that the cell can use.
b. convert potential to kinetic energy.
c. convert kinetic to potential energy.
d. create energy in the cell.
12. Which of the following statements concerning the synthesis of ATP in the mitochondria is true?
a. ATP synthesis cannot occur without the presence of ATP synthase.
b. The proton-motive force is the establishment of a charge and concentration gradient across the mitochondrial
membrane.
c. The proton-motive force is necessary to drive protons back across the membrane through channels established by the
ATP synthase channel protein.
d. All of the above
Knowledge and Synthesis Answers
1. c. Glycolysis proceeds during both fermentation and cellular respiration. Only in cellular respiration is oxygen needed
as the terminal electron acceptor of the pathway.
2. d. During glycolysis, 6-C glucose is broken down into two 3-C pyruvate molecules. In the process, four total ATP are
produced but two are consumed, leaving a net production of two ATP molecules.
3. c. Most of the ATP produced during cellular respiration is produced as electron transport and chemiosmosis are
coupled in oxidative phosphorylation.
4. a. The electron transport chain is responsible for oxidizing NADH + H+ back to NAD+.
5. c. Both ATP and NADH + H+ allosterically control metabolism. ATP controls both phosphofructokinase and isocitrate
dehydrogenase, which are commitment steps for glycolysis and the citric acid cycle respectively. NADH + H+ controls
isocitrate dehydrogenase.
6. c. The mitochondrial membrane is necessary for the anchoring of proteins as well as the establishment of a barrier
across which a gradient can be established.
7. a. A molecule is oxidized when it loses electrons or protons and is reduced when it gains electrons or protons.
8. d. Oxidizing agents accept electrons and cause oxidation of another molecule. Reducing agents donate electrons and
cause the reduction of another molecule.
9. d. Cyanide stops aerobic cellular respiration because cytochrome c oxidase loses the ability to reduce oxygen to
water. Those cells that can switch to anaerobic respiration (fermentation) do so. Brain cells cannot make that switch and
so are killed.
10. b. In the absence of oxygen, cells that cannot go through fermentation die.
11. a. Cellular respiration is the cell’s way of converting potential energy in the chemical bonds of glucose to potential
energy that the cell ultimately can use.
12. d. The proton-motive force results in a concentration and charge gradient across the mitochondrial membrane. In
order for that gradient to equalize, the protons must flow through a channel protein. If this channel protein has an
associated ATP synthase, ATP is generated as protons flow through.
TEXTBOOK SELF QUIZ QUESTIONS
1. The role of oxygen gas in our cells is to
a. catalyze reactions in glycolysis.
b. produce CO2.
c. form ATP.
d. accept electrons from the electron transport chain.
e. react with glucose to split water.
2. Oxidation and reduction
a. entail the gain or loss of proteins.
b. are defined as the loss of electrons.
c. are both endergonic reactions.
d. always occur together.
e. proceed only under aerobic conditions.
3. NAD+ is
a. a type of organelle.
b. a protein.
c. present only in mitochondria.
d. a part of ATP.
e. formed in the reaction that produces ethanol.
4. Glycolysis
a. takes place in the mitochondrion.
b. produces no ATP.
c. has no connection with the respiratory chain.
d. is the same thing as fermentation.
e. reduces two molecules of NAD+ for every glucose molecule processed.
5. Fermentation
a. takes place in the mitochondrion.
b. takes place in all animal cells.
c. does not require O2.
d. requires lactic acid.
e. prevents glycolysis.
6. Which statement about pyruvate is not true?
a. It is the end product of glycolysis.
b. It becomes reduced during fermentation.
c. It is a precursor of acetyl CoA.
d. It is a protein.
e. It contains three carbon atoms.
7. The citric acid cycle
a. takes place in the mitochondrion.
b. produces no ATP.
c. has no connection with the respiratory chain.
d. is the same thing as fermentation.
e. reduces two NAD+ for every glucose processed.
8. The electron transport chain
a. operates in the mitochondrial matrix.
b. uses proteins embedded within a membrane.
c. always leads to the production of ATP.
d. regenerates reduced coenzymes.
e. operates simultaneously with fermentation.
9. Compared to anaerobic metabolism, aerobic breakdown of glucose produces
a. more ATP.
b. pyruvate.
c. fewer protons for pumping in mitochondria.
d. less CO2.
e. more oxidized coenzymes.
10. Which statement about oxidative phosphorylation is not true?
a. It is the formation of ATP by the respiratory chain.
b. It is brought about by the chemiosmotic mechanism.
c. It requires aerobic conditions.
d. In eukaryotes, it takes place in mitochondria.
e. Its functions can be served equally well by fermentation.
Answers
1. d
2. d
3. e
4. e
5. c
6. d
7. a
8. b
9. a
10. e
ONLINE QUIZ QUESTIONS
1.In the presence of oxygen, the energy-rich product(s) of glycolysis in human cells is/are
a.carbon dioxide.
b.ADP.
c.ATP and NADH.
d.NAD and FAD.
e.lactic acid and ATP.
Answer: c
2.If oxygen is not present, yeast cells break down glucose into
a.carbon dioxide and water.
b.carbon dioxide and lactic acid.
c.carbon dioxide and ethanol.
d.NADH and ATP.
e.lactic acid and ATP.
Answer: c
3.When oxygen is available as the final electron acceptor
a.five pathways operate.
b.glycolysis takes place first.
c.the citric acid cycle does not function.
d.the respiratory chain does not function.
e.the pyruvate produced by glycolysis is further metabolized by fermentation.
Answer: b
4.Which of the following about the citric acid cycle is true?
a.The citric acid cycle takes place in the mitochondrion.
b.Acetyl CoA shuttles acetate to the citric acid cycle.
c.The inputs to the citric acid cycle are carbon dioxide, reduced electron carriers and a small amount of ATP.
d.The citric acid cycle is the link between glycolysis and all other reactions of cellular respiration.
e.The citric acid cycle occurs only in the absence of oxygen.
Answer: b
5.Which of the following about fermentation is true?
a.It requires lactic acid.
b.It takes place in all animal cells.
c.It does not requires oxygen.
d.It always results in the production of lactic acid.
e.It prevents glycolysis.
Answer: c
6.The terminal electron acceptor of electron transport is
a.CO2
b.C6H12O6.
c.pyruvate.
d.H2O.
e.O2.
Answer: e
7.Which of the following is not true about catabolic interconversions?
a.Proteins are hydrolyzed to their amino acid building blocks.
b.Polysaccharides are broken down into glycerol and fatty acids.
c.Glycerol is converted to dihydroxyacetone phosphate.
d.When glucose passes through glycolysis and the citric acid cycle its energy is captured in NADH and ATP.
e.Fatty acids are converted to acetate and then acetyl CoA in the mitochondria.
Answer: b
8.The respiratory chain
a.operates only in the absence of oxygen.
b.produces ATP via the proton motive force and the enzyme ATP synthase.
c.leads to the production of ADP.
d.regenerates reducing agents for glycolysis and the citric acid cycle.
e.operates simultaneously with fermentation.
Answer: b
9.Which statement about the chemiosmotic mechanism is not true?
a.Protons are pumped across a membrane.
b.Protons return through the membrane by way of a channel protein.
c.ATP is required for the protons to return.
d.Proton pumping is associated with the respiratory chain.
e.The membrane in question is the inner mitochondrial membrane.
Answer: c
10.In terms of efficiency at converting the energy of glucose to energy in ATP,
a.aerobic glycolysis is better than the citric acid cycle.
b.aerobic respiration is about 40% efficient.
c.anaerobic conditions are much less efficient than aerobic.
d.eukaryotic cells are more efficient than prokaryotic cells.
e.the electron transport chain is not necessary for high efficiency.
Answer: c
8
Photosynthesis: Energy from the Sun
TEST FILE QUESTIONS
Fill in the Blank
1. During the light reactions of photosynthesis, the synthesis of _______ is coupled to the diffusion of protons.
Answer: ATP
2. Atmospheric CO2 enters plant leaves through openings called _______.
Answer: stomata
3. In the 1800s, the summarized chemical reaction for photosynthesis was incorrect because it left out _______ as a
product.
Answer: water
4. In noncyclic photophosphorylation, the electrons for the reduction of chlorophyll in photosystem II come from
_______.
Answer: water
5. When _______ are exposed to light and CO2, four-carbon compounds are the first carbon-containing products.
Answer: C4 plants
6. During the process of _______, rubisco catalyzes the reaction of RuBP with oxygen.
Answer: photorespiration
7. A group of scientists led by _______ conducted experiments demonstrating that RuBP is the CO2 acceptor in the dark
reactions of photosynthesis.
Answer: Calvin
8. When researchers shifted isolated chloroplasts from a low pH solution to a more alkaline solution, ATP synthesis
occurred, even in the absence of light. This experiment was used to support the _______ mechanism of ATP formation
in chloroplasts.
Answer: chemiosmotic
9. During cyclic photophosphorylation, the energy of photons is converted to the chemical energy of the product,
_______.
Answer: ATP
10. In C3 plants, the Calvin–Benson cycle occurs in the chloroplasts of _______ cells, whereas in C4 plants the cycle occurs
in the _______ cells.
Answer: mesophyll; bundle sheath
11. In both photosynthesis and respiration, _______ synthesis is coupled to the diffusion of protons across a membrane.
Answer: ATP
12. The dark reactions take place in the (dark/light) _______.
Answer: light
13. NADP is the abbreviation for _______.
Answer: nicotinamide adenine dinucleotide phosphate
14. The Calvin–Benson cycle is sometimes called the _______.
Answer: dark reactions
15. The O2 found in Earth’s atmosphere is generated from the photosystem _______ of noncyclic photophosphorylation.
Answer: II
16. During cyclic photophosphorylation, _______ rather than NADP+ receives the electron from ferredoxin.
Answer: plastoquinone
17. The most abundant enzyme in the biosphere is _______.
Answer: rubisco (or RuBP carboxylase)
18. The absorption spectrum of chlorophyll a is (different from/similar to) _______ the action spectrum of chlorophyll a.
Answer: similar to
19. The wide range of wavelengths that photons can have is shown by the _______.
Answer: electromagnetic spectrum
STUDY GUIDE QUESTIONS
Knowledge and Synthesis Questions
1. The main purpose of photosynthesis is to
a. consume CO2.
b. produce ATP.
c. convert light energy to chemical energy.
d. produce starch.
2. Which of the following best represent the components that are necessary for photosynthesis to take place?
a. Mitochondria, accessory pigments, visible light, water, and CO2
b. Chloroplasts, accessory pigments, visible light, water, and CO2
c. Mitochondria, chlorophyll, visible light, water, and O2
d. Chloroplasts, chlorophyll, visible light, water, and CO2
3. Chlorophyll is suited for the capture of light energy because
a. certain wavelengths of light raise it to an excited state.
b. in its excited state chlorophyll gives off electrons.
c. chlorophyll’s structure allows it to attach to thylakoid membranes.
d. All of the above
4. Plants give off O2 because
a. O2 results from the incorporation of CO2 into sugars.
b. plants do not respire because they photosynthesize.
c. water is the initial proton donor, leaving O2 as a photosynthetic by-product.
d. All of the above
5. Cyclic and noncyclic electron flow are used in plants to
a. meet the ATP demands of the Calvin–Benson cycle.
b. avoid producing excess NADPH + H+.
c. balance ATP and NADPH + H+ ratios in the chloroplast.
d. All of the above
6. Which of the following statements concerning the light reactions of photosynthesis is true?
a. Photosystem I can operate independently of photosystem II.
b. Photosystems I and II are activated by different wavelengths of light.
c. Photosystems I and II transfer electrons and create proton gradients across the thylakoid membrane.
d. All of the above
7. ATP is produced during the light reactions via
a. CO2 fixation.
b. chemiosmosis.
c. reduction of water.
d. All of the above
8. Because of the properties of chlorophyll, plants need adequate __________ light to grow properly.
a. green
b. blue and red
c. infrared
d. ultraviolet
9. Which of the following statements concerning the Calvin–Benson cycle is not true?
a. Light energy is not required for the cycle to proceed.
b. CO2 is assimilated into sugars.
c. RuBP is regenerated.
d. It uses energy stored in ATP and NADPH + H+.
10. Which of the following statements concerning rubisco is true?
a. Rubisco is an enzyme.
b. Rubisco catalyzes both the beginning steps of photorespiration and the Calvin–Benson cycle.
c. Rubisco is the most abundant protein on earth.
d. All of the above
11. Which of the following begins the Calvin–Benson cycle and is the commitment step that results in the entire pathway
being carried out?
a. 3PG is reduced to G3P using ATP and NADPH + H+.
b. RuBP is regenerated.
c. CO2 and RuBP join forming 3PG.
d. As a cycle, it can start at any point.
12. The Calvin–Benson Cycle results in the production of
a. glucose.
b. starch.
c. rubisco.
d. G3P.
13. Which of the following statements regarding photorespiration is true?
a. Photorespiration is a metabolically expensive pathway.
b. Photorespiration is avoided when CO2 is abundant.
c. Photorespiration reduces the overall CO2 that is converted to carbohydrates.
d. All of the above
14. The fixation of CO2 by PEP carboxylase functions to
a. concentrate CO2 for use in photosynthetic cells.
b. allow plants to close stomata without having photorespiration occur.
c. allow plants to photosynthesize in the dark.
d. Both a and b
15. CAM plants differ from C4 plants in that
a. CO2 is stored as malic acid.
b. photosynthesis can occur at night in these plants.
c. their stomata close during periods that favor photorespiration.
d. they use PEP carboxylase to fix CO2.
16. Which of the following statements is true regarding the relationship between photosynthesis and cellular respiration
in plants?
a. Photosynthesis occurs in specialized photosynthetic cells.
b. Cellular respiration occurs in specialized respiratory cells.
c. Cellular respiration and photosynthesis can occur in the same cell.
d. Both a and c
Answers
Knowledge and Synthesis Questions
1. c. Photosynthetic organisms are the only life forms capable of trapping light energy and converting it to chemical
energy. Because of this they form the basis of food chains.
2. d. Chloroplasts are the site of the photosynthetic reactions; chlorophyll is excited by photons of light and serve as
reaction centers for the photosystems; visible light is necessary to excite chlorophyll and accessory pigments; water is
the initial electron donor for the pathway; and CO2 is necessary to make precursor molecules for energy storage.
3. d. The “tails” of chlorophyll molecules are associated with the thylakoid membranes of the chloroplasts. This close
membrane association assists with establishing the proton-motive force that will drive ATP synthesis. When excited by
light, the chlorophyll moves into an excited state and passes electrons to acceptor molecules. This begins to set up the
proton gradient across the membrane that will drive ATP synthesis.
4. c. Water is split at photosystem II to donate electrons to the reaction center. The resulting protons are moved across
the membrane to establish the proton-motive force and O2 is given off as a by-product.
5. d. ATP is required at higher levels in the Calvin–Benson cycle than NADPH + H+ is; therefore, there must be a
mechanism for producing additional ATP. Cyclic electron flow provides that mechanism. If noncyclic electron flow were
to be sped up to meet ATP needs, an excess of NADPH + H+ would result. Shifting between cyclic and noncyclic flow
balances ATP/NADPH + H+ ratios.
6. d. Photosystems I and II operate depending on whether electron flow is cyclic or noncyclic. Activity is controlled by
the ATP levels in the chloroplast. Photosystem II is activated by light of a higher energy level than photosystem I. Both
photosystems transfer electrons and create proton gradients across the thylakoid membranes.
7. b. In the light reactions, ATP synthesis occurs when protons flow through an ATP synthase channel protein in the
thylakoid membrane. This is a chemiosmotically driven process.
8. b. Chlorophyll and accessory pigments absorb light in the blue and orange-red wavelengths of visible light. Green light
is reflected; therefore, plants appear green.
9. a. Light energy is required for the Calvin–Benson cycle to proceed. ATP synthesis is dependent on light energy, and the
Calvin–Benson cycle is dependent on ATP.
10. d. Rubisco, the most abundant enzyme on earth, has both oxygenase and carboxylase activities.
11. c. The first step of the Calvin–Benson cycle is the fixation of CO2 into 3PG. This is the regulatory step, and it requires
ATP and NADPH + H+.
12. d. The Calvin–Benson cycle produces only G3P. G3P can then be metabolized into storage products like sugars and
starch.
13. d. Photorespiration uses as much ATP as photosynthesis, but results in no energy gains for the plant and reduces net
carbon fixation by 25 percent compared with the Calvin–Benson cycle. If CO2 is abundantly available, rubisco acts as a
carboxylase rather than an oxygenase.
14. d. Plants do not photosynthesize in the dark. PEP carboxylase allows the fixation of CO2 and the concentration of it at
rubisco.
15. a. CAM plants functionally store CO2 as malic acid.
16. d. Photosynthesis occurs only in cells that have the necessary structures, but cellular respiration occurs in every living
cell.
TEXTBOOK SELF QUIZ QUESTIONS
1. In noncyclic photosynthetic electron transport, water is used to
a. excite chlorophyll.
b. hydrolyze ATP.
c. reduce chlorophyll.
d. oxidize NADPH.
e. synthesize chlorophyll.
2. Which statement about light is true?
a. An absorption spectrum is a plot of biological effectiveness versus wavelength.
b. An absorption spectrum may be a good means of identifying a pigment.
c. Light need not be absorbed to produce a biological effect.
d. A given kind of molecule can occupy any energy level.
e. A pigment loses energy as it absorbs a photon.
3. Which statement about chlorophylls is not true?
a. They absorb light near both ends of the visible spectrum.
b. They can accept energy from other pigments, such as carotenoids.
c. Excited chlorophyll can either reduce another substance or fluoresce.
d. Excited chlorophyll may be an oxidizing agent.
e. They contain magnesium.
4. In cyclic electron transport,
a. oxygen gas is released.
b. ATP is formed.
c. water donates electrons and protons.
d. NADPH + H+ forms.
e. CO2 reacts with RuBP.
5. Which of the following does not happen in noncyclic electron transport?
a. Oxygen gas is released.
b. ATP forms.
c. Water donates electrons and protons.
d. NADPH + H+ forms.
e. CO2 reacts with RuBP.
6. In the chloroplasts,
a. light leads to the pumping of protons out of the thylakoids.
b. ATP forms when protons are pumped into the thylakoids.
c. light causes the stroma to become more basic than the thylakoids.
d. protons return passively to the stroma through protein channels.
e. proton pumping requires ATP.
7. Which statement about the Calvin–Benson cycle is not true?
a. CO2 reacts with RuBP to form 3PG.
b. RuBP forms by the metabolism of 3PG.
c. ATP and NADPH + H+ form when 3PG is reduced.
d. The concentration of 3PG rises if the light is switched off.
e. Rubisco catalyzes the reaction of CO2 and RuBP.
8. In C4 photosynthesis,
a. 3PG is the first product of CO2 fixation.
b. rubisco catalyzes the first step in the pathway.
c. four-carbon acids are formed by PEP carboxylase in bundle sheath cells.
d. photosynthesis continues at lower CO2 levels than in C3 plants.
e. CO2 released from RuBP is transferred to PEP.
9. Photosynthesis in green plants occurs only during the day. Respiration in plants occurs
a. only at night.
b. only when there is enough ATP.
c. only during the day.
d. all the time.
e. in the chloroplast after photosynthesis.
10. Photorespiration
a. takes place only in C4 plants.
b. includes reactions carried out in peroxisomes.
c. increases the yield of photosynthesis.
d. is catalyzed by PEP carboxylase.
e. is independent of light intensity.
Answers
1. c
2. b
3. d
4. b
5. e
6. c
7. c
8. d
9. d
10. b
ONLINE QUIZ QUESTIONS
1.The overall reaction CO2 + H2O + NADPH + ATP → sugar + NADP + ADP + P
a.describes the light reactions of photosynthesis.
b.is exergonic.
c.occurs only at night.
d.requires many enzymes.
e.occurs only in the thylakoid membranes.
Answer: d
2.The light reactions of photosynthesis
a.convert light energy into chemical energy.
b.occur in all plant and animal cells.
c.occur only at night.
d.occur in both chloroplasts and mitochondria.
e.produce ADP from ATP.
Answer: a
3.Which statement about accessory pigments is not true?
a.Phycobilins absorb yellow-green, yellow and orange wavelengths.
b.Accessory pigments absorb photons intermediate in energy between the red and blue wavelengths.
c.Accessory pigments absorb blue and red wavelengths.
d.Carotenoids absorb photons in the blue and blue-green wavelengths and appear deep yellow.
e.Accessory pigments transfer a portion of energy to chlorophylls.
Answer: c
4.In noncyclic electron flow,
a.light energy is used to reduce water.
b.ATP and NADPH + H+ is formed.
c.only NADPH + H+ is formed.
d.only ATP is formed.
e.water is split to transfer oxygen to chlorophyll.
Answer: b
5.The chemical source of molecular oxygen O2 in photosynthesis is
a.CO2.
b.C6H12O6.
c.H2O.
d.NADP.
e.chlorophyll.
Answer: c
6.The NADPH required for CO2 fixation is formed
a.by the reduction of oxygen.
b.by the hydrolysis of ATP.
c.during photosystem I in noncyclic photosynthesis.
d.only in C4 plants.
e.in the mitochondria.
Answer: c
7.Which of the following is not a process of the Calvin–Benson Cycle?
a.For every "turn" of the cycle, with one CO2 fixed, the CO2 acceptor is regenerated.
b.CO2 combines with RuMP forming 3PG.
c.One-sixth of the G3P is used to make sugars.
d.Five-sixths is processed in the complex reactions that produce RuMP.
e.3PG is reduced to G3P in a two-step reaction requiring ATP and NADPH + H+.
Answer: b
8.In C3 photosynthesis,
a.PEP is the primary CO2 acceptor.
b.there are two classes of chloroplasts.
c.the photosynthetic cells of the leaf are mesophyll and bundle sheath.
d.there can be extensive photorespiration.
e.the first product of CO2 fixation is a 4-carbon compound.
Answer: d
9.Light reactions and the Calvin–Benson cycle occur in the
a.stroma.
b.chloroplasts.
c.cell wall.
d.mitochondria.
e.thykaloids.
Answer: e
10.Which of the following is true of photorespiration?
a.It takes place only in C4 plants.
b.It includes reactions carried out in peroxisomes.
c.It increases the yield of photosynthesis.
d.It is catalyzed by PEP carboxylase.
e.It is independent of light intensity.
Answer: b
11.Movement of hydrogen ions through the ATP synthetase pore fuels the later stages of photosynthesis.
a. true
b. false
Answer: a
12.Which of the following statements concerning photophosphorylation is false?
a. In the electron transport chain, electrons are passed through electron carriers via redox reactions.
b. Pigment molecules capture energy until the energy reaches a chlorophyll molecule.
c. Plastoquinone is reduced and cytochrome is oxidized when electrons move from one to the other.
d. NADP reductase reduces NADP+, producing NADPH and H+.
e. The reaction center is where light energy from a photon is absorbed and transferred to a chlorophyll molecule.
Answer: c
13.Chloroplasts
a. contain thylakoids, which are flattened sacs with chlorophyll inside.
b. are found in the mitochondria.
c. are found in both animal and plant cells.
d. are found only in plant cells.
e. a and d.
Answer: e
14.During cyclic photophosphorylation, which is (are) reduced using excited electrons form chlorophyll?
a. P 680
b. NADP
c. P 690
d. water
e. None of the above
Answer: e
15.The excited electrons that are removed from chlorophyll may be used to reduce
a. NADP.
b. water.
c. oxygen.
d. ATP.
e. glucose.
Answer: b