Chapter 11: Oxidative Phosphorylation
16. What would happen to the ETC and oxidative phosphorylation pathway in the presence of excess NADH if the mitochondrial matrix were not closed, but opened up to the cytoplasm? a. The ETC complexes would function as normal, but no ATP would be made. b. The ETC and synthesis of ATP would continue as normal. c. The ETC complexes would transfer electrons from NADH to O2, but no protons would be pumped. d. The NADH would react directly with O2, generating excess heat.
ANS: A DIF: Difficult REF: 11.1 OBJ: 11.1.d. Describe the role of the electron transport system. MSC: Applying
17. The TCA cycle is dependent on O2 to a. enable the regeneration of the NAD+ by the electron transport system. b. oxidize the sugar carbons to CO2. c. support cellular combustion reactions. d. serve as a substrate for the oxidoreductase enzymes.
ANS: A DIF: Difficult REF: 11.1 OBJ: 11.1.d. Describe the role of the electron transport system. MSC: Applying
47. An ATP synthase enzyme with more than 10 c subunits in the F0 stalk would a. require more protons to complete one 360° rotation. b. result in more ATP synthesis per 360° turn. c. require fewer protons to rotate 360°. d. result in less ATP synthesis per 360° turn.
ANS: A DIF: Difficult REF: 11.3 OBJ: 11.3.b. Explain the mechanism whereby proton flow through ATP synthase results in ATP synthesis. MSC: Applying
56. Which one of the following statements about the glycerol phosphate shuttle is true? a. It involves the transfer of electrons from cytoplasmic NADH to dihydroxyacetone phosphate (DHAP) to yield glycerol phosphate. b. It is more efficient than the malate aspartate shuttle. c. NADH produced in the cytoplasm by glycolysis ultimately leads to NADH in mitochondria. d. Glycerol phosphate diffuses into the mitochondria.
ANS: A DIF: Difficult REF: 11.4 OBJ: 11.4.b. Distinguish between mechanisms of electron transfer from NADH into the mitochondrial matrix in liver versus muscle cells. MSC: Understanding
70. Thermogenin (or uncoupling protein) is not toxic like 2,4-dinitrophenol because the protein a. is typically expressed in adipose tissues where ample fat calories are found. b. is less efficient at proton dissipation. c. cannot leave the mitochondria. d. is naturally occurring and not synthetic.
ANS: A DIF: Difficult REF: 11.5 OBJ: 11.5.c. Explain why some uncouplers (such as thermogenin) are adaptive to survival in certain animals. MSC: Evaluating
4. What are the principle physiological electron donors for the mitochondrial electron transport pathway? a. FADH2 and NADH b. FADH2, NADH, and NADPH c. NADH only d. UQH2, NADH, and FADH2
ANS: A DIF: Easy REF: 11.1 OBJ: 11.1.a. Summarize the purpose of the electron transport system. MSC: Remembering
3. The ultimate electron acceptor of the mitochondrial electron transport system is a. O2. b. NADH. c. H2O. d. cytochrome c.
ANS: A DIF: Easy REF: 11.1 OBJ: 11.1.a. Summarize the purpose of the electron transport system. MSC: Understanding
25. The electron transport complexes found in the electron transport system a. contain multiple electron transfer cofactors that facilitate electron transfer through the complexes. b. are bound to the outer mitochondrial membrane. c. pump protons from outside the mitochondria to the mitochondrial matrix on electron transfer. d. absorb light energy that results in electron transfer.
ANS: A DIF: Easy REF: 11.2 OBJ: 11.2.a. List the major components of the electron transport system. MSC: Analyzing
37. What active site cofactor is found in the electron transport system protein called cytochrome c? a. heme b. FeS cluster c. Flavin d. quinone
ANS: A DIF: Easy REF: 11.2 OBJ: 11.2.c. Hypothesize why cytochrome c is highly conserved in nature. MSC: Remembering
68. What is the cellular location of eukaryotic thermogenin (or uncoupling protein)? a. mitochondrial inner membrane b. mitochondrial matrix c. cytoplasm d. both cytoplasm and mitochondrial matrix
ANS: A DIF: Easy REF: 11.5 OBJ: 11.5.c. Explain why some uncouplers (such as thermogenin) are adaptive to survival in certain animals. MSC: Understanding
75. How are many mitochondrial diseases passed on from parents to offspring? a. through the mother only b. through the father only c. through an equal distribution from both parents d. by random mutations in the mitochondrial genome
ANS: A DIF: Easy REF: 11.5 OBJ: 11.5.e. Identify the reason why mitochondrial disorders are passed through the maternal line only. MSC: Remembering
6. Which of the following statements about the chemiosmotic theory is true? a. It requires an enclosed mitochondrial membrane. b. The membrane ATPase (or ATP synthase) has no significant role in the theory. c. Energy is coupled through a transmembrane electron gradient. d. It explains how ATP energy is used to create a pH gradient.
ANS: A DIF: Medium REF: 11.1 OBJ: 11.1.a. Summarize the purpose of the electron transport system. MSC: Analyzing
43. The catalytic headpiece of the ATP synthase enzyme is primarily composed of which subunits? a. a hexameric α3β3 ring b. a circle of ≥10 c subunits c. the F0 subunit d. γ, Δ, and ε subunits
ANS: A DIF: Medium REF: 11.3 OBJ: 11.3.a. Describe the organization and structure of ATP synthase. MSC: Remembering
51. The resting state of the three β subunits in the ATP synthase enzyme is best described as a. one O, one L, and one T conformation. b. all in O conformations. c. all in L conformations. d. one L and two O conformations.
ANS: A DIF: Medium REF: 11.3 OBJ: 11.3.c. State the three basic principles of the binding change mechanism. MSC: Applying
61. If the mitochondrial ATP synthase were inhibited, but the electron transport chain was allowed to run continuously, the pH of the cytoplasm would a. decrease. b. increase. c. remain unchanged. d. increase immediately and then decrease.
ANS: A DIF: Medium REF: 11.5 OBJ: 11.5.a. List the major activators and inhibitors of the electron transport system and ATP synthesis. MSC: Applying
67. What happens to patients given the proton gradient uncoupler 2,4-dinitrophenol? a. They undergo rapid decrease in body temperature as a result of lack of mitochondrial electron transport. b. They experience lower cellular pH as a result of rapid proton gradient dissipation. c. Their mitochondrial membranes fail as a result of rapid proton gradient release. d. Their body temperatures rise as a result of heat release from gradient uncoupling.
ANS: A DIF: Medium REF: 11.5 OBJ: 11.5.b. Classify the role of 2,4-dinitrophenol as it relates to the electron transport system. MSC: Applying
74. Which tissue types are affected the most by inherited mitochondrial disorders? a. those tissues with the highest levels of mitochondria and high levels of activity b. heart tissue c. liver tissue d. those tissues with the lowest levels of mitochondria
ANS: A DIF: Medium REF: 11.5 OBJ: 11.5.e. Identify the reason why mitochondrial disorders are passed through the maternal line only. MSC: Analyzing
48. What would happen to a mutated ATP synthase enzyme where the proton binding aspartate residue on the c subunits was mutated to an alanine? a. The enzyme would make ATP as normal in the presence of a proton gradient. b. The enzyme would not make ATP in the presence of a proton gradient. c. The enzyme would make ATP without the need for a proton gradient. d. The rotor would rotate in response to a proton gradient, but no ATP would be made.
ANS: B DIF: Difficult REF: 11.3 OBJ: 11.3.b. Explain the mechanism whereby proton flow through ATP synthase results in ATP synthesis. MSC: Evaluating
60. Electrons from a succinate molecule can enter into the ETC and result in enough pumped protons to make how many ATPs? a. 2.0 b. 1.5 c. 1.0 d. 2.5
ANS: B DIF: Difficult REF: 11.4 OBJ: 11.4.c. State net yield of ATP per glucose in liver and muscle cells. MSC: Applying
26. Identify the correct order of electron transfers in the electron transport chain starting from FADH2. a. complex I → complex II → complex III → complex IV b. complex II → complex III → cytochrome c → complex IV c. complex II → coenzyme Q → complex IV → ATP synthase d. complex I → coenzyme Q → complex III → complex IV
ANS: B DIF: Easy REF: 11.2 OBJ: 11.2.a. List the major components of the electron transport system. MSC: Understanding
27. Which is the only electron carrier in the electron transport system that is not embedded in a membrane? a. ATP b. cytochrome c c. coenzyme Q d. complex I
ANS: B DIF: Easy REF: 11.2 OBJ: 11.2.a. List the major components of the electron transport system. MSC: Understanding
39. What enzyme uses the proton motive force for its driving force? a. complex IV b. ATP synthase c. complex III d. complex I
ANS: B DIF: Easy REF: 11.2 OBJ: 11.2.d. Explain the role of the proton motive force. MSC: Remembering
49. In yeast, it is estimated that approximately __________ H+ are required by ATP synthase per ATP synthesized. a. 1 b. 3 c. 9 d. 10
ANS: B DIF: Easy REF: 11.3 OBJ: 11.3.b. Explain the mechanism whereby proton flow through ATP synthase results in ATP synthesis. MSC: Remembering
57. Which mechanism is the most efficient at moving NADH equivalents from the cytoplasm into the mitochondria? a. citrate shuttle b. malate-aspartate shuttle c. glyoxylate shunt d. glycerol phosphate shuttle
ANS: B DIF: Easy REF: 11.4 OBJ: 11.4.b. Distinguish between mechanisms of electron transfer from NADH into the mitochondrial matrix in liver versus muscle cells. MSC: Remembering
1. The major purpose of the electron transport system is to a. reduce oxygen to water. b. reoxidize NADH and use that energy to pump protons across a membrane. c. produce ATP. d. produce NADH for cellular respiration.
ANS: B DIF: Medium REF: 11.1 OBJ: 11.1.a. Summarize the purpose of the electron transport system. MSC: Understanding
10. Mitochondria a. selectively transport molecules from the cytoplasm to the intermembrane space. b. maintain a pH gradient across the inner mitochondrial membrane. c. are found one per cell. d. have a matrix that is continuous with the cytoplasm.
ANS: B DIF: Medium REF: 11.1 OBJ: 11.1.c. Describe the structure of the mitochondrion. MSC: Understanding
11. Mitochondria a. have a porous inner membrane and nonporous outer membrane. b. have a higher pH inside the matrix than outside during active electron transport. c. have an outer membrane that is composed of lipids and protein electron transport complexes. d. generate ATP for the cell under anaerobic and aerobic conditions.
ANS: B DIF: Medium REF: 11.1 OBJ: 11.1.c. Describe the structure of the mitochondrion. MSC: Understanding
15. The energy released during mitochondrial electron transport processes is used to a. make ATP. b. pump protons across the membrane. c. heat the mitochondria. d. synthesize carbohydrates.
ANS: B DIF: Medium REF: 11.1 OBJ: 11.1.d. Describe the role of the electron transport system. MSC: Analyzing
22. The first enzyme in the electron transport system is referred to as complex I, otherwise known as a. ATP synthase. b. NADH-ubiquinone oxidoreductase. c. succinate dehydrogenase. d. cytochrome c oxidase.
ANS: B DIF: Medium REF: 11.1 OBJ: 11.1.f. Name the major enzymes of the electron transport system. MSC: Understanding
28. Which statement is true of the mitochondrial electron transport system? a. All the electron carriers are located in enzyme complexes. b. All the electrons in the chain end up on O2 to produce water. c. The pH drops in the mitochondria as electrons pass through the system. d. Protons are pumped from the inner membrane space to the mitochondrial matrix during the electron transfer.
ANS: B DIF: Medium REF: 11.2 OBJ: 11.2.a. List the major components of the electron transport system. MSC: Analyzing
41. Protons in the mitochondria are a. the driving force for the electron transfers in the electron transport system. b. pumped by mitochondrial electron transport system enzymes. c. pumped inside the mitochondria using ATP energy. d. the cause of a lower pH inside the mitochondria than outside the mitochondria.
ANS: B DIF: Medium REF: 11.2 OBJ: 11.2.d. Explain the role of the proton motive force. MSC: Analyzing
40. What best describes the driving force for ATP synthesis in the mitochondria? a. Electron transport from electron transport system complexes. b. The higher pH inside the mitochondria that results from electron transfer. c. The large drops in ΔG resulting from electron transfer in the ETC. d. The substrate level phosphorylations of the TCA cycle and glycolysis.
ANS: B DIF: Medium REF: 11.2 OBJ: 11.2.d. Explain the role of the proton motive force. MSC: Evaluating
45. ATP synthesis occurs a. on the outer mitochondrial membrane. b. at the ATP synthase complex after ADP and Pi are transported into the mitochondria. c. as a result of the leakage of H+ back out of the mitochondria. d. from the electron transfer reactions through complex IV.
ANS: B DIF: Medium REF: 11.3 OBJ: 11.3.b. Explain the mechanism whereby proton flow through ATP synthase results in ATP synthesis. MSC: Evaluating
53. What type of transport is illustrated by the mitochondrial ATP/ADP translocase? a. symporter b. antiporter c. facilitated diffusion d. primary active transporter
ANS: B DIF: Medium REF: 11.4 OBJ: 11.4.a. Describe how ADP, ATP, and Pi are moved across the inner mitochondrial membrane. MSC: Applying
14. What is the fate of NADH after it donates its electrons to the electron transport system? a. NAD+ is excreted from the cell and sent to the liver for final degradation. b. NADH is used for cellular biosynthesis. c. NAD+ is re-reduced by the TCA cycle or glycolysis and returns to electron transport system, where the process is repeated. d. NAD+ is fed into the TCA cycle for oxidation of CO2.
ANS: C DIF: Difficult REF: 11.1 OBJ: 11.1.d. Describe the role of the electron transport system. MSC: Evaluating
20. A decrease in __________ would be LEAST likely to affect the processes of the electron transport system. a. oxygen concentrations in the cell b. the TCA cycle activity c. cellular CO2 concentrations d. the concentration of cellular NADH
ANS: C DIF: Difficult REF: 11.1 OBJ: 11.1.e. State the overall reaction of the electron transport system. MSC: Analyzing
29. For one electron entering the electron transport chain at complex I, how many times is it handed off between redox active cofactors on its way through the enzyme complexes to end up on O2? a. ~2000 b. ~200 c. ~20 d. ~2
ANS: C DIF: Difficult REF: 11.2 OBJ: 11.2.a. List the major components of the electron transport system. MSC: Evaluating
58. How many ATPs are obtained from one acetyl-CoA run once through the TCA cycle, assuming that all resulting NADH and FADH2 is used by the electron transport chain and oxidative phosphorylation to make ATP? a. 6.5 b. 9 c. 10 d. 11
ANS: C DIF: Difficult REF: 11.4 OBJ: 11.4.c. State net yield of ATP per glucose in liver and muscle cells. MSC: Applying
66. What would happen if mitochondria were treated with a proton gradient uncoupler, such as 2,4-dinitrophenol? a. Electron transfer would stop. b. Complex I would become reduced, and complexes III and IV would become oxidized. c. Protons would be pumped by the mitochondrial electron transport chain, although no ATP would be synthesized. d. Reducing equivalents, in the form of NADH, would no longer be consumed.
ANS: C DIF: Difficult REF: 11.5 OBJ: 11.5.b. Classify the role of 2,4-dinitrophenol as it relates to the electron transport system. MSC: Applying
24. Which of the following is an electron carrier in the mitochondrial electron transport system? a. proton b. water c. quinone d. ATP
ANS: C DIF: Easy REF: 11.2 OBJ: 11.2.a. List the major components of the electron transport system. MSC: Understanding
30. Which one of the following is involved in the flow of electrons from NADH through the electron transport system to molecular oxygen (O2)? a. ATP synthase b. complex II c. complex III d. ATP
ANS: C DIF: Easy REF: 11.2 OBJ: 11.2.b. Describe the roles of complexes I, III, and IV of the electron transport system. MSC: Remembering
31. Which is NOT involved in the transfer of reducing equivalents from succinate to molecular oxygen (O2)? a. cytochrome c b. coenzyme Q c. complex I d. complex II
ANS: C DIF: Easy REF: 11.2 OBJ: 11.2.b. Describe the roles of complexes I, III, and IV of the electron transport system. MSC: Remembering
34. The electron transport chain component that transfers electrons directly to oxygen is a. complex I. b. cytochrome c. c. complex IV. d. NADH.
ANS: C DIF: Easy REF: 11.2 OBJ: 11.2.b. Describe the roles of complexes I, III, and IV of the electron transport system. MSC: Understanding
42. ATP synthase is located in or on the a. cytoplasm. b. intermembrane space of the mitochondria. c. inner mitochondrial membrane. d. outer mitochondrial membrane.
ANS: C DIF: Easy REF: 11.3 OBJ: 11.3.a. Describe the organization and structure of ATP synthase. MSC: Remembering
59. How many ATPs are produced from the complete metabolism of one glucose molecule, assuming that all resulting NADH and FADH2 is used by the electron transport chain and oxidative phosphorylation to make ATP? a. 4 b. 16 c. 32 d. 102
ANS: C DIF: Easy REF: 11.4 OBJ: 11.4.c. State net yield of ATP per glucose in liver and muscle cells. MSC: Remembering
72. What is the primary fuel metabolized by the mitochondria in brown adipose tissue of hibernating animals? a. glucose b. NADH c. lipid d. ATP
ANS: C DIF: Easy REF: 11.5 OBJ: 11.5.d. Describe brown adipose tissue and explain its role in certain species. MSC: Understanding
2. Approximately how many more ATPs are made from one glucose molecule under aerobic conditions with oxidative phosphorylation than under anaerobic conditions? a. 0 b. 2 c. 30 d. 104
ANS: C DIF: Medium REF: 11.1 OBJ: 11.1.a. Summarize the purpose of the electron transport system. MSC: Analyzing
8. In the mitochondrial electron transport system, the electron from NADH moves from __________ the mitochondria through the protein complexes to __________ the mitochondria. a. outside; outside b. outside; inside c. inside; inside d. inside; outside
ANS: C DIF: Medium REF: 11.1 OBJ: 11.1.b. Compare the direction of proton flow in the mitochondrion to that in the chloroplast. MSC: Remembering
21. Which of the following is NOT a part of oxidative phosphorylation? a. NADH is oxidized to NAD+. b. O2 is reduced to H2O. c. Electrons from O2 are transferred to ATP. d. The pumping of protons is coupled with the formation of ATP.
ANS: C DIF: Medium REF: 11.1 OBJ: 11.1.e. State the overall reaction of the electron transport system. MSC: Analyzing
33. A characteristic of complex III is that it a. transports electrons from cytochrome c to complex IV. b. is reduced by FADH2. c. uses the Q cycle mechanism to oxidize ubiquinone. d. participates in electron transfer when the donor is NADH but not when the donor is succinate (or FADH2).
ANS: C DIF: Medium REF: 11.2 OBJ: 11.2.b. Describe the roles of complexes I, III, and IV of the electron transport system. MSC: Understanding
52. The __________ causes the catalytic headpiece of ATP synthase to change conformation. a. rotation of the circle of the α3β3 subunits b. movement of the circle of ~10 c subunits c. interaction with the rotating central γ subunit d. binding of ADP and Pi
ANS: C DIF: Medium REF: 11.3 OBJ: 11.3.c. State the three basic principles of the binding change mechanism. MSC: Understanding
64. The main activator molecule of the ATP synthesis and the electron transport system is a. ATP. b. H+. c. ADP. d. NAD+.
ANS: C DIF: Medium REF: 11.5 OBJ: 11.5.a. List the major activators and inhibitors of the electron transport system and ATP synthesis. MSC: Understanding
69. Which animal would have the lowest levels of brown adipose tissue? a. newborn human b. hibernating squirrel c. migrating duck d. polar bear
ANS: C DIF: Medium REF: 11.5 OBJ: 11.5.c. Explain why some uncouplers (such as thermogenin) are adaptive to survival in certain animals. MSC: Evaluating
71. Brown adipose tissue is brown in color because of a. increased levels of thermogenin, or uncoupling protein. b. increased muscle fiber content. c. increased numbers of mitochondria. d. decreased levels of lipid.
ANS: C DIF: Medium REF: 11.5 OBJ: 11.5.d. Describe brown adipose tissue and explain its role in certain species. MSC: Evaluating
19. Which reaction does the concept of oxidative phosphorylation refer to? a. O2 + ADP + Pi → 2 H2O + ATP b. NADH + H+ + 1/2 O2 → NAD+ + H2O c. ADP + Pi → ATP d. NADH + 1/2 O2 + H+ + ADP + Pi → NAD+ + ATP + H2O
ANS: D DIF: Difficult REF: 11.1 OBJ: 11.1.e. State the overall reaction of the electron transport system. MSC: Understanding
35. Complex IV in the mitochondrial electron transport chain belongs to which enzyme class? a. lyase b. hydrolase c. transferase d. oxidoreductase
ANS: D DIF: Difficult REF: 11.2 OBJ: 11.2.b. Describe the roles of complexes I, III, and IV of the electron transport system. MSC: Applying
38. The structure of the electron transport system protein called cytochrome c is highly conserved in nature because the a. enzyme has the rare ability to bind O2 and reduce it. b. protein active site contains a cofactor unique to the electron transport system. c. protein is located inside the mitochondria of eukaryotic cells. d. protein plays an important role in the electron transport system and in other critical cellular pathways such as apoptosis.
ANS: D DIF: Difficult REF: 11.2 OBJ: 11.2.c. Hypothesize why cytochrome c is highly conserved in nature. MSC: Evaluating
50. Which part of the native ATP synthase enzyme is stationary and does NOT rotate during ATP synthesis? a. the rotor b. the circle of c subunits c. the central γ subunit connecting the rotor to the catalytic headpiece d. the catalytic headpiece
ANS: D DIF: Difficult REF: 11.3 OBJ: 11.3.c. State the three basic principles of the binding change mechanism. MSC: Analyzing
62. Inhibitors of the electron transport system, such as cyanide (CN−) and carbon monoxide (CO), inhibit complex IV by binding to the heme iron cofactor. What is the resulting effect on oxidative phosphorylation? a. Electrons pass through the electron transport system, but no protons are pumped. b. Protons are pumped, but no electron transport occurs. c. The electron transport system occurs normally, but no ATP is synthesized. d. Electron transport is disabled, and no protons are pumped.
ANS: D DIF: Difficult REF: 11.5 OBJ: 11.5.a. List the major activators and inhibitors of the electron transport system and ATP synthesis. MSC: Understanding
7. Protons are pumped by mitochondria during active electron transport a. into the thylakoid lumen. b. outside the outer mitochondrial membrane. c. into the mitochondrial matrix. d. outside the inner mitochondrial membrane.
ANS: D DIF: Easy REF: 11.1 OBJ: 11.1.b. Compare the direction of proton flow in the mitochondrion to that in the chloroplast. MSC: Understanding
36. What is the location of the electron transport system protein called cytochrome c? a. cytoplasm b. mitochondrial matrix c. inner mitochondrial membrane d. intermembrane space
ANS: D DIF: Easy REF: 11.2 OBJ: 11.2.c. Hypothesize why cytochrome c is highly conserved in nature. MSC: Remembering
73. The role of brown adipose tissue is to a. efficiently generate ATP from fat tissue. b. metabolize excess fat calories. c. store excess calories as fat. d. generate heat for the organism.
ANS: D DIF: Easy REF: 11.5 OBJ: 11.5.d. Describe brown adipose tissue and explain its role in certain species. MSC: Understanding
5. Which process or pathway describes the coupling of the oxidation reaction of NADH with the formation of ATP? a. electron transport system b. chemiosmotic theory c. proton motive force d. oxidative phosphorylation
ANS: D DIF: Medium REF: 11.1 OBJ: 11.1.a. Summarize the purpose of the electron transport system. MSC: Remembering
9. Which statement comparing chloroplasts and mitochondria is true? a. Chloroplasts and mitochondria each contain two membranes. b. Chloroplasts and mitochondria use electrons from NADH to create a proton gradient. c. Chloroplasts pump protons outside the organelle, while mitochondria pump protons inside the inner part of the organelle. d. Chloroplasts and mitochondria use energy from a proton gradient to make ATP.
ANS: D DIF: Medium REF: 11.1 OBJ: 11.1.b. Compare the direction of proton flow in the mitochondrion to that in the chloroplast. MSC: Analyzing
12. Studies of the inner mitochondrial membrane reveal its composition to be approximately 20% lipid bilayer and 80% protein. What is true of these proteins? a. Abundant collagen proteins form connective tissues to strengthen the membrane against the pH gradient. b. High levels of proteins are required to metabolize glucose in the glycolysis pathway for rapid energy production. c. The proteins form highly folded cristae structures. d. The proteins are largely electron transport complexes and ATP synthase enzymes.
ANS: D DIF: Medium REF: 11.1 OBJ: 11.1.c. Describe the structure of the mitochondrion. MSC: Understanding
13. As electrons from NADH pass through the electron transport system, a. the oxidized form of ADP is reduced to ATP. b. the reduction potential of the mitochondria becomes more thermodynamically favorable. c. the resulting electron gradient is used to make ATP. d. protons are pumped across the mitochondrial membrane to create a pH gradient.
ANS: D DIF: Medium REF: 11.1 OBJ: 11.1.d. Describe the role of the electron transport system. MSC: Understanding
23. The last enzyme in the electron transport system, where O2 is reduced to water, is called a. NADH-ubiquinone oxidoreductase. b. ATP synthase. c. ubiquinone cytochrome c oxidoreductase. d. cytochrome c oxidase.
ANS: D DIF: Medium REF: 11.1 OBJ: 11.1.f. Name the major enzymes of the electron transport system. MSC: Remembering
32. What is the reaction catalyzed by complex III in the electron transport system? a. UQH2 + O2 → UQ + H2O b. UQH2 + complex IV+ → UQ + complex IV c. FADH2 + UQ → FAD + UQH2 d. UQH2 + cytochrome c+ → UQ + cytochrome c
ANS: D DIF: Medium REF: 11.2 OBJ: 11.2.b. Describe the roles of complexes I, III, and IV of the electron transport system. MSC: Remembering
44. The ATP synthase enzyme contains a central stalk embedded in the mitochondrial membrane. What part of this stalk rotates? a. the α3β3 ring b. the F1 subunit c. the d, h, and OSCP subunits d. the ring of c subunits
ANS: D DIF: Medium REF: 11.3 OBJ: 11.3.a. Describe the organization and structure of ATP synthase. MSC: Remembering
46. What is the driving force for ATP synthesis by the ATP synthase enzyme? a. The electron transfers through the protein complexes. b. ADP + Pi → ATP c. The oxidation of NADH to NAD+. d. The pH gradient across the inner mitochondrial membrane.
ANS: D DIF: Medium REF: 11.3 OBJ: 11.3.b. Explain the mechanism whereby proton flow through ATP synthase results in ATP synthesis. MSC: Understanding
54. During transfer of ATP, ADP, and Pi, some of the proton gradient is lost in the a. movement of ATP into the mitochondria by the ATP/ADP translocase. b. movement of ATP out of the mitochondria. c. transport of ADP into the mitochondria by the ADP translocase. d. transport of Pi into the mitochondria by the phosphate translocase.
ANS: D DIF: Medium REF: 11.4 OBJ: 11.4.a. Describe how ADP, ATP, and Pi are moved across the inner mitochondrial membrane. MSC: Remembering
55. Which one of the following correctly designates the number of ATPs generated by the reducing molecules shown below? a. NADH from the TCA cycle—1.5 ATP b. NADH from the cytosol (glycerol phosphate shuttle)—2.25 ATP c. NADH from the cytosol (malate-aspartate shuttle)—1.5 ATP d. FADH2 from the TCA cycle—1.5 ATP
ANS: D DIF: Medium REF: 11.4 OBJ: 11.4.b. Distinguish between mechanisms of electron transfer from NADH into the mitochondrial matrix in liver versus muscle cells. MSC: Remembering
63. The drug oligomycin inhibits ATP synthase by preventing protons from flowing through the enzyme. Oligomycin must bind to the __________ of ATP synthase. a. catalytic headpiece b. F1 subunit c. ATP binding site d. F0 subunit of
ANS: D DIF: Medium REF: 11.5 OBJ: 11.5.a. List the major activators and inhibitors of the electron transport system and ATP synthesis. MSC: Applying
65. What is the effect of oligomycin, an ATP synthase inhibitor, on the mitochondrial oxidative phosphorylation pathway? a. The mitochondria cannot reduce NADH or make ATP. b. No proton gradient is formed, and no ATP is synthesized. c. Protons leak back into the cytoplasm. d. The proton gradient is formed, but no ATP synthesis can occur.
ANS: D DIF: Medium REF: 11.5 OBJ: 11.5.a. List the major activators and inhibitors of the electron transport system and ATP synthesis. MSC: Applying