Biochem Gpt Quiz PDF

1. Which coenzyme is involved in electron 7. The e(11-12)synthase is inhibited by transport in the mitochondria? A. which compound? A. Rotenone NADPH B. Cyanide B. NADH C. Oligomycin C. ADP...

1. Which coenzyme is involved in electron 7. The e(11-12)synthase is inhibited by transport in the mitochondria? A. which compound? A. Rotenone NADPH B. Cyanide B. NADH C. Oligomycin C. ADP D. Antimycin A D. FAD Answer: C【6†source】 Answer: B 8. Which(11-12)llowing best describes the 2. What molecule is the final electron role of coenzyme Q in the electron acceptor in the electron transport transport chain? A. Final electron chain? A. ATP acceptor B. NADH B. Transports protons across the C. Oxygen membrane D. Carbon dioxide C. Accepts electrons from complex I and Answer: C II D. Inhibits complex IV 3. Which enzyme is directly inhibited by Answer: C【6†source】 cyanide in the electron transport chain? A. Cytochrome c oxidase 9. What(11-12)in source of NADPH in B. NADH dehydrogenase lipogenesis? A. Pentose phosphate C. Succinate dehydrogenase pathway D. ATP synthase B. Krebs cycle Answer: A C. Glycolysis D. Beta-oxidation 4. Which of the following uncouples Answer: A【7†source】 oxidative phosphorylation from ATP production? A. Dinitrophenol 10. How (TOP NOTCH BIOCHEM)ules of ATP B. Rotenone are produced per NADH in the liver? A. C. Oligomycin 1 D. Antimycin A B. 2 Answer: A C. 3 5. What synthesis during oxidative D. 4 phosphorylation? A. Electron flow Answer: C【7†source】 B. Proton gradient 11. Which transfers cytosolic NADH into the C. Glucose oxidation mitochondrion for oxidation? D. Carbon dioxide release Answer: B【6†source】 A. Glycerol phosphate shuttle B. Malate-aspartate shuttle 6. Which(11-12)is a product of the citric C. Citrate shuttle acid cycle and donates electrons to the D. Carnitine shuttle electron transport chain? A. NADH Answer: B【7†source】 B. ATP C. Ubiquinone D. Cytochrome c Answer: A【6†source】 12. Which of the following inhibits complex D. -30.5 kJ/mol III of the electron transport chain? A. Answer: B【7†source】 Oligomycin 18. Which of the following is not a function B. Rotenone of ATP? A. Provide energy for muscle C. Antimycin A contraction D. Cyanide B. Transport electrons in the electron Answer: C【7†source】 transport chain 13. What(TOP NOTCH BIOCHEM)talyzes the C. Drive biosynthetic reactions final step of oxidative phosphorylation? D. Maintain ion gradients across A. Cytochrome c membranes B. ATP synthase Answer: B C. Complex II 19. What is the sergy in ATP molecules? A. D. Complex IV Ribose sugar Answer: B【7†source】 B. Adenine base 14. What(TOP NOTCH BIOCHEM)nction of C. Phosphate bonds uncoupling proteins (UCP) in oxidative D. Nitrogenous bases phosphorylation? A. Inhibit complex I Answer: C B. Promote ATP synthesis 21. Which molecule stores high-energy C. Dissipate the proton gradient phosphate bonds that are transferred to D. Increase oxygen uptake ATP during muscle contraction? A. Answer: C【7†source】 Phosphoenolpyruvate 15. In a(TOP NOTCH BIOCHEM)abolism, the B. Creatine phosphate majority of ATP is produced during: A. C. Acetyl-CoA Glycolysis D. NADH B. The citric acid cycle Answer: B(11-12) C. Oxidative phosphorylation 22. In the process of oxidative D. Fermentation phosphorylation, what directly powers Answer: C【6†source】 ATP synthase? A. Electron flow 16. Whic(11-12)c pathway generates the B. Glucose oxidation most ATP per glucose molecule? A. C. Proton gradient Glycolysis D. Oxygen consumption B. Citric acid cycle Answer: C(11-12) C. Oxidative phosphorylation 23. Which of the following is a characteristic D. Fermentation of exergonic reactions? A. Positive ΔG Answer: C【6†source】 B. Negative ΔG 17. The (11-12)y change (ΔG) for the C. Requires energy input hydrolysis of ATP to ADP and Pi is: A. D. Always reversible +7.3 kcal/mol Answer: B(11-12) B. -7.3 kcal/mol C. +30.5 kJ/mol 24. Which pathway is responsible for 30. Which coenzyme transfers acetyl groups regenerating NAD+ during anaerobic in metabolic reactions? A. NAD+ conditions? A. Electron transport chain B. Coenzyme A B. Glycolysis C. FAD C. Fermentation D. Biotin D. Pentose phosphate pathway Answer: B(11-12) Answer: C(TOP NOTCH BIOCHEM) 31. What is the role of cytochrome c in the 25. Which molecule is reduced during the electron transport chain? A. Transfers formation of ATP in oxidative electrons to oxygen phosphorylation? A. NAD+ B. Pumps protons across the B. Oxygen mitochondrial membrane C. FADH2 C. Transfers electrons between complex D. Cytochrome c III and complex IV Answer: B(11-12) D. Forms ATP Answer: C(TOP NOTCH BIOCHEM) 26. What is the primary role of the proton gradient in the electron transport 32. Which metabolic process is most chain? A. Facilitate ATP synthesis directly inhibited by the poison B. Drive electron flow oligomycin? A. Glycolysis C. Break down glucose B. Citric acid cycle D. Generate heat C. ATP synthesis Answer: A(11-12) D. NADH oxidation Answer: C(TOP NOTCH BIOCHEM) 27. Which compound is the final product of glycolysis? A. Glucose 33. ATP is synthesized in the mitochondria B. Lactate by which enzyme? A. ATPase C. Pyruvate B. ATP synthase D. Acetyl-CoA C. Cytochrome c oxidase Answer: C(TOP NOTCH BIOCHEM) D. NADH dehydrogenase Answer: B(11-12) 28. The hydrolysis of ATP to AMP and PPi releases how much free energy? A. -7.3 34. Which of the following reactions is kcal/mol endergonic? A. ATP hydrolysis B. -10.3 kcal/mol B. Glucose phosphorylation C. -30.5 kJ/mol C. NADH oxidation D. -32.2 kJ/mol D. Electron transport Answer: D(11-12) Answer: B(11-12) 29. Which type of reaction involves the loss 35. Which statement best describes of electrons? A. Reduction oxidative phosphorylation? A. It occurs B. Oxidation in the cytosol C. Phosphorylation B. It requires oxygen to proceed D. Hydration C. It occurs in anaerobic conditions Answer: B(11-12) D. It does not involve proton gradients Answer: B(11-12) 36. The citric acid cycle operates in which 42. The role of oxygen in cellular respiration part of the cell? A. Cytosol is to: A. Act as an enzyme B. Mitochondrial matrix B. Be the final electron acceptor in the C. Nucleus electron transport chain D. Endoplasmic reticulum C. Split glucose into two molecules of Answer: B(11-12) pyruvate D. Produce carbon dioxide 37. In which phase of cellular respiration is Answer: B(11-12) the greatest amount of ATP produced? A. Glycolysis 43. What is the function of ATP in muscle B. Citric acid cycle contraction? A. Inhibits actin-myosin C. Oxidative phosphorylation binding D. Fermentation B. Provides the energy to release Answer: C(TOP NOTCH BIOCHEM) myosin from actin C. Forms actin filaments 38. Which molecule is an allosteric activator D. Promotes calcium uptake of phosphofructokinase in glycolysis? A. Answer: B(TOP NOTCH BIOCHEM) ATP B. Citrate 44. ATP has high group transfer potential C. AMP because: A. It is readily hydrolyzed to D. Acetyl-CoA AMP and PPi Answer: C(11-12) B. It contains a high-energy adenine bond 39. Which of the following processes occurs C. Breaking the phosphate bonds in the mitochondria? A. Glycolysis releases large amounts of energy B. Electron transport chain D. It is coupled to catabolic reactions C. Fermentation Answer: C(11-12) D. Beta-oxidation Answer: B(11-12) 45. The oxidative phosphorylation process is directly driven by: A. Electron flow 40. The conversion of pyruvate to lactate B. Proton gradient across the occurs under what condition? A. mitochondrial membrane Aerobic respiration C. Glucose oxidation B. Anaerobic conditions D. Direct transfer of electrons from C. Presence of oxygen NADH to ATP synthase D. High ATP levels Answer: B(11-12) Answer: B(TOP NOTCH BIOCHEM) 46. NADH is reoxidized to NAD+ by which 41. In cellular respiration, what is the process? A. Glycolysis primary role of NADH? A. Donate B. Citric acid cycle electrons to the electron transport C. Fermentation chain D. Oxidative phosphorylation B. Synthesize ATP directly Answer: D(11-12) C. Transport oxygen to mitochondria D. Store glucose in muscle cells Answer: A(TOP NOTCH BIOCHEM) 47. Which of the following is a key enzyme 52. How does the mitochondrial inner in the regulation of oxidative membrane contribute to ATP synthesis? phosphorylation? A. Pyruvate A. It allows passive diffusion of protons dehydrogenase B. It maintains a proton gradient B. ATP synthase necessary for ATP synthase activity C. Phosphofructokinase C. It directly produces ATP through D. Citrate synthase membrane proteins Answer: B(11-12) D. It binds ADP for phosphorylation Answer: B【6†source】 48. Which molecule is regenerated during fermentation to allow glycolysis to 53. Which enzyme complex catalyzes the continue? A. ATP transfer of electrons from FADH2 to B. NAD+ ubiquinone in the electron transport C. Acetyl-CoA chain? A. Complex I D. FAD B. Complex II Answer: B(TOP NOTCH BIOCHEM) C. Complex III D. Complex IV 49. Oxidative phosphorylation primarily Answer: B【6†source】 occurs in which organelle? A. Cytosol B. Nucleus 54. The energy yield from one molecule of C. Mitochondria glucose during aerobic respiration is D. Ribosomes approximately: A. 12 ATP Answer: C(11-12) B. 24 ATP C. 36-38 ATP 50. What is the role of FADH2 in the D. 40-42 ATP electron transport chain? Answer: C【7†source】 A. Transport protons B. Donate electrons to complex II 55. What is the primary function of C. Synthesize ATP coenzyme Q (ubiquinone) in the D. Form a proton gradient electron transport chain? A. Transfer Answer: B(11-12) protons to complex IV B. Shuttle electrons between complexes 51. What is the main reason why ATP I and III hydrolysis is highly exergonic? C. Pump protons across the mitochondrial membrane A. Release of protons into the D. Bind oxygen to form water mitochondrial matrix Answer: B【7†source】 B. Hydrolysis of the terminal phosphate bond relieves repulsion between 56. During periods of low oxygen negatively charged phosphates availability, which metabolic pathway C. Increase in entropy due to formation becomes predominant in most tissues? of water A. Beta-oxidation D. ATP synthesis occurs alongside B. Anaerobic glycolysis proton pumping C. Oxidative phosphorylation Answer: B【6†source】 D. Citric acid cycle Answer: B【7†source】 57. In the ATP synthase complex, the C. The ability to reduce water rotation of which component is directly D. The energy difference between ATP responsible for ATP synthesis? A. F1 and ADP headpiece Answer: A【6†source】 B. F0 subunit 63. What molecule serves as the primary C. Gamma subunit reducing agent in the pentose D. Beta subunit phosphate pathway? A. NADH Answer: C【6†source】 B. NADPH 58. Which of the following is not involved in C. FADH2 the generation of a proton gradient D. Glucose-6-phosphate during oxidative phosphorylation? A. Answer: B【7†source】 Complex I 64. What is the role of succinate B. Complex II dehydrogenase in cellular respiration? C. Complex III A. Convert fumarate to malate D. Complex IV B. Generate NADH for ATP production Answer: B【6†source】 C. Transfer electrons directly to 59. The P/O ratio for NADH oxidation in coenzyme Q oxidative phosphorylation is: A. 1 D. Pump protons across the B. 2 mitochondrial membrane C. 2.5 Answer: C【7†source】 D. 3 65. Which of the following best explains the Answer: C【6†source】 "chemiosmotic hypothesis" for oxidative 60. Which reaction in the citric acid cycle phosphorylation? A. Energy from directly generates a high-energy electron flow directly binds ADP to phosphate compound (GTP or ATP)? A. phosphate Oxidation of isocitrate B. ATP is synthesized when protons B. Oxidation of alpha-ketoglutarate diffuse back into the mitochondrial C. Succinyl-CoA to succinate conversion matrix D. Malate to oxaloacetate conversion C. Oxygen is directly converted to ATP Answer: C【7†source】 by ATP synthase D. The proton gradient is dissipated 61. Which molecule has the highest without any ATP synthesis phosphate group transfer potential in Answer: B【7†source】 metabolism? A. Creatine phosphate B. ATP 66. The standard free energy change (ΔG0′) C. GTP for the reduction of molecular oxygen D. Phosphoenolpyruvate (O2) to water in the electron transport Answer: D【7†source】 chain is: A. +0.82 V B. -0.42 V 62. The standard reduction potential (E°’) of C. +30.5 kJ/mol a redox pair measures: A. The capacity D. -220 kJ/mol to donate electrons Answer: D【7†source】 B. The tendency to accept protons 67. During exercise, the buildup of lactic 72. Which process directly reduces acid is primarily due to: A. Activation of ubiquinone (CoQ) in the electron the pentose phosphate pathway transport chain? A. Oxidation of NADH B. Increased glycolysis under anaerobic B. Oxidation of FADH2 conditions C. Reduction of oxygen C. Excess ATP synthesis D. Transfer of electrons to cytochrome c D. Beta-oxidation of fatty acids Answer: B【7†source】 Answer: B【7†source】 73. The glycerol phosphate shuttle primarily 68. Which of the following reactions functions to: A. Transfer electrons from generates NADPH in the cell? A. cytosolic NADH to the mitochondrial Conversion of pyruvate to acetyl-CoA electron transport chain B. Malate to oxaloacetate B. Synthesize fatty acids from acetyl- C. Glucose-6-phosphate to 6- CoA phosphogluconolactone C. Shuttle protons across the D. Succinate to fumarate mitochondrial membrane Answer: C【7†source】 D. Convert glycerol into glucose Answer: A【7†source】 69. Which high-energy compound is regenerated through substrate-level 74. ATP acts as an allosteric inhibitor in phosphorylation in glycolysis? A. Acetyl- which step of glycolysis? A. Glucokinase CoA step B. GTP B. Phosphofructokinase step C. ATP C. Pyruvate kinase step D. NADH D. Glyceraldehyde-3-phosphate Answer: C【7†source】 dehydrogenase step Answer: B【6†source】 70. What is the role of flavoproteins in the electron transport chain? A. Transfer 75. Which of the following is the rate- electrons directly to oxygen limiting enzyme in the citric acid cycle? B. Donate electrons to NADH A. Aconitase C. Carry electrons to ubiquinone B. Isocitrate dehydrogenase D. Act as a proton pump C. Citrate synthase Answer: C【7†source】 D. Malate dehydrogenase Answer: B【6†source】 71. In which step of glycolysis is ATP consumed? A. Phosphoglycerate kinase 76. Which metabolic pathway produces step acetyl-CoA as an intermediate for B. Pyruvate kinase step energy production? A. Glycolysis C. Hexokinase step B. Pentose phosphate pathway D. Aldolase step C. Beta-oxidation Answer: C【7†source】 D. Gluconeogenesis Answer: C【7†source】 77. In ATP synthesis, what is the direct B. Pyruvate dehydrogenase source of energy that drives the C. Malate dehydrogenase phosphorylation of ADP? A. Glucose D. Phosphofructokinase oxidation Answer: B【6†source】 B. Proton flow through ATP synthase 83. Which of the following best explains C. Oxygen consumption why ATP is considered an “energy D. Cytochrome c oxidation currency” in the cell? A. It contains Answer: B【7†source】 high-energy phosphate bonds 78. What is the fate of excess acetyl-CoA B. It is present in high amounts in the when carbohydrate intake is low and cell fatty acids are being oxidized? A. C. It donates protons to the electron Conversion to glucose transport chain B. Formation of ketone bodies D. It breaks down glucose into pyruvate C. Storage as glycogen Answer: A【6†source】 D. Production of lactate 84. The citric acid cycle is primarily Answer: B【7†source】 regulated by the availability of: A. 79. Which coenzyme is used by both Oxygen complex I and complex II in the electron B. ADP transport chain? A. FAD C. Acetyl-CoA B. NADH D. NADH C. Ubiquinone (CoQ) Answer: D【6†source】 D. Cytochrome c 85. Which metabolic process is activated in Answer: C【7†source】 response to low ATP levels? 80. Under anaerobic conditions, which A. Glycolysis enzyme catalyzes the conversion of B. Fatty acid synthesis pyruvate to lactate? A. Pyruvate C. Glycogenesis dehydrogenase D. Gluconeogenesis B. Lactate dehydrogenase Answer: A【7†source】 C. Succinate dehydrogenase D. Glucose-6-phosphate dehydrogenase 86. What is the primary consequence of Answer: B【7†source】 inhibiting ATP synthase in oxidative phosphorylation? 81. In biological oxidation, which molecule acts as the terminal electron acceptor? A. Increased electron flow through the A. NAD+ electron transport chain B. Oxygen B. Accumulation of protons in the C. Ubiquinone mitochondrial matrix D. FAD C. Collapse of the proton gradient Answer: B【6†source】 across the inner mitochondrial membrane 82. Which enzyme is responsible for the D. Inhibition of oxygen reduction to oxidative decarboxylation of pyruvate? water A. Pyruvate carboxylase Answer: D【7†source】 87. Which of the following statements is 91. Which enzyme is directly responsible for TRUE regarding the P/O ratio for generating NADH in the citric acid cycle? FADH2? A. Succinate dehydrogenase B. Aconitase A. It is higher than that of NADH C. Alpha-ketoglutarate dehydrogenase B. It is approximately 1.5 D. Fumarase C. It is directly responsible for proton Answer: C【7†source】 pumping at complex I D. It represents the number of ATP 92. During oxidative phosphorylation, which molecules produced per electron pair component of ATP synthase rotates to Answer: B【7†source】 catalyze the formation of ATP from ADP and Pi? 88. How do proton ionophores like FCCP and DNP uncouple oxidative A. F1 headpiece phosphorylation? B. F0 rotor C. Gamma subunit A. By directly inhibiting ATP synthase D. Beta subunit activity Answer: C【7†source】 B. By allowing protons to flow across the membrane without passing through 93. Which of the following reactions is ATP synthase directly responsible for regenerating C. By increasing oxygen consumption FADH2 in cellular respiration? without producing ATP A. Citrate to isocitrate D. Both B and C B. Alpha-ketoglutarate to succinyl-CoA Answer: D【6†source】 C. Succinate to fumarate 89. Which of the following metabolic D. Malate to oxaloacetate adaptations would occur during Answer: C【7†source】 prolonged fasting or starvation? 94. Which of the following processes is A. Increased activity of pyruvate kinase least affected by the lack of oxygen? B. Increased glucose oxidation A. Oxidative phosphorylation C. Enhanced production of ketone B. Citric acid cycle bodies from acetyl-CoA C. Glycolysis D. Increased glycolysis in the liver D. Beta-oxidation Answer: C【7†source】 Answer: C【7†source】 90. In muscle cells during vigorous exercise, 95. How does carbon monoxide (CO) inhibit which enzyme catalyzes the formation cellular respiration? of lactate from pyruvate? A. It binds to the iron in hemoglobin A. Lactate dehydrogenase B. Pyruvate carboxylase B. It blocks electron transfer in complex IV C. Pyruvate dehydrogenase C. It increases the efficiency of ATP D. Succinate dehydrogenase synthesis Answer: A【6†source】 D. It uncouples proton pumping from  ATP synthesis 100. Which of the following Answer: B【7†source】 intermediates of the citric acid cycle is directly involved in gluconeogenesis? 96. The main function of cytochrome c oxidase in the electron transport chain A. Citrate is to: B. Alpha-ketoglutarate C. Oxaloacetate A. Accept electrons from NADH D. Succinyl-CoA B. Pump protons across the inner Answer: C【7†source】 mitochondrial membrane C. Transfer electrons from cytochrome c 101. Which electron carrier in the to oxygen, reducing it to water electron transport chain does not D. Transport electrons from complex III directly contribute to proton pumping? to complex I A. Complex I Answer: C【7†source】 B. Complex II C. Complex III 97. What is the effect of oligomycin on D. Complex IV oxidative phosphorylation? Answer: B【7†source】 A. Inhibits ATP synthase by blocking 102. The availability of which proton flow compound regulates the activity of B. Stimulates electron flow through pyruvate dehydrogenase in the complex I mitochondria? C. Allows protons to bypass the F0 complex A. Acetyl-CoA D. Increases the efficiency of ATP B. NADH production C. Citrate Answer: A【7†source】 D. FADH2 Answer: A【7†source】 98. In the context of energy metabolism, a high ATP/ADP ratio in the cell typically: 103. The primary purpose of the A. Inhibits the citric acid cycle malate-aspartate shuttle is to: B. Stimulates glycolysis A. Regenerate NAD+ in the C. Promotes oxidative phosphorylation mitochondria D. Increases proton pumping B. Transfer acetyl-CoA across the Answer: A【6†source】 mitochondrial membrane 99. Which of the following molecules serves C. Convert malate to oxaloacetate in the as a direct allosteric activator of cytoplasm pyruvate carboxylase? D. Generate ATP from glycolysis Answer: A【7†source】 A. ATP B. Acetyl-CoA C. ADP D. NADH Answer: B【7†source】 104. How does the mitochondrial consumption ATP/ADP translocase function in B. Increased proton pumping oxidative phosphorylation? A. Pumps C. Enhanced ATP synthase activity protons into the mitochondrial matrix D. Inhibition of electron flow B. Facilitates the exchange of ATP and Answer: C【7†source】 ADP across the inner mitochondrial 109. The inhibition of complex I in membrane the electron transport chain results in: C. Synthesizes ATP from ADP and Pi A. A build-up of NADH D. Inhibits proton flow through ATP B. Reduced ATP production synthase C. Decreased oxygen consumption Answer: B【6†source】 D. All of the above 105. Which of the following Answer: D【7†source】 statements best describes the role of 110. Which molecule is responsible acetyl-CoA in metabolism? A. It acts as a for shuttling electrons from complex I reducing agent in the electron transport and complex II to complex III in the chain electron transport chain? A. Ubiquinone B. It is a key intermediate in both (CoQ) catabolic and anabolic processes B. Cytochrome c C. It serves as a direct substrate for C. ATP glycolysis D. NADH D. It inhibits the citric acid cycle under low oxygen conditions Answer: A【7†source】 Answer: B【7†source】 111. Which enzyme catalyzes the 106. During gluconeogenesis, decarboxylation of isocitrate in the citric acid cycle? A. Isocitrate dehydrogenase pyruvate is first converted into which B. Alpha-ketoglutarate dehydrogenase compound? A. Acetyl-CoA C. Malate dehydrogenase B. Oxaloacetate D. Fumarase C. Malate D. Citrate Answer: A【7†source】 Answer: B【7†source】 112. In anaerobic conditions, pyruvate is converted into which of the 107. Which metabolic pathway following products to regenerate NAD+? would be expected to increase in the A. Acetyl-CoA liver during extended fasting? A. B. Lactate Glycolysis C. Ethanol B. Fatty acid synthesis C. Beta-oxidation D. Oxaloacetate D. Protein synthesis Answer: B【7†source】 Answer: C【7†source】 113. How does 2,4-Dinitrophenol (DNP) increase metabolic rate while 108. In oxidative phosphorylation, causing weight loss? A. Inhibits what is the immediate effect of glycolysis increased ADP levels in the B. Stimulates proton pumping in the mitochondria? A. Decreased oxygen  electron transport chain of fatty acids C. Uncouples proton gradient from ATP B. Enhanced flux through the electron synthesis, increasing heat production transport chain D. Directly increases NADH production C. Inhibition of pyruvate dehydrogenase Answer: C【7†source】 activity D. Accumulation of ATP in mitochondria 114. Which compound accumulates Answer: C【7†source】 in the cell when pyruvate dehydrogenase is inhibited? 118. What is the primary role of the electron transport chain in maintaining A. Lactate cellular homeostasis? B. Acetyl-CoA C. Oxaloacetate A. Direct generation of glucose from D. Malate pyruvate Answer: A【7†source】 B. Maintenance of the mitochondrial membrane potential 115. Which step in the citric acid C. Production of carbon dioxide from cycle produces FADH2? oxygen A. Conversion of malate to oxaloacetate D. Conversion of ADP into AMP B. Conversion of succinate to fumarate Answer: B【7†source】 C. Conversion of isocitrate to alpha- 119. During anaerobic conditions in ketoglutarate skeletal muscle, which of the following D. Conversion of citrate to isocitrate enzymes shows increased activity to Answer: B【7†source】 compensate for the lack of oxidative 116. Which of the following phosphorylation? accurately describes the mechanism of A. Pyruvate carboxylase action of uncoupling proteins (UCPs) in B. Phosphofructokinase mitochondria? C. Succinate dehydrogenase A. Inhibit the electron transport chain D. Citrate synthase by blocking complex IV Answer: B【7†source】 B. Facilitate proton leakage across the 120. In which part of the electron inner mitochondrial membrane, transport chain does the proton motive bypassing ATP synthase force have the highest potential energy? C. Increase proton pumping across the A. Cytosol mitochondrial membrane to enhance B. Intermembrane space ATP production C. Matrix D. Inhibit oxygen consumption by the D. Outer mitochondrial membrane respiratory chain Answer: B【6†source】 Answer: B【7†source】 117. Which of the following is a direct consequence of an increased NADH/NAD+ ratio in cells under hypoxic conditions? A. Increased beta-oxidation 121. Which of the following 125. How does the glycerol-3- processes is activated by low cellular phosphate shuttle differ from the ATP levels to restore energy balance? malate-aspartate shuttle in transferring electrons from NADH to the A. Gluconeogenesis mitochondria? B. Beta-oxidation C. Glycolysis A. It generates more ATP per electron D. Fatty acid synthesis pair Answer: C【7†source】 B. It transfers electrons directly to complex I 122. Why is oxygen essential in C. It transfers electrons to FAD in oxidative phosphorylation? complex II A. It is the initial electron donor in the D. It only operates during anaerobic electron transport chain metabolism B. It acts as the final electron acceptor Answer: C【7†source】 to form water 126. What is the role of cytochrome C. It catalyzes the synthesis of ATP from c in apoptosis? ADP D. It drives proton pumping through A. It transfers electrons between complexes I-IV complex II and III in the electron Answer: B【6†source】 transport chain B. It binds to complex IV to generate 123. The P/O ratio for FADH2 is lower reactive oxygen species than for NADH because: C. It activates caspases upon release A. FADH2 donates electrons at a later into the cytosol point in the electron transport chain D. It directly inhibits ATP production B. NADH drives more proton pumps per Answer: C【7†source】 electron transfer 127. The enzyme responsible for C. FADH2 produces fewer ATP molecules catalyzing the oxidative decarboxylation D. Both A and B of alpha-ketoglutarate to succinyl-CoA Answer: D【6†source】 is: 124. A patient poisoned by rotenone A. Succinate dehydrogenase exhibits impaired oxidative B. Alpha-ketoglutarate phosphorylation. Rotenone specifically dehydrogenase inhibits which complex of the electron C. Citrate synthase transport chain? D. Isocitrate dehydrogenase A. Complex II Answer: B【7†source】 B. Complex III C. Complex IV D. Complex I Answer: D【7†source】 128. How does cyanide affect cellular 132. Which of the following best respiration at the molecular level? explains why the citric acid cycle cannot function anaerobically? A. It relies on A. Inhibits complex I, halting electron the presence of molecular oxygen to transport oxidize NADH and FADH2 B. Inhibits complex IV, preventing the B. Citrate synthase is inhibited by low reduction of oxygen oxygen levels C. Uncouples the proton gradient from C. Oxygen is required to generate ATP synthesis acetyl-CoA D. Increases the affinity of complex III D. Fumarate cannot be converted to for electrons malate without oxygen Answer: B【7†source】 Answer: A【6†source】 129. During exercise, increased AMP 133. Which of the following best levels activate which enzyme to boost explains why muscle tissue switches to ATP production in muscle cells? lactate fermentation during intense A. Pyruvate dehydrogenase exercise? B. Phosphofructokinase-1 (PFK-1) A. Lactate fermentation produces more C. Lactate dehydrogenase ATP than oxidative phosphorylation D. Pyruvate carboxylase B. NAD+ regeneration in the absence of Answer: B【7†source】 oxygen allows glycolysis to continue 130. Which of the following C. Lactate is a more efficient fuel source processes is most affected by than glucose mitochondrial uncoupling? D. Pyruvate is converted to lactate to reduce cellular pH A. Proton pumping Answer: B【7†source】 B. Electron transport C. ATP synthesis 134. In which step of the electron D. NADH oxidation transport chain is oxygen reduced to Answer: C【6†source】 water? 131. Which metabolic condition A. Complex I leads to the activation of pyruvate B. Complex II dehydrogenase kinase, thus inhibiting C. Complex III the pyruvate dehydrogenase complex? D. Complex IV A. High acetyl-CoA levels Answer: D【7†source】 B. Low ATP levels C. Increased AMP concentrations D. Low NADH levels Answer: A【7†source】 135. Which process describes the 138. In patients with mitochondrial generation of reactive oxygen species myopathies, mutations in mitochondrial (ROS) as a by-product of mitochondrial DNA often affect which process most respiration? severely? A. Transfer of electrons from complex II A. Glycolysis to complex III B. Electron transport and ATP synthesis B. Leakage of electrons at complex I or C. Lipid oxidation III, reducing oxygen to superoxide D. Protein synthesis in the cytosol C. Proton pumping through ATP Answer: B【7†source】 synthase 139. Which of the following steps of D. Formation of water by complex IV the citric acid cycle involves substrate- Answer: B【6†source】 level phosphorylation? A. Citrate to 136. The thermogenesis seen in isocitrate brown adipose tissue (BAT) is largely B. Succinyl-CoA to succinate due to: C. Alpha-ketoglutarate to succinyl-CoA D. Malate to oxaloacetate A. Increased ATP synthesis through Answer: B【7†source】 oxidative phosphorylation B. The action of uncoupling protein-1 140. What is the consequence of an (UCP1), allowing protons to bypass ATP overproduction of reactive oxygen synthase species (ROS) in mitochondria? C. Enhanced glycolysis and glucose A. Enhanced ATP synthesis oxidation B. Increased proton pumping D. Increased oxygen consumption by C. Oxidative damage to mitochondrial complex IV components Answer: B【6†source】 D. Decreased oxygen consumption 137. Which compound plays a key Answer: C【6†source】 role in regulating the rate of oxidative 141. Which enzyme is allosterically phosphorylation by controlling the inhibited by citrate during glycolysis? availability of ADP? A. Hexokinase A. Pyruvate B. Pyruvate kinase B. ATP C. Phosphofructokinase-1 (PFK-1) C. NADH D. Enolase D. Phosphate Answer: C【7†source】 Answer: B【6†source】 142. During beta-oxidation, which enzyme catalyzes the cleavage of a two- carbon unit from the fatty acid chain? A. Acyl-CoA dehydrogenase B. Thiolase C. Enoyl-CoA hydratase  D. Carnitine acyltransferase C. Cytochrome c oxidase Answer: B【7†source】 D. Succinate-Q reductase Answer: C(11-12) 143. Which condition is most likely to cause a significant reduction in the 148. Which unit is used to measure NAD+/NADH ratio? A. Prolonged fasting the heat content (enthalpy) of the B. Hyperoxia reactants and products in C. Hypoxia bioenergetics? D. High glucose intake A. Kelvin Answer: C【6†source】 B. Joules 144. The Warburg effect describes C. Joules per kilogram the observation that cancer cells D. Joules per Kelvin preferentially: A. Use oxidative Answer: B(11-12) phosphorylation for ATP production 149. Which compound inhibits ATP B. Rely on anaerobic glycolysis even in synthase, thus preventing ATP the presence of oxygen production in oxidative C. Inhibit pyruvate dehydrogenase phosphorylation? activity D. Depend on fatty acid oxidation A. Oligomycin Answer: B【7†source】 B. Cyanide C. Malonate 145. In the Cori cycle, lactate D. Barbiturates produced by muscles is transported to Answer: A(11-12) the liver where it is: A. Converted back into pyruvate for gluconeogenesis 150. What is the net ATP gain from B. Converted into acetyl-CoA glycolysis when one molecule of glucose C. Used as a substrate for fatty acid undergoes anaerobic metabolism? synthesis A. 2 D. Oxidized directly for ATP production B. 4 Answer: A【7†source】 C. 6 146. Which enzyme catalyzes the D. 8 oxidation of succinate to fumarate in Answer: A(11-12) both the citric acid cycle and the electron transport chain? A. Complex I B. Complex II C. Complex III D. Complex IV Answer: B(11-12) 147. Cyanide inhibits which complex of the electron transport chain? A. NADH-Q oxidoreductase B. Q-cytochrome c oxidoreductase