{ "chapter": "Bioenergetics", "count": 100, "answerIndex": "zero-based", "notice": "Original practice items including related concept variants; not official examination questions.", "questions": [ { "id": "oxygen-acceptor", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "In aerobic respiration, oxygen is required most directly because it:", "options": [ "Accepts electrons at the end of the transport chain", "Carries ATP into the nucleus", "Splits glucose during glycolysis", "Converts pyruvate into glucose" ], "answer": 0, "explanation": "Oxygen accepts electrons and protons at the end of the electron-transport chain, allowing electron flow and oxidative phosphorylation to continue." }, { "id": "glycolysis-location", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "A cell temporarily loses functional mitochondria but retains an intact cytosol. Which process can still produce a small amount of ATP?", "options": [ "Krebs cycle", "Glycolysis", "Oxidative phosphorylation", "Link reaction" ], "answer": 1, "explanation": "Glycolysis occurs in the cytosol and produces ATP by substrate-level phosphorylation without requiring mitochondria." }, { "id": "proton-gradient", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "The inner mitochondrial membrane suddenly becomes freely permeable to protons. Which event is affected most directly?", "options": [ "DNA transcription in the nucleus", "Glucose entry into glycolysis", "ATP synthesis by chemiosmosis", "Peptide-bond formation on ribosomes" ], "answer": 2, "explanation": "ATP synthase depends on proton flow down an electrochemical gradient. A proton-permeable membrane collapses that gradient." }, { "id": "uncoupler", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "A mitochondrial uncoupler increases proton leakage. Which combination is most likely?", "options": [ "Less oxygen use and more ATP", "More ATP with no heat production", "No electron transport and more ATP", "More oxygen use but less ATP" ], "answer": 3, "explanation": "Electron transport may accelerate while the gradient is dissipated as heat. Oxygen consumption can rise even though ATP production falls." }, { "id": "bioenergetics-atp-coupling-outcome", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "ATP transfers its terminal phosphate to another molecule. Which outcome follows most directly?", "options": [ "The recipient becomes more reactive and can drive an energy-requiring process", "Two pyruvate, a net two ATP and reduced NAD are produced", "Pyruvate is reduced to lactate so glycolysis can continue", "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed" ], "answer": 0, "explanation": "The recipient becomes more reactive and can drive an energy-requiring process. Phosphorylation couples the exergonic hydrolysis of ATP to cellular work." }, { "id": "bioenergetics-atp-coupling-cause", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which change most directly explains this observation: the recipient becomes more reactive and can drive an energy-requiring process?", "options": [ "One glucose molecule completes glycolysis in the cytosol", "ATP transfers its terminal phosphate to another molecule", "Oxygen supply becomes inadequate in an actively contracting muscle", "Pyruvate enters the mitochondrial matrix under aerobic conditions" ], "answer": 1, "explanation": "The recipient becomes more reactive and can drive an energy-requiring process. Phosphorylation couples the exergonic hydrolysis of ATP to cellular work." }, { "id": "bioenergetics-atp-coupling-mechanism", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "After ATP transfers its terminal phosphate to another molecule, which explanation best links the change to its outcome?", "options": [ "A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar", "Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis", "Phosphorylation couples the exergonic hydrolysis of ATP to cellular work", "Pyruvate is decarboxylated, oxidized and joined to coenzyme A" ], "answer": 2, "explanation": "The recipient becomes more reactive and can drive an energy-requiring process. Phosphorylation couples the exergonic hydrolysis of ATP to cellular work." }, { "id": "bioenergetics-glycolysis-outcome", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "After one glucose molecule completes glycolysis in the cytosol, which observation is most likely?", "options": [ "Pyruvate is reduced to lactate so glycolysis can continue", "Carbon dioxide, reduced carriers and a small amount of ATP are generated", "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed", "Two pyruvate, a net two ATP and reduced NAD are produced" ], "answer": 3, "explanation": "Two pyruvate, a net two ATP and reduced NAD are produced. A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar." }, { "id": "bioenergetics-glycolysis-cause", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "A learner records that two pyruvate, a net two ATP and reduced NAD are produced. Which preceding event best accounts for it?", "options": [ "One glucose molecule completes glycolysis in the cytosol", "Pyruvate enters the mitochondrial matrix under aerobic conditions", "Oxygen supply becomes inadequate in an actively contracting muscle", "Acetyl coenzyme A enters the citric-acid cycle" ], "answer": 0, "explanation": "Two pyruvate, a net two ATP and reduced NAD are produced. A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar." }, { "id": "bioenergetics-glycolysis-mechanism", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "After one glucose molecule completes glycolysis in the cytosol, which explanation best links the change to its outcome?", "options": [ "Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis", "A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar", "Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate", "Pyruvate is decarboxylated, oxidized and joined to coenzyme A" ], "answer": 1, "explanation": "Two pyruvate, a net two ATP and reduced NAD are produced. A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar." }, { "id": "bioenergetics-glycolysis-integrated", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which paired outcome and explanation best follows from this condition: one glucose molecule completes glycolysis in the cytosol?", "options": [ "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed — Pyruvate is decarboxylated, oxidized and joined to coenzyme A", "Pyruvate is reduced to lactate so glycolysis can continue — Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis", "Two pyruvate, a net two ATP and reduced NAD are produced — A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar", "Carbon dioxide, reduced carriers and a small amount of ATP are generated — Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate" ], "answer": 2, "explanation": "Two pyruvate, a net two ATP and reduced NAD are produced. A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar." }, { "id": "bioenergetics-anaerobic-lactate-outcome", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "A student models this change: Oxygen supply becomes inadequate in an actively contracting muscle. What should the model predict first?", "options": [ "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed", "Carbon dioxide, reduced carriers and a small amount of ATP are generated", "Electron flow continues and water is formed", "Pyruvate is reduced to lactate so glycolysis can continue" ], "answer": 3, "explanation": "Pyruvate is reduced to lactate so glycolysis can continue. Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis." }, { "id": "bioenergetics-anaerobic-lactate-cause", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "What is the most likely cause when pyruvate is reduced to lactate so glycolysis can continue?", "options": [ "Oxygen supply becomes inadequate in an actively contracting muscle", "Acetyl coenzyme A enters the citric-acid cycle", "Oxygen accepts electrons at the end of the respiratory chain", "Pyruvate enters the mitochondrial matrix under aerobic conditions" ], "answer": 0, "explanation": "Pyruvate is reduced to lactate so glycolysis can continue. Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis." }, { "id": "bioenergetics-anaerobic-lactate-mechanism", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "After oxygen supply becomes inadequate in an actively contracting muscle, which explanation best links the change to its outcome?", "options": [ "Pyruvate is decarboxylated, oxidized and joined to coenzyme A", "Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis", "Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate", "Oxygen combines with electrons and protons, preventing the chain from remaining reduced" ], "answer": 1, "explanation": "Pyruvate is reduced to lactate so glycolysis can continue. Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis." }, { "id": "bioenergetics-anaerobic-lactate-integrated", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which paired outcome and explanation best follows from this condition: oxygen supply becomes inadequate in an actively contracting muscle?", "options": [ "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed — Pyruvate is decarboxylated, oxidized and joined to coenzyme A", "Carbon dioxide, reduced carriers and a small amount of ATP are generated — Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate", "Pyruvate is reduced to lactate so glycolysis can continue — Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis", "Electron flow continues and water is formed — Oxygen combines with electrons and protons, preventing the chain from remaining reduced" ], "answer": 2, "explanation": "Pyruvate is reduced to lactate so glycolysis can continue. Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis." }, { "id": "bioenergetics-link-reaction-outcome", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which immediate result is most consistent with this condition: Pyruvate enters the mitochondrial matrix under aerobic conditions?", "options": [ "Carbon dioxide, reduced carriers and a small amount of ATP are generated", "Electron flow continues and water is formed", "ATP is formed without ATP synthase", "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed" ], "answer": 3, "explanation": "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed. Pyruvate is decarboxylated, oxidized and joined to coenzyme A." }, { "id": "bioenergetics-link-reaction-cause", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which condition would most specifically produce this result: acetyl coenzyme A, carbon dioxide and reduced NAD are formed?", "options": [ "Pyruvate enters the mitochondrial matrix under aerobic conditions", "Acetyl coenzyme A enters the citric-acid cycle", "Oxygen accepts electrons at the end of the respiratory chain", "A phosphorylated metabolic intermediate transfers phosphate directly to ADP" ], "answer": 0, "explanation": "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed. Pyruvate is decarboxylated, oxidized and joined to coenzyme A." }, { "id": "bioenergetics-link-reaction-mechanism", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "After pyruvate enters the mitochondrial matrix under aerobic conditions, which explanation best links the change to its outcome?", "options": [ "Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate", "Pyruvate is decarboxylated, oxidized and joined to coenzyme A", "Oxygen combines with electrons and protons, preventing the chain from remaining reduced", "Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond" ], "answer": 1, "explanation": "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed. Pyruvate is decarboxylated, oxidized and joined to coenzyme A." }, { "id": "bioenergetics-link-reaction-integrated", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which paired outcome and explanation best follows from this condition: pyruvate enters the mitochondrial matrix under aerobic conditions?", "options": [ "Carbon dioxide, reduced carriers and a small amount of ATP are generated — Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate", "Electron flow continues and water is formed — Oxygen combines with electrons and protons, preventing the chain from remaining reduced", "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed — Pyruvate is decarboxylated, oxidized and joined to coenzyme A", "ATP is formed without ATP synthase — Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond" ], "answer": 2, "explanation": "Acetyl coenzyme A, carbon dioxide and reduced NAD are formed. Pyruvate is decarboxylated, oxidized and joined to coenzyme A." }, { "id": "bioenergetics-krebs-cycle-outcome", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Acetyl coenzyme A enters the citric-acid cycle. Which outcome follows most directly?", "options": [ "Reduced NAD carries high-energy electrons to another reaction", "Electron flow continues and water is formed", "ATP is formed without ATP synthase", "Carbon dioxide, reduced carriers and a small amount of ATP are generated" ], "answer": 3, "explanation": "Carbon dioxide, reduced carriers and a small amount of ATP are generated. Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate." }, { "id": "bioenergetics-krebs-cycle-cause", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which change most directly explains this observation: carbon dioxide, reduced carriers and a small amount of ATP are generated?", "options": [ "Acetyl coenzyme A enters the citric-acid cycle", "Oxygen accepts electrons at the end of the respiratory chain", "A phosphorylated metabolic intermediate transfers phosphate directly to ADP", "NAD accepts hydrogen during substrate oxidation" ], "answer": 0, "explanation": "Carbon dioxide, reduced carriers and a small amount of ATP are generated. Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate." }, { "id": "bioenergetics-krebs-cycle-mechanism", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "After acetyl coenzyme A enters the citric-acid cycle, which explanation best links the change to its outcome?", "options": [ "Oxygen combines with electrons and protons, preventing the chain from remaining reduced", "Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate", "Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond", "The coenzyme gains electrons and a proton and can later be reoxidized" ], "answer": 1, "explanation": "Carbon dioxide, reduced carriers and a small amount of ATP are generated. Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate." }, { "id": "bioenergetics-krebs-cycle-integrated", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which paired outcome and explanation best follows from this condition: acetyl coenzyme A enters the citric-acid cycle?", "options": [ "Electron flow continues and water is formed — Oxygen combines with electrons and protons, preventing the chain from remaining reduced", "ATP is formed without ATP synthase — Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond", "Carbon dioxide, reduced carriers and a small amount of ATP are generated — Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate", "Reduced NAD carries high-energy electrons to another reaction — The coenzyme gains electrons and a proton and can later be reoxidized" ], "answer": 2, "explanation": "Carbon dioxide, reduced carriers and a small amount of ATP are generated. Cyclic oxidation transfers electrons to NAD and FAD while regenerating oxaloacetate." }, { "id": "bioenergetics-oxygen-final-outcome", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "After oxygen accepts electrons at the end of the respiratory chain, which observation is most likely?", "options": [ "ATP is formed without ATP synthase", "It generally supports less ATP synthesis than reduced NAD", "Reduced NAD carries high-energy electrons to another reaction", "Electron flow continues and water is formed" ], "answer": 3, "explanation": "Electron flow continues and water is formed. Oxygen combines with electrons and protons, preventing the chain from remaining reduced." }, { "id": "bioenergetics-oxygen-final-cause", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "A learner records that electron flow continues and water is formed. Which preceding event best accounts for it?", "options": [ "Oxygen accepts electrons at the end of the respiratory chain", "NAD accepts hydrogen during substrate oxidation", "A phosphorylated metabolic intermediate transfers phosphate directly to ADP", "Reduced FAD donates electrons to the respiratory chain after the first proton pump" ], "answer": 0, "explanation": "Electron flow continues and water is formed. Oxygen combines with electrons and protons, preventing the chain from remaining reduced." }, { "id": "bioenergetics-oxygen-final-mechanism", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "After oxygen accepts electrons at the end of the respiratory chain, which explanation best links the change to its outcome?", "options": [ "Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond", "Oxygen combines with electrons and protons, preventing the chain from remaining reduced", "Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement", "The coenzyme gains electrons and a proton and can later be reoxidized" ], "answer": 1, "explanation": "Electron flow continues and water is formed. Oxygen combines with electrons and protons, preventing the chain from remaining reduced." }, { "id": "bioenergetics-oxygen-final-integrated", "chapter": "Bioenergetics", "difficulty": "Foundation", "stem": "Which paired outcome and explanation best follows from this condition: oxygen accepts electrons at the end of the respiratory chain?", "options": [ "Reduced NAD carries high-energy electrons to another reaction — The coenzyme gains electrons and a proton and can later be reoxidized", "ATP is formed without ATP synthase — Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond", "Electron flow continues and water is formed — Oxygen combines with electrons and protons, preventing the chain from remaining reduced", "It generally supports less ATP synthesis than reduced NAD — Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement" ], "answer": 2, "explanation": "Electron flow continues and water is formed. Oxygen combines with electrons and protons, preventing the chain from remaining reduced." }, { "id": "bioenergetics-substrate-phosphorylation-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "A student models this change: A phosphorylated metabolic intermediate transfers phosphate directly to ADP. What should the model predict first?", "options": [ "Reduced NAD carries high-energy electrons to another reaction", "It generally supports less ATP synthesis than reduced NAD", "Protons accumulate in the intermembrane space", "ATP is formed without ATP synthase" ], "answer": 3, "explanation": "ATP is formed without ATP synthase. Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond." }, { "id": "bioenergetics-substrate-phosphorylation-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "What is the most likely cause when ATP is formed without ATP synthase?", "options": [ "A phosphorylated metabolic intermediate transfers phosphate directly to ADP", "Reduced FAD donates electrons to the respiratory chain after the first proton pump", "Electrons move through inner-membrane respiratory carriers", "NAD accepts hydrogen during substrate oxidation" ], "answer": 0, "explanation": "ATP is formed without ATP synthase. Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond." }, { "id": "bioenergetics-substrate-phosphorylation-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After a phosphorylated metabolic intermediate transfers phosphate directly to ADP, which explanation best links the change to its outcome?", "options": [ "The coenzyme gains electrons and a proton and can later be reoxidized", "Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond", "Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement", "Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane" ], "answer": 1, "explanation": "ATP is formed without ATP synthase. Substrate-level phosphorylation uses energy already stored in a high-energy phosphate bond." }, { "id": "bioenergetics-nad-electrons-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which immediate result is most consistent with this condition: NAD accepts hydrogen during substrate oxidation?", "options": [ "It generally supports less ATP synthesis than reduced NAD", "Protons accumulate in the intermembrane space", "Reduced NAD carries high-energy electrons to another reaction", "ADP and phosphate are joined to form ATP" ], "answer": 2, "explanation": "Reduced NAD carries high-energy electrons to another reaction. The coenzyme gains electrons and a proton and can later be reoxidized." }, { "id": "bioenergetics-nad-electrons-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which condition would most specifically produce this result: reduced NAD carries high-energy electrons to another reaction?", "options": [ "Protons flow through ATP synthase into the mitochondrial matrix", "Reduced FAD donates electrons to the respiratory chain after the first proton pump", "Electrons move through inner-membrane respiratory carriers", "NAD accepts hydrogen during substrate oxidation" ], "answer": 3, "explanation": "Reduced NAD carries high-energy electrons to another reaction. The coenzyme gains electrons and a proton and can later be reoxidized." }, { "id": "bioenergetics-nad-electrons-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After NAD accepts hydrogen during substrate oxidation, which explanation best links the change to its outcome?", "options": [ "The coenzyme gains electrons and a proton and can later be reoxidized", "Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement", "Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane", "Movement down the electrochemical gradient rotates catalytic parts of ATP synthase" ], "answer": 0, "explanation": "Reduced NAD carries high-energy electrons to another reaction. The coenzyme gains electrons and a proton and can later be reoxidized." }, { "id": "bioenergetics-nad-electrons-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: NAD accepts hydrogen during substrate oxidation?", "options": [ "It generally supports less ATP synthesis than reduced NAD — Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement", "Reduced NAD carries high-energy electrons to another reaction — The coenzyme gains electrons and a proton and can later be reoxidized", "Protons accumulate in the intermembrane space — Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane", "ADP and phosphate are joined to form ATP — Movement down the electrochemical gradient rotates catalytic parts of ATP synthase" ], "answer": 1, "explanation": "Reduced NAD carries high-energy electrons to another reaction. The coenzyme gains electrons and a proton and can later be reoxidized." }, { "id": "bioenergetics-fadh2-entry-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Reduced FAD donates electrons to the respiratory chain after the first proton pump. Which outcome follows most directly?", "options": [ "ADP and phosphate are joined to form ATP", "Protons accumulate in the intermembrane space", "It generally supports less ATP synthesis than reduced NAD", "Its maximum capacity for oxidative phosphorylation can increase" ], "answer": 2, "explanation": "It generally supports less ATP synthesis than reduced NAD. Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement." }, { "id": "bioenergetics-fadh2-entry-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which change most directly explains this observation: it generally supports less ATP synthesis than reduced NAD?", "options": [ "Electrons move through inner-membrane respiratory carriers", "A mitochondrion develops more inner-membrane cristae", "Protons flow through ATP synthase into the mitochondrial matrix", "Reduced FAD donates electrons to the respiratory chain after the first proton pump" ], "answer": 3, "explanation": "It generally supports less ATP synthesis than reduced NAD. Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement." }, { "id": "bioenergetics-fadh2-entry-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After reduced FAD donates electrons to the respiratory chain after the first proton pump, which explanation best links the change to its outcome?", "options": [ "Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement", "Movement down the electrochemical gradient rotates catalytic parts of ATP synthase", "Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane", "Extra membrane provides more space for respiratory complexes and ATP synthase" ], "answer": 0, "explanation": "It generally supports less ATP synthesis than reduced NAD. Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement." }, { "id": "bioenergetics-fadh2-entry-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: reduced FAD donates electrons to the respiratory chain after the first proton pump?", "options": [ "Protons accumulate in the intermembrane space — Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane", "It generally supports less ATP synthesis than reduced NAD — Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement", "Its maximum capacity for oxidative phosphorylation can increase — Extra membrane provides more space for respiratory complexes and ATP synthase", "ADP and phosphate are joined to form ATP — Movement down the electrochemical gradient rotates catalytic parts of ATP synthase" ], "answer": 1, "explanation": "It generally supports less ATP synthesis than reduced NAD. Its electrons drive proton pumping at fewer complexes and create a smaller proton displacement." }, { "id": "bioenergetics-proton-pumping-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After electrons move through inner-membrane respiratory carriers, which observation is most likely?", "options": [ "ADP and phosphate are joined to form ATP", "Its maximum capacity for oxidative phosphorylation can increase", "Protons accumulate in the intermembrane space", "Ethanol and carbon dioxide form while NAD is regenerated" ], "answer": 2, "explanation": "Protons accumulate in the intermembrane space. Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane." }, { "id": "bioenergetics-proton-pumping-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "A learner records that protons accumulate in the intermembrane space. Which preceding event best accounts for it?", "options": [ "Protons flow through ATP synthase into the mitochondrial matrix", "A mitochondrion develops more inner-membrane cristae", "Yeast respires anaerobically with glucose available", "Electrons move through inner-membrane respiratory carriers" ], "answer": 3, "explanation": "Protons accumulate in the intermembrane space. Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane." }, { "id": "bioenergetics-proton-pumping-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After electrons move through inner-membrane respiratory carriers, which explanation best links the change to its outcome?", "options": [ "Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane", "Extra membrane provides more space for respiratory complexes and ATP synthase", "Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD", "Movement down the electrochemical gradient rotates catalytic parts of ATP synthase" ], "answer": 0, "explanation": "Protons accumulate in the intermembrane space. Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane." }, { "id": "bioenergetics-proton-pumping-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: electrons move through inner-membrane respiratory carriers?", "options": [ "ADP and phosphate are joined to form ATP — Movement down the electrochemical gradient rotates catalytic parts of ATP synthase", "Protons accumulate in the intermembrane space — Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane", "Its maximum capacity for oxidative phosphorylation can increase — Extra membrane provides more space for respiratory complexes and ATP synthase", "Ethanol and carbon dioxide form while NAD is regenerated — Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD" ], "answer": 1, "explanation": "Protons accumulate in the intermembrane space. Energy released by electron transfer powers proton pumps in the inner mitochondrial membrane." }, { "id": "bioenergetics-chemiosmosis-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "A student models this change: Protons flow through ATP synthase into the mitochondrial matrix. What should the model predict first?", "options": [ "Its maximum capacity for oxidative phosphorylation can increase", "Ethanol and carbon dioxide form while NAD is regenerated", "ADP and phosphate are joined to form ATP", "Elevated oxygen consumption continues during recovery" ], "answer": 2, "explanation": "ADP and phosphate are joined to form ATP. Movement down the electrochemical gradient rotates catalytic parts of ATP synthase." }, { "id": "bioenergetics-chemiosmosis-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "What is the most likely cause when ADP and phosphate are joined to form ATP?", "options": [ "A mitochondrion develops more inner-membrane cristae", "Yeast respires anaerobically with glucose available", "Vigorous exercise produces lactate faster than it is removed", "Protons flow through ATP synthase into the mitochondrial matrix" ], "answer": 3, "explanation": "ADP and phosphate are joined to form ATP. Movement down the electrochemical gradient rotates catalytic parts of ATP synthase." }, { "id": "bioenergetics-chemiosmosis-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After protons flow through ATP synthase into the mitochondrial matrix, which explanation best links the change to its outcome?", "options": [ "Movement down the electrochemical gradient rotates catalytic parts of ATP synthase", "Extra membrane provides more space for respiratory complexes and ATP synthase", "Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD", "Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores" ], "answer": 0, "explanation": "ADP and phosphate are joined to form ATP. Movement down the electrochemical gradient rotates catalytic parts of ATP synthase." }, { "id": "bioenergetics-chemiosmosis-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: protons flow through ATP synthase into the mitochondrial matrix?", "options": [ "Its maximum capacity for oxidative phosphorylation can increase — Extra membrane provides more space for respiratory complexes and ATP synthase", "ADP and phosphate are joined to form ATP — Movement down the electrochemical gradient rotates catalytic parts of ATP synthase", "Ethanol and carbon dioxide form while NAD is regenerated — Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD", "Elevated oxygen consumption continues during recovery — Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores" ], "answer": 1, "explanation": "ADP and phosphate are joined to form ATP. Movement down the electrochemical gradient rotates catalytic parts of ATP synthase." }, { "id": "bioenergetics-cristae-area-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which immediate result is most consistent with this condition: A mitochondrion develops more inner-membrane cristae?", "options": [ "Ethanol and carbon dioxide form while NAD is regenerated", "Elevated oxygen consumption continues during recovery", "Its maximum capacity for oxidative phosphorylation can increase", "The respiratory quotient approaches one" ], "answer": 2, "explanation": "Its maximum capacity for oxidative phosphorylation can increase. Extra membrane provides more space for respiratory complexes and ATP synthase." }, { "id": "bioenergetics-cristae-area-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which condition would most specifically produce this result: its maximum capacity for oxidative phosphorylation can increase?", "options": [ "A person oxidizes mainly carbohydrate", "Yeast respires anaerobically with glucose available", "Vigorous exercise produces lactate faster than it is removed", "A mitochondrion develops more inner-membrane cristae" ], "answer": 3, "explanation": "Its maximum capacity for oxidative phosphorylation can increase. Extra membrane provides more space for respiratory complexes and ATP synthase." }, { "id": "bioenergetics-cristae-area-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After a mitochondrion develops more inner-membrane cristae, which explanation best links the change to its outcome?", "options": [ "Extra membrane provides more space for respiratory complexes and ATP synthase", "Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD", "Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores", "Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed" ], "answer": 0, "explanation": "Its maximum capacity for oxidative phosphorylation can increase. Extra membrane provides more space for respiratory complexes and ATP synthase." }, { "id": "bioenergetics-cristae-area-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: a mitochondrion develops more inner-membrane cristae?", "options": [ "Ethanol and carbon dioxide form while NAD is regenerated — Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD", "Its maximum capacity for oxidative phosphorylation can increase — Extra membrane provides more space for respiratory complexes and ATP synthase", "Elevated oxygen consumption continues during recovery — Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores", "The respiratory quotient approaches one — Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed" ], "answer": 1, "explanation": "Its maximum capacity for oxidative phosphorylation can increase. Extra membrane provides more space for respiratory complexes and ATP synthase." }, { "id": "bioenergetics-fermentation-yeast-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Yeast respires anaerobically with glucose available. Which outcome follows most directly?", "options": [ "The respiratory quotient approaches one", "Elevated oxygen consumption continues during recovery", "Ethanol and carbon dioxide form while NAD is regenerated", "Many acetyl-CoA and reduced-coenzyme molecules are produced" ], "answer": 2, "explanation": "Ethanol and carbon dioxide form while NAD is regenerated. Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD." }, { "id": "bioenergetics-fermentation-yeast-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which change most directly explains this observation: ethanol and carbon dioxide form while NAD is regenerated?", "options": [ "Vigorous exercise produces lactate faster than it is removed", "Fatty acids undergo beta oxidation", "A person oxidizes mainly carbohydrate", "Yeast respires anaerobically with glucose available" ], "answer": 3, "explanation": "Ethanol and carbon dioxide form while NAD is regenerated. Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD." }, { "id": "bioenergetics-fermentation-yeast-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After yeast respires anaerobically with glucose available, which explanation best links the change to its outcome?", "options": [ "Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD", "Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed", "Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores", "Successive two-carbon units are removed while electrons are transferred to NAD and FAD" ], "answer": 0, "explanation": "Ethanol and carbon dioxide form while NAD is regenerated. Pyruvate is decarboxylated and the product accepts hydrogen from reduced NAD." }, { "id": "bioenergetics-oxygen-debt-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After vigorous exercise produces lactate faster than it is removed, which observation is most likely?", "options": [ "The respiratory quotient approaches one", "Elevated oxygen consumption continues during recovery", "Many acetyl-CoA and reduced-coenzyme molecules are produced", "An electron is raised to a higher energy level and transferred to an acceptor" ], "answer": 1, "explanation": "Elevated oxygen consumption continues during recovery. Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores." }, { "id": "bioenergetics-oxygen-debt-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "A learner records that elevated oxygen consumption continues during recovery. Which preceding event best accounts for it?", "options": [ "A person oxidizes mainly carbohydrate", "Fatty acids undergo beta oxidation", "Vigorous exercise produces lactate faster than it is removed", "Photosystem chlorophyll absorbs a photon" ], "answer": 2, "explanation": "Elevated oxygen consumption continues during recovery. Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores." }, { "id": "bioenergetics-oxygen-debt-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After vigorous exercise produces lactate faster than it is removed, which explanation best links the change to its outcome?", "options": [ "Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed", "Successive two-carbon units are removed while electrons are transferred to NAD and FAD", "Light energy excites a reaction-centre electron and initiates photosynthetic electron flow", "Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores" ], "answer": 3, "explanation": "Elevated oxygen consumption continues during recovery. Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores." }, { "id": "bioenergetics-oxygen-debt-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: vigorous exercise produces lactate faster than it is removed?", "options": [ "Elevated oxygen consumption continues during recovery — Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores", "The respiratory quotient approaches one — Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed", "Many acetyl-CoA and reduced-coenzyme molecules are produced — Successive two-carbon units are removed while electrons are transferred to NAD and FAD", "An electron is raised to a higher energy level and transferred to an acceptor — Light energy excites a reaction-centre electron and initiates photosynthetic electron flow" ], "answer": 0, "explanation": "Elevated oxygen consumption continues during recovery. Additional oxygen supports lactate oxidation, glycogen restoration and replenishment of energy stores." }, { "id": "bioenergetics-respiratory-quotient-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "A student models this change: A person oxidizes mainly carbohydrate. What should the model predict first?", "options": [ "Many acetyl-CoA and reduced-coenzyme molecules are produced", "The respiratory quotient approaches one", "An electron is raised to a higher energy level and transferred to an acceptor", "Electrons, protons and oxygen are produced" ], "answer": 1, "explanation": "The respiratory quotient approaches one. Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed." }, { "id": "bioenergetics-respiratory-quotient-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "What is the most likely cause when the respiratory quotient approaches one?", "options": [ "Fatty acids undergo beta oxidation", "Photosystem chlorophyll absorbs a photon", "A person oxidizes mainly carbohydrate", "Water is split at photosystem II" ], "answer": 2, "explanation": "The respiratory quotient approaches one. Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed." }, { "id": "bioenergetics-respiratory-quotient-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After a person oxidizes mainly carbohydrate, which explanation best links the change to its outcome?", "options": [ "The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation", "Successive two-carbon units are removed while electrons are transferred to NAD and FAD", "Light energy excites a reaction-centre electron and initiates photosynthetic electron flow", "Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed" ], "answer": 3, "explanation": "The respiratory quotient approaches one. Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed." }, { "id": "bioenergetics-respiratory-quotient-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: a person oxidizes mainly carbohydrate?", "options": [ "The respiratory quotient approaches one — Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed", "Many acetyl-CoA and reduced-coenzyme molecules are produced — Successive two-carbon units are removed while electrons are transferred to NAD and FAD", "An electron is raised to a higher energy level and transferred to an acceptor — Light energy excites a reaction-centre electron and initiates photosynthetic electron flow", "Electrons, protons and oxygen are produced — The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation" ], "answer": 0, "explanation": "The respiratory quotient approaches one. Complete carbohydrate oxidation releases approximately one carbon dioxide per oxygen molecule consumed." }, { "id": "bioenergetics-fat-respiration-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which immediate result is most consistent with this condition: Fatty acids undergo beta oxidation?", "options": [ "An electron is raised to a higher energy level and transferred to an acceptor", "Many acetyl-CoA and reduced-coenzyme molecules are produced", "The respiratory chain becomes reduced and ATP synthesis collapses", "Electrons, protons and oxygen are produced" ], "answer": 1, "explanation": "Many acetyl-CoA and reduced-coenzyme molecules are produced. Successive two-carbon units are removed while electrons are transferred to NAD and FAD." }, { "id": "bioenergetics-fat-respiration-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which condition would most specifically produce this result: many acetyl-CoA and reduced-coenzyme molecules are produced?", "options": [ "Water is split at photosystem II", "Photosystem chlorophyll absorbs a photon", "Fatty acids undergo beta oxidation", "Cyanide prevents electrons from passing to oxygen in mitochondria" ], "answer": 2, "explanation": "Many acetyl-CoA and reduced-coenzyme molecules are produced. Successive two-carbon units are removed while electrons are transferred to NAD and FAD." }, { "id": "bioenergetics-fat-respiration-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After fatty acids undergo beta oxidation, which explanation best links the change to its outcome?", "options": [ "Light energy excites a reaction-centre electron and initiates photosynthetic electron flow", "Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient", "The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation", "Successive two-carbon units are removed while electrons are transferred to NAD and FAD" ], "answer": 3, "explanation": "Many acetyl-CoA and reduced-coenzyme molecules are produced. Successive two-carbon units are removed while electrons are transferred to NAD and FAD." }, { "id": "bioenergetics-fat-respiration-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: fatty acids undergo beta oxidation?", "options": [ "Many acetyl-CoA and reduced-coenzyme molecules are produced — Successive two-carbon units are removed while electrons are transferred to NAD and FAD", "Electrons, protons and oxygen are produced — The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation", "An electron is raised to a higher energy level and transferred to an acceptor — Light energy excites a reaction-centre electron and initiates photosynthetic electron flow", "The respiratory chain becomes reduced and ATP synthesis collapses — Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient" ], "answer": 0, "explanation": "Many acetyl-CoA and reduced-coenzyme molecules are produced. Successive two-carbon units are removed while electrons are transferred to NAD and FAD." }, { "id": "bioenergetics-light-absorption-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Photosystem chlorophyll absorbs a photon. Which outcome follows most directly?", "options": [ "Electrons, protons and oxygen are produced", "An electron is raised to a higher energy level and transferred to an acceptor", "The respiratory chain becomes reduced and ATP synthesis collapses", "Heat production rises while ATP yield per oxygen falls" ], "answer": 1, "explanation": "An electron is raised to a higher energy level and transferred to an acceptor. Light energy excites a reaction-centre electron and initiates photosynthetic electron flow." }, { "id": "bioenergetics-light-absorption-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which change most directly explains this observation: an electron is raised to a higher energy level and transferred to an acceptor?", "options": [ "Water is split at photosystem II", "Cyanide prevents electrons from passing to oxygen in mitochondria", "Photosystem chlorophyll absorbs a photon", "A chemical carries protons freely across the inner mitochondrial membrane" ], "answer": 2, "explanation": "An electron is raised to a higher energy level and transferred to an acceptor. Light energy excites a reaction-centre electron and initiates photosynthetic electron flow." }, { "id": "bioenergetics-light-absorption-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After photosystem chlorophyll absorbs a photon, which explanation best links the change to its outcome?", "options": [ "The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation", "Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient", "Electron transport continues but the proton gradient bypasses ATP synthase", "Light energy excites a reaction-centre electron and initiates photosynthetic electron flow" ], "answer": 3, "explanation": "An electron is raised to a higher energy level and transferred to an acceptor. Light energy excites a reaction-centre electron and initiates photosynthetic electron flow." }, { "id": "bioenergetics-light-absorption-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: photosystem chlorophyll absorbs a photon?", "options": [ "An electron is raised to a higher energy level and transferred to an acceptor — Light energy excites a reaction-centre electron and initiates photosynthetic electron flow", "The respiratory chain becomes reduced and ATP synthesis collapses — Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient", "Heat production rises while ATP yield per oxygen falls — Electron transport continues but the proton gradient bypasses ATP synthase", "Electrons, protons and oxygen are produced — The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation" ], "answer": 0, "explanation": "An electron is raised to a higher energy level and transferred to an acceptor. Light energy excites a reaction-centre electron and initiates photosynthetic electron flow." }, { "id": "bioenergetics-photolysis-outcome", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After water is split at photosystem II, which observation is most likely?", "options": [ "The respiratory chain becomes reduced and ATP synthesis collapses", "Electrons, protons and oxygen are produced", "Heat production rises while ATP yield per oxygen falls", "ATP production stops and electron transport soon slows" ], "answer": 1, "explanation": "Electrons, protons and oxygen are produced. The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation." }, { "id": "bioenergetics-photolysis-cause", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "A learner records that electrons, protons and oxygen are produced. Which preceding event best accounts for it?", "options": [ "Cyanide prevents electrons from passing to oxygen in mitochondria", "A chemical carries protons freely across the inner mitochondrial membrane", "Water is split at photosystem II", "ATP synthase proton channels are blocked" ], "answer": 2, "explanation": "Electrons, protons and oxygen are produced. The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation." }, { "id": "bioenergetics-photolysis-mechanism", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "After water is split at photosystem II, which explanation best links the change to its outcome?", "options": [ "Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient", "Electron transport continues but the proton gradient bypasses ATP synthase", "Protons cannot return through the enzyme, so the growing gradient opposes further pumping", "The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation" ], "answer": 3, "explanation": "Electrons, protons and oxygen are produced. The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation." }, { "id": "bioenergetics-photolysis-integrated", "chapter": "Bioenergetics", "difficulty": "Standard", "stem": "Which paired outcome and explanation best follows from this condition: water is split at photosystem II?", "options": [ "Electrons, protons and oxygen are produced — The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation", "The respiratory chain becomes reduced and ATP synthesis collapses — Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient", "Heat production rises while ATP yield per oxygen falls — Electron transport continues but the proton gradient bypasses ATP synthase", "ATP production stops and electron transport soon slows — Protons cannot return through the enzyme, so the growing gradient opposes further pumping" ], "answer": 0, "explanation": "Electrons, protons and oxygen are produced. The oxygen-evolving complex replaces electrons lost by chlorophyll using light-driven water oxidation." }, { "id": "bioenergetics-cyanide-outcome", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "A student models this change: Cyanide prevents electrons from passing to oxygen in mitochondria. What should the model predict first?", "options": [ "Heat production rises while ATP yield per oxygen falls", "The respiratory chain becomes reduced and ATP synthesis collapses", "ATP production stops and electron transport soon slows", "Succinate oxidation and FAD reduction in the cycle decline" ], "answer": 1, "explanation": "The respiratory chain becomes reduced and ATP synthesis collapses. Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient." }, { "id": "bioenergetics-cyanide-cause", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "What is the most likely cause when the respiratory chain becomes reduced and ATP synthesis collapses?", "options": [ "A chemical carries protons freely across the inner mitochondrial membrane", "ATP synthase proton channels are blocked", "Cyanide prevents electrons from passing to oxygen in mitochondria", "Malonate competitively inhibits succinate dehydrogenase" ], "answer": 2, "explanation": "The respiratory chain becomes reduced and ATP synthesis collapses. Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient." }, { "id": "bioenergetics-cyanide-mechanism", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "After cyanide prevents electrons from passing to oxygen in mitochondria, which explanation best links the change to its outcome?", "options": [ "The inhibitor resembles succinate and occupies the enzyme's active site", "Electron transport continues but the proton gradient bypasses ATP synthase", "Protons cannot return through the enzyme, so the growing gradient opposes further pumping", "Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient" ], "answer": 3, "explanation": "The respiratory chain becomes reduced and ATP synthesis collapses. Blocked terminal electron transfer stops proton pumping and dissipates the usable gradient." }, { "id": "bioenergetics-uncoupling-outcome", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which immediate result is most consistent with this condition: A chemical carries protons freely across the inner mitochondrial membrane?", "options": [ "Heat production rises while ATP yield per oxygen falls", "Succinate oxidation and FAD reduction in the cycle decline", "Carbon fixation cannot continue for long even if carbon dioxide is present", "ATP production stops and electron transport soon slows" ], "answer": 0, "explanation": "Heat production rises while ATP yield per oxygen falls. Electron transport continues but the proton gradient bypasses ATP synthase." }, { "id": "bioenergetics-uncoupling-cause", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which condition would most specifically produce this result: heat production rises while ATP yield per oxygen falls?", "options": [ "ATP synthase proton channels are blocked", "A chemical carries protons freely across the inner mitochondrial membrane", "Malonate competitively inhibits succinate dehydrogenase", "The light-dependent reactions stop supplying ATP and reduced NADP" ], "answer": 1, "explanation": "Heat production rises while ATP yield per oxygen falls. Electron transport continues but the proton gradient bypasses ATP synthase." }, { "id": "bioenergetics-uncoupling-mechanism", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "After a chemical carries protons freely across the inner mitochondrial membrane, which explanation best links the change to its outcome?", "options": [ "Protons cannot return through the enzyme, so the growing gradient opposes further pumping", "The inhibitor resembles succinate and occupies the enzyme's active site", "Electron transport continues but the proton gradient bypasses ATP synthase", "The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP" ], "answer": 2, "explanation": "Heat production rises while ATP yield per oxygen falls. Electron transport continues but the proton gradient bypasses ATP synthase." }, { "id": "bioenergetics-uncoupling-integrated", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which paired outcome and explanation best follows from this condition: a chemical carries protons freely across the inner mitochondrial membrane?", "options": [ "ATP production stops and electron transport soon slows — Protons cannot return through the enzyme, so the growing gradient opposes further pumping", "Succinate oxidation and FAD reduction in the cycle decline — The inhibitor resembles succinate and occupies the enzyme's active site", "Carbon fixation cannot continue for long even if carbon dioxide is present — The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP", "Heat production rises while ATP yield per oxygen falls — Electron transport continues but the proton gradient bypasses ATP synthase" ], "answer": 3, "explanation": "Heat production rises while ATP yield per oxygen falls. Electron transport continues but the proton gradient bypasses ATP synthase." }, { "id": "bioenergetics-oligomycin-outcome", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "ATP synthase proton channels are blocked. Which outcome follows most directly?", "options": [ "ATP production stops and electron transport soon slows", "Succinate oxidation and FAD reduction in the cycle decline", "Carbon fixation cannot continue for long even if carbon dioxide is present", "Net carbohydrate production falls" ], "answer": 0, "explanation": "ATP production stops and electron transport soon slows. Protons cannot return through the enzyme, so the growing gradient opposes further pumping." }, { "id": "bioenergetics-oligomycin-cause", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which change most directly explains this observation: ATP production stops and electron transport soon slows?", "options": [ "Malonate competitively inhibits succinate dehydrogenase", "ATP synthase proton channels are blocked", "The light-dependent reactions stop supplying ATP and reduced NADP", "Rubisco binds oxygen more often during hot dry conditions" ], "answer": 1, "explanation": "ATP production stops and electron transport soon slows. Protons cannot return through the enzyme, so the growing gradient opposes further pumping." }, { "id": "bioenergetics-oligomycin-mechanism", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "After ATP synthase proton channels are blocked, which explanation best links the change to its outcome?", "options": [ "The inhibitor resembles succinate and occupies the enzyme's active site", "The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP", "Protons cannot return through the enzyme, so the growing gradient opposes further pumping", "Photorespiration consumes fixed carbon and energy without producing sugar" ], "answer": 2, "explanation": "ATP production stops and electron transport soon slows. Protons cannot return through the enzyme, so the growing gradient opposes further pumping." }, { "id": "bioenergetics-oligomycin-integrated", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which paired outcome and explanation best follows from this condition: ATP synthase proton channels are blocked?", "options": [ "Succinate oxidation and FAD reduction in the cycle decline — The inhibitor resembles succinate and occupies the enzyme's active site", "Carbon fixation cannot continue for long even if carbon dioxide is present — The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP", "Net carbohydrate production falls — Photorespiration consumes fixed carbon and energy without producing sugar", "ATP production stops and electron transport soon slows — Protons cannot return through the enzyme, so the growing gradient opposes further pumping" ], "answer": 3, "explanation": "ATP production stops and electron transport soon slows. Protons cannot return through the enzyme, so the growing gradient opposes further pumping." }, { "id": "bioenergetics-malonate-outcome", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "After malonate competitively inhibits succinate dehydrogenase, which observation is most likely?", "options": [ "Succinate oxidation and FAD reduction in the cycle decline", "Carbon fixation cannot continue for long even if carbon dioxide is present", "Net carbohydrate production falls", "The recipient becomes more reactive and can drive an energy-requiring process" ], "answer": 0, "explanation": "Succinate oxidation and FAD reduction in the cycle decline. The inhibitor resembles succinate and occupies the enzyme's active site." }, { "id": "bioenergetics-malonate-cause", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "A learner records that succinate oxidation and FAD reduction in the cycle decline. Which preceding event best accounts for it?", "options": [ "The light-dependent reactions stop supplying ATP and reduced NADP", "Malonate competitively inhibits succinate dehydrogenase", "Rubisco binds oxygen more often during hot dry conditions", "ATP transfers its terminal phosphate to another molecule" ], "answer": 1, "explanation": "Succinate oxidation and FAD reduction in the cycle decline. The inhibitor resembles succinate and occupies the enzyme's active site." }, { "id": "bioenergetics-malonate-mechanism", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "After malonate competitively inhibits succinate dehydrogenase, which explanation best links the change to its outcome?", "options": [ "The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP", "Photorespiration consumes fixed carbon and energy without producing sugar", "The inhibitor resembles succinate and occupies the enzyme's active site", "Phosphorylation couples the exergonic hydrolysis of ATP to cellular work" ], "answer": 2, "explanation": "Succinate oxidation and FAD reduction in the cycle decline. The inhibitor resembles succinate and occupies the enzyme's active site." }, { "id": "bioenergetics-malonate-integrated", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which paired outcome and explanation best follows from this condition: malonate competitively inhibits succinate dehydrogenase?", "options": [ "The recipient becomes more reactive and can drive an energy-requiring process — Phosphorylation couples the exergonic hydrolysis of ATP to cellular work", "Carbon fixation cannot continue for long even if carbon dioxide is present — The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP", "Net carbohydrate production falls — Photorespiration consumes fixed carbon and energy without producing sugar", "Succinate oxidation and FAD reduction in the cycle decline — The inhibitor resembles succinate and occupies the enzyme's active site" ], "answer": 3, "explanation": "Succinate oxidation and FAD reduction in the cycle decline. The inhibitor resembles succinate and occupies the enzyme's active site." }, { "id": "bioenergetics-calvin-atp-outcome", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "A student models this change: The light-dependent reactions stop supplying ATP and reduced NADP. What should the model predict first?", "options": [ "Carbon fixation cannot continue for long even if carbon dioxide is present", "The recipient becomes more reactive and can drive an energy-requiring process", "Net carbohydrate production falls", "Two pyruvate, a net two ATP and reduced NAD are produced" ], "answer": 0, "explanation": "Carbon fixation cannot continue for long even if carbon dioxide is present. The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP." }, { "id": "bioenergetics-calvin-atp-cause", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "What is the most likely cause when carbon fixation cannot continue for long even if carbon dioxide is present?", "options": [ "Rubisco binds oxygen more often during hot dry conditions", "The light-dependent reactions stop supplying ATP and reduced NADP", "One glucose molecule completes glycolysis in the cytosol", "ATP transfers its terminal phosphate to another molecule" ], "answer": 1, "explanation": "Carbon fixation cannot continue for long even if carbon dioxide is present. The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP." }, { "id": "bioenergetics-calvin-atp-mechanism", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "After the light-dependent reactions stop supplying ATP and reduced NADP, which explanation best links the change to its outcome?", "options": [ "Phosphorylation couples the exergonic hydrolysis of ATP to cellular work", "Photorespiration consumes fixed carbon and energy without producing sugar", "The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP", "A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar" ], "answer": 2, "explanation": "Carbon fixation cannot continue for long even if carbon dioxide is present. The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP." }, { "id": "bioenergetics-calvin-atp-integrated", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which paired outcome and explanation best follows from this condition: the light-dependent reactions stop supplying ATP and reduced NADP?", "options": [ "Net carbohydrate production falls — Photorespiration consumes fixed carbon and energy without producing sugar", "Two pyruvate, a net two ATP and reduced NAD are produced — A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar", "The recipient becomes more reactive and can drive an energy-requiring process — Phosphorylation couples the exergonic hydrolysis of ATP to cellular work", "Carbon fixation cannot continue for long even if carbon dioxide is present — The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP" ], "answer": 3, "explanation": "Carbon fixation cannot continue for long even if carbon dioxide is present. The Calvin cycle needs both energy and reducing power to reduce glycerate phosphate and regenerate RuBP." }, { "id": "bioenergetics-photorespiration-outcome", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which immediate result is most consistent with this condition: Rubisco binds oxygen more often during hot dry conditions?", "options": [ "Net carbohydrate production falls", "Two pyruvate, a net two ATP and reduced NAD are produced", "Pyruvate is reduced to lactate so glycolysis can continue", "The recipient becomes more reactive and can drive an energy-requiring process" ], "answer": 0, "explanation": "Net carbohydrate production falls. Photorespiration consumes fixed carbon and energy without producing sugar." }, { "id": "bioenergetics-photorespiration-cause", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which condition would most specifically produce this result: net carbohydrate production falls?", "options": [ "ATP transfers its terminal phosphate to another molecule", "Rubisco binds oxygen more often during hot dry conditions", "One glucose molecule completes glycolysis in the cytosol", "Oxygen supply becomes inadequate in an actively contracting muscle" ], "answer": 1, "explanation": "Net carbohydrate production falls. Photorespiration consumes fixed carbon and energy without producing sugar." }, { "id": "bioenergetics-photorespiration-mechanism", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "After rubisco binds oxygen more often during hot dry conditions, which explanation best links the change to its outcome?", "options": [ "Phosphorylation couples the exergonic hydrolysis of ATP to cellular work", "A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar", "Photorespiration consumes fixed carbon and energy without producing sugar", "Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis" ], "answer": 2, "explanation": "Net carbohydrate production falls. Photorespiration consumes fixed carbon and energy without producing sugar." }, { "id": "bioenergetics-photorespiration-integrated", "chapter": "Bioenergetics", "difficulty": "Challenge", "stem": "Which paired outcome and explanation best follows from this condition: rubisco binds oxygen more often during hot dry conditions?", "options": [ "The recipient becomes more reactive and can drive an energy-requiring process — Phosphorylation couples the exergonic hydrolysis of ATP to cellular work", "Two pyruvate, a net two ATP and reduced NAD are produced — A sequence of enzyme reactions splits and partially oxidizes the six-carbon sugar", "Pyruvate is reduced to lactate so glycolysis can continue — Lactate dehydrogenase regenerates NAD from reduced NAD for the oxidation step of glycolysis", "Net carbohydrate production falls — Photorespiration consumes fixed carbon and energy without producing sugar" ], "answer": 3, "explanation": "Net carbohydrate production falls. Photorespiration consumes fixed carbon and energy without producing sugar." }, { "chapter": "Bioenergetics", "id": "applied-net-glycolysis", "difficulty": "Standard", "stem": "During glycolysis, one glucose molecule leads to the formation of four ATP molecules, while two ATP molecules are invested. What is the net ATP gain from glycolysis of three glucose molecules?", "options": [ "6 ATP", "2 ATP", "12 ATP", "18 ATP" ], "answer": 0, "explanation": "The net gain is 4 − 2 = 2 ATP per glucose. Three glucose molecules therefore yield a net six ATP in glycolysis." }, { "chapter": "Bioenergetics", "id": "applied-uncoupler-data", "difficulty": "Challenge", "stem": "In isolated mitochondria supplied with substrate and oxygen, a treatment produces the pattern below. Which action best explains it?", "options": [ "Blocking every electron transfer to oxygen", "Making the inner membrane more permeable to protons", "Removing all respiratory substrate", "Increasing the amount of ATP already present" ], "answer": 1, "explanation": "A proton leak dissipates the gradient without ATP synthase. Electron transfer and oxygen use can continue or rise, while ATP synthesis falls.", "visual": { "kind": "table", "caption": "Relative mitochondrial responses", "headers": [ "Measurement", "Before treatment", "After treatment" ], "rows": [ [ "Oxygen consumption", "100", "150" ], [ "ATP synthesis", "100", "20" ] ] } }, { "chapter": "Bioenergetics", "id": "applied-fermentation-role", "difficulty": "Standard", "stem": "Why can muscle cells continue glycolysis for a time when pyruvate is converted to lactate?", "options": [ "Lactate supplies oxygen to mitochondria", "Lactate directly produces most cellular ATP", "The reaction regenerates NAD⁺ needed in glycolysis", "The reaction replaces all enzymes of glycolysis" ], "answer": 2, "explanation": "Reduction of pyruvate oxidizes NADH to NAD⁺. This supports the oxidation step in glycolysis, allowing its substrate-level ATP formation to continue." }, { "chapter": "Bioenergetics", "id": "applied-terminal-acceptor", "difficulty": "Foundation", "stem": "Which label completes the final step of this simplified aerobic electron pathway?", "options": [ "Carbon dioxide", "Glucose", "Pyruvate", "Oxygen" ], "answer": 3, "explanation": "Oxygen accepts electrons at the end of the respiratory electron transport chain and combines with protons to form water.", "visual": { "kind": "flow", "caption": "Direction of electron transfer", "nodes": [ "NADH", "Electron transport carriers", "Final acceptor: ?", "Water formed" ] } } ] }