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Shortcut used: Identify the tested biochemical principle, track charge/carbon/electrons or pathway direction, use the passage data, and reject choices that contradict cellular location or chemical behavior.
Solve in 3 steps:
- Mark the given values and the exact target.
- Apply the relevant formula, rule, or concept.
- Check the final value against the options.
Common mistake: Do not choose an option before confirming the exact demand of the question.
Question 9
Multiple Choice Question
Question
PASSAGE 3 — MITOCHONDRIAL RESPIRATION
Isolated mitochondria receive succinate as the only respiratory substrate. Oxygen consumption and ATP production are measured. Rotenone, an inhibitor of Complex I, causes little change. Antimycin A, an inhibitor of Complex III, stops oxygen consumption. In a separate trial, an uncoupler carries protons across the inner mitochondrial membrane; oxygen consumption rises, but ATP production falls sharply.
QUESTION 9: Antimycin A stops oxygen consumption primarily because it prevents electrons from reaching which terminal electron acceptor?
Explanation
Correct Answer: A
ANSWER
Correct Answer: A
Method / Topic: Biochemistry
The correct answer is A: Molecular oxygen. In oxidative phosphorylation, molecular oxygen is the terminal electron acceptor at Complex IV and is reduced to water. Blocking Complex III prevents electrons from reaching Complex IV, so oxygen cannot accept them and its consumption stops.
Why this answer is correct
The correct option matches the required rule and the given information.
Short Explanation
The correct answer is A: Molecular oxygen. In oxidative phosphorylation, molecular oxygen is the terminal electron acceptor at Complex IV and is reduced to water. Blocking Complex III prevents electrons from reaching Complex IV, so oxygen cannot accept them and its consumption stops.
Detailed Explanation
Question
PASSAGE 3 — MITOCHONDRIAL RESPIRATION
Isolated mitochondria receive succinate as the only respiratory substrate. Oxygen consumption and ATP production are measured. Rotenone, an inhibitor of Complex I, causes little change. Antimycin A, an inhibitor of Complex III, stops oxygen consumption. In a separate trial, an uncoupler carries protons across the inner mitochondrial membrane; oxygen consumption rises, but ATP production falls sharply.
QUESTION 9: Antimycin A stops oxygen consumption primarily because it prevents electrons from reaching which terminal electron acceptor?
ANSWER
Correct Answer: A
Method / Topic: Biochemistry
In oxidative phosphorylation, molecular oxygen is the terminal electron acceptor at Complex IV and is reduced to water. Blocking Complex III prevents electrons from reaching Complex IV, so oxygen cannot accept them and its consumption stops. To solve this kind of MCAT biochemistry
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Question 9
Learn + Solve: Shortcut, Trap & Fast Route Click to view shortcut, steps, and common mistake
Learn + solve
Shortcut used, common trap, and the fastest solving route
Shortcut used: Identify the tested biochemical principle, track charge/carbon/electrons or pathway direction, use the passage data, and reject choices that contradict cellular location or chemical behavior.
Solve in 3 steps:
- Mark the given values and the exact target.
- Apply the relevant formula, rule, or concept.
- Check the final value against the options.
Common mistake: Do not choose an option before confirming the exact demand of the question.
Question
PASSAGE 3 — MITOCHONDRIAL RESPIRATION Isolated mitochondria receive succinate as the only respiratory substrate. Oxygen consumption and ATP production are measured. Rotenone, an inhibitor of Complex I, causes little change. Antimycin A, an inhibitor of Complex III, stops oxygen consumption. In a separate trial, an uncoupler carries protons across the inner mitochondrial membrane; oxygen consumption rises, but ATP production falls sharply. QUESTION 9: Antimycin A stops oxygen consumption primarily because it prevents electrons from reaching which terminal electron acceptor?
Explanation
Correct Answer: A
ANSWER
Correct Answer: A
Method / Topic: Biochemistry
The correct answer is A: Molecular oxygen. In oxidative phosphorylation, molecular oxygen is the terminal electron acceptor at Complex IV and is reduced to water. Blocking Complex III prevents electrons from reaching Complex IV, so oxygen cannot accept them and its consumption stops.
Why this answer is correct
The correct option matches the required rule and the given information.
Short Explanation
The correct answer is A: Molecular oxygen. In oxidative phosphorylation, molecular oxygen is the terminal electron acceptor at Complex IV and is reduced to water. Blocking Complex III prevents electrons from reaching Complex IV, so oxygen cannot accept them and its consumption stops.
Detailed Explanation
Question
PASSAGE 3 — MITOCHONDRIAL RESPIRATION
Isolated mitochondria receive succinate as the only respiratory substrate. Oxygen consumption and ATP production are measured. Rotenone, an inhibitor of Complex I, causes little change. Antimycin A, an inhibitor of Complex III, stops oxygen consumption. In a separate trial, an uncoupler carries protons across the inner mitochondrial membrane; oxygen consumption rises, but ATP production falls sharply.
QUESTION 9: Antimycin A stops oxygen consumption primarily because it prevents electrons from reaching which terminal electron acceptor?
ANSWER
Correct Answer: A
Method / Topic: Biochemistry
In oxidative phosphorylation, molecular oxygen is the terminal electron acceptor at Complex IV and is reduced to water. Blocking Complex III prevents electrons from reaching Complex IV, so oxygen cannot accept them and its consumption stops. To solve this kind of MCAT biochemistry
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