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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 8
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 8: Which immediate membrane-level effect best explains the uncoupler results?
Explanation
Correct Answer: D
ANSWER
Correct Answer: D
Method / Topic: Biochemistry
The correct answer is D: Dissipation of the proton-motive force without ATP synthase. The uncoupler returns protons to the matrix independently of ATP synthase, collapsing the electrochemical gradient. Electron transport speeds up in an attempt to restore the gradient and consumes more oxygen, but the proton flow no longer drives efficient ATP synthesis.
Why this answer is correct
The correct option matches the required rule and the given information.
Short Explanation
The correct answer is D: Dissipation of the proton-motive force without ATP synthase. The uncoupler returns protons to the matrix independently of ATP synthase, collapsing the electrochemical gradient. Electron transport speeds up in an attempt to restore the gradient and consumes more oxygen, but the proton flow no longer drives efficient ATP synthesis.
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 8: Which immediate membrane-level effect best explains the uncoupler results?
ANSWER
Correct Answer: D
Method / Topic: Biochemistry
The uncoupler returns protons to the matrix independently of ATP synthase, collapsing the electrochemical gradient. Electron transport speeds up in an attempt to restore the gradient and consumes more oxygen, but the proton flow no longer drives efficient ATP synthesis. To solve this kind of MCAT biochemistry
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Question 8
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 8: Which immediate membrane-level effect best explains the uncoupler results?
Explanation
Correct Answer: D
ANSWER
Correct Answer: D
Method / Topic: Biochemistry
The correct answer is D: Dissipation of the proton-motive force without ATP synthase. The uncoupler returns protons to the matrix independently of ATP synthase, collapsing the electrochemical gradient. Electron transport speeds up in an attempt to restore the gradient and consumes more oxygen, but the proton flow no longer drives efficient ATP synthesis.
Why this answer is correct
The correct option matches the required rule and the given information.
Short Explanation
The correct answer is D: Dissipation of the proton-motive force without ATP synthase. The uncoupler returns protons to the matrix independently of ATP synthase, collapsing the electrochemical gradient. Electron transport speeds up in an attempt to restore the gradient and consumes more oxygen, but the proton flow no longer drives efficient ATP synthesis.
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 8: Which immediate membrane-level effect best explains the uncoupler results?
ANSWER
Correct Answer: D
Method / Topic: Biochemistry
The uncoupler returns protons to the matrix independently of ATP synthase, collapsing the electrochemical gradient. Electron transport speeds up in an attempt to restore the gradient and consumes more oxygen, but the proton flow no longer drives efficient ATP synthesis. To solve this kind of MCAT biochemistry
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