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Question #45914
The Question
According to the chemiosmotic hypothesis, the F0-F1 ATP synthase couples the proton motive force to ATP synthesis. However, under severe mitochondrial stress where the electron transport chain is completely inhibited (e.g., by cyanide) and the proton gradient collapses, the mitochondrion must still maintain its membrane potential to prevent cell death. If cytosolic ATP is abundant, how does the F0-F1 complex respond to this specific thermodynamic shift?
Options
- A.
It acts as an ATPase, hydrolyzing ATP at the F1 headpiece to pump protons from the matrix to the intermembrane space through F0.
- B.
It reverses electron flow through Complex I to re-establish the proton gradient without consuming ATP.
- C.
The F0 integral membrane protein actively transports protons into the matrix, while F1 halts ATP synthesis.
- D.
It uncouples from the proton gradient, allowing free diffusion of protons into the matrix to generate heat instead of ATP.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
ATP_Synthase|Complex_I|Redox_Potential
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students rigidly memorize ATP synthase as a unidirectional 'ATP generator' driven by a proton gradient.
They fail to recognize that enzymes catalyze reversible reactions based on thermodynamic equilibrium.
When the proton gradient collapses but ATP is high, the enzyme reverses, becoming an ATP-consuming proton pump to save the organelle's membrane potential.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Respiration in Plants - Class 11 |
| Concept | Chemiosmotic ATP Yield |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |