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MBBS QUESTION #10338
Question 1
ATP synthase generates ATP by harnessing the proton-motive force built up across the inner mitochondrial membrane by the electron transport chain. A compound that makes the inner mitochondrial membrane permeable to protons — dissipating this gradient without directly inhibiting electron transport — is classified as:
  • A competitive inhibitor of Complex I
  • An uncoupler of oxidative phosphorylation (e.g., 2,4-dinitrophenol)✔️
  • A direct inhibitor of ATP synthase (Complex V) itself
  • An inhibitor of the citric acid cycle
Correct Answer Explanation
Uncouplers such as 2,4-dinitrophenol allow protons to leak back across the inner mitochondrial membrane independent of ATP synthase, dissipating the proton gradient as heat rather than ATP; electron transport (and oxygen consumption) actually increases to compensate, while ATP production falls — historically (and dangerously) exploited as a weight-loss agent.