The chemiosmotic hypothesis proposed by Peter Mitchell explains how electron transport drives ATP synthesis. According to this hypothesis, the immediate energy source for ATP synthase is which of the following?
- A A high-energy phosphorylated intermediate (X~P)
- B The proton motive force across the inner mitochondrial membrane ✓
- C Direct transfer of electrons to ADP
- D Hydrolysis of GTP by the F1 subunit
Correct answer: B. The proton motive force across the inner mitochondrial membrane
Explanation
Mitchell's chemiosmotic hypothesis states that electron transport creates an electrochemical proton gradient (proton motive force) across the inner mitochondrial membrane, and ATP synthase harnesses this gradient to drive ATP synthesis. No high-energy phosphorylated intermediate is involved. Distractor A represents the chemical coupling hypothesis that Mitchell's work replaced. Distractor C is mechanistically incorrect; electrons flow through complexes, not to ADP.
Reference: Lehninger Principles of Biochemistry, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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