Rotenone (a pesticide) is a classic inhibitor of which complex in the electron transport chain, and which substrate pair's re-oxidation is blocked?

• A Complex II (succinate dehydrogenase); FADH2 re-oxidation
• B Complex I (NADH:ubiquinone oxidoreductase); NADH re-oxidation ✓
• C Complex III (cytochrome bc1); ubiquinol re-oxidation
• D Complex IV (cytochrome c oxidase); cytochrome c re-oxidation

Explanation

Rotenone specifically inhibits Complex I (NADH dehydrogenase / NADH:ubiquinone oxidoreductase) by binding to the NADH-binding domain, preventing transfer of electrons from NADH to ubiquinone (CoQ10). This blocks re-oxidation of mitochondrial NADH from TCA cycle. Rotenone is used experimentally to model Parkinson's disease (mitochondrial dysfunction in dopaminergic neurons). Antimycin A inhibits Complex III; cyanide and carbon monoxide inhibit Complex IV; oligomycin inhibits ATP synthase (Complex V).

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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