Read the following Assertion (A) and Reason (R) carefully and choose the correct option:
Assertion (A): In eukaryotic cells, the majority of the ATP produced during aerobic respiration is generated through oxidative phosphorylation in the mitochondria.
Reason (R): Oxidative phosphorylation relies on a proton gradient across the inner mitochondrial membrane, established by the electron transport chain, which drives ATP synthesis via chemiosmosis.
- A(A) is false, but (R) is true
- BBoth (A) and (R) are true, but (R) is not the correct explanation of (A)
- C(A) is true, but (R) is false
- DBoth (A) and (R) are true, and (R) is the correct explanation of (A)
Show answer and explanation
Correct answer: (d) Both (A) and (R) are true, and (R) is the correct explanation of (A)
Explanation
Both statements are true, and (R) explains (A).
- (A): of the roughly 30–32 ATP made from one glucose molecule in aerobic respiration, most (about 26–28) come from oxidative phosphorylation in the mitochondria. Glycolysis and the Krebs cycle make only a few by substrate-level phosphorylation.
- (R): the electron transport chain in the inner mitochondrial membrane pumps protons (H⁺) out, building a proton gradient. The protons flow back through ATP synthase, which uses this energy to make ATP. This is chemiosmosis, proposed by Peter Mitchell.