Read the following Assertion (A) and Reason (R) carefully and choose the correct option:
Assertion (A): In eukaryotic cells, the majority of 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.

Correct option is D

The correct answer is (d) Both (A) and (R) are true, and (R) is the correct explanation of (A)

Explanation:

• Assertion (A) is true: While glycolysis and the TCA cycle produce some ATP directly, about 90% of the ATP in aerobic respiration is generated in the final stage.
• Reason (R) is true: The Electron Transport Chain (ETC) pumps protons into the intermembrane space.
• The resulting proton motive force drives protons back through ATP synthase.
• This process of using a proton gradient to synthesize ATP is known as chemiosmosis, proposed by Peter Mitchell.
• Since R describes exactly how the ATP mentioned in A is produced, it is the correct explanation.

• The inner mitochondrial membrane is folded into cristae to increase surface area for these reactions.
• One molecule of NADH produces approximately 2.5 ATP, and one FADH2 produces 1.5 ATP.

• Incorrect; A is a fundamental concept of cellular biology.

• Incorrect; the mechanism in R is the direct cause of the efficiency noted in A.

• Incorrect; R accurately describes the Chemiosmotic Hypothesis.