In aerobic cellular respiration, which process produces the greatest amount of ATP per molecule of glucose?

• A. Pyruvate oxidation (conversion of pyruvate to acetyl-CoA)
• B. Citric acid (TCA) cycle substrate-level phosphorylation
• C. Oxidative phosphorylation (electron transport chain coupled to chemiosmosis)
• D. Glycolysis

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the overall process of aerobic cellular respiration, which includes glycolysis, pyruvate oxidation, the citric acid (TCA) cycle, and oxidative phosphorylation.
2. Step 2: Identify the ATP yield from each stage: glycolysis produces a small amount of ATP via substrate-level phosphorylation; pyruvate oxidation itself does not produce ATP directly but generates electron carriers; the TCA cycle produces some ATP (or GTP) via substrate-level phosphorylation and more electron carriers.
3. Step 3: Recognize that oxidative phosphorylation, which includes the electron transport chain and chemiosmosis, uses the high-energy electrons from NADH and FADH2 generated in previous steps to produce the majority of ATP by creating a proton gradient that drives ATP synthase.
4. Step 4: Compare the ATP yields quantitatively: glycolysis and the TCA cycle produce a few ATP molecules directly, while oxidative phosphorylation produces the largest number of ATP molecules per glucose molecule.
5. Step 5: Conclude that oxidative phosphorylation is the process that produces the greatest amount of ATP per molecule of glucose in aerobic respiration.