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

• A. Glycolysis
• B. Citric acid (TCA) cycle substrate-level phosphorylation
• C. Fermentation (e.g., lactate fermentation)
• D. Oxidative phosphorylation via the electron transport chain and ATP synthase

Answer: (D)

Verified step by step guidance

1. Identify the main stages of aerobic cellular respiration: glycolysis, the citric acid (TCA) cycle, and oxidative phosphorylation (electron transport chain and ATP synthase).
2. Understand that glycolysis and the TCA cycle produce ATP directly through substrate-level phosphorylation, but in relatively small amounts per glucose molecule.
3. Recognize that fermentation, such as lactate fermentation, occurs under anaerobic conditions and yields much less ATP compared to aerobic respiration.
4. Focus on oxidative phosphorylation, which uses the electron transport chain to create a proton gradient that drives ATP synthase to produce ATP in large quantities.
5. Conclude that oxidative phosphorylation yields the greatest amount of ATP per glucose molecule because it efficiently harnesses energy from NADH and FADH2 generated in earlier steps.