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

• A. Substrate-level phosphorylation during the citric acid (TCA) cycle
• B. Pyruvate oxidation (conversion of pyruvate to acetyl-CoA)
• C. Oxidative phosphorylation via the electron transport chain and ATP synthase
• D. Substrate-level phosphorylation during 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 via the electron transport chain and ATP synthase.
2. Step 2: Identify the ATP yield from substrate-level phosphorylation during glycolysis and the TCA cycle, noting that these steps produce a relatively small, fixed number of ATP molecules per glucose.
3. Step 3: Recognize that pyruvate oxidation itself does not directly produce ATP but generates important electron carriers (NADH) that feed into the electron transport chain.
4. Step 4: Focus on oxidative phosphorylation, where NADH and FADH2 donate electrons to the electron transport chain, creating a proton gradient across the inner mitochondrial membrane.
5. Step 5: Understand that ATP synthase uses this proton gradient to drive the synthesis of a large amount of ATP, making oxidative phosphorylation the process that produces the greatest amount of ATP per glucose molecule in eukaryotic cells.