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

• A. Oxidative phosphorylation (electron transport chain coupled to ATP synthase)
• B. Citric acid cycle (Krebs cycle) substrate-level phosphorylation
• C. Fermentation (lactate or ethanol production)
• D. Glycolysis

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the overall process of aerobic cellular respiration, which includes glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation (electron transport chain coupled to ATP synthase). Each stage contributes differently to ATP production.
2. Step 2: Recall that glycolysis produces a small amount of ATP directly through substrate-level phosphorylation and also generates NADH, which will be used later in oxidative phosphorylation.
3. Step 3: Recognize that the citric acid cycle also produces ATP (or GTP) via substrate-level phosphorylation, but its main contribution is generating high-energy electron carriers (NADH and FADH2) that feed into the electron transport chain.
4. Step 4: Understand that oxidative phosphorylation uses the electrons from NADH and FADH2 to create a proton gradient across the mitochondrial membrane, which drives ATP synthase to produce ATP in large quantities.
5. Step 5: Compare the ATP yields from each process: glycolysis and the citric acid cycle produce ATP directly but in smaller amounts, while oxidative phosphorylation produces the greatest amount of ATP per glucose molecule by harnessing the energy from electron carriers.