Which process in aerobic cellular respiration produces the greatest number of ATP molecules?

• A. Fermentation
• B. Citric acid cycle (Krebs cycle)
• C. Glycolysis
• D. Electron transport chain and oxidative phosphorylation

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the overall process of aerobic cellular respiration, which includes glycolysis, the citric acid cycle (Krebs cycle), and the electron transport chain coupled with oxidative phosphorylation. Each step contributes to ATP production.
2. Step 2: Recall that glycolysis occurs in the cytoplasm and breaks down glucose into pyruvate, producing a small amount of ATP (2 ATP molecules per glucose molecule) and NADH.
3. Step 3: Next, the citric acid cycle (Krebs cycle) occurs in the mitochondrial matrix. It generates NADH and FADH2, which are high-energy electron carriers, along with a small amount of ATP (2 ATP molecules per glucose molecule).
4. Step 4: The electron transport chain and oxidative phosphorylation occur in the inner mitochondrial membrane. NADH and FADH2 donate electrons to the electron transport chain, creating a proton gradient that drives ATP synthesis via ATP synthase. This process produces the majority of ATP in aerobic respiration (approximately 28-34 ATP molecules per glucose molecule).
5. Step 5: Compare the ATP yield from each process. Glycolysis and the citric acid cycle produce small amounts of ATP, while the electron transport chain and oxidative phosphorylation generate the greatest number of ATP molecules, making it the most significant contributor to ATP production in aerobic respiration.