During aerobic cellular respiration in eukaryotic cells, which metabolic stage produces the largest amount of ATP through oxidative phosphorylation?

Answer and explanation

Correct answer: B. Electron transport chain and chemiosmosis

  1. Step 1: Review ATP yields per glucose molecule across metabolic stages: Glycolysis yields 2 net ATP; Krebs cycle yields 2 ATP/GTP.
  2. Step 2: The electron transport chain uses proton gradients established by NADH and FADH2 across the inner mitochondrial membrane.
  3. Step 3: ATP synthase generates approximately 26 to 28 ATP molecules via chemiosmosis during oxidative phosphorylation.
  4. Step 4: Conclude that electron transport and chemiosmosis yield the vast majority of ATP.
Answer
Electron transport chain and chemiosmosis.
Why not the others: 'Glycolysis in the cytosol' generates only 2 net ATP via substrate-level phosphorylation; 'Pyruvate oxidation in the mitochondrial matrix' generates NADH and CO2 but 0 direct ATP; 'The citric acid (Krebs) cycle' generates only 2 direct ATP/GTP molecules.

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