How many ATP are formed in the Electron Transport Chain per glucose?

• A. 2
• B. 4
• C. 34
• D. 38

Answer: (C)

The main idea is that most ATP in aerobic respiration comes from oxidative phosphorylation in the electron transport chain, using the electrons carried by NADH and FADH2 to pump protons and drive ATP synthesis.

From one glucose, glycolysis, pyruvate oxidation, and the citric acid cycle produce a total of 10 NADH and 2 FADH2. In the electron transport chain, each NADH typically yields about 3 ATP and each FADH2 about 2 ATP. That gives 10 × 3 + 2 × 2 = 34 ATP formed through oxidative phosphorylation.

Keep in mind the exact number can vary slightly depending on how the NADH from glycolysis is shuttled into the mitochondria (which can change the ATP per NADH), but 34 ATP is the standard figure used in many A-level energy system calculations for the ATP produced by the ETC per glucose. The ATP produced directly by substrate-level phosphorylation in glycolysis and the citric acid cycle is counted separately from this ETC yield.