Glycolysis outputs

• A. 2 NAD+, 2 FADH2
• B. 2 CO2 and 2 ATP
• C. 2 molecules of pyruvate, 2 NADH, 2 ATP (net)
• D. 2 lactate

Answer: (C)

Glycolysis breaks one glucose into two pyruvate molecules while harvesting energy as NADH and ATP. In the energy investment phase, two ATP are used, but in the payoff phase four ATP are produced, giving a net gain of two ATP per glucose. At the same time, two NAD+ molecules are reduced to NADH, so two NADH are generated. Therefore, the outputs are two pyruvate, two NADH, and a net two ATP per glucose. CO2 is not released during glycolysis; it’s released later when pyruvate is oxidized to acetyl-CoA and during the TCA cycle. FADH2 is not produced in glycolysis; it appears in other steps of cellular respiration. Under anaerobic conditions, pyruvate can be converted to lactate to regenerate NAD+, but that produces lactate rather than changing the basic glycolysis outputs.