Question

When a molecule of pyruvic acid is converted to lactic acid, there is a

• A. loss of 3 molecules of ATP.
• B. gain of 6 molecules of ATP.
• C. gain of 2 molecules of ATP.
• D. loss of 6 molecules of ATP.

Answer 1

The correct option is A loss of 3 molecules of ATP.

When pyruvate is reduced to lactate, a molecule of NADH is oxidized to produce $NA{D}^{+}$. If this NADH molecule had been oxidized by the electron transport chain, 3 ATP molecules would have been produced, which does not happen in this case.