ATP formation occurs during all of the following steps of aerobic respiration except:

Explanation

Pyruvic acid oxidation does not directly produce ATP. Instead, it involves the conversion of pyruvate into acetyl-CoA, yielding NADH but no ATP. In contrast, glycolysis produces a net gain of 2 ATP per glucose molecule, the Krebs cycle generates ATP through substrate-level phosphorylation, and the electron transport chain produces ATP through oxidative phosphorylation. Therefore, pyruvic acid oxidation is the correct answer, as it is the step in aerobic respiration where ATP formation does not occur directly.