THE FORMATION OF ACETYL COENZYME A
The two pyruvate molecules formed from a single glucose molecule now enter the mitochondrion in eukaryotes. There, each is converted to acetyl coenzyme A (acetyl-CoA).

First, a molecule of CO₂ is removed from each pyruvate, forming a two-carbon fragment. These two-carbon molecules are oxidized—that is, electrons are removed and used to form a total of two NADH molecules (to be used later). Then, each oxidized, two-carbon fragment—an acetyl group—is attached to coenzyme A, forming acetyl-CoA.