Pyruvate enters the mitochondria. There it undergoes decarboxylation, dehydrogenation by pyruvate dehydrogenase to form two-carbon acetate and carbon dioxide. The removal of carbon dioxide from pyruvate is called decarboxylation. Decarboxylation is accompanied by dehydrogenation the removal of hydrogen. The hydrogen reduces NAD to reduced NAD.The acetate reacts with coenzyme A (coA) to form acetyl coA.NAD is positive and the equation for the reduction can be written asNAD+ + H2 → NADH + H+ or just reduced NAD.