In Kreb's cycle oxidation occurs by dehyrdrogenation in which the hydrogen released is accepted by hydrogen acceptors like NAD and FAD. A total of five steps involve the dehydrogenation reaction involving the enzyme dehydrogenase, in which there are four points in the cycle where NAD+ is reduced to NADH + H+ and one point FAD+ is reduced to FADH2.

The enzymes like pyruvic dehydrogenase, isocitric dehydrogenase, alpha-ketoglutaric acid dehydrogenase, succinate dehydrogenase and malate dehydrogenase are involved in this process.