And so to begin, let's focus on step three that is catalyzed by the allosteric enzyme isocitrate dehydrogenase. So we can break down step three into two steps. We have three A and three B. In three A we have the oxidation reduction step. This basically takes place or the isocytrate is oxidized into an intermediate oxylociate. In the process, we reduce the NAD plus coenzyme into NADH and the NADH can then be used by the electron transport chain as we'll discuss in the future lecture.