So the only difference between citrate and isocytrate is the position of this hydroxyl group. It is moved from this location onto this location here. Now, once we form the isocytrate, which, by the way, is actually an endergonic reaction, we essentially use up about 6.3 kilojoules per mole of energy. Now, once we actually form this isocitrate, now it is ready to actually undergo the first oxidative decarboxylation step that takes place in the citric acid cycle. So what we mean by an oxidative decarboxylation step is we actually have two reactions taking place. We have an oxidation reduction reaction, and we have a decarboxylation step.