So we have that shown here. And the key here is, because we form this thio ester bond, it will be very unstable, high in energy. And when we cleave this bond, it will release a certain amount of free energy that will allow us to actually carry out step five. Now, let's go back to step four in a moment, for a moment, because we didn't mention the enzyme that catalyzes this step. So we have the substrate molecule is alpha ketoglutrate, and the enzyme is basically a dehydrogenase complex. So alpha ketoglutterate, dehydrogenase complex.