And this step three is catalyzed by the enzyme known as isocytrade, because that's the substrate molecule to the dehydrogenase enzyme. So isositrade dehydrogenase. And remember, whenever you hear the word dehydrogenase, what that means is we're going to have an oxidation reduction reaction, which electrons are going to be transferred onto a carrier molecule, in this particular case, the nicotine amide at any dinucleotide NAD plus. So in step three, we basically reduce the NAD plus into NADH and the H ion. And the two electrons essentially come from this molecule here. So this is the Hydride ion that is transferred onto the NAD plus to form the NADH.