Now, like any dehydrogenase, alcohol dehydrogenase will essentially catalyze the transfer of a Hydride group from that NADH onto this acetolaldehyde. Now, if we examine the active side of the alcohol dehydrogenase we're going to see a zinc ion. And what that zinc ion does? Well, first of all, it interacts with the active side of that enzyme. So it actually binds with residues on that active side. To be more specific, it binds with with 216 residues and one histidine residue.