And this is what we're going to focus on in this lecture. Now, complex four is also known as cytochrome C oxidase. And along complex four, what happens is the electrons are transferred from cytochrome C molecules onto oxygen. So we generate water molecules, and we also help establish a proton electrical chemical gradient that will be used by ATP synthase to actually generate those high energy ATP molecules. Now, complex four contains two important groups. One of the group are the heme groups, and the other groups are copper atoms.