Fact number two in eukaryotic cells to cells in our own body, we actually have a single polypeptide chain, a single protein known as fatty acid synthase that catalyzes the elongation, the formation of fatty acid molecules. And this fatty acid synthase actually contains seven different catalytic sites, which each carries out its own specific function, as we'll see in the next lecture. Now, in addition to these seven catalytic sites on the fatty acid synthase, we also have a domain we call the Acyl carrier protein domain, or ACP domain. And attached onto this acid carrier protein is a phosphopancy thion molecule, which is a vitamin B five derivative. So, to see exactly what we mean, let's take a look at the following diagram. So, we have the fatty acid synthase shown in red, and that contains seven catalytic sites which are not shown.