So in eukaryotic cells, Pyruvate dehydrogenase complex is controlled via phosphorylation, a form of covalent modification. So let's study this diagram for just a moment. So this is our Pyruvate dehydrogenase complex in its active form. And notice it is not phosphorylated. But under certain conditions we have a kinase that is actually attached onto the e two component of the complex. This kinase is stimulated and we'll see what stimulates it.