Now we begin with glucose one phosphate and we end with glucose six phosphate. But what we actually don't show in this diagram is that we actually have an intermediate molecule involved and that intermediate molecule is glucose 116 bisphosphate. So if we examine the active side of this enzyme, phosphogluca mutase, we're going to see a modified serine residue. And that Serene residue actually plays a catalytic role of catalyzing this reaction. So inside the active side of this enzyme, we have a serine that has been modified. We attached a phosphoryl group onto that Serene.