The diagram is of digestive enzyme. It shows four stages. The first stage shows the substrate and enzyme apart, with the active site labelled, and the label: substrate entering active site of enzyme. Second stage shows the two now together and points to the fact that the enzyme slightly morphs so the substrate fits. It has the label: enzyme/substrate complex. The third stage shows the enzyme breaking the substrate into products with the label: enzyme/products complex. The final stage shows the two products leaving the active site of the enzyme, with the label: products leaving active site of enzyme.