So creatine kinase is this enzyme that essentially transforms ATP molecules and creatine molecules into phosphoriaine and ATP molecules, it basically catalyzes the formation of a high energy molecule that is used by the muscle cells of our body. So to demonstrate how this reaction takes place, let's take a look at the following four diagrams. So this green structure is the active side of the creatine kinase. And what happens is we have these two substrate molecules, the ATP is our A and the Creatine is our B. And notice in this particular reaction, because we're dealing with a random sequential reaction, the order at which these two reactors, the two substrates, actually bind onto the active side does not matter. We can either have the ATP bind first, followed by the creatine, or we can have the creatine bind first followed by the ATP.