And these high energy ATP molecules which are so abundant inside our cells can easily be used and very effectively be used to actually transfer that phosphoryl molecule. Number five is, and we'll discuss this in much more detail, we have the process of amplification that takes place whenever protein kinases are involved. And that's because usually a single protein kinase enzyme can actually catalyze many enzymes at once. And so if each one of these enzymes itself carries out some type of reaction, the protein kinase, by activating all these other enzymes, basically amplifies the result. It amplifies all these different types of reactions and that greatly speeds up the number of substrate molecules which are transformed to the product molecules. And we'll discuss this in much more detail in a future lecture.