And we'll discuss the steps involved in much more detail in the next several lectures. In this lecture, we're simply going to paint a general description, a general picture of what takes place inside the active site and how Serene is actually involved in breaking and catalyzing those peptide bonds so we see that experimental data suggests that Chimotrypsin uses a two step mechanism to actually hydrolyze peptide bonds. Now, the way that scientists actually studied the reaction mechanism of Chimotrypsin is by using a special type of substrate molecule that once we react that substrate molecule with the activity, the product that is produced gives off a color. And so we can study the absorption of light when that colored product is produced. And that will give us information as to what happens in that reaction when we use climate trypsin. So, once again, to monitor the reaction progress, we generally use a substrate that changes color when it reacts with the active side.