For example, Pepsi functions optimally at a PH of about two. Now, if we examine and study the small intestine which basically contains the enzymes that are involved in breaking down the macromolecules into their constituent parts which are then ingested into our blood. So basically, enzymes in the small intestine function optimally at a slightly basic PH of about 8.0. Now, if the PH changes in either direction the activity of our enzyme will basically decrease symmetrically as shown in the following diagram. Notice in this case we have a sharp drop but in this case we have the same exact slope on both sides. So basically, if this y axis is the rate of activity of the enzyme and the x axis is our PH and a PH of about 8.0 the enzymes in our small intestines, such as Chimetrypsin and Tryptin basically function optimally at this PH of 8.0.