Pepsin

Pepsin is the digestive enzyme in the stomach that slices up other protein molecules. Pepsin is a protein that utterly (i.i) destroys, lol, other proteins that are eaten by vertebrates such as ourselves. In this case, in the picture I gloriously created, part of it, is another protein that actually inhibits pepsin from doing it's job. As I've indicated in one of the posts below. Proteins are the little people-like molecule machines that make life Go! They are made of a long chain of amino acid units, of which there are twenty kinds. The combination of amino acid units determines the function, and shape of the protein in the cell. The backbone is the identical part of each amino acids that links hand to hand from one end to the other. It's course is indicated by the pink ribbon, the backbone that links together is the grey, the blue are what are known as side chains, that make each kind of the twenty amino acids distinct, and determine the atomic interactions of the protein with itself in folding into a shape, and with the environment, how it functions.