Now, when we ingest the proteins, they usually come in either the tertiary or quarterly form. And what our body has to do is basically denature these proteins, basically break down the structure of the protein into the primary form, and we'll discuss how our body actually does this in the next several lectures. One of the ways is by using a very high acidity special type of cells known as parietal, cells in our stomach are capable of secreting gastric acid, hydrochloric acid that basically denatures our proteins. And once we denature them, our proteolytic enzymes can hydrolyze them via the process of hydrolysis, our catabolic reaction that breaks down these proteins. Now, our body uses 20 different types of amino acids. Now, all these 20 different types of amino acids are alpha amino acids.