We also have tertiary, which basically refers to the three dimensional structure of our protein. We have second there, which refers to either the beta pleated sheets or the alpha helixes. And we also have primary, which is basically the long sequence of amino acids inside the protein. 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.