The primary structure of a polypeptide describes that polypeptide as being a linear polymer of a specific sequence of amino acids. Now, once the polypeptide forms its primary structure, what happens next? Well, next, that primary polypeptide begins to twist and begins to turn via these regular patterns. And there are four different types of regular patterns. We have alpha helixes, we have beta pleated sheets, we have beta turns, and we have omega loops. And these four different types of regular patterns compose the secondary structure of our protein, of our polypeptide.