And these peptide bonds have a double bond character. And what that means is they don't actually rotate, but all the other single bonds inside the polypeptide chain do rotate. And it's the rotation of these other single bonds inside the polypeptide chain that allows the linear polypeptide to eventually fold into the beta pleated sheet, into the alpha helix, into the beta turn and our omega loop. Now, once we form these regular patterns, the question is what exactly stabilizes these structures and allows them to exist in the first place? Well, it's the hydrogen bonds that exist between the amino acids in that polypeptide chain, as we'll see in just a moment, that allows each one of these secondary structures to actually exist in the first place. So let's begin with the alpha helix.