So from this discussion we saw that because we have these peptide bonds that have double bond character, there is no rotation about the atoms between our peptide bonds. Now, the question is the following. Notice we have a linear polymer of amino acids, but the final three dimensional structure proteins is not a linear structure, it's a convoluted structure. So eventually, to go from our primary linear structure to the three dimensional convoluted structure of our protein, we have to actually rotate our bonds. But if these green bonds cannot rotate, which bonds could rotate? Well, it turns out that in any one of these amino acids, these bonds cannot rotate, but these bonds can.