And this carbon atom is this carbon atom right here. So even though these cannot actually rotate, this carbon between the nitrogen and our alpha carbon and this bond between the alpha carbon and this carbon of the carbonyl, they can actually rotate. And these are known as torsion angles. So we have torsion angle Phi and torsion angle, Phi. The Phi angle is the angle of rotation about the single bond between the nitrogen and the alpha carbon, while the PSI angle is the angle of rotation about the single bond between the alpha carbon and the carbon of the carbon dill. Now, why is it that these can rotate and the peptide bond can?