Now, under normal physiological conditions, at a neutral PH, this polypeptide will always have polarity. And what that means is on one end of the polypeptide chain, the alpha amino group will contain a full positive charge, and at the other end, the alpha carboxyl group will contain a full negative charge. And so we have polarity as a result of these two different charges. Now, by convention, the beginning of the polypeptide is always set to be at the positive end at the alpha amino group, and the end is always set to be at the negative side at the alpha carboxyl group. So we always read the amino acids beginning from the alpha amino side and ending at the alpha carboxyl side. Now, notice if we go along the polypeptide chain, we will see a repeating unit of three atoms.