What is unusual about the peptide bond compared to the other covalent bonds that form the polypeptide backbone? A) The side chains only face internally, excluding them from interacting with water.

B) The single bonds on either side of the peptide bond cannot rotate, making the peptide backbone very rigid.

C) There is an amino group on one end of the backbone and an aldehyde group on the other.

D) Peptide bonds behave like double bonds in terms of stability and lack of movement of atoms around the bond.