 Welcome to Chemical Hair Bonds, the peptide bond. A strand of hair has four chemical bonds, peptide, disulfide, salt, and hydrogen. The peptide bond is also called an end bond. It joins amino acids together to form polypeptide chains. Watch as the amino acids form a chain. The polypeptide chains form the smallest individual strands of keratin. Of all the chemical bonds in the hair, the peptide bonds are the strongest. During normal chemical processes in the salon, the peptide bonds are not altered. There is no change. When the peptide bonds break, the hair becomes damaged and weak and it can break. The peptide bond is the strongest bond in the hair. Thank you for completing this activity on Chemical Hair Bonds, the peptide bond.