Which structural bond must be broken to change hair from straight to curly during a perm?

Which structural bond must be broken to change hair from straight to curly during a perm?

• A. Disulfide bonds
• B. Hydrogen bonds
• C. Ionic bonds
• D. Peptide bonds

Answer: (A)

Hair shape is held together by covalent cross-links in the keratin proteins, and the key one for a perm is the disulfide bond. A reducing agent used in perming breaks these disulfide bonds, allowing the hair to be rearranged around rods. Then an oxidizing step reforms new disulfide bonds in the new configuration, locking in the curl. Hydrogen bonds and ionic bonds can influence temporary shape and are easily broken by moisture or pH changes, but they don’t produce a lasting change. Peptide bonds form the protein backbone and aren’t the bonds targeted to create a permanent curl. So the bond that must be broken to change straight hair into curly during a perm is the disulfide bond.

Hair shape is held together by covalent cross-links in the keratin proteins, and the key one for a perm is the disulfide bond. A reducing agent used in perming breaks these disulfide bonds, allowing the hair to be rearranged around rods. Then an oxidizing step reforms new disulfide bonds in the new configuration, locking in the curl. Hydrogen bonds and ionic bonds can influence temporary shape and are easily broken by moisture or pH changes, but they don’t produce a lasting change. Peptide bonds form the protein backbone and aren’t the bonds targeted to create a permanent curl. So the bond that must be broken to change straight hair into curly during a perm is the disulfide bond.