PSI Cosmetology Practice Exam

What does a chemical relaxer change in the hair?

1. Cuticle structure

2. Disulfide bonds

3. Hydrogen bonds

4. Peptide bonds

The correct answer is: Disulfide bonds

A chemical relaxer primarily alters the disulfide bonds within the hair. Disulfide bonds are strong covalent bonds that form between the sulfur atoms in two cysteine amino acids, providing structure and strength to the hair. When a chemical relaxer is applied, it breaks these bonds, allowing the hair to be reshaped and made into a straighter form. After the disulfide bonds are broken, the hair can be styled in a new direction that has less curl or wave, achieving a smoother look. This process is essential in hair straightening treatments that aim to reduce frizz and create a sleek appearance. Once the hair is neutralized, the disulfide bonds can be re-formed in this new, straighter position, stabilizing the new hair shape. Other types of bonds, such as cuticle structure, hydrogen bonds, and peptide bonds, play different roles in the hair’s overall integrity and appearance but are not directly altered in the same manner by a chemical relaxer. The cuticle is the outer layer of the hair and is not structurally changed by a relaxer; hydrogen bonds are temporary and can be reformed with moisture and heat; peptide bonds are responsible for the primary structure of proteins and are not affected