What type of reaction occurs when hair is permed?

When hair is permed, a chemical reaction occurs that specifically breaks and reforms disulfide bonds within the hair's keratin structure. This process is fundamental to the perming technique, as it allows the hair to take on a new shape or texture.

During the perming process, a solution containing ammonium thioglycolate or another chemical agent is applied to the hair. This solution breaks the existing disulfide bonds that contribute to the hair's natural texture. Once the hair is wrapped around rods or curlers, a neutralizing solution is applied. This solution causes the broken disulfide bonds to reform in a new configuration, effectively setting the hair into its new curled style.

By understanding this chemical interaction, it's clear why the correct answer is focused on the breaking and reforming of bonds as the key mechanism behind how perms create lasting changes in hair texture. This is essential knowledge for anyone in the field of hair design.