Which hair structure must be permanently broken to achieve a change from straight to curly hair?

To achieve a change from straight to curly hair in the perming process, disulfide bonds need to be permanently broken. Disulfide bonds are strong chemical bonds formed between the sulfur atoms in the amino acid cysteine, which are crucial for maintaining the natural shape and structure of the hair. When these bonds are broken, the hair can be reshaped into a new style, such as curls, by using a perm solution.

This process allows the hair to adopt a new shape, which will hold until the disulfide bonds are reformed either naturally through hair growth or through the use of specific chemical processes. The ability to permanently break and re-form these bonds is central to the effectiveness of perming.

While hydrogen bonds, salt bonds, and peptide bonds also play roles in hair structure, they do not provide the same level of durability against changes as disulfide bonds. Hydrogen bonds, for instance, are weaker and can be temporarily altered through moisture and heat rather than permanently broken. Salt bonds function similarly, being relatively weak and easily altered. Peptide bonds are responsible for linking amino acids together in the protein structure of hair but do not directly influence the hair's shape in the context of perming.