Which of the following is a temporary side bond that can reform?

A salt bond is a type of temporary side bond formed between positively and negatively charged locations on the hair's protein chains. These bonds can easily break and reform due to changes in pH and moisture content. For instance, when hair is wet, these bonds can be disrupted, and when the hair dries, they re-establish, allowing for the temporary alterations in hairstyle that can be achieved with wet styling techniques.

In contrast, peptide bonds are strong, permanent connections that occur between amino acids in the hair's structure, contributing to the protein backbone. Covalent bonds are even stronger and more stable, involving the sharing of electrons; they do not reform easily, which makes them crucial for the overall structure of hair protein as well. Disulfide bonds, created between cysteine amino acids, are also strong and contribute significantly to the hair's strength and shape but require specific chemical processes or heat to break and reform.

Understanding these differences helps in recognizing how certain treatments can affect hair's structure temporarily or permanently.