Final answer:
Chemical relaxers break disulfide bonds in curly hair, allowing hair to be reshaped into a straighter form, while perms break these bonds in straight hair to reshape it around forms for curls. Both processes involve denaturation of the keratin protein, but the results can be temporary as hair gradually reverts to its original structure.
Step-by-step explanation:
The hair's structure is significantly altered when either chemical relaxers or perms are applied. Chemical relaxers work by breaking the disulfide bonds within keratin, the protein that gives hair its shape. This process involves the use of chemicals such as lye or no-lye relaxers which break the disulfide bonds between cysteine residues in the keratin structure. Heat application causes a physical change by breaking additional hydrogen bonds, allowing curly hair to be rearranged into a straighter form. Once the hair is straightened and allowed to cool without these bonds, the hair remains straight until it is physically manipulated or the disulfide bonds are reformed.
On the other hand, a chemical perm works by initially breaking down the disulfide bonds in straight hair using a solution containing a reducing agent. The hair is then wrapped around forms and an oxidation solution is applied to reform the disulfide bonds, causing the hair to take on the new shape of the curl. The reformation of these bonds in a new position results in a change of the hair's shape to the curled form, thus giving straight hair a permanent wave.
Both processes are examples of denaturation, where the protein structure of keratin is altered. It should be noted, however, that this alteration can sometimes be temporary or less long-lasting than desired due to the hair's ability to gradually revert to its original structure by forming new disulfide bonds over time or upon exposure to various factors such as water or incorrect hair care practices.