Question

when hair is curled with a curling iron, what types of bonds are formed?

Answer 1

Curling of hair:

We know that hair is almost completely made up of protein. The main protein involved in this is $\alpha$ -keratin.

$\alpha$-keratin has a structure of helix in which the protein strands twists upon itself.

Many protein helices combine to form a filament, like a straight rope, where each strands are made up of the coiled proteins.

There are two types of bonding involved in this, which holds each strands together. Hydrogen bonding as well as disulphide bond.

Disulphide bond is formed between sulphur atoms of adjacent strands of protein.

disulphide bond is the bond responsible for holding protein together and to give a straight structure to hair.

When hair is curled with a curling iron, the disulphide bond between hair will break and the helix strands will unwrap from the "rope" like structure.

As we wrap the hair around curlers and shape into a new shape we desire, new disulphide bonds will be formed and it will keep the new desired curly structure together.