The basic protein of hair is the keratin. Keratin is a fibrous protein which is insoluble in water. Fibrous proteins are long and narrow strands. Keratin molecules are held by hydrogen bonds, giving hair its structure.
Hydrogens bonds are easily broken and formed; [for example straightening curly hairs. Hydrogen bonds are broken when heated, hairs are straightened, the hydrogen bonds form again holding its stucture (straight) unless water is applied which disrupt the hydrogen bonds.]
A protective layer composed of overlapping cells, like fish scales or roof tiles, but facing downwards. The outer cuticle holds your hair in your hair follicle by means of a Velcro-like bond. It also minimizes the movement of water (moisture) in and out of the underlying cortex.
