Keratin is one of a family of fibrous proteins. Keratin is what makes up hair in animals, as well as horns, nails, hooves, shells, beaks, and feathers. The name comes from Greek word keras meaning "horn".
Variety of animal uses change
Keratins are the main constituent of structures that grow from the skin:
- the α-keratins in the hair (including wool), horns, nails, claws and hooves of mammals
- the harder β-keratins in the scales and claws of reptiles, their shells (chelonia, such as tortoise, turtle, terrapin), and in the feathers, beaks, and claws of birds. These keratins are formed mainly in beta sheets. However, beta sheets are also found in α-keratins.