Keratins
keratins
Keratin is a family of fibrous structural proteins. Keratin is the key structural material making up the outer layer of human skin. It is the key structural component of hair and nails, and it provides the necessary strength and toughness for masticatory organs, such as the tongue and the hard palate. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized tissues found in reptiles, birds, amphibians, and mammals. The only other biological matter known to approximate the toughness of keratinized tissue is chitin.