noun, plural: keratins
Scleroproteins or the fibrous proteins are one of the three major types of proteins; the other two are spheroproteins and membrane proteins. Scleroproteins are characterized by their long protein filaments. They act as structural proteins. They are usually water-insoluble. Some of the scleroproteins are keratin, collagen, elastin, and fibroin.
Keratins are fibrous structural proteins that constitute various biological structures such as hair, nails, skin, feathers, hooves, horns, etc. They are made up of coiled polypeptide chains and when they combine they form supercoils.
Keratins protect epithelial cells from damage. Skin cells that are constantly exposed to pressure and rubbing leads to the formation of calluses. The skin thickens and the epidermal cells undergo cornification. Cornification is a process in which a keratinized layer of epidermis forms and serves as an epidermal barrier. During cornification, keratin fills up the cell resulting in the loss of cytoplasmic organelles and the cessation of metabolism. Ultimately, the fully keratinized cells undergo a programmed cell death.
Word origin: Greek keras (horn) + -in
- Stratified squamous epithelium
- Pilar cyst
- keratinous (adjective, relating to keratin; horny)