Fibrous structural protein of hair, nails, hooves, wool, feathers, and skin. A quarter of the amino acids in keratin are cystine, whose ability to form strong bridging (disulfide) bonds with other cystine units accounts for keratin's great stability. Keratin does not dissolve in cold or hot water and does not easily undergo proteolysis. Its fibres are 10–12% longer at maximum water content (about 16%) than when dry. The sulfurous smell of burning keratin is distinctive.

This entry comes from Encyclopædia Britannica Concise.
For the full entry on keratin, visit

Seen & Heard

What made you look up keratin? Please tell us what you were reading, watching or discussing that led you here.

Get Our Free Apps
Voice Search, Favorites,
Word of the Day, and More
Join Us on FB & Twitter
Get the Word of the Day and More