Keratin

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Not to be confused with kerogen or carotene
Microscopy of keratin filaments inside cells.

Keratins are a family of fibrous proteins; they are what make up hair in animals, as well as horns, nails, hooves, shells, beaks, and feathers. The name comes from Greek word keras meaning "horn".

Keratins are tough and insoluble. They form the hard but non-mineral structures in reptiles, birds, amphibians and mammals. A similar biological toughness is found in chitin.

Variety of animal uses[change | change source]

Keratins are the main constituent of structures that grow from the skin:

Arthropods such as crustaceans often have parts of their armor or exoskeleton made of keratin, sometimes in combination with chitin.

Keratins are also found in the gastrointestinal tracts of many animals, including roundworms (who also have an outer layer made of keratin).

Although it is now difficult to be certain, the scales, claws, some protective armour and the beaks of dinosaurs would, almost certainly, have been composed of a type of keratin.

Silk[change | change source]

The silk fibroins produced by insects and spiders are often classified as keratins, though it is unclear whether they are phylogenetically related to vertebrate keratins.

Silk found in insect pupae, and in spider webs and egg casings, also has twisted β-pleated sheets incorporated into fibers wound into larger supermolecular aggregates.

References[change | change source]

  1. Kreplak L, Doucet J, Dumas P, Briki F (2004). "New aspects of the alpha-helix to beta-sheet transition in stretched hard alpha-keratin fibers". Biophys J 87 (1): 640-7. PMID 15240497.

Other websites[change | change source]