Keratin Keratin Keratin () is one of a family of fibrous structural proteins. It is the key structural material making up hair, horns, claws, hooves, and the outer layer of human skin. Keratin is also the protein that protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized epidermal appendages found in reptiles, birds, amphibians, and mammals. The only other biological matter known to approximate the toughness of keratinized tissue is chitin. Keratin derives from Greek ' from '
What Is the Fastest Thing in the World? What Is the Fastest Thing in the World? What Is the Fastest Thing in the World? is a Greek fairy tale collected by Georgios A. Megas in "Folktales of Greece". It is Aarne-Thompson type 875 and has many Greek and Slavic variants, generally revolving about the exchange of clever answers. This type of tale is the commonest European tale dealing with witty exchanges. In ballad form, the clever answers to the riddles, and the winning of a husband by them, are found in Child ballad 1, "Riddles Wisely Expounded". A brother argue over how they should split their land, some