
thumb|300px|Microscopy of keratin filaments inside cells
Keratins are tough, fibrous proteins that form filaments inside cells and provide structural support. They are important because they help make up key parts of the body like hair, nails, and skin, giving these tissues their strength and resilience.
AI-generated from the Wikipedia summary — may contain errors.
thumb|300px|Microscopy of keratin filaments inside cells
Keratin () is one of a family of structural fibrous proteins also known as scleroproteins. It is the key structural material making up scales, hair, nails, feathers, horns, claws, hooves, and the outer layer of skin in tetrapod vertebrates. Keratin also 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. Excessive keratinization participate in fortification of certain tissues such as in horns of cattle and rhinos, and armadillos' osteoderm. The only other biological matter known to approximate the toughness of keratinized tissue is chitin. Keratin comes in two types: the primitive, softer forms found in all vertebrates and the harder, derived forms found only among sauropsids (reptiles and birds).
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