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Keratin

Keratin is fibrous protein in hair, scales, nails, feathers, horns, claws, hooves, and the outer layer of skin among vertebrates.There are a large number of cysteine residues which form disulfide bridges between the long chains and make the keratin strong, inflexible and insoluble.Keratin is extremely insoluble in both water and organic solvents.Spider silk is also a fibrous protein, but it is made of proteins called spidroins, not keratin.The more disulfide bridges it contains, the less flexible the structure.

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Specification: OCR Biology A (H020), AS-level, 2.1.2 Biological molecules. Topic: Biological Molecules.

Key terms in this lesson

disulfide bridge
A covalent bond formed between two cysteine residues that helps stabilise the tertiary or quaternary structure of a protein.
fibrous protein
An insoluble, structural protein made of long, parallel polypeptide chains, such as collagen or keratin.

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