Keratin is a protein found in hair and skin. It is a fibrous protein and has a coiled structure similar to that of a telephone cord. The structure is described as an alpha helix. A human hair strand is made up of many alpha helices. This diagram shows three alpha helices interwoven to make a protofibril. Eleven protofibrils are bonded and coiled together to make a microfibril. Hundreds of these microfibrils are combined together into an irregular bundle called a macrofibril. These in turn are mixed with dead and living cells to make a complete strand of hair.
