Keratin Diagram. The consensus amino acid sequence is a repeating heptamer of a b c d e f g n where residues a and d are non polar. The epidermis is epithelium composed of multiple layers of cells.
As these keratinized cells age on the skin the body sloughs off the dead or damaged cells. It is the key structural material making up scales hair nails feathers horns claws hooves and the outer layer of skin among vertebrates. According to healthline the keratin forms a tight mesh making it impenetrable unless damaged.
Type i with acidic amino acid residues and type ii with basic amino residues.
One strand of type i fibre and one strand of type ii fibre spiral together to form coiled coil dimers. Keratin hardens as keratinocytes found in epithelial cells produce more and more keratin. Keratin also protects epithelial cells from damage or stress. The polypeptide chains include many sulphur containing amino acids and these help to give the keratin molecules their characteristic strength.