Substance common in skin and hair is?

Ans. is 'a' i.e., Keratin * Keratin is a family of fibrous structural proteins. Keratin is the protein that protects epithelial cells from damage or stress.* Keratin is the key component of our skin, hair and nails. Its protein building blocks have amino acid chains, coiled, cross-linked and classified as either hard or soft.* The soft a-keratins are found in the hair, stratum corneum & nails* The harder b-keratins are found in nails.* Internal linkages provide keratin with its stability, enzyme resistance and insolubility (although it can absorb water).* Keratin monomers assemble into bundles to form intermediate filaments.* Keratin filaments are abundant in keratinocytes in the cornified layer of the epidermis