This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy of Skin, Subject name: Skin
[{'content': 'Substance common in skin and hair is? \nSelect and explain. \nA. Keratin, B. Laminin, C. Nectin, D. Vimentin', 'role': 'user'}, {'content': "Answer: A \nExplanation: 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", 'role': 'assistant'}]