Which fibrous protein is the principal component of hair and nails?

• A. Keratin
• B. Collagen
• C. Elastin
• D. Myosin

Answer: (A)

Hair and nails are built mainly from keratin, a tough fibrous structural protein. In these tissues, keratin forms hard keratin with strong disulfide bonds that make hair and nails rigid and resistant to wear, giving them their characteristic strength and durability. Collagen is the main protein in connective tissues, providing support in skin and tendons but not forming the hard structures of hair and nails. Elastin adds stretchiness to skin and vessels, not the rigid framework of hair and nails. Myosin is a motor protein involved in muscle contraction, not a structural component of hair or nails. So keratin is the principal fibrous protein in hair and nails.