What is a fibrous protein that is the principal component of hair and nails?

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

Answer: (B)

Hair and nails derive their strength from a fibrous protein called keratin. Keratin is tough, insoluble, and organized into fibers that provide rigidity and resilience, which is essential for withstanding everyday wear and tear. Its structure is rich in cysteine, forming many disulfide bonds that cross-link the proteins and lock in rigidity, giving hair its shape and nails their hard, protective surface. While collagen is the main protein in connective tissues like skin and bones, and elastin contributes elasticity to some tissues, neither is the primary component of hair and nails. Fibrin is involved in blood clotting, not in the structural makeup of hair or nails. Thus, keratin is the key protein that makes hair and nails fibrous and strong.