What is the role of keratin in the epidermis?

• A. Provides toughness and waterproofing to the skin and nails
• B. Stores energy
• C. Produces sweat
• D. Provides pigment

Answer: (A)

Keratin gives the epidermis its toughness and waterproofing. It’s a fibrous protein produced by keratinocytes; as skin cells move toward the surface, they fill with keratin, flatten, and eventually die to form the stratum corneum, a durable, water-resistant outer layer that protects deeper tissues. This same keratin in its hard form also strengthens nails and gives hair its resiliency. The other roles listed don’t fit keratin: energy storage is handled by fats and glycogen, sweating is produced by sweat glands, and pigment comes from melanin produced by melanocytes.