What is a defining characteristic of keratin in the epidermis?

Keratin is a crucial structural protein found in the epidermis, the outermost layer of the skin. One of its defining characteristics is that it provides tough, waterproof protection. This property is essential because it helps prevent water loss from the body and protects against environmental hazards such as pathogens, chemicals, and physical abrasions.

The keratinocytes, which are the predominant cell type in the epidermis, produce keratin as they migrate toward the surface of the skin. As these cells move up, they undergo a process called keratinization, where they fill with keratin, lose their nuclei, and eventually create a protective layer of dead cells that forms the outer barrier of the skin. This keratinized layer is integral to maintaining the skin's integrity and overall health, contributing to its barrier function.

The other options do not accurately reflect the primary role of keratin in the epidermis. While lubrication is essential for many body functions, it is not the primary role of keratin, which is designed for protection. Cellular respiration is a process that occurs in all living cells, and keratin does not play a role in this process. Finally, although some components of the skin help absorb UV radiation, keratin itself is primarily involved in protection rather than