Which protein helps to waterproof the skin?

Keratin is a key protein that plays a crucial role in waterproofing the skin. It is a fibrous structural protein that is a major component of the epidermis, the outermost layer of the skin. Keratin helps to form a protective barrier that prevents water loss from the body and also protects against external environmental factors, such as pathogens and chemicals.

In the process of keratinization, skin cells produce and accumulate keratin, leading to the formation of a tough and resilient layer that maintains skin hydration while keeping harmful substances out. This waterproofing property is essential for maintaining homeostasis in the body, as it ensures that vital fluids do not evaporate excessively.

Other proteins such as collagen and elastin contribute to the strength and elasticity of the skin but do not serve the specific purpose of waterproofing. Melanin, on the other hand, primarily functions in providing pigmentation and protecting against UV radiation, rather than contributing to the skin's ability to prevent water loss. Therefore, keratin is the correct answer when discussing the protein responsible for waterproofing the skin.