Which substance protects the skin from UV radiation?

Melanin is the substance that protects the skin from ultraviolet (UV) radiation. It is a pigment produced by specialized cells called melanocytes, primarily located in the skin. Melanin absorbs UV radiation and dissipates it as heat, which helps to prevent damage to the DNA in skin cells that can lead to skin cancer and other forms of skin damage. The amount of melanin in a person's skin contributes to their skin color and plays a critical role in the body's defense against the harmful effects of sun exposure.

Keratins, while important structural proteins in the skin, hair, and nails, do not have protective properties against UV radiation. Collagen contributes to the skin's strength and elasticity but also does not offer protection from UV rays. Cholesterol, although it plays various roles in cellular function and is a component of cell membranes, does not have a direct role in protecting the skin from UV radiation.