Final answer:
Protection from UV radiation is not a function of sebum. Sebum's roles include lubricating the skin, protecting against bacteria, and preventing water loss, but UV protection is afforded by melanin, not sebum.
Step-by-step explanation:
The function of sebum that is NOT correct is protection from UV radiation. Sebum indeed has several key functions like lubrication of the skin, protection from bacteria due to its antibacterial properties, and prevention of water loss as it waterproofs the skin and hair. However, it does not offer protection from UV radiation. While sebum helps maintain the skin's integrity, this is primarily achieved through a barrier function against moisture loss and bacterial invasion. It is actually the melanin in the epidermis that provides some level of UV protection by absorbing and dissipating ultraviolet light. Therefore, the protection from UV radiation is not a role of sebum.