Final answer:
Dead epidermal cells contain keratin, a protein produced by keratinocytes which provides a protective barrier for the skin.
Step-by-step explanation:
The protein found in dead epidermal cells is keratin. Keratinocytes, which make up the majority of cells in the epidermis, produce keratin as they mature and move up through the layers of the epidermis. By the time keratinocytes reach the surface, they are mostly filled with keratin and have undergone a programmed death process called apoptosis, leaving behind a layer of dead cells that forms a barrier to protect the underlying living tissues from environmental damage, pathogens, and water loss.