What characteristic is associated with keratin in the skin?

The characteristic associated with keratin in the skin is that it provides a protective layer. Keratin is a fibrous protein found in the outermost layer of the skin, known as the epidermis. It plays a crucial role in the skin's barrier function, helping to protect underlying tissues from environmental damage, pathogens, and dehydration. By forming a tough and resilient outer layer, keratin contributes significantly to the skin's overall health and integrity.

As for the other characteristics: giving skin a yellow undertone isn’t related to keratin; instead, skin tones are influenced by melanin and other pigments. Controlling moisture retention is more closely related to the lipid barrier and natural moisturizing factors rather than keratin itself. Lastly, regulating temperature is primarily managed by blood flow and sweat production, not by keratin’s structural role in the skin.