What role does keratin play in hair structure?

Keratin is a fibrous protein that forms the fundamental building blocks of hair, skin, and nails. In the context of hair structure, keratin plays a crucial role in providing strength and elasticity. This protein is structured in a way that allows hair strands to withstand various forms of stress, including stretching and bending without breaking. The unique arrangement of keratin proteins contributes to the overall integrity and durability of the hair, making it less prone to damage from environmental factors or styling practices.

While other options relate to important qualities of hair, they focus on different aspects. For example, shine and luster are influenced more by the cuticle layer of the hair shaft and hair care products rather than the keratin itself. Color retention is primarily dependent on the hair's pigmentation and external factors like UV exposure or chemical treatments. Moisture retention is often influenced by conditioning agents or oils used in hair care products that coat the hair, rather than the inherent properties of keratin.

Thus, recognizing keratin's specific function helps to understand why it is vital for maintaining the structural integrity of hair, emphasizing its role in providing strength and elasticity.