The primary protein that makes up hair is called:

• A. Keratin
• B. Collagen
• C. Elastin
• D. Melanin

Answer: (A)

Hair is built mainly from keratin, a strong fibrous protein that forms the core structure of the strand. Keratin contains many sulfur-rich amino acids that create disulfide bonds, giving hair its strength, rigidity, and ability to hold its shape. The cortex and cuticle of the hair shaft are composed of keratinized cells, which is why keratin is the dominant protein in hair.

Other proteins in the body serve different roles. Collagen is primarily in connective tissues, elastin provides elasticity in skin and blood vessels, and melanin is the pigment that gives hair its color. Because hair’s main, structural component is keratin, that is the best answer.