Side bonds account for the hair's what property?

• A. Elasticity
• B. Texture
• C. Porosity
• D. Density

Answer: (A)

Side bonds form a network within the keratin of the hair that gives it elasticity—the ability to stretch under tension and bounce back when released. Hydrogen bonds, salt bonds, and disulfide bonds all contribute to this resilience. When hair is stretched, the weaker hydrogen and salt bonds break and quickly reform as tension is removed, while disulfide bonds provide more lasting strength and can be rearranged during chemical treatments. This bond system mainly governs how much the hair can lengthen and still return to its original shape. Texture, porosity, and density are influenced by other factors: texture relates to surface feel and diameter, porosity to cuticle condition and moisture exchange, and density to how many hairs grow per area.