Which statement best describes how human hair is formed?

Which statement best describes how human hair is formed?

• A. Salt bonds connect to amino acids
• B. Hydrogen bonds create a chemical change
• C. Amino acids cause a simple physical change
• D. Bonding of protein chains to other protein chains

Answer: (D)

Hair is a protein fiber made from keratin, which comes from long chains of amino acids linked together. Those chains don’t stay isolated; they bond with and cross-link to other protein chains to form a strong, fibrous structure. That inter-chain bonding builds the actual hair filament, not just a simple change within a single molecule. While weaker interactions like salt bonds and hydrogen bonds affect styling and moisture sensitivity, they aren’t responsible for creating the hair’s basic fiber. And amino acids alone don’t produce the organized, bonded fiber—you need the chains to link up with other chains to form the cohesive hair structure.

Hair is a protein fiber made from keratin, which comes from long chains of amino acids linked together. Those chains don’t stay isolated; they bond with and cross-link to other protein chains to form a strong, fibrous structure. That inter-chain bonding builds the actual hair filament, not just a simple change within a single molecule. While weaker interactions like salt bonds and hydrogen bonds affect styling and moisture sensitivity, they aren’t responsible for creating the hair’s basic fiber. And amino acids alone don’t produce the organized, bonded fiber—you need the chains to link up with other chains to form the cohesive hair structure.