Which macromolecule is primarily used for growth and repair of body structures?

• A. Carbohydrates
• B. Lipids
• C. Proteins
• D. Nucleic acids

Answer: (C)

Proteins are the main macromolecule used for growth and repair because building and maintaining body structures relies on amino acids assembled into structural and functional proteins. Structural proteins like collagen, elastin, and keratin provide the framework for skin, bones, tendons, and hair, while muscle proteins such as actin and myosin support tissue strength and function. Enzymes, which are proteins, drive the chemical reactions needed to synthesize new tissues and heal injuries. Transport and signaling proteins coordinate the delivery of materials and communication essential for repair. Other macromolecules play important roles—carbohydrates and lipids supply energy and form membranes, and nucleic acids store and convey genetic information that guides protein production—but the actual building blocks and machinery for growth and repair come from proteins.