Which class of nutrients is made up of amino acids and is needed to build and repair body structures and regulate processes?

• A. Protein
• B. Carbohydrate
• C. Lipid
• D. Nucleic acid

Answer: (A)

Proteins are built from amino acids and serve as the workhorses for both structure and regulation in the body. When amino acids link together, they form proteins that become the main components of our tissues—collagen strengthens connective tissue, keratin strengthens hair and nails, and actin and myosin drive muscle contraction. Beyond structure, many proteins regulate how the body functions: enzymes catalyze chemical reactions, hormones coordinate activities, antibodies defend against invaders, and transport proteins move substances in and out of cells. Because of these roles, proteins are the nutrients most directly described as needed to build and repair body structures and to regulate processes.

Carbohydrates mainly provide immediate energy and some structural support in plants; lipids store large amounts of energy and form cell membranes; nucleic acids store genetic information and guide protein synthesis but are not the amino-acid polymers primarily used to build tissues and regulate bodily functions.