Which term best describes large biomolecules that perform most functions in cells and are made of amino acids?

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

Answer: (A)

Proteins are the large biomolecules built from amino acids linked by peptide bonds, and their varied shapes let them perform most jobs in the cell. The sequence of amino acids creates a unique structure that folds into specific three-dimensional forms, which in turn determines function. Enzymes are proteins that speed up chemical reactions, structural proteins provide support and shape, transport proteins move molecules across membranes, signaling proteins relay messages, antibodies defend against invaders, and many other roles hinge on these versatile molecules.

Carbohydrates are mainly sugars and starches that provide energy and some structural support. Nucleic acids (DNA and RNA) store and transfer genetic information and guide protein production. Lipids store energy and form membranes but are not built from amino acids. Since the defining feature here is being a polymer of amino acids that carries out a wide range of cellular activities, proteins best fit the description.