Which macromolecule is the most abundant organic compound in the human body and performs many functions including catalyzing reactions and providing structure?

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

Answer: (C)

Proteins handle many essential tasks in the body, including speeding up chemical reactions and giving structures their form. Enzymes, which are a type of protein, catalyze nearly every metabolic reaction, making processes like digestion and energy production possible. At the same time, structural proteins form the framework of tissues and cells—collagen, for example, provides strength to skin, bones, and connective tissue, while keratin strengthens hair and nails, and components of the cytoskeleton help cells maintain shape and organization.

Proteins are the most abundant organic macromolecule in the human body by mass, reflecting how central these roles are to life. Nucleic acids mainly store and transmit genetic information, lipids are key building blocks of membranes and energy stores, and carbohydrates mainly serve as quick energy sources and some structural roles. The combination of being both highly abundant and performing diverse, vital functions makes proteins the best answer.