What term describes a protein that speeds up chemical reactions in organisms?

• A. Hormone
• B. Antibody
• C. Enzyme
• D. Receptor

Answer: (C)

Enzymes are proteins that act as biological catalysts, speeding up chemical reactions by lowering the activation energy needed for the reaction to proceed. They do this by providing an active site where substrates bind with specificity, so each enzyme typically catalyzes a particular reaction or acts on a specific substrate. Hormones are signaling molecules that coordinate activities between cells and tissues; antibodies are immune proteins that recognize and bind foreign substances; receptors are proteins that bind signaling molecules to trigger a cellular response. While all of these are important proteins, they do not primarily function to accelerate chemical reactions, making enzyme the best description for a protein that speeds up reactions.