Which term describes the enzyme that speeds up chemical reactions in living organisms?

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

Answer: (A)

Enzymes are biological catalysts that speed up chemical reactions in living organisms. They work by lowering the activation energy required for a reaction to proceed, so reactions occur much faster than they would otherwise. Enzymes are highly specific for their substrates, with each enzyme typically acting on a particular molecule or set of related molecules at its active site. This specificity and catalytic action are what let processes like digestion proceed efficiently, for example amylase breaking down starch or proteases breaking down proteins. In contrast, a hormone is a signaling molecule that regulates body processes, an antibody helps defend against pathogens, and a receptor binds signals to trigger a response—none of these primarily serve to accelerate chemical reactions.