Enzyme
MCAT glossary · Biological & Biochemical Foundations of Living Systems
Definition
A biological catalyst, almost always a protein, that accelerates a specific reaction.
Enzyme in plain English
An enzyme is a biological helper (almost always a protein) that makes a specific chemical reaction happen way faster without being used up itself — a catalyst. Reactions often need a big shove of energy to get going, and an enzyme lowers that hurdle, like a key-shaped tool that holds the reacting pieces in exactly the right position so they click together easily. Each enzyme is picky, working on just one reaction or molecule, which is why your body has thousands of them. Without enzymes, the reactions keeping you alive would run so slowly you'd basically be frozen in place.
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