Science
What is An enzyme?
An enzyme is a biological catalyst — usually a protein — that speeds up chemical reactions in living things without being used up. Enzymes make essential reactions, such as digesting food and copying DNA, happen fast enough to sustain life.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains an enzyme.
Key things to understand
- 1Each enzyme has a specific shape that fits a particular molecule (its substrate), like a lock and key.
- 2They lower the energy needed to start a reaction, so it proceeds far faster.
- 3Enzymes are not consumed — one molecule can catalyze the same reaction over and over.
- 4They work best within specific temperature and pH ranges; extremes can 'denature' (deform) them.
- 5Examples include amylase, which breaks down starch, and DNA polymerase, which copies DNA.
Frequently asked questions
- What happens if an enzyme is denatured?
- Heat or extreme pH can change an enzyme's shape so its substrate no longer fits, and it stops working — one reason a high fever is dangerous.
- Are all enzymes proteins?
- Almost all are proteins, though a few are RNA molecules called ribozymes. Either way, they speed up specific reactions.
- Why is each enzyme so specific?
- Its active site has a precise shape and chemistry that fits only certain molecules, so each enzyme catalyzes only its particular reaction.