Enzyme
Definition and meaning of Enzyme in chemistry.
An enzyme is a biological catalyst, usually a protein, that speeds up the rate of a specific biochemical reaction in living organisms. Like all catalysts, an enzyme lowers the activation energy of a reaction and is not consumed by it.
In more detail
Each enzyme has a uniquely shaped region called the active site that fits its substrate, an idea often described by the 'lock and key' model. Because this shape depends on the enzyme's structure, extremes of temperature or pH can distort it and stop the enzyme working, a change called denaturation. Enzymes are usually named after the reaction they catalyze and end in '-ase', such as lactase or protease.
Key facts
| Also known as | Biological catalyst |
|---|---|
| Made of | Protein (a few are RNA) |
| Acts on | A specific substrate |
| Field | Biochemistry |
The enzyme amylase, found in saliva, breaks down starch into simpler sugars during digestion.
Frequently asked questions
Are all enzymes proteins?
Almost all enzymes are proteins. A small number are made of RNA and are called ribozymes, but these are exceptions.
What can stop an enzyme from working?
High temperatures, or a pH far from the enzyme's optimum, can denature it, changing the shape of the active site so the substrate no longer fits. Certain inhibitor molecules can also block it.