Enzymes
Biology: Cambridge International GCSE Supplement, topic 5.1.1
Enzymes
Enzymes are proteins that increase the speed of reactions in organisms. Without enzymes, chemical reactions in organisms would be too slow to sustain life. They are often called biological catalysts.
Active site
- To catalyse (speed up) a reaction, the reacting chemical (substrate) must bind to the enzyme's active site.
- The active site will only fit specific substrates to form an enzyme-substrate complex.
Lock and key
- The active site is like a lock and the substrate is like a key.
- In the same way, there is usually only one enzyme for every substrate (or one key for each lock).
Unchanged
- Enzymes don't change when they catalyse a reaction.
- This means that they are not used up, and one enzyme molecule can catalyse many substrate molecules, one after the other.
Test yourself on Enzymes
What is another name for an enzyme?
Which of the following describe an enzyme's active site?