How do enzymes work?
Short answer
Enzymes are proteins that act as biological catalysts: they speed up reactions without being used up. Each enzyme has an active site with a specific shape that only fits one substrate, like a lock and key. The substrate binds to form an enzyme-substrate complex, the reaction happens, and the products are released.
Step by step
- The substrate collides with the enzyme and fits into the active site.
- An enzyme-substrate complex forms.
- The reaction takes place and the products leave the active site.
- The enzyme is unchanged and can be used again.
- High temperatures or extreme pH change the shape of the active site, so the enzyme is denatured and stops working.
Worked example
Effect of temperature
- Activity rises as temperature increases, because collisions are more frequent
- Human enzymes work best at about 37 °C, the optimum
- Above the optimum, activity falls sharply as the enzyme denatures
Common mistakes
- Saying enzymes are killed. They are not alive; they are denatured.
- Saying the substrate and active site are the same shape. They are complementary.
- Thinking cold denatures enzymes. Low temperatures only slow them down.
Useful for:GCSEA LevelWAECMatricBac
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