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Role of Enzymes (Edexcel IGCSE Biology)
Revision Note
Enzymes as Biological Catalysts
- Enzymes are proteins that act as biological catalysts to speed up the rate of a chemical reaction without being changed or used up in the reaction
- They are biological because they are made in living cells
- Enzymes are necessary to all living organisms as they maintain reaction speeds of all metabolic reactions at a rate that can sustain life
- For example, if we did not produce digestive enzymes, it would take around 2 - 3 weeks to digest one meal; with enzymes, it takes around 4 hours
- Often the products of one reaction are the reactants for another (and so on)
The mechanism of enzyme action
- Enzymes are specific to one particular substrate(s) as the active site of the enzyme, where the substrate attaches, is a complementary shape to the substrate
- When the substrate moves into the enzyme’s active site they become known as the enzyme-substrate complex
- After the reaction has occurred, the products leave the enzyme’s active site as they no longer fit it and it is free to take up another substrate
- Step One: Enzymes and substrates randomly move about in solution
- Step Two: When an enzyme and its complementary substrate randomly collide an enzyme-substrate complex forms, and the reaction occurs
- Step Three: A product (or products) forms from the substrate(s) which are then released from the active site. The enzyme is unchanged and will go on to catalyse further reactions
How enzymes work
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