Role of Enzymes (Edexcel IGCSE Biology)
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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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