Enzymes (Cambridge (CIE) IGCSE Biology): Revision Note

What are enzymes?

• Enzymes are:

  • Catalysts that speed up the rate of a chemical reaction without being changed or used up in the reaction

  • Proteins

  • Biological catalysts (biological because they are made in living cells, catalysts because they speed up the rate of chemical reactions without being changed)

  • Necessary to all living organisms as they maintain reaction speeds of all metabolic reactions (all the reactions that keep an organism alive) 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

How do enzymes work?

Enzyme substrate specificity

• Enzymes are specific to one particular substrate (molecule/s that get broken down or joined together in the reaction) as the enzyme is a complementary shape to the substrate

• The product is made from the substrate(s) and is released

Enzyme specificity: lock and key model of enzyme activity