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Effect of pH and Temperature
Enzymes in Living Things
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The following article is incomplete and will be updated shortly.


Enzymes are biological catalysts.  Catalysts increase the rate of chemical reactions without being changed themselves - i.e. you get the catalyst back at the end.  Enzymes are protein molecules and are made up of longs chains of amino acids.  These long chains are folded to produce a special shape (called the active site) which enables other molecules to fit into the enzyme.  This shape is vital for the enzyme's function.  High temperatures destroy this special shape - and the enzyme is denatured.  (Never say enzymes have been killed by high temperatures as they are not living - only living things can be killed or die).


How enzymes work

The substrate (reactant) fits into the active site of the enzyme - just like a key fits into a lock.  The enzyme and the substrate bind together to form an enzyme-substrate complex.  The binding of the substrate to an enzyme helps a chemical reaction to take place, often making it occur thousands of times faster than if the enzyme was not present.  The reaction occurs rapidly and the products are released from the surface of the enzyme.  Enzymes are used in living organisms to join together small molecules to make larger ones as well as breaking up larger ones.  The diagrams below show how enzymes work.