What are enzymes?
Enzymes are Organic compound made up of amino acid molecules. One of the three main food groups, proteins are needed by the body for cell growth and repair. that function as biological A substance that changes the rate of a chemical reaction without being changed by the reaction itself.. So, they are molecules that speed up a chemical reaction without being changed by the reaction.
Lock and key hypothesis
Enzymes are folded into complex 3D shapes that allow smaller molecules to fit into them. The place where these molecules fit is called the The part of the enzyme to which a specific substrate can attach or fit on to..
In the Model which compares the specificity of enzymes with a key and its lock., the shape of the active site matches the shape of its substrate molecules. This makes enzymes highly specific. Each type of enzyme can usually catalyse only one type of reaction (some may catalyse a few types of reactions).
The diagram shows how this works. In this example, the enzyme splits one molecule into two smaller ones.
Denaturing enzymes
If enzymes are exposed to extremes of pH or high temperatures the shape of their active site may change.
If this happens then the substrate will no longer fit into the enzymes. This means the key will no longer fit the lock. We say that the enzyme has been denatured.
