Enzyme specificity

Each different type of enzyme will usually act on only one substrate to catalyse one biological reaction. Enzymes are specific because different enzymes have differently shaped active sites. The shape of the active site of an enzyme is complementary to the shape of its specific substrate. This means they are the correct shapes to fit together.

Three enzymes, represented as ovals with sections missing.  Enzyme type 1 has two circle shapes missing.  Enzyme type 2 has a triangular shape missing and Enzyme type 3 has a hexagon shape missing.  These are all specific substrates of the enzymes.

Temperature has an effect on enzyme activity.

A graph with rate of enzyme activity on the y axis and temperature, centigrade, on the x axis.  The plotted line climbs slowly at approximates 20 degrees until about half way along the x axis. It then climbs steeply reaching optimum temperature before falling steeply back to 0.

The graph shows that enzymes have a lower activity at low temperatures and high temperatures. The temperature at which enzyme activity is highest is called the optimum temperature.