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To survive, grow and multiply living cells depend on various chemical
reactions within the cell.
In living cells these reactions are helped by substances called
enzymes which are special types of proteins. Enzymes speed up
the reactions without themselves being used up. Without enzymes
the reactions would be too slow to support life processes.
Each enzyme needs certain chemical and physical conditions to
function efficiently. For example, the temperature and the acidity
of the cellular environment are two important factors that influence
how well an enzyme works.
This has an important application to food preservation. Enzymes
produced by micro-organisms (e.g. bacteria) cause food decay.
The decay can be slowed down by interfering with the enzyme action.
This can be done by lowering the temperature by putting the food
in the refrigerator (picture at left) or changing the acidity
by pickling the food with an acid such as vinegar (picture at
right).
Hence, enzymes need the right chemical and physical conditions
to work efficiently.
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