Background On Enzymes

Background On Enzymes

Enzymes are biological catalysts. They speed up the chemical reactions

which go on inside living things. Without enzymes reactions would be

so slow that eventually life would grind to a halt.

There are many different types of enzymes and each of them is

extremely efficient at doing their job. For example, some of the

reactions which take place in our cells, e.g. the liver, produce a

by-product called hydrogen peroxide. Hydrogen peroxide is very

poisonous so it must be gotten rid very quickly. An enzyme called

catalase breaks the hydrogen peroxide down into two harmless

substances, water and oxygen.

Enzymes have 5 important properties:

1. They are always proteins- this is why we need protein in our diet.

2. They are specific in their action- this means that each enzyme

controls one particular reaction, or type of reaction. Therefore

maltase will only act on maltose and sucrase on sucrose.

3. They can be used over and over again- this is because they are not

altered by the reaction in which they take part. However an enzyme

molecule will eventually run down and has to be replaced.

4. They are destroyed by heating- enzymes like all proteins are

destroyed by heating. This is called denaturation. Most enzymes stop

working if the temperature rises to about 45°C - destroys active site.

5. They are sensitive to pH- the term pH refers to the acidity of the

alkalinity of a solution. Most enzymes work better in neutral

conditions.

How do enzymes work? Molecules are constantly moving about and bumping

into each other. When a substrate molecule bumps into a molecule of

the right enzyme it fits into a depression on the surface of the

enzyme molecule ( a bit like a jigsaw puzzle.) this depression is

called the active site. The reaction then takes place and the

molecules of product leave this active site, freeing it up for another

substrate molecule.

The active site of a particular enzyme has a specific shape into which

only one kind of substrate will fit rather like a key fits into a