ENZYMES AND CATALYST

A catalyst is any substance that speeds up the rate of any chemical reaction. It does not take part in the reaction itself. It is only there to increase the rate at which the reaction proceed. It can therefore be used over and over again.

In the living organism, the biological catalyst is referred to as an enzyme.
Characteristics of enzymes:

• Enzymes are proteins in nature. They can, therefore, be denatured. That is, they can be destroyed or damaged by extreme conditions of temperature and pH. 
• Enzymes work within a narrow temperature  and pH ranges. 
• Enzymes have active sites when the substrate binds. Substrate is the substance that the enzyme binds to for chemical reaction to occur.
• Enzymes work by lowering the activation energy. Activation energy is the minimum energy that is needed to be overcome before the reactants can be converted into products. 
• Enzyme activity increases with increase in the substrate until saturation is reached and then the rate of activity slows down.
• Enzymes are specific in nature, that is, they work on only specific substances. It is like lock and key. For every lock, there is a particular key that fits it.
• Certain drugs can compete with the substrate for the active site. This can lead to inhibition ot the enzyme. This is referred to as competitive inhibition. 
• There is also non-competitive inhibition where the drug competes for sites other than the active sites. These sites are know as allosteric site.