Question

Write a short note on the following (a) enzyme specificity (b) enzyme inhibition

Answer 1

Enzymes are organic compounds produced by the living cells to speed up the spontaneous biochemical reactions in and outside the cells in living organisms.
The process of speeding up chemical reactions is called catalysis, and the substances that speed up the reactions are called catalytic compounds or catalysts.

Complete answer:
Enzyme specificity: The enzyme is specific in their action.
An enzyme may catalyze only a particular kind of reaction, or may even act on a particular substrate only
For example, the enzyme lactase catalyzes the hydrolysis of lactose and no other disaccharide.
The specificity of an enzyme results from its unique 3 - dimensional shape.

Enzyme inhibition: To somehow reduce or stop the action of the enzyme is called inhibition.
Certain chemicals also limit or prevent the function of enzymes. They are called inhibitors.
They act in three different ways -
1. Competitive inhibition: This is brought about by a substance that closely resembles the substrate in molecular structure. Such a substance is called a competitive inhibitor or substrate analog.
2. Noncompetitive inhibition: This is brought about by a substance which does not resemble the substrate in structure. The noncompetitive inhibitor binds to the enzyme at some other than the substrate-binding site and no product is formed. Cyanide inhibits the mitochondrial enzyme cytochrome oxidase which is essential for cellular respiration. This kills animals.
3. Allosteric inhibition: Change of active site form prevents the binding of substrate to the enzyme and stops the reaction. This process is called allostery or allosteric inhibition. The enzymes with allosteric sites are called allosteric enzymes.

Additional Information: The enzymes are generally complex macromolecules of globular proteins. Being protein macromolecules, the enzymes have a very high molecular weight.
1. The enzyme does not start a chemical reaction but only accelerates it.
2. The enzyme combines temporarily with the substrate molecules but is not consumed or changed permanently in the reaction they catalyze.
3. The enzyme-controlled reaction is reversible. Most enzymes have a high turnover number. The enzyme is thermolabile i.e. heat sensitive.

Note: As the enzymes are secreted by living cells and they speed up chemical reactions, they are known as biocatalysts.