CBSE Class 11-science Answered

• Enzymes are proteins in nature.
• They are produced by the living cells to accelerate the biochemical reactions inside and outside the cells in living organisms. Hence, they are called biocatalysts.
• The active site is the site on the enzyme molecule to which a substrate binds, and it helps to catalyse the chemical reaction.

• Oxidoreductases: They catalyse oxidation or reduction of their substrates.
• Transferases: They catalyse specific functional group (other than hydrogen ions) from one substrate to the other substrate.
• Hydrolases: Enzymes bring about the breakdown of large complex organic molecules into smaller molecules by adding water.
• Lyases: They catalyse the breakdown of certain covalent bonds and the removal of groups without hydrolysis.
• Isomerases: These enzymes bring intermolecular arrangements of atoms in the molecules and thus form one isomer from another.
• Ligases: These enzymes catalyse the joining of two molecules to form a compound.

Mechanism of Enzyme Action

• Substrate binds to the active site and fits itself perfectly into the active site.
• The binding induces little alternation in the shape of the enzyme so that the substrate can fit more tightly.
• The active site once in close proximity of the substrate breaks the chemical bonds of the substrate, and a new enzyme-product complex is formed.
• Once the new bonds are formed, the enzyme releases the product molecule.
• The free enzyme is again ready to bind to another molecule of the substrate.
• The active site is always specific with the reactive site present on the substrate.

Properties of enzymes

1. Enzymes are complex macromolecules with high molecular weight.

2. Enzymes are specific in action.

3. They show maximum activity at optimum pH at 6-8.