chemistry 12th class cbse notes

Enzymes

  • Enzymes are biological catalysts. Chemically all enzymes are globular proteins.
  • Being proteins, they have colloidal nature and get inactivated during reactions and have to be constantly replaced by synthesis in the body.
  • Enzymes are needed only in small quantities for the progress of a reaction.
  • Enzymes are very selective and specific for a particular reaction.
  • Enzymes lower the energy barrier that reactants must pass over to form the products.
  • An enzyme molecule may contain a nonprotein part which is known as prosthetic group.
  • For example, the enzyme that catalyses hydrolysis of maltose into glucose is named as maltase.

Enzymes

Mechanism of Enzyme Action

Enzymes are needed only in small quantities for the progress of a reaction. Similar to the action of chemical catalysts, enzymes are said to reduce the magnitude of activation energy.

For example, activation energy for acid hydrolysis of sucrose is 6.22 kJ mol-1, while the activation energy is only 2.15 kJ mol-1 when hydrolysed by the enzyme, sucrase.

 

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