Coenzymes, Cofactors and Prosthetic Groups

  • Created by: Freja
  • Created on: 24-04-21 13:51
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  • Coenzymes, Cofactors and Prosthetic Groups
    • Some enzymes need non-protein components to help them catalyse reactions. These components are called:
      • Cofactors
      • Coenzymes- a cofactor that is an organic molecule
    • How they are obtained
      • Coenzymes- obtained from the diet from vitamins~ vitamin B3 and vitamin B5
      • Inorganic Cofactors-obtained from the diet from minerals~ iron, calcium, chloride and zinc ions
    • E.g. Amylase
      • Contains an inorganic cofactor- chloride ion, which is not permnent.
      • Involved in the breakdown of starch and helps with the formation of correctly shaped active site.
    • Prosthetic Groups
      • Prosthetic groups are cofactors
      • They are a permanent feature of the protain.
      • e.g. Carbonic anhydrase has zinc ions as part of its structure.
      • They are required by certain enzymes to carry out their catalytic function.
    • Precursor Activation
      • Inactive precursor enzymes- enzymes produced in an inactive form.
      • Some enzymes can be dangerous and can cause danger to cells and tissue, and therefore need to be produced in an inactive form.
      • Some enzymes may need to be produced in an inactive form as they only need to be active in certain conditions.
      • They often need to underfgo a change in tertiary structure to become activated.
      • Precursor enzymes can have a change in tertiary structure due to another enzyme, a change in pH or a change in temperature.
        • Precursor enzymes hat are activated in these ways are called ZYMOGENS or PRO-ENZYMES.
          • e.g. inactive pepsinogen
            • Used in the stomach to digest proteins.
            • The acidic conditions in the stomach causes the pepsinogen to change tertiary structure and it transforms into the active enzyme pepsin.
            • As activation only occurs in acidic conditions, the rest of the body tissues are protected against the digestive action of pepsin on protein molecules as conditions are not acidic.
  • Before the cofactor is added to a precursor enzyme it is called an APOENZYME
  • When the cofactor is added and the enzyme becomes activated, it is called a HOLO-ENZYME


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