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.
- e.g. inactive pepsinogen
- Precursor enzymes hat are activated in these ways are called ZYMOGENS or PRO-ENZYMES.
- Some enzymes need non-protein components to help them catalyse reactions. These components are called:
- 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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