4.4 Cofactors Coenzymes and Prosthetic Groups

• What are cofactors and how are they obtained

  -Inorganic molecules​

  -A non-protein component necessary for the effective function of an enzyme

  -Obtained as minerals (via diet or absorption form soil)
• Cofactors transfer..

  -atoms or groups from one reaction to another in multi-step pathways. ​

  -Can form part of the enzymes active site
• What is an example of a cofactor

  -Amylase requires Chloride ions for it to correctly form its active site and break down starch
• What are coenzymes

  -A non-protein organic molecule, not permanently attached to an enzyme, but needed to allow the enzyme to function.

  -Derived from vitamins
• What is one example of a coenzyme

  -Vitamin B is needed for the synthesis of NAD-coenzyme needed in respiration

  -This transfers H+ ions between molecules.
• What is another example of a coenzyme

  -Coenzyme A (CoA) is derived from vit B5

  -Also required in respiration; facilitates breakdown of fatty acids and carbohydrates.
• What are prosthetic groups

  -Prosthetic groups act as cofactors. ​

  -Prosthetic groups can be vitamins, metal ions, lipids or CHO’s
• A p group is required by an enzyme to be able to carry out its...

  catalytic function
• Prosthetic groups are tightly

  -bound and a permanent feature of the protein

  -e.g haemoglobin
• What is an example of P group

  -Carbonic Anhydrase – requires Zn2+ to metabolise CO2
• What is precursor activation?

  -Many enzymes are produced as inactive precursor enzymes. ​

  -Precursor enzymes need to be activated.
• What does this activation help avoid

  -unnecessary damage to cells and tissues and helps to control reaction rate
• What does activation involve

  -change in tertiary shape which can be brought about by the addition of a cofactor
• What is an enzyme before activation

  -apoenzyme
• After activation


  -holoenzyme
• What can the conformation change of an active site be brought about by?

  -Action of a different enzyme (cleaves bonds) ​

  -Change in pH ​

  -Change in temperature
• Define a proenenzyme/zymogens


  -‘A zymogen is an inactive precursor of an enzyme that requires a biological change to become active.’
• What is an example of a precursor

  -Inactive pepsinogen is released into stomach acid pH brings about the transformation into active enzyme pepsin.

  -helps protect body tissues against digestive action of pepsin