cofactors, coenzymes and prosthetic groups 4.4 Flashcards
what are cofactors
a non-protein ‘helper’ that help the enzyme to carry out its function
they may transfer atoms or groups from 1 reaction to another or they may actually form part of the active site
what is the difference between cofactors and coenzymes
if a cofactor is made of an organic molecule it is called a coenzyme
how are cofactors obtain by the body
inorganic cofactors are obtained via the diet as minerals, including iron, calcium, chloride and zinc ions
whats an example of an enzyme that contains a cofactor group
amylase contains cl- ion
how are coenzymes obtain by the body
many coenzymes are derived from vitamins, a class of organic molecule found in the diet
what is an example of a coenzyme
vitamin B3 is used to synthesis NAD, a coenzyme responsible for the transfer of hydrogen atoms between molecules involved in respiration
what are prosthetic groups
- type of cofactors
- they are required by certain enzymes to carry out function
- prosthetic groups are permanent bond to protein
whats an example of a prosthetic group
iron in haemoglobin
for example zinc ions form an important part of the structure of carbonic anhydrase, an enzyme necessary for the metabolism of carbon dioxide
what are inactive precursor enzymes
many enzymes are produced in an inactive form, known as inactive precursor enzymes
why would enzymes be produced in their inactive forms
stops them catalysing reactions when unwantedly
how are most precursor enzymes activated
explain the biology of it as well
Precursor enzymes often need to undergo a change in shape (tertiary structure), particularly to the active site, to be activated
this can be achieved by the addition of a cofactor.
what is an apoenzyme and a holoenzyme
- apoenzyme: inactive precursor enzyme that does not yet have its cofactor
- holoenzyme: after the cofactor has been added to an apoenzyme and activated it becomes a holoenzyme
what are zymogens/proenzymes
sometimes the change in tertiary structure is brought about by the action of another enzyme, such as protease, which cleaves certain bonds in the molecule.
conditions such as PH and temperature results in a change in tertiary structure and activates a precursor enzyme.
These types of precursors enzymes are called zymogens or proenzymes
what is an example of a zymogen or proenzyme
When inactive pepsinogen is released into the stomach to digest proteins, the acid PH brings about the transformation into the active enzyme pepsin. This adaptation protects the body tissues against the digestive action of pepsin
what is the coagulation cascade
Blood-clotting begins when platelets aggregate at the site of tissue damage. The aggregated platelets release clotting factors including factor X
Factor X in important in blood-clotting mechanism. It is an enzyme that is dependent on the cofactor vitamin K for activation. Activated factor X catalyses the conversion of prothrombin into thrombin by cleaving bonds in the molecule, Thrombin is a protease and catalyses the conversion of soluble fibrinogen to insoluble fibrin fibres. Fibrin molecules together with platelets from a blood clot
The series of successive enzyme activations in blood clotting is called the coagulation cascade
