AS Biology, Chapter 4, Cofactor, Coenzymes and Prosthetic groups
How can a cofactor activate a precursor enzyme? What is the precursor protein called BEFORE a cofactor is added? What is the precursor protein called AFTER a cofactor is added and the enzyme is activated?
- Addition of cofactor, changes proteins shape so become activated. - apoenzyme (inactive) - holoenzyme (active)
Give an example of a cofactor...
- Chloride ions (Cl-) are cofactors for the enzyme amylase which breaks down starch. - the chloride ion is necessary for the formation of a correctly shaped active site.
What do you call a cofactor that is an organic molecule?
- a coenzyme
What way, other than adding cofactors, changes the tertiary structure of a precursor enzyme? Also, what are these precursor enzymes called
- changes in conditions, such as PH and temp - this changes the PE shape, making it active. - these types of enzymes are called zymogens or proenzymes.
What do you call an enzyme that is produced in an inactive form? Why are some enzymes inactive?
- inactive precursor enzymes - some can cause damage within cells producing them, or to tissues where they are released - OR enzymes whose actions need to be controlled and only activated under certain conditions.
What changes do precursor enzymes need to undergo in order to become activated?
- need to undergo a change in shape in their tertiary structure, particularly to the AS to be activated.
What do coenzymes do?
- they participate in the reaction and are changed by it. - act as carriers, moving chemical groups between different enzymes. - they're continually recycled during this process
What is vitamin 5 used to make?
- used to make coenzyme A. - coenzyme A is essential in the breakdown of fatty acids and carbohydrates in respiration.
What is vitamin B3 used for?
- used to make the coenzyme, NAD (nicotinamide adenine dinucleotide) - a coenzyme responsible for the transfer of hydrogen atoms between molecules involved in respiration. - NADP plays similar role in photosynthesis, also derived by vitamin B3
What is a cofactor?
-It a inorganic non-protein component bound to an enzyme to help it bind to a substrate. - They don't directly participate in reaction - So aren't used up -They actually form part of the AS
What is a prosthetic group in an enzyme?
1) If a cofactor is tightly bound to the enzyme, it's known as a prosthetic group. 2) It forms a permanent feature of the protein.
Give an example of a prosthetic group in an enzyme...
1) Zinc ions are a prosthetic group for carbonic anhydrase. 2) carbonic 1 is an enzyme in red blood cells, which catalyses production of carbonic acid from water and carbon dioxide. 3) Zinc ions are a permanent part of the enzyme's active site
What happens when inactive pepsingogen is released into the stomach to digest proteins?
1) the acid PH brings about the transformation into active enzyme pepsin. 2) This adaptation protects body tissues against the digestive action of pepsin.
Vitamins are often sources of what?
Coenzymes
How do proteases / other enzymes change the tertiary structure of a precursor protein?
it cleaves certain bonds in the molecule
