Module 2 Section 4 - Cofactors and Enzyme Inhibition Flashcards
What are cofactors
Substances that are non protein that are bound to enzymes to allow them to work
Some cofactors are
Inorganic molecules or ions
How do cofactors work
They work by helping the enzyme and substrate to bind together
Do cofactors participate in the reaction
No, so they aren’t used up or changed in any way by the reaction
What are coenzymes
Cofactors that are organic molecules
Do coenzymes participate in reactions
Yes, they participate in reactions and are changed by it
Coenzymes often act as….
Carriers, moving chemical groups between different enzymes.
Are coenzymes recycled
Yes, they are continually recycled during this process - vitamins are often sources of coenzymes
What is a prosthetic group
A cofactor that is tightly bound to the enzyme
How can enzyme activity be prevented
By enzyme inhibitors
What are enzyme inhibitors
Molecules that bind to the enzyme that they inhibit
Enzyme inhibition can be either
Competitive
Non competitive
What is a competitive inhibitor
Molecules that have similar shape to that of the substrate molecule
Why is it called competitive
Because they compete with the substrate molecules to bind to the active site, but no reaction takes place. They block the active site so the substrate doesn’t fit in
How much the enzyme is inhibited depends …
On the relative concentrations of the inhibitor and the substrate
If there’s high concentration of the inhibitor…
It’ll take up nearly all the active sites and hardly any of the substrate will get to the enzyme - decreasing rate of reaction
If there’s a higher concentration of substrate….
Then the substrates chances of getting to an active site before the inhibitor increase meaning increasing substrate will increase rate of reaction
Where do non competitive inhibitor molecules bind to
The allosteric site (away from the active site)
Why does the non competitive inhibitor binding to the allosteric site cause
Causes the active site to change shape - so the substrate molecule no longer fits
Why are non competitive inhibitors called non competitive
Because they don’t compete with the substrate molecules to bind to the active site because they are a different shape
What difference will Increasing the substrate make to the rate of reaction on non competitive inhibition
Enzyme activity will still be inhibited
Inhibitors can be ….
Reversible
Non-Reversible
What does the reversibility of inhibitors depend on
The strength of the bonds between the enzyme and the inhibitor
What is the reversibility if the bonds between the enzyme and inhibitor is strong covalent bonds
Non reversible, because the inhibitor can’t be removed easily
What is the reversibility if the bonds between enzyme and inhibitor is weak hydrogen or ionic bonds
Reversible, the inhibitor can be removed
Some drugs and metabolic poisons are….
Enzyme inhibitors
Some medical drugs are enzyme inhibitors e.g.
Some Antiviral drugs - reverse transcriptase inhibitors
Some antibiotics - penicillin
Metabolic poisons are often enzyme inhibitors e.g.
Cyanide
Malonate
Arsenic
What are metabolic pathways regulated by
End-product inhibition
What is a metabolic pathway
A series of connected metabolic reactions. The product of the first reaction takes part in the second and so on. Each reaction is catalysed by a different enzyme
What is product inhibition
Enzymes that are inhibited by the product of the reaction they catalyse
What is end-product inhibition
When the final product in a metabolic pathway inhibits an enzyme that acts earlier on in the pathway
What is the reversibility of product and end-product inhibition
Reversible, so when the level of the product starts to drop, the level of inhibition will start to fall and the enzyme can start to function again - this means more product can be made
Enzymes are sometimes synthesised as
Inactive precursors in metabolic pathways to prevent causing damage to cells e.g. proteases.
Part of the precursor molecules…
Inhibits it’s action as an enzyme, once it is removed the enzyme becomes active
