ENZYMES: reversible and irreversible inhibition

Question 1

define: enzyme inhibitior

Answer 1

molecule that binds to an enzyme, which reduces its activity and interferes with the enzyme in some say.

Question 2

define: irreversible enzyme inhibitor

Answer 2

compounds that bind covalently to an enzyme. This alters its structure and hence that of the active site, and permanently inactivates the enzyme as the enzyme and inhibitor can’t dissociate due to covalent bond.

Question 3

example of irr enz inh?

Answer 3

poisons: eg. cyanide is an irreversible inhibitor of cytochrome c oxidase, a key enzyme in the electron transport chain. It stops production of ATP in aerobic respiration, leading to death.

Question 4

define: reversible enzyme inhibitors?

Answer 4

compounds that bond non-covalently to enzymes, leading to temporary inactivation of the enzyme – the enzyme and inhibitor cam dissociate due to non covalent bonds.

Question 5

two types of reversible enzyme inhibition?

Answer 5

competitive/non competitive inhibition

Question 6

define: competitive inhibition

Answer 6

compounds with a similar shape to the substrate molecule. They can bind to the active site in place of the substrate (hence, competitive inhibition)

Question 7

why is competitive inhibition usually temporary?

Answer 7

inhibitor moves away from active site

Question 8

effect of substrate conc on ror, when there’s competitive inhibitiors?

Answer 8

as it increases (and the inhibitor conc stays the same), there is an increased chance that the substrate will bind to the active site instead of the inhibitor, resulting in a greater rate of reaction.

Question 9

define: non-competitive inhibition

Answer 9

compounds that bind to the enzyme at a site other than the active site (allosteric site), which causes the shape of the enzyme, and hence the active site to change. The active site and the enzyme will no longer be complementary, so it won’t be functional.

Question 10

how does allosteric bonding site enable regulation of metabolic pathways

Answer 10

through endproduct inhibition

Question 11

define: end product inhibition

Answer 11

when the end product of a metabolic pathway binds non competitively to the first enzyme in the pathway which stops further action of the pathway.