enzyme inhibitors Flashcards
(35 cards)
define inhibitor
substrance that reduces or stops a reaction
define competitive inhibition
inhibition of an enzyme where the inhibitor molecule has a similar shape to the substrate molecule and competes with the substrate for the enzymes active site. it blocks the active site preventing the formation of ESC
define non-competitive inhibition
inhibition of an enzyme where the competitor molecule attaches to a part of the enzyme molecule but not the active site. this changes the shape of the active site preventing ES complexes from forming as the enzymes active site is no longer complementary to the substrate molecule
how do inhibitors reduce the activity of an enzyme
by combining with the enzyme molecule in a way that influences how the substrate binds to the enzyme or affects the enzymes turnover number
how do inhibitors work
they either block the active site or change the shape of the active site to inhibit ESC formation and product formation
can inhibitors be reversible or irreversible
both - it depends on whether the inhibitory effect is permanent or not
what is reversible inhibition
weaker hydrogen bonds or weak ionic bonds. the inhibitor can be removed
what is non reversible inhibition
stronger covalent bonds - the inhibitor cannot be easily removed
what is a competitive inhibitor
interferes with the active site so the substrate doesnt bind. it competes with the substrate
how does competitive inhibition work
a molecule or part of a molecule with a similar shape of an enzyme can fit into the active site of an enzyme. this blocks the substrate from entering the active site preventing the enzyme from catalysing the reaction
what is the result of competitive inhibition
the enzyme cant carry out its function and is inhibited.
what do the substrate and inhibitor molecules compete for
substrate and inhibitor molecules compete with eachother to bind to the enzymes active site reducing the number of substrate molecules binding to the active sites and slowing down the ROR
does competitive inhibition have a reversible effect
most competitive inhibitors only bind temporarily so they have a reversible effect (except aspirin)
what happens if you increase the concentration of an inhibitor
ROR decreases as less ESC form
what happens if you increase the concentration of substrate
ROR increases as more ESC form
with an ROR graph with substrate concentration plotted, what will happen to the graph if you add a competitive inhibitor
it reduces the rate of reaction but doesnt affect the Vmax - if the substrate concentration is increased there will be more substrate than inhibitor so Vmax can be reached
what is Vmax
maximum initial velocity or rate of an enzyme catalysed reaction
what is an inactivator
if the competitive inhibitor binds irreversibly to the enzyme’s active site
examples of competitive inhibitors
statins - used in synthesising cholesterol. its a reversible inhibitor prescribed to help people reduce cholesterol levels
aspirin - irreversibly inhibits enzymes involved with pain and fever
what is a non competitive inhibitor
it doesnt compete with the substrate. the non competitive inhibitor changes the shape of the enzyme so it cannot bind to the substrate
how does non competitive inhibition work
the inhibitor binds to the enzyme at the allosteric site. the binding of the inhibitor causes the tertiary structure of the enzyme to change so the active site changes shape.
what happens if the active site changes shape
this results in the active site no longer having a complementary shape to the substrate so it can’t bind to the enzyme. the enzyme cannot carry out its function and is inhibited
in a ROR graph with substrate concentration plotted what happens to the graph if you add a non competitive inhibitor
increasing the concentration of substrate concentration wont overcome the effect of the inhibitor. invreasing the concentration of the inhibitor will decrease the rate as more active sites are unavailable
what are examples of non competitive inhibitors
organophosphates
proton pump inhibitors
