section 4: enzymes - topic 4: cofactors & enzyme inhibition Flashcards
what is a cofactor?
a non-protein substance bound to an enzyme.
what are inorganic cofactors?
cofactors that are inorganic molecules or ions.
how do inorganic cofactors work?
by helping the enzyme and substrate bind together.
they don’t directly participate in the reaction so aren’t used up or changed in any way.
what is an example of an inorganic cofactor?
chloride ions (Cl-) are inorganic cofactors for the enzyme amylase.
what are organic cofactors called?
coenzymes.
how do coenzymes work?
they participate in the reaction and are changed by it.
they often act as carriers, moving chemical groups between different enzymes.
they’re continually recycled during this process.
what are often sources of coenzymes? example.
vitamins.
the coenzyme NAD is derived from vitamin B3.
what is a prosthetic group?
this is if a cofactor is tightly bound to the enzyme.
what is an example of a prosthetic group?
zinc ions are a prosthetic group for carbonic anhydrase (an enzyme in red blood cells which catalyses the production of carbonic acid from water and carbon dioxide).
the zinc ions are a permanent part of the enzymes active site.
what is an enzyme inhibitor?
molecules that bind to the enzyme that they inhibit.
what are the two types of inhibitors?
competitive.
non-competitive.
how do competitive inhibitors work?
competitive inhibitor molecules have a similar shape to that of substrate molecules.
they compete with the substrate molecules to bind to the active site, but no reaction takes place.
instead, they block the active site, so no substrate molecule can fit in it.
what happens if there’s a high concentration of the competitive inhibitor?
it will take up nearly all the active sites and hardly any of the substrate will get to the enzyme.
why does increasing the substrate concentration increase the rate of reaction (up to a point)?
if there’s a higher concentration of substrate, then the substrates chances of getting to an active site before the inhibitor increase.
