cofactors and coenzymes Flashcards
(26 cards)
what is a cofactor
a substance that has to be present to ensure an enzyme catalysed reaction takes place
which cofactors are part of the enzyme structure
prosthetic group
which cofactors form temporary associations with the enzyme structure
inorganic cofactors and organic coenzymes
which is organic - cofactors or coenzymes
coenzymes
which is inorganic - cofactors or coenzymes
cofactors
why are cofactors sometimes necessary
some enzymes need a non-protein component to help them carry out their function
where are cofactors obtained from
the diet as minerals including iron, calcium, chloride and zinc ions
what is the cofactor for the enzyme amylase
the enzyme amylase which catalyses a starch breakdown contains a chloride ion thats necessary for the formation of a correctly shaped active site
how are coenzymes obtained
many coenzymes are derived from vitamins, a class or organic molecule found in the diet.
what is Vitamin B3 used for
synthesising NAD a coenzyme responsible for transferring hydrogen atoms between molecules involved in respiration. it also synthesises NADP for photosynthesis
which class of vitamins is used to make coenzymes
B vitamins
are coenzymes made out of protein
no, they are organic (carbon)
describe coenzymes
some bind temporarily to the active site of enzyme molecules either just before or at the same time the substrate binds.
others are permanently bound to the enzyme often in or near the active site
can coenzymes be used again
the coenzymes are chemically changed during the reaction and need to be recycled to their original state sometimes by a different enzyme
what do inorganic cofactors do
they help stabilise the structure of the enzyme and may actually take part in the reaction
what can happen when certain ions temporarily bind to the substrate or enzyme molecule
they may ease the formation of enzyme substrate complexes and increase the rate of reaction
what can some cofactors do
some cofactors change the charge distribution on the surface of the substrate molecule or on the surface of the enzymes active site and make the temporary bonds in the ESC easier to form
what are prosthetic groups
a cofactor that is permanently bound by covalent bonds to an enzyme molecule
how are prosthetic groups similar to cofactors
they are required by certain enzymes to carry out their catalytic function
what is the difference between cofactors and prosthetic groups
while cofactors bind loosely to proteins in order to activate them, prosthetic groups are tightly bound and form a permanent feature of the protein
summarise cofactors
-inorganic
-obtained through minerals in diet
-non permanent binding
-bind at active site or allosteric site
-e.g. amylase (Cl- ions)
summarise coenzymes
-organic
-obtained through vitamins in diet
-permanent or non permanent
-bind at active or allosteric site
-NAD/coenzyme A
summarise prosthetic groups
-inorganic/organic
-obtained through vitamins and minerals in diet
-permanent
-bind at active site or allosteric site
-carbonic anhydrase (Zn2+ ion)
inorganic partner molecule obtained through diet that binds temporarily to the allosteric or active site
cofactor
