enzymes - cofactors Flashcards
define cofactor
a substance that has to be present to ensure that an enzyme - catalysed reaction takes place at the appropriate rate
define prosthetic groups
a non-protein component that forms a permanent part of a functioning protein molecule
define temporary cofactors
these are substances that bind to the enzyme for a short time (temporarily) while the reaction is happening
what are 2 examples of temporary cofactors
coenzymes and mineral Ion cofactors
define coenzymes
small organic non-protein molecules that bind temporarily to the active site of enzyme molecules either before or at the same times that the substrate binds
define mineral ion cofactors
a type of temporary cofactor that is an inorganic ion (doesn’t contain carbon)
define enzyme substrate complex
complex formed by temporary binding of enzyme and substrate molecules during an enzyme-catalysed reaction
what do some enzymes need and why ?
cofactors
- they only work if another small non-protein molecule is attached to them
–> especially those involved in catalysing oxidation-reduction reactions
- as some enzymes wouldn’t be able to do their job as efficiently
what is the function of a prosthetic group ?
it is permanently bound by covalent bonds to an enzyme molecule
what does the enzyme carbonic anhydrase contain and where ?
a zinc ion in the active site
what is the function of carbonic anhydrase ?
- catalyses the interconversion of carbon dioxide and water to carbonic acid
–> which then breaks down to protons and hydrogen-carbonate ions
where is the enzyme found ?
- erythrocytes (RBC)
what are most enzyme-catalysed reactions and depending on what ?
reversible reaction and depending on the concentration of the substrate or product molecules
what is the balanced equation for the reaction including carbonic anhydrase ?
CO2 + H2 –> H2CO3 ??????
why is the reaction including carbonic anhydrase important ?
as it enables carbon dioxide to be carried in the blood from respiring tissue to the lungs
why is zinc important to humans ?
for polypeptide hormone , insulin , to function properly
what does some enzymes work better in ?
in the presence of ions that are not permanently bound to them
what happens during an enzyme-catalysed reaction and what does it form ?
- the enzyme + substrate molecules temporarily bind together to form –> enzyme substrate complex
what does the presence of certain ions do ?
may temporarily bind to either the substrate
what may the presence of certain ions do ?
the enzyme molecule may ease the formation of such E-S-c
–> increases the rate of the enzyme catalysed reaction
what do some cofactors acts as ?
co-substrates as the substrate together form the correct shape to bind to the active site of the enzyme
what do some cofactors change and why ?
- the charge distribution
–>on the surface of the substrate molecule
OR
–>on the surface of the enzyme’s active site
–> which makes the temporary bonds in the E-S-c easier to form
what does amylase digest into and will only function if ?
starch into maltose and if chloride ions are present
what are coenzymes not made of ?
protein and they are organic