5156793
Cofactors
- Some enzymes
need help
- ->particularly those involved in
catalysing oxidation- reduction
reactions, can only work if another
small non-protein molecule is attached
to them =moles called cofactors
- ->particularly those involved in
catalysing oxidation- reduction
reactions, can only work if another
small non-protein molecule is attached
to them =moles called cofactors
- Prosthetic groups
- ~cofactor that's permanently bound,
by covalent bonds, to an enzyme
molecule, is called a prosthetic group
- ~enzyme carbonic anhydrase contains zinc ion
permanently bound, as a prosthetic group, to
its active site =>enzyme found in erythrocytes
& catalyses the interconversion of CO2 & H2O
to carbonic acid, which then breaks down to
protons & hydrogencarbonate ions
- ~as with most enzyme- catalysed
reactions, this reaction may proceed in
either direction, depending on the conc
of substrate or product moles
- ~the reaction is vitally important, as it
enables CO2 to be carried in the blood from
respiring tissues to the lungs
- ~the reaction is vitally important, as it
enables CO2 to be carried in the blood from
respiring tissues to the lungs
- ~as with most enzyme- catalysed
reactions, this reaction may proceed in
either direction, depending on the conc
of substrate or product moles
- ~enzyme carbonic anhydrase contains zinc ion
permanently bound, as a prosthetic group, to
its active site =>enzyme found in erythrocytes
& catalyses the interconversion of CO2 & H2O
to carbonic acid, which then breaks down to
protons & hydrogencarbonate ions
- ~cofactor that's permanently bound,
by covalent bonds, to an enzyme
molecule, is called a prosthetic group
- Other cofactors
- ~whereas the zinc associated with carbonic anhydrase is
present in a compound that is permanently bond to the
enzyme's active site, some enzymes work better in the
presence of ions that aren't permanently bound to them
->these ions also cofactors
- ~during enzyme- catalysed reaction, the enzyme & substrate molecules
temporarily bind together to form an enzyme- substrate complex.
->presence of certain ions that may temporarily bind to either the substrate
or enzyme molecule may ease the formation of such enzyme-substrate
complexes & therefore incr the rate of enzyme- catalysed reaction
- *some cofactors act as co-substates
->they & the substrate together form
the correct shape to bind to the
active site of the enzyme
- *some cofactors change the charge distribution on the
surface of the substrate molecule or on the surface of
the enzyme's active site, & make the temporary bonds in
the enzyme- substrate complex easier to form
- ~the enzyme amylase digests starch
to maltose, & will only function if
chloride ions are present
- ~the enzyme amylase digests starch
to maltose, & will only function if
chloride ions are present
- *some cofactors act as co-substates
->they & the substrate together form
the correct shape to bind to the
active site of the enzyme
- ~whereas the zinc associated with carbonic anhydrase is
present in a compound that is permanently bond to the
enzyme's active site, some enzymes work better in the
presence of ions that aren't permanently bound to them
->these ions also cofactors
- Coenzymes
- ~coenzymes are small organic non- protein moles that bind
temporarily to the active site or enzyme molecule ->either just
before/ at same time the substrate binds ->coenzymes are
chemically changed during the reaction, & they need to be recycled
to their original state (sometimes by diff enzyme)
- ~coenzymes are small organic non- protein moles that bind
temporarily to the active site or enzyme molecule ->either just
before/ at same time the substrate binds ->coenzymes are
chemically changed during the reaction, & they need to be recycled
to their original state (sometimes by diff enzyme)
- Some vitamins are
sources of coenzymes
- ~many coenzymes are derived from water- soluble
vitamins ->if these vitamins are deficient in the diet
of humans, then certain diseases may result.
- ~many coenzymes are derived from water- soluble
vitamins ->if these vitamins are deficient in the diet
of humans, then certain diseases may result.
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