 Hydrogen
peroxide is a nasty molecule that can cause damage to cells.
It is produced in other places in the body and one of the main functions
of peroxisomes comes from the hydrogen peroxide degradation function via
the enzyme catalase. Peroxisomes get their names from this
function. Hydrogen peroxide from both outside of peroxisomes (oxidation
of xanthine) and those molecules produced inside via beta-oxidation of
fatty acids is split into harmless water and oxygen by catalase. H2O2
---->
H2O + 1/2 O2 .... which means: 2 H2O2
---->
2 H2O + O2
Questions
|
Why does hydrogen
peroxide bubble when
I apply it to a cut?
|
What does catalase
look like?
R
|
How does catalase
work?
R
|
How can oxygen
be harmful?
R
|
|
Find out: BUBBLES
|
Find out: SHAPE
|
Find out: Ref1
or Ref2
|
Find out: HARM
|
So now
we have discovered why oxygen consumption outside of mitochondria is not
mentioned much. Oxygen is used by urate oxidase and
acyl-CoA
oxidase, but it is reformed by catalase. So is oxygen
important? Well.... if you have no oxygen, then you are dead because
your cells can not produce enough ATP to match the demand, but if you have
oxygen available, oxidation in peroxisomes is absolutley necessary for
normal health. We see this from all of the diseases linked to either
1) defective enzymes or 2) defective creation of peroxisomes. (To learn
more: DISEASE)
Finally
note that in Step 2, one oxygen (O2) is used but only half an
oxygen is regenerated.... so the net reaction is a significant use of oxygen.
Two are used.... one is regenerated....
Can one say that this peroxisomal activity significantly contributes
to cellular oxygen consumption levels?
It depends
upon the dietary intake of long-chain fatty acids and the amount of urate
production.
It is safe to say however, that oxygen is used in another place in
animal cells besides mitochondria....
so go out there and win a bet or two!!
5
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