In the next reaction and I wanna remind
you that from this point forward
everything will be doubled.
So we actually have two glyceraldehyde-3-phosphate
and we are gonna produced
2 molecules of 1,3-bisphosphoglycerate.
Now this reaction is important because it is the
only oxidation that occurs in glycolysis.
We think about glycolysis
as being a pathway this very
oxidated, but in-fact it's not. There
is only one oxidation that occurs.
We think about glycolysis being oxidated because of the
product that later get oxidized in other pathways.
This reaction is an interesting
one. Okay? We see for example
on the left we have an aldehyde
and on the right we have an ester.
That's the indication that
we have had in oxidation.
The delta G zero prime for this reaction is
a little positive. It's 6.3 kJ/mol
but again the cell doesn't
have a big problem with that.
The difference here is that if we look
at what's happening in this reaction,
a phosphate is being added directly
onto the acid to make the
ester, on the right side.
When we did a similar reaction for glucose going to
glucose-6-phosphate we had to couple that to ATP.
And the same thing happened when we went
fructose-6-phosphate to fructose-1,6 bisphosphate.
We had to use the energy of ATP. So why don't
we have to use the energy of ATP here?
The answer is because we have an oxidation. Remember that
oxidative reactions generate energy and the energy of this
oxidation is helping to favor
this reaction going forward.
The oxidation of course generates
electrons so we see NAD+ becoming NADH.