it actually has to do a little dance around this pathway,
and we will see how that happens in pathway of gluconeogenesis.
Now glycolysis is, as I said
regulated by 3 enzymes
and the third enzyme after hexokinase
and PFK is this reaction.
Now I might seem odd that the last step of the reaction
is regulated but there is very good reason why.
This reaction is inhibited by ATP.
ATP we have learned is
a indicator of high energy.
Do we want glycolysis continuing
if this cell has high energy?
The answer is we don't. But once we make
PEP, by God this thing gonna forward because it's
pretty hard to stop such an energetic reaction.
Regulating a reaction that wants to go
forward very bad is important.
Inhibition of this enzyme by
ATP is a big consideration.
Now another thing that's important to alanine
and amino acids, why is that in here.
Well pyruvate is readily
converted into alanine.
An excess of alanine indicates you probably
have too much pyruvate to begin with.
Now this enzyme is the enzyme that I
described before that was activated
in that push pull reaction of aldolase.
As fructose-1,6-bisphosphate starts to accumulate,
it will activate pyruvate kinase and what
happens when you activate pyruvate kinase
well by God PEP is gonna go to pyruvate.
Well then what's gonna go
to PEP? 2-phosphoglycerate.
And what's gonna go to 2-phosphoglycerate? 3-phosphoglycerate.
Every reaction proceeding the pyruvate kinase reaction
is gonna be pulled by activating this enzyme.
And what's activating it? The
molecule that's activating it
is the molecule that needs
to get converted into
dihydroxyacetone phosphate. It's a perfect setup.
The pushing and pulling reaction is signaling
a head to say, "We need some help here guys"
And that guy that's helping
them is pyruvate kinase.
The enzyme is also regulated by phosphorylation.
You put a phosphate on this
enzyme it can be turned off.
And so regulation as we will see
is very important in considering
how gluconeogenesis or the
synthesis of glucose is important.
Okay so we have seen overall, that
glucose plus 2 ADPs plus 2 phosphates plus 2 NADs
gives an overall product of 2 pyruvates, 2 ATPs,
2NADHs plus the other things that you see here.
Remember we put 2 ATPs in to begin with,
but we had 2 reactions at
the end each of which generated
an ATP and since they are
doubled we generated 4.
2 in, 4 out, a net of 2.