Now in the cori cycle these things become very
apparent in terms of what's actually happening.
In the cori cycle, this process
occurs when the body is exercising.
So, let's imagine that you are out running, going jogging,
while you are jogging what can happen is,
your muscle cells are exercising
and as your muscle cells are exercising
they are going through glycolysis;
because, breaking down glucose
is going to give ATP energy
that the cells need to function. In the case of a
muscle cell they are contracting and working very hard.
The problem with muscle cells is
that if you work really hard
is that the cell can work faster
than the blood supply can deliver
oxygen to those muscle cells.
Well from other discussion I've had in these presentations,
it should be obvious what happens at that point.
Pyruvate gets fermented and that fermenting a
pyruvate produces the molecule lactate.
And lactate is unfortunately a dead end metabolically.
The cell that doesn't have any oxygen
can't do anything with lactate
and that's the circumstance that
the muscle cell find itself in.
Lactate at that point is dumped into the blood stream.
And it's dumped into the blood stream; because,
the muscle has no use for that molecule. Well
that turns out not to just be an accident.
But it works to help ultimately feed
the muscle cell, as we shall see.
The lactate leaves the muscle cell, travels
in the blood and goes to the liver.
And in the liver, the liver is in a different
circumstance. The liver is not exercising
The liver is close to the lungs, in terms of
oxygen, and the liver has plenty of oxygen.
So as a consequence of that the liver
is able to convert lactate
under conditions of high oxygen back to pyruvate.
So it has reversed the reaction that was
necessary in the low oxygen conditions.
In the high oxygen conditions, that it exists in.
Well the liver, of course, is the organ of the body
that's primarily responsible for making glucose.
So pyruvate is a starting
point for gluconeogenesis
So the liver takes the pyruvate and makes glucose;
because, it has got plenty of energy. It’s not exercising.
The liver takes that glucose then and does what,
it dumps that into blood and in the
blood it goes back to the muscle cell.
So this cyclic pathway that we can see
here looks like a futile cycle.
In fact, in the cell, it
would be a futile cycle.
But in the body it's an essential process to
feed muscle cells during times of heavy exercise.