Now a quick work about these taxis or limousines.
The taxis and limousines are in actually limited supply.
So there aren't quite enough of them
in town to pick up all of the kids.
And so we'll further the analogy
by saying that these NAD cars need to be recycled.
In essence, they need to drop off a kid for a moment
so that they can go back and pick up others.
Perhaps they are dropping them off at dinner,
and then they'll go pick up some other kids,
so that they can drop them off at dinner, pick up
the other kids and take them to the dance, so on and so forth.
The point being we need to recycle NAD+
so it can pick up more electrons and more hydrogens.
There are three ways that this happens
that we'll be covering in this series.
First of all, we have the one where we see oxygen present.
In our bodies, if oxygen is present, we'll continue on through
pyruvate oxidation, which allows the return of those NAD cars or taxis.
And then we're able to go on into the Krebs cycle
and make tons of ATP.
Other organisms use different mechanisms, or we will use
a different mechanism should there not be oxygen present.
So in our case, let's say there's not oxygen present,
then we will form a lactate in order to recycle the NAD
and into the glycolysis scheme so that we can capture more electrons
and continue the cycle.
In the case of yeast, we'll also examine because it's interesting
that consider the production of ethanol.
You'll notice that yeast don't use up oxygen at all. You can
carbonate beverages. They produce alcohol in the form of ethanol.
Its another mean simply of recycling our NAD
to pick up more electrons and keep glycolysis going.
Without the recycling, then glycolysis will come to a hault.