So here you can see a little bit more detail about how
our four major macromolecules are broken down.
Previously we have explored polysaccharides or the breakdown
of simple sugars from glucose through glycolysis to form
pyruvate to Acetyl-CoA. And Acetyl-CoA goes into the Krebs
cycle and then we can go on into electron transport chain
and oxidative phosphorylation in order to generate tons
of ATP. Other fuels will come into the pathway
at different points. For example if we were to look at
lipids and fats, we see that they are broken down
into glycerol and fatty acids. And then we can make some
Acetyl-CoA through the process of beta oxidation.
And those will enter the Krebs cycle. And then finally we
can look at proteins. Generally we are not set up to
metabolize proteins directly. You will notice that there is
a little bit more going on with proteins. They are broken down
into amino acids as we digest them and then they will
enter at various points throughout the Krebs cycle.
This is probably the most diverse way of metabolizing fuels
because we are made of proteins and it doesn't really make
sense for us to use proteins as a primary fuel, because then
we would very easily break down our own proteins which is
not really somewhere we want to go. So, all protein
diets may be not such a great idea right.
The other thing we could look at are nucleic acids, and again
it really doesn't make sense for us to have a easy pathway
for digesting nucleic acids. They are not a preferred fuel.
We don't want to be just breaking down our own DNA and RNA
in order to make ATP of it. We have much more important
uses for our proteins as well as nucleic acids.
So primarily, we will look at the
breakdown of carbohydrates and fats.
But I'll also show you where proteins could be
cycled into the whole metabolic process.