Entry Points into Cellular Respiration

00:00 So here you can see a little bit more detail about how our four major macromolecules are broken down.

00:07 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.

00:43 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.

01:08 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.

01:32 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.

01:55 So primarily, we will look at the breakdown of carbohydrates and fats.

02:02 But I'll also show you where proteins could be cycled into the whole metabolic process.