And so all these trillions of cells which use these food particles to metabolize them into ATP produce these CO2 molecules and they essentially take these CO2 molecules and dump them into the blood plasma. Why? Well, because as the blood plasma circulates through our blood vessels, through our cardiovascular system, eventually the CO2 molecules will end up in the alveoli of the lungs. And it's the function, it's the responsibility of these alveoli to basically expel all that CO2 to the outside environment out of our body. And then the plants and trees can basically use the CO2 to produce the sugar molecules and then we can eat the sugar molecules and that process basically continues. Now, the problem with this is when all these trillions of metabolizing cells dump CO2 into our blood plasma, the CO2 molecules themselves are non polar.