Posted by Frank Day (63.201.228.13) on January 18, 2004 at 12:14:36:
In Reply to: Oxygen and movement ? posted by Peter Studer on January 18, 2004 at 10:53:10:
I believe the solubility of oxygen is .003 in water. So, if the concentration of oxygen in the lungs is 100% then the concentration in the water next to the lungs, when inn equilibrium, is .3%. This is not enough to sustain life so the body came up with hemoglobin. Oxygen will preferentially bind to hemoglobin in the lungs. It turns out that with normal hemoglobin concentrations in the blood that when the concentration of oxygen in the lungs is about 20% (the same as air) the concentraition of oxygen in the blood, bound to hemoglobin is about 20%. Since the hemoglobin is fully bound, increasing the amount of oxygen in the lungs cannot bind more oxygen to the hemoglobin and can only increase the amount dissolved in the water. At .003 compared to .2 this is a miniscule increase.
Once the blood gets to the muscle tissue and enters the capillaries, the reduced oxygen concentration (and increased CO2 concentration) there causes the oxygen to leave the hemoglobin and diffuse into the cell. (The hemoglobin then carries the CO2 back to the lungs to be exhaled in the opposite process). The only place that oxygen is actually necessary is in the mitochondria of the cell, that is where metabolism occurs. To do this you need a heart and lungs and blood with hemoglobin, and capillaries, and enzymes, etc. etc. If you can't get it there you can forget about exercising (or living for that matter). Oxygen delivery to the tissues is mostly about diffusion.
Hope this makes it clearer.
Next week we will have our first test!