Explain the concentration gradients of O2 and CO2 in the alveoli and associated capillaries of the lungs.?

Question

How does the concentration gradient affect the rate at which gas dissolves in a liquid?

Answer 1

The blood that is pumped from the heart through the lungs contains excess carbon dioxide and is low in oxygen. So the capillaries release carbon dioxide into the alveoli, and absorb oxygen.

So the air in the alveoli builds up more carbon dioxide than in the atmosphere, and diffuses away (as well as being expelled when you breathe out). Similar principles apply to the concentration gradients of oxygen and in the blood of the capillaries.

It is the concentration, not the concentration gradient, that directly determines how fast the gas dissolves. However, diffusion along the concentration gradient is one of the ways in which concentrations even out.