Question

In order for carbon dioxide to leave the alveoli and enters the blood would there a lower or higher concentration of carbon dioxide in in the alveoli compared to blood and why

a) Lower concentration; to facilitate diffusion.
b) Higher concentration; to promote gas exchange.
c) Equal concentration; maintaining equilibrium.
d) Variable concentration; depends on oxygen levels.

Answer 1

For carbon dioxide to leave the alveoli and enter the blood, it relies on a higher concentration of carbon dioxide in the blood than in the alveoli to promote gas exchange, facilitated by diffusion along a pressure gradient.

Step-by-step explanation:

In order for carbon dioxide to leave the alveoli and enter the blood, there must be a higher concentration of carbon dioxide in the blood than in the alveoli. The correct answer to the student's question is b) Higher concentration; to promote gas exchange. This is because gas exchange across the respiratory membrane, including that of carbon dioxide, is primarily driven by a pressure gradient, according to Dalton's law and Henry's law. Carbon dioxide diffuses down its pressure gradient from areas of higher pressure to areas of lower pressure.

The alveolar PCO₂ is usually around 40 mm Hg, whereas in the blood of the capillaries the carbon dioxide pressure is about 45 mm Hg. Thus, the partial pressure of carbon dioxide is higher in the blood than in the alveoli, which facilitates the diffusion of carbon dioxide from the blood into the alveoli.