Question

Which of the following is true about the exchange of gases in the lungs?

• A. The concentration of carbon dioxide is higher in blood
• B. The concentration of carbon dioxide is higher in air
• C. The concentration of carbon dioxide is the same in blood and air
• D. The concentration of carbon dioxide in the lungs varies

Answer 1

The correct option is A

The concentration of carbon dioxide is higher in blood

The air in the lungs has a higher concentration of oxygen than that of oxygen-depleted blood and a lower concentration of carbon dioxide. This concentration gradient allows for gas exchange during respiration. When a substance diffuses, it moves from a region of higher concentration to a region of lower concentration. Thus, carbon dioxide is expelled from the blood into the air in the lungs because the concentration of carbon dioxide in the blood is greater than that in the air.