Question

Teacher said “The air is purified at the alveoli”. Shishir was curious and asked how it happens. The teacher went on and explained how capillaries are intertwined with the alveoli and at the boundaries, diffusion occurs and air is purified. If it is true, what causes this diffusion? Select the best option.

• A. High concentrations of oxygen in the alveoli and that of $C{O}_2$ in the blood.
• B. High concentrations of $C{O}_2$ in the alveoli and and that of oxygen in the blood.
• C. High concentration of $C{O}_2$ in the alveoli.
• D. Low concentration of $C{O}_2$ in the alveoli.

Answer 1

The correct option is A High concentrations of oxygen in the alveoli and that of $C{O}_2$ in the blood.

Diffusion takes place when there are molecules of higher concentration on one side of a membrane and molecules of lower concentrations on the other side. The diffusion occurs from the side of higher concentration to the lower concentration side.

${CO}_2$ produced in the cells is diffused into the blood and this blood is called deoxygenated blood and the concentrations of the constituents are - oxygen-16$\%$ and carbon dioxide - 4$\%$. Similarly, the air inhaled by us has 21$\%$ of oxygen and 0.04$\%$ of carbon dioxide.

So at the capillaries in the lungs, the $C{O}_2$ diffuses from the blood into the alveoli and oxygen diffuses from alveoli into the blood due to the concentration differences.