Question

The exchange of gases in the alveoli of the lungs takes place by

• A. active transport
• B. passive transport
• C. simple diffusion
• D. osmosis

Answer 1

The correct option is C

simple diffusion

The correct option is C.

Explanation of the correct option:

1. The partial pressure of oxygen is higher in the alveoli (104 mm Hg) in comparison to the deoxygenated blood (40 mm Hg), which causes diffusion of oxygen from the alveoli to the blood.
2. The partial pressure of carbon dioxide in alveoli (40 mm Hg) is less contrasted with the blood coming from tissues (45 mm Hg), leading to the release of CO₂ in alveoli.

Explanation of the incorrect option:

Option A:

1. This is a biological process in which the molecules move against the concentration gradient & require chemical energy to move biochemical compounds from the lower region to a high region.
2. Therefore, the process uses ATP – Adenosine triphosphate to pump the molecules by a concentration gradient.

Option B:

1. In the said biological process, energy is not required for transporting molecules, as the biochemicals move from the region of higher concentration to the region of lower concentration.
2. All the particles which are easily soluble are then transported by passive transport.
3. This process is carried out to maintain balance and equilibrium levels in a cell.
4. Osmosis, diffusion, and facilitated diffusion are some of the common examples of passive transport.

Option D:

1. Osmosis is a passive process and happens without any expenditure of energy.
2. It involves the movement of molecules from a region of higher concentration to the lower concentration until concentrations become equal on either side of the membrane.

Final answer: The exchange of gases in the alveoli of the lungs takes place by simple diffusion.