Gas exchange occurs in the lungs by what process?

• A. Convection
• B. Diffusion
• C. Osmosis
• D. Filtration

Answer: (B)

Gas exchange in the lungs primarily occurs through the process of diffusion. This method involves the movement of molecules from an area of higher concentration to an area of lower concentration. In the context of the respiratory system, oxygen from the air inside the alveoli (tiny air sacs in the lungs) moves into the blood, where the concentration of oxygen is lower. Similarly, carbon dioxide from the blood, which is present at a higher concentration, diffuses into the alveoli to be exhaled.

This mechanism is essential for efficient gas exchange because it maximizes the gradient between the gases in the alveoli and the blood, ensuring that oxygen enters the bloodstream and carbon dioxide is expelled effectively. The surface area of the alveoli, along with their thin walls, facilitates this process, making diffusion the most efficient way for gas transport during respiration.

Other processes such as convection, osmosis, and filtration do not describe the movement of gases in the lungs accurately, as they pertain to different mechanisms within biological systems or fluid dynamics.