Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What is the functional advantage of having thinner walls in the air passageways of the lungs?

1. To enhance structural support

2. To improve gas diffusion

3. To allow for easier movement of air

4. To prevent water loss

The correct answer is: To improve gas diffusion

Having thinner walls in the air passageways of the lungs provides a significant functional advantage by improving gas diffusion. The primary role of the lungs is to facilitate the exchange of gases—specifically, the uptake of oxygen and the release of carbon dioxide. Thinner walls maximize the surface area relative to volume, allowing gases to diffuse more efficiently through the respiratory membranes. The process of gas diffusion relies heavily on the concentration gradient, where oxygen and carbon dioxide move from areas of higher concentration to areas of lower concentration. Thinner walls shorten the distance that these gases must traverse, thus enhancing the overall rate of diffusion. This increased efficiency is crucial for meeting the metabolic demands of the body, especially during activities that require higher oxygen consumption, such as exercise. Other options, while relevant to different biological contexts, do not directly address the primary role of thin walls in the gas exchange process within the lungs.