What is the primary purpose of gas exchange in the alveoli?

The primary purpose of gas exchange in the alveoli is to deliver oxygen to the bloodstream and remove carbon dioxide from it. The alveoli are tiny air sacs in the lungs where this crucial exchange occurs. When we inhale, fresh oxygen enters the alveoli and diffuses across the thin walls into the surrounding capillaries, where it binds to hemoglobin in red blood cells for transport throughout the body. Simultaneously, carbon dioxide, a waste product of cellular respiration, moves from the blood into the alveoli to be exhaled. This process is vital for maintaining the body's oxygen levels and preventing the accumulation of carbon dioxide, which can be harmful if allowed to build up in the bloodstream.

While the other options mention functions related to respiration or the respiratory system, they do not capture the fundamental role that alveoli play in supporting cellular metabolism by facilitating the exchange of oxygen and carbon dioxide.