Which process is essential for the exchange of gases in the lungs?

Diffusion is the correct answer because it is the primary process through which gases are exchanged in the lungs. In the alveoli, the tiny air sacs in the lungs, oxygen from the inhaled air diffuses across the alveolar membrane into the bloodstream, where it binds to hemoglobin in red blood cells. Simultaneously, carbon dioxide, which is a waste product of cellular metabolism, diffuses from the bloodstream into the alveoli to be exhaled. This movement occurs because gases naturally move from areas of higher concentration to areas of lower concentration, a principle known as the concentration gradient.

In the context of human respiration, this gas exchange is critical for delivering oxygen to tissues throughout the body while removing carbon dioxide, thereby maintaining homeostasis and normal metabolic functions. The other processes mentioned, such as filtration, osmosis, and endocytosis, do not play a primary role in the gas exchange mechanism that occurs in the lungs.