Which term describes the exchange of oxygen and carbon dioxide?

• A. Oxygenation
• B. Ventilation
• C. Cell
• D. Respiration

Answer: (D)

Respiration is the process of exchanging gases between the air and the blood, and between the blood and tissues, so oxygen can reach cells and carbon dioxide can be removed as a waste product. It includes external respiration—the diffusive exchange of O2 into blood and CO2 out of blood in the lungs—and internal respiration—gas exchange at the tissues where O2 leaves the blood to be used for cellular metabolism and CO2 returns to the blood. This gas exchange is driven by differences in partial pressures and occurs across the respiratory membrane. Ventilation is just the movement of air in and out of the lungs, which supports respiration but isn’t the gas exchange itself. Oxygenation refers specifically to loading oxygen onto hemoglobin, which is part of the oxygen transport process but not the exchange between air, blood, and tissues. The exchange of oxygen and carbon dioxide is described by respiration.