Consider the following statements regarding human respiratory physiology: 1. The exchange of oxygen and carbon dioxide across the alveolar-capillary membrane occurs entirely through passive diffusion driven by partial pressure gradients. 2. Carbon dioxide is transported in human blood predominantly as dissolved gas molecules directly in the blood plasma. Which of the statements given above is/are correct?

💡 Solution & Explanation

Respiratory gas exchange across pulmonary alveoli relies strictly on passive diffusion down partial pressure gradients between alveolar air and pulmonary capillary blood. However, carbon dioxide is transported primarily in the form of bicarbonate ions dissolved in plasma, with lesser amounts bound to hemoglobin or dissolved as gas. Oxygen is transported mainly bound to hemoglobin inside red blood cells. The partial pressure of oxygen in arterial blood is approximately 100 millimeters of mercury.