Question

Diffusion of gases over the respiratory surface occurs because of ________.

• A. the $pCO_{2}$ is more in alveoli than in blood
• B. the $pCO_{2}$ is more in blood than in tissues
• C. the $pO_{2}$ is more in alveoli than in blood
• D. the $PO_{2}$ is more in tissues than in blood

Hint:

Gases always move from an area of high partial pressure to low partial pressure.

Answer 1

The Correct Option is C

Step 1: Concept
Gas exchange occurs via passive diffusion based on partial pressure gradients.
Step 2: Analysis
For Oxygen ($O_2$) to enter the blood, its partial pressure ($pO_2$) must be higher in the lungs (alveoli) than in the deoxygenated blood. Conversely, for $CO_2$ to leave, its partial pressure ($pCO_2$) must be higher in the blood than in the alveoli.
Step 3: Conclusion
Diffusion of Oxygen occurs because $pO_2$ is higher in the alveoli.
Final Answer:(C)