Correct Option
The correct option is 1 and 3 only.
Explanation
Gas exchange in the lungs occurs primarily at the level of the alveoli through the process of simple diffusion. This physical process is governed by specific factors such as pressure differences, the solubility of the gases involved, and the characteristics of the diffusion membrane.
Statement-wise Analysis
- Statement 1 is Correct: The primary driving force for the diffusion of gases (Oxygen and Carbon dioxide) is the partial pressure gradient. Gases move from a region of higher partial pressure to a region of lower partial pressure. For instance, oxygen moves from the alveoli (high pO2) to the blood (low pO2).
- Statement 2 is Incorrect: The solubility of gases significantly affects the rate of diffusion. Carbon dioxide is approximately 20-25 times more soluble than oxygen. Consequently, the amount of CO2 that can diffuse through the diffusion membrane per unit difference in partial pressure is much higher than that of O2.
- Statement 3 is Correct: The thickness of the diffusion membrane is inversely proportional to the rate of diffusion. The diffusion membrane in the lungs is extremely thin (less than 1 millimeter total thickness) to maximize the rate of gas exchange. Any increase in thickness would hinder the diffusion process.
Key Takeaway
Key Takeaway: The rate of diffusion of gases in the lungs depends on the partial pressure gradient, the solubility of the gases, and the thickness of the diffusion membrane (inversely related).