Correct Option
The correct option is 2 only.
Explanation
Respiration involves the exchange of gases (oxygen and carbon dioxide) between the atmosphere and the body's cells. This process relies on the physical principle of simple diffusion, where gases move from regions of higher partial pressure to regions of lower partial pressure.
Statement-wise Analysis
- Statement 1 is Incorrect. Gas exchange occurs at two distinct sites in the body, not just one.
- Alveolar level: Exchange takes place between the alveoli of the lungs and the blood capillaries. Here, oxygen moves into the blood, and carbon dioxide moves out.
- Tissue level: Exchange takes place between the systemic blood capillaries and the body tissues. Here, oxygen moves from the blood into the tissues, and carbon dioxide moves from the tissues into the blood.
- Statement 2 is Correct. The rate of diffusion is governed by specific physical factors:
- Partial Pressure Gradient: This is the primary driving force. Gases diffuse from areas of high partial pressure to areas of low partial pressure.
- Thickness of the Membrane: The diffusion rate is inversely proportional to the thickness of the diffusion membrane. The alveolar-capillary membrane is extremely thin (less than 1 millimeter) to facilitate rapid exchange.
- Solubility of Gases: Gases with higher solubility diffuse faster. For instance, CO2 is much more soluble than O2, allowing it to diffuse rapidly even with a smaller pressure gradient.
Key Takeaway
Key Takeaway: Gas exchange occurs at both the alveolar site (pulmonary exchange) and the tissue site (systemic exchange). The efficiency of this process depends on the partial pressure gradient, the solubility of the gases, and the thickness of the diffusion membrane.