Correct option is D
The diffusion rate of gases through the alveolocapillary membrane depends on their solubility and molecular weight. N₂O (Nitrous Oxide) diffuses through the membrane the fastest under normal conditions because it has high solubility in plasma and a small molecular size.
Information Booster:
- The diffusion rate of a gas is determined by its solubility in the blood, its molecular weight, and the partial pressure gradient between the alveoli and capillaries.
- Nitrous Oxide (N₂O) is an example of a gas that is highly soluble in blood and has a low molecular weight, leading to rapid diffusion across the alveolocapillary membrane.
- Oxygen (O₂), though less soluble than N₂O, diffuses efficiently due to the large partial pressure gradient between the alveoli and the blood.
- Carbon Dioxide (CO₂), despite being more soluble in blood than O₂, has a slower diffusion rate due to its larger molecular weight.
- Carbon Monoxide (CO) has a very high affinity for hemoglobin, which affects its diffusion dynamics despite its small molecular size.
Additional Information:
- (a) CO: Incorrect — While CO has a high affinity for hemoglobin, its diffusion rate is not as fast as N₂O.
- (b) O₂: Incorrect — O₂ is less soluble than N₂O but diffuses relatively well due to the high partial pressure gradient.
- (c) CO₂: Incorrect — Despite its high solubility, CO₂ has a slower diffusion rate compared to N₂O due to its larger molecular size.
