Gas diffusion across lung membranes relies on solubility in lipids

Steps:

• Identify that O2 and CO2 diffuse passively down concentration gradients through lipid bilayers.
• Note CO2 has higher lipid solubility than O2, allowing faster diffusion despite similar molecular sizes.
• Match options to table rows describing properties like solubility (higher for CO2) or diffusion rates.
• Select row(s) where CO2 value exceeds O2, indicating correct diffusion behavior.

Why D is correct:

• Row 5 shows CO2 diffusion rate (5) equaling or exceeding O2 (4), aligning with Fick's law where flux = permeability × area × ΔP, and CO2's higher permeability due to lipid solubility.

Why the others are wrong:

• A and B both list "3 2", implying equal or lower CO2 diffusion, contradicting CO2's superior solubility.
• C lists "5 4", specifying only one row without acknowledging variability in CO2 rates.

Final answer: D