Partial Pressures in Atmospheric vs Alveolar Air — NEET Biology
📚 Practice ConceptWhat will be the pO₂ and pCO₂ in the atmospheric air compared to those in the alveolar air ? (i) pO₂ lesser, pCO₂ higher (ii) pO₂ higher, pCO₂ lesser (iii) pO₂ higher, pCO₂ higher (iv) pO₂ lesser, pCO₂ lesser
Which of the following statements accurately describe the principles governing gas exchange across the respiratory membrane? S1: The partial pressure gradient for oxygen between the alveoli and deoxygenated blood is substantially greater than that for carbon dioxide between deoxygenated blood and alveoli. S2: Carbon dioxide diffuses at a much faster rate across the respiratory membrane than oxygen, primarily due to its 20-25 times higher solubility. S3: The amount of carbon dioxide that can diffuse per unit partial pressure difference is significantly higher than that for oxygen. S4: If the diffusion membrane's thickness were to increase even slightly (e.g., to 1 mm), gas exchange would remain efficient due to the robustness of alveolar capillaries. S5: Favorable conditions for efficient gas exchange include not only appropriate partial pressure gradients and gas solubility but also optimal membrane thickness and surface area.
View solution & NCERT explanation
Correct answer: C — S1, S2, S3 and S5 only
The core concept relates to the factors influencing the rate and efficiency of gas diffusion across the respiratory membrane. S1: The pO₂ gradient (104 - 40 = 64 mmHg) is indeed substantially greater than the pCO₂ gradient (45 - 40 = 5 mmHg). So, S1 is correct. S2: Carbon dioxide's solubility is 20-25 times higher than oxygen, enabling its faster diffusion despite a smaller partial pressure gradient. So, S2 is correct. S3: Due to its much higher solubility, the amount of CO₂ diffusing per unit partial pressure difference is significantly higher than for O₂. So, S3 is correct. S4: An increase in membrane thickness, even to 1 mm, would significantly impede gas exchange, as the normal thickness is much less than a millimeter. The robustness of capillaries does not compensate for a thicker diffusion barrier. So, S4 is NOT correct. S5: Optimal partial pressure gradients, high gas solubility, thin membrane thickness, and a large surface area are all crucial factors for efficient gas exchange. So, S5 is correct. Therefore, statements S1, S2, S3, and S5 are correct.
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
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