Gas Exchange Only Occurs in Alveoli — NEET Biology
📚 Practice ConceptDiffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why?
Which of the following statements regarding the exchange part of the human respiratory system and the diffusion membrane are correct? S1. Alveoli and their ducts together constitute the exchange surface for diffusion of respiratory gases. S2. The diffusion membrane consists of alveolar epithelium, capillary endothelium and a basement substance between them. S3. Extremely small thickness of the diffusion membrane facilitates rapid diffusion of oxygen and carbon dioxide. S4. Increase in thickness of the basement substance enhances the rate of gaseous exchange. S5. Large surface area of alveoli contributes significantly to efficient gaseous exchange. S6. Gaseous exchange across the alveoli occurs by active transport mechanisms. Choose the correct option:
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Correct answer: A — S1, S2, S3 and S5 are correct
The exchange part of the respiratory system is formed by alveoli and their ducts, which provide the site for diffusion of gases (S1 correct). The diffusion membrane is composed of alveolar squamous epithelium, capillary endothelium and a basement substance (S2 correct). Its very small thickness favours rapid diffusion of O2 and CO2 (S3 correct). An increase in thickness would hinder, not enhance, diffusion (S4 incorrect). The large surface area of alveoli plays a major role in efficient gaseous exchange (S5 correct). Diffusion of respiratory gases occurs by simple diffusion, not active transport (S6 incorrect). Hence, the correct set is S1, S2, S3 and S5.
What does NCERT say about Diffusion gases occurs alveolar?
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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.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.