Home / Question Bank / Biology / Breathing and Exchange of Gases / Question 7 NEET Biology Class 11 Transport of gases — carbon dioxide Hard Single correct
Only a small fraction of the CO₂ produced by tissues travels dissolved in plasma. Which of the following correctly describes how most CO₂ is carried in the blood, and which enzyme catalyses the key step of this route? (A) About 70% of CO₂ is carried as carbamino-haemoglobin, formed by CO₂ binding directly to the haem group of haemoglobin, a reaction catalysed by carbonic anhydrase (B) Nearly all CO₂ diffuses freely and travels dissolved in plasma, since CO₂, unlike O₂, needs no carrier (C) About 70% of CO₂ is transported as bicarbonate ions, formed after CO₂ combines with water inside RBCs to give carbonic acid, which dissociates into H⁺ and HCO₃⁻; carbonic anhydrase, abundant in RBCs, catalyses the CO₂ + H₂O step (D) About 70% of CO₂ combines irreversibly with plasma proteins to form stable carbaminohaemoglobin, catalysed by RuBisCO present in RBCs Show answer and explanation ← Question 6 All Breathing and Exchange of Gases questions Question 8 → More NEET Biology chapters © 2026 Lumi (Aikolumi Software Pvt Ltd). Original questions written by Lumi. Free to view and practise on this site. Copying, republishing or reproducing these questions, options or solutions, in print or online, is not permitted.
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