CO₂ Transport and Bicarbonate Formation — NEET Biology
📚 Practice ConceptAt the tissue site where partial pressure of CO₂ is high due to catabolism, CO₂ diffuses into blood (RBCs and plasma) and forms HCO₃⁻ and H⁺. At the alveolar site where pCO₂ is low, the reaction proceeds in the opposite direction leading to the formation of CO₂ and H₂O. Thus, CO₂ trapped as bicarbonate at the tissue level and transported to the alveoli is released out as CO₂. Every 100 ml of deoxygenated blood delivers approximately 4 ml of CO₂ to the alveoli.
Which of the following statements are correct regarding carbon dioxide transport from systemic tissues? S1: At the tissue site, where partial pressure of CO₂ (pCO₂) is high due to catabolism, CO₂ diffuses into blood (RBCs and plasma). S2: The enzyme carbonic anhydrase, which facilitates the conversion of CO₂ and H₂O, is present only in minute quantities in the plasma and is absent in RBCs. S3: The binding of CO₂ to hemoglobin to form carbamino-haemoglobin is mainly promoted by low pCO₂ and high pO₂ conditions. S4: Most of the bicarbonate ions (HCO₃⁻) formed from CO₂ within the RBCs largely remain inside the RBCs, contributing to their osmotic balance. S5: Every 100 ml of deoxygenated blood delivers approximately 4 ml of CO₂ to the alveoli.
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