NEETZoologyBreathing and Exchange of Gases
Consider the following reversible reaction involved in the transport of respiratory gases: CO ₂ + H ₂ O H ₂ CO ₃ HCO ₃^- + H ^+ Which specific condition at the alveolar site drives this reaction to the left (towards the formation of CO ₂ and H ₂ O ), and what is the relative concentration of the enzyme catalyzing this reaction in the blood plasma?
Options
- AHigh p O ₂ drives the reaction; the enzyme is present in high concentration in plasma
- BLow p CO ₂ drives the reaction; the enzyme is present in high concentration in plasma
- CLow p CO ₂ drives the reaction; the enzyme is present in minute quantities in plasma
- DHigh p CO ₂ drives the reaction; the enzyme is present in minute quantities in plasma
Correct answer
C. Low p CO ₂ drives the reaction; the enzyme is present in minute quantities in plasma
Step-by-step solution
The reaction is catalyzed by the enzyme carbonic anhydrase. According to NCERT, RBCs contain a very high concentration of carbonic anhydrase, while only minute quantities of the same are present in the blood plasma. At the tissue site, high p CO ₂ drives the reaction to the right (forming bicarbonate and hydrogen ions). However, at the alveolar site where p CO ₂ is low, the reaction proceeds in the opposite direction (to the left), leading to the formation of CO ₂ and H ₂ O so that carbon dioxide can be exhaled. Th