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NEST2026BiologyBreathing and Exchange of Gases

Carbonic anhydrase catalyzes the following reaction in red blood cells. CO ₂ + H ₂ O H ₂ CO ₃ HCO ₃^- + H ^+ This reaction acts as a buffering system in blood. Consequence of failure of the enzyme to catalyze the reverse reaction is:

Options

  1. AThe p CO ₂ increases and the affinity of haemoglobin for CO ₂ increases.
  2. BBlood becomes acidic and the formation of carbamino-haemoglobin decreases.
  3. CThe p O ₂ of the blood decreases and the affinity of haemoglobin for O ₂ increases.
  4. DBlood becomes acidic and the affinity of haemoglobin for O ₂ decreases.

Correct answer

D. Blood becomes acidic and the affinity of haemoglobin for O ₂ decreases.

Step-by-step solution

The given reaction is CO ₂ + H ₂ O H ₂ CO ₃ HCO ₃^- + H ^+ . The forward reaction primarily occurs in the tissues where CO ₂ concentration is high, leading to the formation of H ^+ and HCO ₃^- . The reverse reaction occurs in the alveoli of the lungs, where H ^+ and HCO ₃^- recombine to form CO ₂ and H ₂ O , allowing CO ₂ to be exhaled. If the enzyme carbonic anhydrase fails to catalyze the reverse reaction, H ^+ and HCO ₃^- will not be converted back into CO ₂ and H ₂ O . This will lead to an accumulation of H ^+

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