NEETZoologyBreathing and Exchange of Gases
In the tissues, carbon dioxide diffuses into red blood cells (RBCs) and reacts with water in the presence of the enzyme carbonic anhydrase to form carbonic acid, which then dissociates into bicarbonate and hydrogen ions ( H^+ ). How does the generation of these H^+ ions directly assist in the delivery of oxygen to the tissues?
Options
- AThe H^+ ions increase the affinity of haemoglobin for oxygen, shifting the oxygen dissociation curve to the le
- BThe bicarbonate ions bind to the heme group of haemoglobin, physically displacing the bound oxygen molecules.
- CThe H^+ ions decrease the affinity of haemoglobin for oxygen, shifting the oxygen dissociation curve to the ri
- DThe consumption of water during the reaction shrinks the RBC, which forces oxygen to diffuse out into the tiss
Correct answer
C. The H^+ ions decrease the affinity of haemoglobin for oxygen, shifting the oxygen dissociation curve to the ri
Step-by-step solution
In the tissues, the partial pressure of CO₂ is high. CO₂ enters the RBCs and undergoes hydration catalyzed by carbonic anhydrase to form H₂CO₃ , which dissociates into HCO₃^- and H^+ . The accumulation of H^+ ions increases the H^+ concentration (lowers the pH) inside the RBC. A higher H^+ concentration decreases the affinity of haemoglobin for oxygen. This causes the oxygen dissociation curve to shift to the right, thereby facilitating the dissociation of oxygen from oxyhaemoglobin and its delivery to the tissues.