Question

1. If HCO₃^- did not diffuse out of the red blood cell, what would occur?

1. The red blood cell would become acidic.
2. The pH of red blood cells would decrease.
3. The plasma pH would be destabilized.
4. Increased levels of Cl^- would enter the red blood cell.

Answer 1

Ans- (c). The plasma pH will be destabilized

Majority of CO2 is carried as a part of the bicarbonate buffer system. In this system, CO2 diffuses into the red blood cells. Carbonic anhydrase in the RBC converts CO2 into carbonic acid ( H2CO3). Carbonic acid is unstable and dissociates into bicarbonate and hydrogen ions. Since CO2 is quickly converted into bicarbonate ions, this reaction allows uptake of carbon dioxide into blood down its concentration gradient. It also results in production of H+ ions. If too much H+ is produced it alters blood pH. The newly synthesized bicarbonate ion is transported out of RBC into the plasma in exchange of Chloride ion called chloride shift.

Therefore if more bicarbonate ions remains in the RBC it will lead to increase in basicity and therefore pH increases so 1st and 2nd are wrong. And since there cannot be chloride shift there will be destabilization of pH.