Which of the following reversible reactions of carbon dioxide explains how hemoglobin serves as a transporter of carbon dioxide?
A)reaction with the imidazole group of the distal histidine where oxygen would normally be bound
B)reaction with the carboxyl group of glutamic acid to form a carbonic acid anhydride
C)reaction with the N-terminal amino groups to form a carbamate
D)reaction with the hydroxyl group of serine to form a carbonate
E)none of the above

Question

Quizplus · Accepted Answer

When carbon dioxide enters red blood cells, it reacts with water to form carbonic acid, which then spontaneously dissociates to form bicarbonate and a hydrogen ion. This is catalyzed by the enzyme carbonic anhydrase. The bicarbonate ions diffuse out of the red blood cells, while to maintain ion balance, negatively charged Cl- ions diffuse in. However, some carbon dioxide is also transported by hemoglobin. Specifically, some of the carbon dioxide reacts with the N-terminal amino groups of the globin chains to form carbamate. The carbamate binds to the protonated form of the amino acids, stabilizing the T state of the hemoglobin molecule, thus promoting the release of oxygen and enhancing the amount of carbon dioxide that can be transported by hemoglobin.

Which of the Following Reversible Reactions of Carbon Dioxide Explains