Bicarbonate: A good buffer for blood

Most carbon dioxide generated during metabolism is transported in the form of bicarbonate ions, which result from the dissociation of carbonic acid formed in the red blood cells from the chemical union of carbon dioxide and water. Hydrogen ions from the dissociation are bound to hemoglobin and other proteins, serving to buffer the blood. The entire process is reversed when blood enters the lungs, allowing free carbon dioxide to diffuse into the environment.

One of the most important cases of chemical balance in the blood is the exchange of the gases oxygen and carbon dioxide. The hemoglobin also helps the blood transport carbon dioxide and assists in buffering the blood. Carbon dioxide diffuses into the blood plasma and then into the red blood cells, where the CO2 is converted to bicarbonate. Carbon dioxide first reacts with water to form carbonic acid, which then dissociates into a hydrogen ion and a bicarbonate ion. As blood flows through the lungs, the process is reversed. Diffusion of CO2 out of the blood shifts the chemical equilibrium within red cells in favor of the conversion of bicarbonate to CO2. Carbonic acid dissociates into a bicarbonate ion and a hydrogen ion. Hemoglobin binds most of the H+ ions from carbonic acid, preventing them from acidifying the blood. The reversibility of the carbonic acid-bicarbonate conversion also helps buffer the blood, releasing or removing H+.

Overall, Bicarbonate is a good buffer for blood because of its remarkable ability to resist changes in pH at given regions indicated by the minimum slope on its titration curves. These curves are when both the concentrations of the weak acid and its conjugate base are equal. If the pH of the blood falls, the concentration of H2CO3 increases to eat up the H+. In addition H2CO3 dissociates to form CO2 and H20. If the pH of the blood increases, the concentration of HCO3- increases to release H+. In this case CO2 and H2O react to form H2CO3 to replenish the supply of H+.