Final answer:
The buffering capacity of blood is maintained by a reversible exchange process between bicarbonate and chloride ions, known as the chloride shift, which occurs in the erythrocytes and contributes to the acid-base balance by maintaining pH levels within the normal range.
Step-by-step explanation:
The buffering capacity of blood is maintained by a reversible exchange process between bicarbonate (HCO3-) and chloride (Cl-). This is known as the chloride shift, where chloride ions are exchanged for bicarbonate ions in the erythrocytes. This exchange helps to regulate the pH of blood by buffering changes that would make the blood more acidic. When carbon dioxide (CO2) enters the red blood cells, it is rapidly converted into carbonic acid (H2CO3) by the enzyme carbonic anhydrase. Carbonic acid then dissociates into bicarbonate and hydrogen ions. Bicarbonate ions are transferred out of the red blood cells in exchange for chloride ions, which do not alter the electrical charge of erythrocytes or the blood.
Moreover, the level of bicarbonate in the blood is regulated through the renal system, where bicarbonate ions in the renal filtrate are conserved and passed back into the blood, contributing to the body's acid-base balance. The bicarbonate buffer system, which includes bicarbonate ions and carbonic acid, is the primary buffering system of the interstitial fluid (IF) that surrounds the cells throughout the body. It helps maintain the pH within the normal range of 7.35 to 7.45.