What is the role of bicarbonate (HCO3-) in acid-base balance?

Bicarbonate (HCO3-) plays a crucial role in maintaining acid-base balance in the body primarily through its interaction with the kidneys. The kidneys filter bicarbonate from the blood and can reabsorb it back into the bloodstream to help maintain optimal pH levels. When the body becomes too acidic, the kidneys increase the reabsorption of bicarbonate from the renal tubules, which helps neutralize excess hydrogen ions, thus raising blood pH towards a more alkaline state. Conversely, if the body is too alkaline, the kidneys can excrete more bicarbonate to help lower blood pH.

The synthesis of bicarbonate in the body is not necessary for its role in acid-base homeostasis, as it can be recycled and managed by the kidneys without additional synthesis. While bicarbonate itself is not produced by the lungs, carbon dioxide produced during metabolism is exhaled, and its concentration influences the equilibrium of bicarbonate in the blood. Bicarbonate does not decrease blood pH levels; rather, it acts as a buffer, helping to stabilize pH within a normal range.