Which buffer system is most predominant in the body?

Which buffer system is most predominant in the body?

• A. Bicarbonate/carbonic acid
• B. Acetate/acetic acid
• C. Phosphate/phosphorous acid
• D. Hemoglobin

Answer: (A)

The bicarbonate/carbonic acid system is the body's main extracellular buffer. As metabolism produces CO2, it dissolves in water to form carbonic acid, which dissociates into bicarbonate and hydrogen ions. The lungs can rapidly adjust CO2 levels, and the kidneys regulate bicarbonate reabsorption and new bicarbonate generation, providing strong, ongoing pH control. The Henderson–Hasselbalch relationship shows pH is set by the ratio of bicarbonate to dissolved CO2; around physiological pH, this ratio is about 20:1, so buffering is dominated by bicarbonate in the blood and extracellular fluids. Other buffers—like phosphate—play important roles inside cells and in renal tubules, and hemoglobin buffers within red blood cells, but they do not provide the same level of systemic buffering capacity as the bicarbonate system.

The bicarbonate/carbonic acid system is the body's main extracellular buffer. As metabolism produces CO2, it dissolves in water to form carbonic acid, which dissociates into bicarbonate and hydrogen ions. The lungs can rapidly adjust CO2 levels, and the kidneys regulate bicarbonate reabsorption and new bicarbonate generation, providing strong, ongoing pH control. The Henderson–Hasselbalch relationship shows pH is set by the ratio of bicarbonate to dissolved CO2; around physiological pH, this ratio is about 20:1, so buffering is dominated by bicarbonate in the blood and extracellular fluids. Other buffers—like phosphate—play important roles inside cells and in renal tubules, and hemoglobin buffers within red blood cells, but they do not provide the same level of systemic buffering capacity as the bicarbonate system.