Hemoglobin contributes approximately what fraction of the buffering capacity of blood?

Hemoglobin contributes approximately what fraction of the buffering capacity of blood?

• A. 5%
• B. 20%
• C. 35%
• D. 50%

Answer: (C)

Hemoglobin serves as a major intracellular buffer, especially in red blood cells, where it can take up hydrogen ions that are generated as CO2 is transported and converted to carbonic acid. Deoxyhemoglobin (HHb) has sites that readily accept H+, helping to keep blood pH from dropping. The buffering capacity of blood is shared among several systems, with the bicarbonate/carbonic acid system in plasma providing extracellular buffering and other buffers like plasma proteins and phosphate contributing as well. When you add up all of these buffers in a typical resting blood sample, hemoglobin accounts for roughly a third to a little over a third of the total buffering capacity, commonly rounded to about 35%. That’s why 35% is the best answer.

Hemoglobin serves as a major intracellular buffer, especially in red blood cells, where it can take up hydrogen ions that are generated as CO2 is transported and converted to carbonic acid. Deoxyhemoglobin (HHb) has sites that readily accept H+, helping to keep blood pH from dropping. The buffering capacity of blood is shared among several systems, with the bicarbonate/carbonic acid system in plasma providing extracellular buffering and other buffers like plasma proteins and phosphate contributing as well. When you add up all of these buffers in a typical resting blood sample, hemoglobin accounts for roughly a third to a little over a third of the total buffering capacity, commonly rounded to about 35%. That’s why 35% is the best answer.