Buffering Action of Hemoglobin
Start with the big picture
Hemoglobin is a major intracellular, non-bicarbonate buffer in blood. Its histidine imidazole groups can accept or release protons, making them effective near physiologic pH. Deoxyhemoglobin binds H⁺ more readily than oxyhemoglobin, so oxygen unloading in tissues favors proton uptake, while oxygen loading in the lungs promotes proton release. This oxygen–proton coupling links hemoglobin buffering with the Bohr effect and the conversion of carbon dioxide between CO₂ and bicarbonate. Hemoglobin also buffers H⁺ released during carbaminohemoglobin formation. Its contribution varies with hemoglobin concentration, and 2,3-BPG can influence proton acceptance indirectly. Acting rapidly alongside bicarbonate, phosphate, and plasma proteins, hemoglobin helps support blood acid–base balance.
What you'll learn
- Explain how histidine imidazole groups contribute to hemoglobin’s buffering action.
- Compare proton binding by oxyhemoglobin and deoxyhemoglobin.
- Describe how oxygen loading and unloading affect H⁺ handling in lungs and tissues.
- Relate hemoglobin buffering to bicarbonate formation and carbon dioxide transport.
- Identify factors that influence hemoglobin’s contribution to blood buffering.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
