Buffer Systems in the Body (Bicarbonate, Phosphate, Protein Buffers)
Start with the big picture
Bicarbonate is the principal extracellular buffer. Its effectiveness reflects abundant plasma bicarbonate and the lungs’ ability to remove CO₂; the Henderson–Hasselbalch relationship connects pH with the bicarbonate-to-PaCO₂ ratio. The kidneys also support this system by reabsorbing filtered bicarbonate and generating new bicarbonate during acid excretion. Phosphate is especially relevant inside cells and in renal tubular fluid, where it can accept secreted hydrogen ions, though its lower total body amount limits systemic capacity. Proteins contribute substantially to intracellular buffering; hemoglobin is important in blood, while plasma proteins add a smaller extracellular contribution. The lesson also introduces buffer capacity and the isohydric principle, which explains how buffer pairs in a solution are connected.
What you'll learn
- Describe why bicarbonate is the major extracellular buffer.
- Explain how ventilation and renal processes regulate the bicarbonate system.
- Identify where phosphate buffering is most effective and how it supports renal acid excretion.
- Summarize the roles of intracellular proteins, hemoglobin, and plasma proteins in buffering.
- Explain the isohydric principle and factors that influence buffer capacity.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
