Buffering Systems
Start with the big picture
A buffer consists of a weak acid and its conjugate base, or the reverse, and resists pH change when small amounts of acid or base are added. The main physiological systems are bicarbonate, hemoglobin, phosphate, and ammonia. Bicarbonate is the principal extracellular-fluid buffer; its effectiveness reflects regulation of CO₂ by the lungs and bicarbonate by the kidneys, as well as its open-system behavior. Hemoglobin buffers hydrogen ions in red blood cells and supports CO₂ transport. Phosphate contributes in intracellular fluid and renal tubular fluid, while ammonia serves as a renal buffer that adapts during acidosis. The lesson also compares buffer effectiveness and connects buffering to clinical context.
What you'll learn
- Define a buffer and explain how it limits changes in pH.
- Identify the major physiological buffer systems and their principal locations or roles.
- Describe why the bicarbonate system is effective despite its low pKₐ.
- Explain the roles of hemoglobin, phosphate, and ammonia in buffering.
- Relate increased ammonium excretion to chronic acid load.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
