What are the three major buffer systems?

The three major buffer systems are the carbonic acid bicarbonate buffer system, the phosphate buffer system, and the protein buffer system. Each buffer system's characteristics and functions are listed in the bulleted points below.

1. Carbonic acid bicarbonate buffer system - The carbonic acid-bicarbonate buffer system plays a major role in maintaining pH homeostasis of the blood. Carbonic acid-bicarbonate buffer system converts strong acids to a weak acid (carbonic acid) and strong bases to a weak base (bicarbonate ion).
2. Phosphate buffer system - This system consists of phosphoric acid in equilibrium with dihydrogen phosphate ion, and hydrogen. The pKa for the phosphate buffer is 6-8, which allows the buffer to function in its ideal buffering range. It is important to note the phosphate buffer system operates in the internal fluids of cells.
3. Protein buffer system - The protein buffer system helps to maintain acidity in the interior and exterior of cells. Hemoglobin can function as an effective buffer due its ability to bind to small amounts of acids in blood, before it changes the pH of the blood. Histidine can also function as a good buffer.