The pH (or the amount of hydrogen ions (H+) in a solution) level of the blood is important in ensuring the proper functionality of biological systems. The optimal pH level of the blood is 7.4, which is maintained by three different types of buffer systems working in the body. The addition of an acid or a base to a substance changes its pH level. A buffer is a solution (or a substance) that has the ability to maintain pH and bring it back to its optimal value. It does this by the additional or removal of hydrogen ions. Buffers working in the body fluid adjust the pH level of the blood and function to lower pH if its level rises above 7.4 by making the blood slightly more acidic. If the pH of blood falls below 7.4, buffers act to take up hydrogen atoms and decrease the acidity of the blood.
Protein Buffer Systems
Proteins are the most important and widely operating buffers in the body fluid. The protein buffer system is an integral component of the body's pH controlling mechanism. Protein buffers are either intracellular or extracellular. Their functionality is mainly intracellular focused and include haemoglobin (Hb). Hb is the protein that functions to transport oxygen within the body. Plasma proteins function as buffers but their amount is small in comparison with the intracellular protein buffers. Protein buffers include basic group, and acidic protein buffer groups, that act as hydrogen ion depletors or donors to maintain the pH level at 7.4. The most well-known protein buffers include 0.1 M NaH2PO4, pH 6.2 (Activation buffer), PBS, pH 7.4 (Alternate Coupling Buffer) and the PBS, 1 per cent BSA, pH 7.4 (Assay Buffer).
Phosphate Buffer System
The phosphate buffer system is comprised of two ions: hydrogen phosphate ions and dihydrogen phosphate ions. The pH level of the blood drops below 7.4 when the H+ ions in the bloodstream increase. Hydrogen phosphate ions accept all additional H+ ions to reestablish the equilibrium between the hydroxide and hydrogen ions in the blood. When the pH level of the blood increases above 7.4, the dihydrogen phosphate ions release additional hydrogen ions to reinstate the pH level of the blood to its optimal 7.4.
Bicarbonate Buffer System
The bicarbonate buffer system functions to maintain the pH level in the blood of mammals. It also plays a major role in the formation of acid in the stomach, and to neutralise the pH of chyme that enters the small intestine from the stomach. The bicarbonate buffer system manages acid/base imbalances and effectively manages the release of excess carbon dioxide as a bi-product of cellular respiration.