What are the three major buffer systems of the body and how do they work?

The human body maintains a delicate balance of acid-base levels to ensure proper functioning of cells and organs. Buffer systems play a crucial role in maintaining this balance by regulating the pH of bodily fluids. There are several buffer systems in the body, but three major ones are:

Bicarbonate Buffer System:
The bicarbonate buffer system operates mainly in the extracellular fluid, including the blood. It consists of carbonic acid (H2CO3) and bicarbonate ions (HCO3-). When an acid (H+) is added to the system, it combines with bicarbonate ions to form carbonic acid, which can then be converted into water and carbon dioxide by the enzyme carbonic anhydrase. This reaction helps to prevent a significant decrease in pH. Conversely, when a base (OH-) is added, it combines with carbonic acid to form bicarbonate ions, thereby preventing a significant increase in pH.

Phosphate Buffer System:
The phosphate buffer system operates both inside and outside cells. It consists of dihydrogen phosphate ions (H2PO4-) and monohydrogen phosphate ions (HPO4^2-). In this system, when an acid is added, it combines with the monohydrogen phosphate ions to form dihydrogen phosphate ions, thereby preventing a significant decrease in pH. On the other hand, when a base is added, it combines with the dihydrogen phosphate ions to form monohydrogen phosphate ions, preventing a significant increase in pH.

Protein Buffer System:
Proteins, particularly hemoglobin and albumin, act as buffers inside and outside cells. The amino acid side chains in proteins can accept or donate hydrogen ions (H+), depending on the pH of the environment. When the pH decreases (acidic conditions), the protein buffer system can accept H+ ions, preventing a significant decrease in pH. Conversely, when the pH increases (basic conditions), the protein buffer system can release H+ ions, preventing a significant increase in pH.

These buffer systems work together to maintain the pH within a narrow range, allowing proper cellular function and physiological processes to occur. They act rapidly to minimize changes in pH and help stabilize the acid-base balance in the body.