Human blood as a buffer solution

Human blood contains a buffer of carbonic acid (H2CO3) and bicarbonate anion (HCO3-) in order to maintain blood pH between 7.35 and 7.45, as a value higher than 7.8 or lower than 6.8 can lead to death. In this buffer, hydronium and bicarbonate anion are in equilibrium with carbonic acid. Furthermore, the carbonic acid in the first equilibrium can decompose into CO2 gas and water, resulting in a second equilibrium system between carbonic acid and water. Because CO2 is an important component of the blood buffer, its regulation in the body, as well as that of O2 , is extremely important. The effect of this can be important when the human body is subjected to strenuous conditions.

In the body, there exists another equilibrium between hydronium and oxygen which involves the binding ability of hemoglobin. An increase in hydronium causes this equilibrium to shift towards the oxygen side, thus releasing oxygen from hemoglobin molecules into the surrounding tissues/cells. This system continues during exercise, providing continuous oxygen to working tissues.

the blood buffer is:

H3O++HCO−3⇌H2CO3+H2O

H3OHCO3H2CO3H2O

With the following simultaneous equilibrium:

H2CO3⇌H2O+CO2

Maintaining a constant blood pH is critical for the proper functioning of our body. The buffer that maintains the pH of human blood involves a carbonic acid and bicarbonate ion.

When any acidic substance enters the bloodstream, the bicarbonate ions neutralize the hydronium ions forming carbonic acid and water. Carbonic acid is already a component of the buffering system of blood. Thus hydronium ions are removed, preventing the pH of blood from becoming acidic.

Chemical reaction diagram of bicarbonate ions neutralizing hydronium ions forming carbonic acid and water

On the other hand, when a basic substance enters the bloodstream, carbonic acid reacts with the hydroxide ions producing bicarbonate ions and water. Bicarbonate ions are already a component of the buffer. In this manner, the hydroxide ions are removed from blood, preventing the pH of blood from becoming basic.

If our blood pH goes to anything below 6.8 or above 7.8, cells of the body can stop functioning and the person can die. This is how important the optimum pH of blood is!

Enzymes are very specific in nature, and function optimally at the right temperature and the right pH; if the pH of blood goes out of range, the enzymes stop working and sometimes enzymes can even get permanently denatured, thus disabling their catalytic activity. This in turn affects a lot of biological processes in the human body, leading to various diseases.