Q. The importance of pH maintenance in blood.
Maintenance of the pH in blood and in intracellular fluids is absolutely crucial to the processes that occur in living organisms. This primarily because the functioning of enzymes-catalysts for these processes - is sharply pH dependent. The normal pH value of blood plasma is 7.4. Severe illness or death can result from sustained variations of a few tenths of pH unit.
Among the factors that lead to a condition of acidosis, in which there is a decrease in the pH of blood are heart failure, kidney failure diabetes mellitus, persistent diarrhoea or a long term high protein diet.A temporary condition of acidosis may result from prolonged, intensive exercise. Alkalosis, which causes increase in pH of blood may occur as a result of severe vomiting over breathing or exposure to high altitudes.
Several factors are involved in the control of the pH of blood. A particularly important one is the ratio of dissolved HCO−3 to H2CO3. CO2(g) is moderately soluble in water and in aqueous solution reacts only to a limited extent to produce H2CO3.
CO2+H2O⇌H2CO3(aq)
H2CO3+H2O⇌HCO−3+H3O+ , pKa1=6.11
HCO−3+H2O⇌CO2−3+H3O+, pKa2=10.25
In the
H2CO3,
HCO−3 buffer system, we deal only with the first ionization step
(Ka1):
H2CO3 is a weak acid and
HCO−3 is the conjugate base (salt).
CO2 enters the blood from tissues as the by -product of a metabolic reaction. In the lungs,
CO2(g) is exchanged for
O2(g), which is transported throughout the body by the blood.Important diagnostic analysis in the blood is :
