Question

Utilizing the idea that gasses can evolve during certain chemical reactions, explain how the lungs can be used to remove acid from the blood. Explain each step very carefully. What happens when a hydrogen proton (acid for the purposes of this course) reacts with the bicarbonate ion?

Answer 1

Ans. Blood exhibits buffering activity due to bicarbonate buffer system in it. It consists of carbonic acid (H2CO3) and bicarbonate ion (HCO3-) as central components.

The enzyme carbonic anhydrase catalyzes the following reversible reactions-

CO2 + H2O  H2CO3  H+ + HCO3-

It is noteworthy that the reaction also occurs without requiring the enzyme.

The bicarbonate buffer system in blood works as follow-

I. When blood pH lowers (become more acidic)-

Le Chatelier’s principle states "if a dynamic equilibrium is disturbed by changing the conditions (Concentration, Volume, Pressure, temperature, etc.), the position of equilibrium shifts to counteract the change to reestablish an equilibrium".

When blood pH lowers, formation of carbonic acid is favored. As a result, pH elevates (from acidic to neutral) due to decrease in concentration of protons.

H+ + HCO3- -------> H2CO3 ; [H+] is lowered, pH increased from acidic back to neutral.

II. When blood pH increases (become more alkaline)-

When blood pH lowers, dissociation of carbonic acid to produce more H+ is favored. Formation of more H+ lowers the pH from alkaline back to neutral.

H2CO3 ---------> H+ + HCO3- ; [H+] is increased, pH lowers from alkali back to neutral.