Answer
Blood levels of hydrogen bicarbonate [HCO3-] are normally higher in systemic blood plasma than in the plasma of blood in the pulmonary circulation.
Work Step by Step
In the pulmonary circulation HCO3 of plasma diffuses into erythrocytes and combine with H+ ions to form bicarbonic (H2CO3). Bicarbonic acid ( a weak acid ) dissociates into CO2 and H20. CO2 diffuses out of the RBCs into plasma, thence diffuses into alveoli and is exhaled. So plasma of pulmonary blood looses bicarbonate ions.
In Systemic blood carbon dioxide picked up all over the body is in solution blood plasma. The high plasma partial pressure plus the high [CO2] causes CO2 to diffuse into he RBCs. In the RBCs, CO2 and H20 combine,-- under the influence of carbonic anhydrase to form H2C03. Bicarbonic acid, a weak acid readily dissociates to a give bicarbonate ions and H+ cations. The bicarbonate ions diffuse out of the RBCs into the blood plasma of the systemic circulation. Thus, the [HCO3-} becomes higher in the systemic blood plasma than in pulmonary blood plasma.
