Approximately seventy percent of carbondioxide absorbed by the blood will be transported to the lungs
(a) as bicarbonate ions
(b) in the form of dissolved gas molecules
(c) by binding to RBC
(d) as carbamino - haemoglobin
(a) as bicarbonate ions
Explanation:
CO2 from the respiratory tissues to the lungs is transported by the blood in 3 ways:
(i) In dissolved state or as a physical solution: Very small amount is physically dissolved in plasma (7% i.e. 0.3 ml of CO2 by each 100 ml of blood).
(ii) Bicarbonate ions: About 70% (i.e. 2.5 ml per 100 ml of blood) CO2 diffuses in plasma & then into RBCs where it (in the presence of carbonic anhydrase) combines with H2O to form carbonic acid which is almost spontaneously dissociated into hydrogen ion and bicarbonate ions.
(iii) Carbaminohaemoglobin : 23% (i.e. 1 ml of CO2 per 100 ml of blood) combines with haemoglobin forming an unstable compound.