The key factor in the transpo of carbon dioxide as bicarbonate is
High-Yield Explanation
Since the Pco2 in the tissue is high,CO2 diffuses from tissues into the plasma. From there it enters the RBC which contains plenty of carbonic anhydrase. In blood,70% of CO2 is transpoed as HCO3 by the action of carbonic anhydrase. Reference:Textbook of medical physiology-Geetha N,2nd edition,page no:245.