Zoology - Breathing and Exchange of Gases Question with Solution | TestHub

Carbon dioxide molecules are transported in the blood from body tissues to the lungs by one of three methods: dissolution directly into the blood, binding to haemoglobin, or carried as a bicarbonate ion. About 5 to 7 percent of all carbon dioxide is dissolved in the plasma. About 10 percent of carbon dioxide can bind to plasma proteins or can enter red blood cells and bi nd to hemoglobin to form carbaminohemoglobin. The majority of carbon dioxide molecules ( 85 percent) are carried as part of the bicarbonate buffer system. In this system, carbon dioxide diffuses into the red blood cells. Related Theory Carbonic anhydrase within the red blood cells converts the carbon dioxide into carbonic acid $\left({\mathrm{H}}_2{\mathrm{CO}}_3\right)$. Carbonic acid is an unstable intermediate molecule that immediately dissociates into bicarbonate ions $\left({\mathrm{HCO}}_3^{-}\right)$ and hydrogen $\left({\mathrm{H}}^{+}\right)$ions. Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood down its concentration gradient.