Explanation

$\mathbf{C}\mathbf{O}_{\mathbf{2}}$ transport in blood : Transport of $CO_{2}$ by blood is must easier/simple than that of $O_{2}$ due to high solubility of $CO_{2}$ in water. Most of the$\ CO_{2},\ i.e.,$ 70% of $CO_{2}$ is transported as bicarbonate $(HCO_{3}^{-})$ in blood. 23% as carbaminohaemoglobin $(HbCO_{2})$ and 7% of $CO_{2}$ is dissolved in the plasma. $CO_{2}$ produced by the tissues, diffuses passively into the blood plasma and reacts with water forming carbonic acid. The reaction occurs very rapidly inside RBCs because of the presence of enzyme carbonic anhydrase. Chloride shift : To maintain electro-chemical neutrality of plasma many chloride ions diffuse from plasma into RBCs and bicarbonates pass out. The chloride content of RBCs increases when oxygenated blood becomes deoxygenated. This is termed as chloride shift or Hamburger shift. Haldane’s effect : Oxygenated blood behaves as strong acid. More and more oxyhaemoglobin is formed in lungs, which releases $H^{+}\ ,\ i.e.,$ increasing the acidity of blood. This $H^{+}$ combines with bicarbonate forming carbonic acid and soon dissociates.