Q.CO2 is transported through blood to lungs as

Oxygen and carbon dioxide are carried through the blood by very different routes because of their different solubilities. Oxygen is poorly soluble in plasma, so about 97% is carried bound to haemoglobin inside red blood cells (forming oxyhaemoglobin) and only about 3% travels dissolved in plasma. Carbon dioxide, far more soluble, is carried by three simultaneous routes - about 7-10% dissolved in plasma, 20-25% bound to haemoglobin as carbaminohaemoglobin, and about 70% converted to bicarbonate ions in plasma via the enzyme carbonic anhydrase. Haemoglobin, the respiratory pigment responsible for O2 and CO2 binding, is a conjugated protein made of globin (~96%) and the iron-containing pigment haem (~4%); each molecule carries four iron atoms and can bind up to four O2 molecules. Methaemoglobin, in which the haem iron is oxidised to the ferric state, cannot bind oxygen at all and …