How does carbon dioxide travel through theespiratory system? Explain the role of theenzyme involved during respiration.[OR]
Explain the transport of `CO_(2)` from tissues to the lungs.

Explanation

Transport of Carbon-dioxide : Blood transports `CO_(2)` from the tissue cells to the lungs in three ways,
(i) Dissolved in plasma : about 7- 10 % of `CO_(2)` is transported in a dissolved form in the plasma.
(ii) Bound to haemoglobin : About 20-25 % of dissolved `CO_(2)` is bound and carried in the RBCs as carbaminohaemoglobin `(Hb CO_(2))`
`CO_(2)+ Hb hArr Hb CO_(2)`
(iii) As bicarbonate ions in plasma : A bout 70 % of `CO_(2)` is transported by `pCO_(2)` and the degree of haemoglobin oxygenatoin. RBCs contain a high concentration of the enzyme , carbonic anhydrase,Whereas small amounts of carbonic anhydrase is present in the plasma. 2. At the tissues the `pCO_(2)` is high due to catabolism and diffuses into the blood to form `HCO_(3)^(-)` and `H+` ions. When `CO_(2)` diffuses into the RBCs it comines with water forming carbonic acid `(H_2CO_3)` catalyzed by carbonic anhydrase. Carbonic acid is unstable and dissociates into hydrogen and bicarbonate ions. < br> 3. Carbonic anhydrase facilitates the reaction is both directinos.
4. The `HCO_(3)^(-)` moves quickly form the RBCs into the plasma, where it is carried to the lungs. At the alveolar site where `pCO_(2)` is low, the reaction is reversed leading to the formation of `CO_(2)` and water. Thus `CO_(2)` trapped as `HCO_(3)` - at the tissue level it is transported to the alveoli and released out as `CO_(2)`
5. Every 100 mL of deoxygenated blood delives 4 mL of `CO_(2)` to the alveoli for elimination.