State the different modes of $CO_{2}$ transport in blood.

(N/A) $CO_{2}$ is carried by blood in three main forms:
$1$. As Carbamino-haemoglobin: About $20-25$ percent of $CO_{2}$ is carried by haemoglobin. This binding is related to the partial pressure of $CO_{2}$. $pO_{2}$ is a major factor which affects this binding. When $pCO_{2}$ is high and $pO_{2}$ is low (as in tissues),more $CO_{2}$ binds to haemoglobin. Conversely,when $pCO_{2}$ is low and $pO_{2}$ is high (as in alveoli),$CO_{2}$ dissociates from haemoglobin.
$2$. As Bicarbonates: About $70$ percent of $CO_{2}$ is transported as bicarbonates $(HCO_{3}^{-})$. $RBCs$ contain a high concentration of the enzyme carbonic anhydrase,which facilitates the reaction: $CO_{2} + H_{2}O \rightleftharpoons H_{2}CO_{3} \rightleftharpoons HCO_{3}^{-} + H^{+}$. At the tissue site,$CO_{2}$ diffuses into blood and forms $HCO_{3}^{-}$ and $H^{+}$. At the alveolar site,the reaction proceeds in the opposite direction to release $CO_{2}$.
$3$. Dissolved in Plasma: About $7$ percent of $CO_{2}$ is carried in a dissolved state through the blood plasma.