Question

Assertion : At the tissue level, $70$ percent of $C{O}_2$ formed from catabolism is trapped as bicarbonate in the RBCs.
Reason : At tissue level, carbonic anhydrase in $RBCs$ facilitates the formation of $C{O}_2$ and $H_{2}O$ from bicarbonate.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (C)

$RBCs$ contain a very high concentration of carbonic anhydrase enzyme which facilitates the following reaction in both directions.

At the tissue site where partial pressure of $C{O}_2$ is high due to catabolism, $C{O}_2$ diffuses into blood ($RBCs$ and plasma) and forms $HC{O}_3$ and $H^{+}$. At the alveolar site where $PC{O}_2$ is low, the reaction proceeds in the opposite direction leading to the formation of $C{O}_2$ and $H_{2}O$.