Q200 / 200 · NEET 2024 (Re-NEET) · Zoology

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: During the transportation of gases, about $20-25$ percent of $\mathrm{CO}_2$ is carried by Haemoglobin as carbamino-haemoglobin. Reason R: This binding is related to high $\mathrm{pCO}_2$ and low $\mathrm{pO}_2$ in tissues. In the light of the above statements, choose the correct answer from the options given below.

  • A
    A is true but $R$ is false.
  • B
    A is false but $R$ is true.
  • Correct answer
    C
    Both A and R are true and R is the correct explanation of A .
  • D
    Both A and R are true but R is NOT the correct explanation of A .

Solution

The correct answer is option (3) as nearly $20-25$ precent of $\mathrm{CO}_2$ is transported by RBCs whereas 70 percent of it is carried as bicarbonate. About 7 percent of $\mathrm{CO}_2$ is carried in a dissolved state through plasma. The binding of $\mathrm{CO}_2$ with haemoglobin is related to the partial pressure of $\mathrm{CO}_2 . \mathrm{pO}_2$ is a major factor which could affect this binding. When $\mathrm{pCO}_2$ is high and $\mathrm{pO}_2$ is low as in the tissues, more binding of $\mathrm{CO}_2$ occurs. Percentage of a gas transported depends upon its partial pressure. If partial pressure decreases, the transportation of gases also decrease with haemoglobin. So, Reason is the correct explanation of Assertion.

Hence, the correct answer is option: 'C'.

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