The respiratory pathway is an amphibolic pathway as it involves both anabolism and catabolism. The respiratory quotient depends upon the type of respiratory substance used during respiration.
Assertion (A): The respiratory quotient is the ratio of CO2 evolved to O2 consumed in respiration. Reason (R): The respiratory quotient depends upon the type of respiratory substrate used during respiration.
Correct answer: A — If both assertion and reason are true and the reason is the correct explanation of the assertion.
NCERT states “The ratio of the volume of CO2 evolved to the volume of O2 consumed in respiration is called the respiratory quotient (RQ)” (Assertion true). NCERT also states “The respiratory quotient depends upon the type of respiratory substrate used during respiration.” The Reason explains WHY RQ is significant - because it varies with substrate type (true and explanatory).
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