Respiratory Quotient for Proteins — NEET Biology
📚 Practice ConceptWhen proteins are respiratory substrates the ratio would be about 0.9.
Which of the following statements regarding Respiratory Quotient (RQ) and its variations are correct? S1: The RQ value is calculated as the ratio of the volume of CO₂ evolved to the volume of O₂ consumed during respiration. S2: In certain succulent plants, like CAM plants, RQ values can fluctuate significantly throughout a 24-hour cycle due to the alternate synthesis and breakdown of organic acids. S3: During anaerobic respiration, the RQ is considered infinite because no carbon dioxide is released in the absence of oxygen. S4: The RQ for carbohydrates like glucose is consistently 1.0 because they possess a balanced proportion of carbon, hydrogen, and oxygen atoms. S5: When proteins are used as respiratory substrates, their RQ value typically falls below 0.7 due to their complex structure and low oxygen content.
View solution & NCERT explanation
Correct answer: A — S1, S2 and S4
Let's evaluate each statement: S1: This statement is correct. The NCERT defines RQ as the ratio of the volume of CO₂ evolved to the volume of O₂ consumed during respiration. S2: This statement is correct. In CAM plants, organic acids are synthesized at night and broken down during the day, leading to fluctuations in the respiratory substrate and thus the RQ value. S3: This statement is incorrect. While RQ is infinite during anaerobic respiration (because O₂ consumption is zero), CO₂ can still be released, for example, in alcoholic fermentation where pyruvic acid is converted to CO₂ and ethanol. S4: This statement is correct. NCERT states that for carbohydrates, such as glucose, when completely oxidized, the RQ is 1.0 due to equal amounts of CO₂ evolved and O₂ consumed. S5: This statement is incorrect. The RQ for proteins is approximately 0.9, which is not typically below 0.7 (the RQ for fats like tripalmitin is 0.7). Based on the evaluation, statements S1, S2, and S4 are correct. Therefore, option A is the correct answer.
What does NCERT say about When proteins are respiratory?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.