ATP Yield in Aerobic Respiration — NEET Biology
📚 Practice ConceptBut this kind of assumptions are not really valid in a living system; all pathways work simultaneously and do not take place one after another; substrates enter the pathways and are withdrawn from it as and when necessary; ATP is utilised as and when needed; enzymatic rates are controlled by multiple means. Yet, it is useful to do this exercise to appreciate the beauty and efficiency of the living system in extraction and storing energy. Hence, there can be a net gain of 38 ATP molecules during aerobic respiration of one molecule of glucose.
Which of the following statements accurately describe the dynamic nature and regulation of the respiratory pathway in living cells? S1: Respiratory intermediates cannot be withdrawn from the pathway as this would halt energy production. S2: Substrates like carbohydrates, fats, and proteins must strictly enter the respiratory pathway at its initial step to ensure orderly energy extraction. S3: The respiratory pathway is considered amphibolic because its intermediates can be diverted for the synthesis of other necessary compounds, making it both catabolic and anabolic. S4: In a living system, all metabolic pathways, including respiration, work simultaneously and substrates can be withdrawn or enter the pathways as and when needed. S5: Enzymatic rates within the respiratory pathway are controlled by multiple means, contributing to its flexibility and responsiveness to cellular needs.
View solution & NCERT explanation
Correct answer: C — S3, S4 and S5 are correct
The respiratory pathway is dynamic and regulated, adapting to cellular needs. S1: Incorrect. Respiratory intermediates can indeed be withdrawn for the synthesis of other compounds, which is a key aspect of its amphibolic nature. The NCERT mentions, "intermediates in the pathway are utilised to synthesise any other compound" (referring to an assumption not valid in living systems, implying the opposite occurs). S2: Incorrect. Different substrates enter the pathway at various points, not strictly at the initial step. The NCERT states, "Other substrates can also be respired... but then they do not enter the respiratory pathway at the first step." S3: Correct. This accurately defines the amphibolic nature. The NCERT states, "Because the respiratory pathway is involved in both anabolism and catabolism, it would hence be better to consider the respiratory pathway as an amphibolic pathway rather than as a catabolic one." S4: Correct. Living systems are complex, with interconnected pathways. The NCERT states, "all pathways work simultaneously and do not take place one after another; substrates enter the pathways and are withdrawn from it as and when necessary." S5: Correct. The regulation of enzymatic rates allows for cellular control over respiration. The NCERT states, "enzymatic rates are controlled by multiple means." Therefore, statements S3, S4, and S5 are correct, making option C the correct answer. The question emphasizes the non-rigid, flexible, and regulated nature of cellular respiration.
What does NCERT say about But this kind assumptions?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.