Practice free Respiration (Botany) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
Which of the following statements about anaerobic conditions mentioned in the context is true?
The text states, 'Even among present-day living organisms, we know of several that are adapted to anaerobic conditions.'
Carbohydrates are the most common respiratory substrates. What is their Respiratory Quotient (RQ) when completely oxidized?
The NCERT states, 'When carbohydrates are used as substrate and are completely oxidised, the RQ will be 1, because equal amounts of $CO_2$ and $O_2$ are evolved and consumed, respectively, as shown in the equation below: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + Energy$ . Thus, RQ = $6/6 = 1$.'
Which of the following statements BEST defines an amphibolic pathway?
The NCERT text states: 'The respiratory pathway is an amphibolic pathway as it involves both anabolism and catabolism.' This clearly defines an amphibolic pathway as one that participates in both constructive and destructive metabolic processes.
The respiratory pathway is considered amphibolic because:
The NCERT states, 'Since respiration involves breakdown of substrates, the respiratory process has traditionally been considered a catabolic process... But... it is these very compounds that would be withdrawn from the respiratory pathway for the synthesis of the said substrates.' This dual role of breaking down substrates and providing precursors for synthesis makes it amphibolic.
If fatty acids are to be utilized as a respiratory substrate, they are first degraded to:
The NCERT text mentions: 'Fats would need to be broken down into glycerol and fatty acids first. If fatty acids were to be respired they would first be degraded to acetyl CoA and enter the pathway.'
Glycerol, when used as a respiratory substrate, enters the pathway after being converted to:
The NCERT states: 'Glycerol would enter the pathway after being converted to PGAL.'
Proteins, after degradation by proteases and deamination, can enter the respiratory pathway as:
According to the NCERT: 'The proteins would be degraded by proteases and the individual amino acids (after deamination) depending on their structure would enter the pathway at some stage within the Krebs’ cycle or even as pyruvate or acetyl CoA.'
Which of the following is an example of an anabolic process within the respiratory pathway?
Anabolism refers to synthesis. While the respiratory pathway primarily involves catabolic breakdown for energy, intermediates can be 'withdrawn from the respiratory pathway for the synthesis of the said substrates,' such as fats, which is an anabolic process.
A key characteristic that distinguishes the respiratory pathway as amphibolic is that its intermediates:
The NCERT states: 'the carbon skeleton produced during respiration is used as precursors for biosynthesis of other molecules in the cell.' This highlights the anabolic role of respiratory intermediates, making the pathway amphibolic.
Why is it inaccurate to purely label the respiratory pathway as 'catabolic'?
The NCERT explicitly questions this understanding: 'But is this understanding correct? We have discussed above, at which points in the respiratory pathway different substrates would enter if they were to be respired... What is important to recognise is that it is these very compounds that would be withdrawn from the respiratory pathway for the synthesis of the said substrates.' This demonstrates its amphibolic nature.
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The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.