Respiration in Plants NEET PYQReal NEET & AIPMT 2005–2021 questions, year-tagged, with solutions
By the RankUp team, founded by Dr. Deepak Sahu (MBBS Gold Medalist, NEET PG AIR 1731) · Updated
Every Respiration in Plants question from the NEET & AIPMT papers on this site (2005–2021), newest first. Each is tagged with its paper. Tap an option to check your answer and read the explanation.
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Respiration in Plants previous year questions
22 questions. Tap an option to check your answer.
Q1NEET 2021
Which of the following statements is incorrect ?
Not quite — the answer is B.
In the electron transport chain one NADH + H⁺ yields 3 ATP and one FADH₂ yields 2 ATP, so the statement has the numbers swapped and is incorrect. Oxygen acts only at the end as the final electron acceptor, and ATP is made by complex V (ATP synthase) using the proton gradient.
Q2NEET 2020 · Q85
The number of substrate level phosphorylations in one turn of citric acid cycle is:
Not quite — the answer is B.
In one turn of the Krebs cycle only one substrate-level phosphorylation occurs: succinyl-CoA is converted to succinic acid with formation of one GTP (or ATP). The other ATP comes from oxidative phosphorylation of NADH and FADH₂, so zero, two or three are wrong.
Q3NEET 2019 · Q95
Respiratory Quotient (RQ) value of tripalmitin is :
Not quite — the answer is B.
2 C₅₁H₉₈O₆ + 145 O₂ → 102 CO₂ + 98 H₂O + energy, so RQ = 102/145 ≈ 0.7. RQ values for fats are below 1 because fats need more oxygen for oxidation; values like 0.07 are off by a factor of ten.
Q4NEET 2019 · Q148
Conversion of glucose to glucose-6-phosphate, the first irreversible reaction of glycolysis, is catalyzed by :
Not quite — the answer is B.
Hexokinase phosphorylates glucose to glucose-6-phosphate using ATP. Phosphofructokinase catalyses the later phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate.
Q5NEET 2018 · Q96
What is the role of NAD⁺ in cellular respiration?
Not quite — the answer is B.
NAD⁺ is a coenzyme that accepts electrons and hydrogen during glycolysis and the Krebs cycle, becoming NADH, and hands them to the electron transport chain. It is not an enzyme itself, and it is not a final electron acceptor; NADH is reoxidised during fermentation but the final acceptor there is an organic molecule such as pyruvate or acetaldehyde.
Q6NEET 2018 · Q170
Which of these statements is incorrect?
Not quite — the answer is D.
Oxidative phosphorylation is carried out by the electron transport chain and ATP synthase located in the inner mitochondrial membrane, not the outer membrane. The other statements are correct: glycolysis is cytosolic and needs a supply of NAD⁺, and TCA enzymes lie in the matrix (succinate dehydrogenase being bound to the inner membrane).
Q7NEET 2017 · Q68
Which statement is wrong for Krebs' cycle?
Not quite — the answer is D.
The Krebs cycle begins when acetyl CoA condenses with oxaloacetic acid and water to form citric acid, not with pyruvic acid; pyruvate is converted to acetyl CoA before the cycle. The cycle does have three NAD⁺ reductions, one FAD reduction and substrate-level GTP formation from succinyl CoA.
Q8NEET 2017 (Gujarati paper) · Q65
Which of the following values will depict correct respiratory quotient when tripalmitin (a fatty acid) is used as a respiratory substrate?
Not quite — the answer is B.
For tripalmitin, 2C₅₁H₉₈O₆ + 145 O₂ → 102 CO₂ + 98 H₂O, so RQ = 102/145 ≈ 0.7. Fats are poor in oxygen and need more O₂ than the CO₂ they release; an RQ of 1 applies to carbohydrates.
Q9NEET 2016 Phase 2 · Q108
Which of the following biomolecules is common to respiration-mediated breakdown of fats, carbohydrates and proteins?
Not quite — the answer is D.
Fatty acids are broken down by beta-oxidation to acetyl CoA, glucose gives pyruvate which becomes acetyl CoA, and many amino acids also enter as acetyl CoA, so it is the common entry point into the Krebs cycle. Pyruvic acid is not formed from fatty acids, and the sugar phosphates belong only to glycolysis.
Q10NEET 2016 Phase 2 · Q142
Oxidative phosphorylation is
Not quite — the answer is D.
In oxidative phosphorylation electrons removed from substrates (as NADH and FADH₂) pass along the electron transport chain, and the energy released drives ATP synthase to make ATP from ADP and Pi. Direct transfer of a phosphate from a substrate to ADP is substrate-level phosphorylation.
Q11AIPMT 2015
Cytochromes are found in:
Not quite — the answer is D.
Cytochromes are electron carriers of the electron transport chain, which lies in the inner mitochondrial membrane, folded into cristae. The matrix holds the Krebs cycle enzymes, not the cytochromes.
Q12AIPMT 2014
In which one of the following processes CO₂ is not released?
Not quite — the answer is C.
In lactic acid fermentation pyruvate is reduced directly to lactate by NADH, with no decarboxylation step, so no CO₂ is given off. Alcoholic fermentation releases CO₂ when pyruvate is decarboxylated to acetaldehyde, and aerobic respiration in both plants and animals releases CO₂ in the link reaction and the Krebs cycle.
Q13AIPMT 2011 Mains
In mitochondria, protons accumulate in the
Not quite — the answer is A.
During electron transport, complexes in the inner membrane pump protons from the matrix into the intermembrane space, where they build up; their return through ATP synthase drives ATP formation. Protons are pumped out of the matrix, so they do not accumulate there.
Q14AIPMT 2010 Prelims · Q142
The energy releasing metabolic process in which substrate is oxidised without an external electron acceptor is called
Not quite — the answer is C.
In fermentation, NADH from glycolysis is reoxidised by reducing an internal organic molecule (pyruvate or acetaldehyde), so no external electron acceptor such as O₂ is needed. Aerobic respiration uses O₂ as the final external acceptor. Glycolysis is only one stage and needs NAD⁺ to be regenerated.
Q15AIPMT 2009 Prelims · Q102
Aerobic respiratory pathway is appropriately termed:
Not quite — the answer is B.
NCERT calls the respiratory pathway amphibolic because it breaks down substrates (catabolism) and also supplies intermediates for synthesis of fatty acids, amino acids etc. (anabolism). Calling it only catabolic misses this dual role.
Q16AIPMT 2008 Prelims · Q131
The chemiosmotic coupling hypothesis of oxidative phosphorylation proposes that adenosine triphosphate (ATP) is formed because
Not quite — the answer is D.
According to the chemiosmotic hypothesis, the electron transport chain pumps protons into the intermembrane space, building a proton gradient across the inner mitochondrial membrane. Protons flowing back through F₀-F₁ ATP synthase drive ATP formation; high-energy protein intermediates were part of an older, rejected hypothesis.
Q17AIPMT 2008 Prelims · Q140
The energy releasing process in which the substrate is oxidised without an external electron acceptor is called
Not quite — the answer is B.
In fermentation the NADH produced during glycolysis is reoxidised by passing electrons to an organic product of the substrate itself (pyruvate or acetaldehyde), so no external acceptor such as O₂ is needed. Aerobic respiration depends on oxygen as the terminal external acceptor.
Q18AIPMT 2007 Prelims · Q146
All enzymes of TCA cycle are located in the mitochondrial matrix except one which is located in inner mitochondrial membranes in eukaryotes and in cytosol in prokaryotes. This enzyme is
Not quite — the answer is C.
Succinate dehydrogenase is bound to the inner mitochondrial membrane, where it also forms complex II of the electron transport chain. Lactate dehydrogenase is not a Krebs cycle enzyme at all, and the other dehydrogenases are in the matrix.
Q19AIPMT 2007 Prelims · Q173
The overall goal of glycolysis, Krebs cycle and the electron transport system is the formation of
Not quite — the answer is D.
Respiration oxidises glucose in many small enzyme-controlled steps so that the released energy can be trapped as ATP gradually rather than lost as heat in one burst. These pathways break sugars down; they do not make sugars or nucleic acids.
Q20AIPMT 2007 Prelims · Q179
Which one of the following mammalian cells is not capable of metabolising glucose to carbon dioxide aerobically?
Not quite — the answer is C.
Mature mammalian red blood cells lack mitochondria, so they cannot run the Krebs cycle and electron transport and depend on glycolysis to lactate. Liver, muscle and white blood cells have mitochondria and respire aerobically.
Q21AIPMT 2006 Prelims · Q136
How many ATP molecules could maximally be generated from one molecule of glucose, if the complete oxidation of one mole of glucose to CO₂ and H₂O yields 686 kcal and the useful chemical energy available in the high energy phosphate bond of one mole of ATP is 12 kcal ?
Not quite — the answer is C.
If all 686 kcal could be stored in ATP at 12 kcal per ATP, the maximum would be 686 / 12 ≈ 57 ATP. Thirty is close to the real yield from respiration, but the question asks for the theoretical maximum from the numbers given.
Q22AIPMT 2005 Prelims · Q153
During which stage in the complete oxidation of glucose are the greatest number of ATP molecules formed from ADP ?
Not quite — the answer is B.
Most of the ATP from aerobic respiration (about 34 of 38 in the older count) is made by oxidative phosphorylation as NADH and FADH₂ pass electrons down the electron transport chain. Glycolysis and the Krebs cycle make only a few ATP directly, by substrate-level phosphorylation.
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