Respiration in Plants is a Class 11 Botany chapter in the NEET (UG) syllabus. NEET720 has 721 reviewed practice questions on it, each with a quick answer and a step-by-step explanation. The 8 questions below are free and fixed, so you can bookmark this page; the full chapter, plus mistake tracking and spaced revision, is in the app.
121
easy
449
medium
151
hard
Topics covered
Glycolysis and Fermentation · Krebs Cycle · Electron Transport and Energy Yield · Cyanide-Resistant Pathway · Respiratory Substrates and RQ · Respiration vs Photosynthesis · Factors Affecting Respiration Rate · Anaerobic Respiration in Plants · Climacteric Respiration · Total ATP Accounting · Oxidative phosphorylation · Electron transport system · Mitochondrion · Respiration and photosynthesis · Respiration in tissues · Respiration rate · Cellular respiration · Respiration and germination · Pyruvate oxidation · ATP balance sheet · Fat Mobilization and the Glyoxylate Cycle · Fat Mobilization and Beta-Oxidation · Factors Affecting the Rate of Respiration · Respiration under Waterlogged Conditions · Respiration and Gas Exchange · Glycolysis · Aerobic Respiration · Amphibolic Pathway · Respiratory Substrates · Cellular Respiration Overview · Respiration in Plants · Respiration · Pentose Phosphate Pathway · ATP accounting chain · Fermentation regulation · Respiratory quotient · Alternative oxidase pathway · Climacteric fruit ripening · Anoxia tolerance · Glycolysis regulation
8 free Respiration in Plants practice questions with answers
Choose an answer in your head before opening it. Each explanation says why the correct option is right and, where relevant, why the tempting wrong option is wrong.
Question 1 · easy · Electron Transport and Energy Yield
The electron transport chain (ETC) of aerobic respiration is located in which part of the mitochondrion?
- A.Outer mitochondrial membrane
- B.Inner mitochondrial membrane
- C.Mitochondrial matrix
- D.Intermembrane space
Show answer and explanation
Answer: B. Inner mitochondrial membrane
The ETC complexes are integral proteins embedded in the inner mitochondrial membrane, which is thrown into cristae to increase surface area.
NCERT states that the electron transport system (Complex I-IV) along with ATP synthase are located on the inner mitochondrial membrane. The outer membrane is smooth and permeable to most small molecules via porins; the matrix houses the Krebs cycle enzymes and pyruvate dehydrogenase; the intermembrane space accumulates protons pumped across the inner membrane but does not itself contain the carrier complexes.
Common mistake: Placing the ETC in the matrix along with the Krebs cycle enzymes.
Key point: ETC and ATP synthase = inner mitochondrial membrane; Krebs cycle = matrix.
Question 2 · easy · Electron Transport and Energy Yield
Complex I of the electron transport chain is also known as:
- A.Succinate dehydrogenase
- B.NADH dehydrogenase
- C.Cytochrome c oxidase
- D.Cytochrome bc1 complex
Show answer and explanation
Answer: B. NADH dehydrogenase
Complex I (NADH dehydrogenase) accepts electrons from NADH produced during glycolysis, pyruvate oxidation and the Krebs cycle.
NADH generated in the matrix donates its electrons to Complex I (NADH dehydrogenase), which then passes them via ubiquinone toward Complex III. Complex II is succinate dehydrogenase, Complex III is cytochrome bc1, Complex IV is cytochrome c oxidase.
Common mistake: Naming Complex I as succinate dehydrogenase.
Key point: NADH enters the chain at Complex I; remember I-II-III-IV order and their common names.
Question 3 · medium · Electron Transport and Energy Yield
FADH2 generated during the Krebs cycle donates its electrons to the electron transport chain by entering at:
- A.Complex I, the same point as NADH
- B.Complex II, bypassing Complex I
- C.Complex III directly
- D.Complex IV directly
Show answer and explanation
Answer: B. Complex II, bypassing Complex I
FADH2 (produced at the succinate dehydrogenase step of the Krebs cycle) donates electrons to Complex II, which feeds ubiquinone directly, bypassing Complex I.
Complex II is succinate dehydrogenase itself, the enzyme that oxidizes succinate to fumarate while reducing FAD to FADH2 in situ within the inner membrane. Because Complex II electrons enter downstream of Complex I, fewer protons are pumped across the membrane per FADH2 compared to per NADH, explaining the lower ATP yield of FADH2 relative to NADH.
Common mistake: Assuming NADH and FADH2 both enter the chain identically at Complex I.
Key point: FADH2 enters at Complex II, not Complex I — this is why it yields less ATP than NADH.
Question 4 · easy · Electron Transport and Energy Yield
Which complex of the electron transport chain transfers electrons to molecular oxygen, the final electron acceptor, forming water?
- A.Complex I
- B.Complex II
- C.Complex III
- D.Complex IV (cytochrome c oxidase)
Show answer and explanation
Answer: D. Complex IV (cytochrome c oxidase)
Complex IV, cytochrome c oxidase, is the terminal complex that reduces O2 to H2O using electrons delivered by cytochrome c.
Electrons flow sequentially Complex I/II to ubiquinone to Complex III to cytochrome c to Complex IV, where they finally combine with O2 and protons to form water. This is why oxygen is essential for aerobic respiration to continue — without it, electron flow backs up and the chain halts.
Common mistake: Believing Complex III is the last step since it directly precedes cytochrome c.
Key point: Complex IV = cytochrome c oxidase = terminal electron acceptor step forming H2O.
Question 5 · medium · Electron Transport and Energy Yield
Which pair of molecules functions as MOBILE electron carriers, shuttling electrons between the fixed protein complexes of the ETC?
- A.Ubiquinone and cytochrome c
- B.NADH and FADH2
- C.ATP synthase and pyruvate dehydrogenase
- D.Complex I and Complex III
Show answer and explanation
Answer: A. Ubiquinone and cytochrome c
Ubiquinone (coenzyme Q) shuttles electrons from Complex I/II to Complex III, while cytochrome c shuttles electrons from Complex III to Complex IV.
Unlike the large multi-subunit complexes I-IV that are fixed within the membrane, ubiquinone is a small lipid-soluble molecule that diffuses within the membrane, and cytochrome c is a small peripheral protein on the outer face of the inner membrane in the intermembrane space — both mobile, linking the fixed complexes in sequence.
Common mistake: Calling NADH/FADH2 the mobile carriers of the chain instead of electron donors that feed it.
Key point: Ubiquinone links I/II to III; cytochrome c links III to IV — both are mobile carriers.
Question 6 · medium · Electron Transport and Energy Yield
During oxidative phosphorylation, protons are pumped from the mitochondrial matrix into the intermembrane space by Complexes I, III and IV. What is the immediate consequence of this pumping?
- A.A pH decrease and positive charge build-up in the matrix
- B.Direct phosphorylation of ADP within the intermembrane space without ATP synthase
- C.Diffusion of electrons back into the matrix to re-reduce NAD+
- D.An electrochemical proton gradient (proton motive force) across the inner membrane, with the intermembrane space more acidic and positive
Show answer and explanation
Answer: D. An electrochemical proton gradient (proton motive force) across the inner membrane, with the intermembrane space more acidic and positive
Proton pumping creates a proton-rich, more acidic and more positively charged intermembrane space relative to the matrix, establishing the proton motive force that drives ATP synthase.
As electrons pass through Complexes I, III and IV, energy released is used to actively transport H+ ions from the matrix to the intermembrane space. This generates both a concentration gradient (pH gradient) and an electrical gradient across the inner membrane — together the proton motive force — which is dissipated productively only through ATP synthase, driving ATP formation as protons flow back into the matrix.
Common mistake: Reversing which compartment becomes proton-rich.
Key point: Proton pumping makes the intermembrane space acidic and positive relative to the matrix — this gradient is the proton motive force.
Question 7 · medium · Electron Transport and Energy Yield
As per the commonly cited NCERT approximation, the complete aerobic oxidation of one glucose molecule (glycolysis + link reaction + Krebs cycle + ETC) yields approximately how many ATP molecules?
- A.2 ATP
- B.8 ATP
- C.36 ATP
- D.100 ATP
Show answer and explanation
Answer: C. 36 ATP
NCERT commonly cites approximately 36 ATP as the total yield per glucose from complete aerobic respiration, combining substrate-level phosphorylation and oxidative phosphorylation.
This figure sums 2 ATP (glycolysis, net substrate-level) + 2 ATP-equivalent (Krebs cycle GTP) + ATP generated via the ETC from the ~10 NADH and ~2 FADH2 produced across glycolysis, link reaction and Krebs cycle. The exact number varies by textbook and shuttle-system convention (some sources cite 36-38), but NCERT's commonly used figure is 36 ATP. Students should understand this is an approximate accounting figure, not a fixed universal constant.
Common mistake: Quoting only the 2 net ATP of glycolysis as the total respiratory yield.
Key point: NCERT's standard approximate figure: ~36 ATP per glucose via aerobic respiration.
Question 8 · medium · Electron Transport and Energy Yield
Arrange the following in the correct sequence of electron flow through the mitochondrial electron transport chain, starting from NADH oxidation: (i) Cytochrome c (ii) Complex III (cytochrome bc1) (iii) Complex I (NADH dehydrogenase) (iv) Ubiquinone (v) Complex IV (cytochrome c oxidase)
- A.(iii) → (iv) → (ii) → (i) → (v)
- B.(iii) → (i) → (iv) → (ii) → (v)
- C.(iv) → (iii) → (ii) → (i) → (v)
- D.(iii) → (iv) → (v) → (ii) → (i)
Show answer and explanation
Answer: A. (iii) → (iv) → (ii) → (i) → (v)
Electrons flow: Complex I to ubiquinone to Complex III to cytochrome c to Complex IV, finally reducing oxygen to water.
NADH reduces Complex I; Complex I passes electrons to the lipid-soluble ubiquinone, which diffuses to Complex III; Complex III passes electrons to the small mobile protein cytochrome c; cytochrome c delivers electrons to Complex IV, which reduces O2 to H2O. Memorizing this order (I → Q → III → cyt c → IV) is essential for sequence-based NEET questions.
Common mistake: Swapping the order of the two mobile carriers, ubiquinone and cytochrome c.
Key point: Order: Complex I → ubiquinone → Complex III → cytochrome c → Complex IV.
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Questions about Respiration in Plants for NEET
How many NEET questions does NEET720 have on Respiration in Plants?＋
NEET720 has 721 reviewed practice questions on Respiration in Plants (Botany): 121 easy, 449 medium and 151 hard. 8 of them are free on this page with full explanations; the rest are available in the app.
Is Respiration in Plants a Class 11 or Class 12 chapter for NEET?＋
Respiration in Plants is a Class 11 Botany chapter in the NEET (UG) syllabus. Read the NCERT chapter first, then practise chapter-wise MCQs and previous-year questions.
How should I practise Respiration in Plants for NEET?＋
Attempt the questions below without looking at the options for more than a few seconds, mark your answer, then read the explanation even when you were right. Record every mistake and revisit it after a gap. On NEET720 this happens automatically: wrong answers go to your Mistake Book and are scheduled for spaced revision.
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Questions are original NEET720 compositions reviewed for correctness, syllabus fit and option quality. Counts update as the bank grows (721 active practice questions in this chapter today).