NEET BotanyUpdated 19 Oct 2026

Respiration in Plants: NEET PYQs and weightage

Respiration in Plants carries 2.5 of 100 Botany marks in NEET by past-paper share: 20 of the 793 tagged NEET Botany PYQs in the ViJEEta bank (NEET 2013–2026). It ranks 16 of 21 Botany chapters.

Take the 25-question Respiration in Plants test Key facts ↓All NEET Botany chapters

2.5/100 Weight in Botany

Exam importance (3/5, by past-paper share)

20 NEET PYQs

426 Practice questions

339 With measured difficulty

How the weight is computed: this chapter's tagged NEET PYQs divided by all tagged NEET Botany PYQs in the bank (20 of 793), times 100, with repeated questions counted once. The bank does not store the year of each NEET question, so none is printed. Computed from the bank at build time. Updated 19 Oct 2026.

Respiration in Plants: key facts for NEET

17 facts the paper keeps asking, each with how it is asked. Copy it onto one page of your notebook: that page is this chapter's handbook.

Respiration and respiratory substrate
Respiration is the oxidation (breaking of $C - C$ bonds) of complex compounds inside cells to release energy; the compounds oxidised are respiratory substrates, and glucose is the favoured one.
Asked as: Which is the most common respiratory substrate, or which statement correctly defines respiration?
Gas exchange in plants
Plants have no specialised respiratory organs; gas exchange happens by diffusion through stomata and lenticels, helped by loosely packed parenchyma with air spaces.
Asked as: Why can plants manage without respiratory organs? (Each part handles its own gases, demand is low, and diffusion distances are short.)
Glycolysis (EMP pathway)
Glycolysis is the EMP pathway (Embden, Meyerhof, Parnas). It runs in the cytoplasm of all living organisms and splits 1 glucose into 2 pyruvic acid; it is the only respiratory process in anaerobes.
Asked as: Site of glycolysis, or match the scientists to the EMP pathway.
Entry of sugars into glycolysis
Invertase splits sucrose into glucose and fructose; hexokinase phosphorylates them to glucose-6-phosphate, which isomerises to fructose-6-phosphate. Glycolysis is a chain of 10 enzyme reactions.
Asked as: Match the enzyme to its step (invertase, hexokinase).
ATP-consuming steps of glycolysis
ATP is used at 2 steps: glucose $\to$ glucose-6-phosphate, and fructose-6-phosphate $\to$ fructose 1,6-bisphosphate.
Asked as: In which conversions is ATP consumed in glycolysis?
NADH- and ATP-forming steps of glycolysis
$NADH + H^{+}$ forms at PGAL $\to$ BPGA. ATP forms at BPGA $\to$ 3-PGA and at PEP $\to$ pyruvic acid.
Asked as: Identify the step that is an oxidation, or the steps that make ATP directly.
Alcoholic and lactic acid fermentation
In alcoholic fermentation (yeast), pyruvic acid $\to C O_{2}$ + ethanol via pyruvic acid decarboxylase and alcohol dehydrogenase. In muscles short of $O_{2}$ , pyruvic acid $\to$ lactic acid via lactate dehydrogenase. $NADH + H^{+}$ is reoxidised to $NA D^{+}$ in both.
Asked as: Match the enzyme to the fermentation type, or name the reducing agent.
Energy yield and limit of fermentation
Fermentation releases less than $7%$ of the energy in glucose; yeast poisons itself at about $13%$ alcohol.
Asked as: What is the maximum alcohol concentration in naturally fermented beverages?
Oxidative decarboxylation of pyruvate
In the mitochondrial matrix, pyruvate undergoes oxidative decarboxylation by pyruvic dehydrogenase (needs $NA D^{+}$ , CoA, $M g^{2 +}$ ) to give acetyl CoA, $C O_{2}$ and NADH. That is 2 NADH per glucose.
Asked as: Which cofactors/coenzymes does pyruvate dehydrogenase need?
Krebs' cycle: early steps
Krebs' (TCA/citric acid) cycle, named after Hans Krebs, runs in the matrix. Acetyl group + OAA (4C) + water $\to$ citric acid (6C) via citrate synthase, then isocitrate $\to$ $α$ -ketoglutaric acid (5C) $\to$ succinyl-CoA.
Asked as: First product of the Krebs' cycle, or the carbon number of OAA / $α$ -KG / citric acid.
Substrate level phosphorylation and yield per turn
The conversion of succinyl-CoA $\to$ succinic acid makes 1 GTP (substrate level phosphorylation), which is then used to make ATP. Each turn of the cycle produces 3 $NADH + H^{+}$ and 1 $FAD H_{2}$ .
Asked as: Which step of the TCA cycle shows substrate level phosphorylation?
Electron transport system (ETS)
ETS is on the inner mitochondrial membrane: complex I (NADH dehydrogenase) $\to$ ubiquinone (which also gets electrons from $FAD H_{2}$ via complex II) $\to$ complex III (cytochrome $b c_{1}$ ) $\to$ cytochrome c $\to$ complex IV (cytochrome c oxidase: cyt a, $a_{3}$ and 2 copper centres).
Asked as: Which carrier is mobile between complex III and IV? (Cytochrome c, attached to the outer surface of the inner membrane.)
Oxidative phosphorylation
1 NADH gives 3 ATP and 1 $FAD H_{2}$ gives 2 ATP. $O_{2}$ is the final hydrogen acceptor and is reduced to water. ATP made using redox energy is called oxidative phosphorylation.
Asked as: What is the role of $O_{2}$ in respiration, or how many ATP come from one $FAD H_{2}$ ?
ATP synthase (complex V)
ATP synthase (complex V) has two parts. $F_{1}$ is the peripheral headpiece and holds the ATP-synthesis site. $F_{0}$ is integral to the membrane and forms the proton channel. 4 $H^{+}$ move from the intermembrane space to the matrix for each ATP.
Asked as: Which part forms the proton channel, or how many $H^{+}$ are needed per ATP?
Respiratory balance sheet
The theoretical net gain is 38 ATP per glucose in aerobic respiration, compared with a net 2 ATP in fermentation. The 38 figure assumes a sequential pathway, glycolytic NADH entering mitochondria, no intermediates withdrawn, and only glucose respired.
Asked as: Which assumption is NOT made in the ATP balance sheet?
Amphibolic pathway
The respiratory pathway is amphibolic (both catabolic and anabolic). Fatty acids enter as acetyl CoA, glycerol as PGAL, and amino acids (after deamination) as pyruvate, acetyl CoA or Krebs' intermediates.
Asked as: At what point does glycerol or a fatty acid enter respiration, or why is the pathway called amphibolic?
Respiratory quotient (RQ)
$RQ = \frac{volume of C O _{2} evolved}{volume of O _{2} consumed}$
Carbohydrates give 1, fats less than 1 (tripalmitin $\frac{102}{145} \approx 0.7$ ), and proteins about 0.9.
Asked as: What is the RQ of tripalmitin or of fats, or which substrate gives $RQ = 1$ ?

Trap

Glycolysis makes 4 ATP directly but uses 2, so the net is only 2 ATP per glucose. Also, O₂ is not used in the Krebs' cycle itself; it acts only at the end of the ETS as the final hydrogen acceptor.

How does NEET ask Respiration in Plants?

8 real previous-year questions from this chapter, as printed in the paper, each with its worked solution. Answer the first one here with no sign-in.

Q1BotanyNEET UG PYQElectron Transport System and Oxidative Phosphorylation

Try right here · No sign-in

Which of these statements is incorrect?

Answer key (D) & worked solution

Correct answer: Option D

All the required enzyme for oxidative phosphorylation is present on inner mitochondrial membrane hence it takes place in the inner mitochondrial membrane.

Q2BotanyNEET UG PYQGlycolysis

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: ATP is used at two steps in glycolysis. Reason R: First ATP is used in converting glucose into glucose-6-phosphate and second ATP is used in conversion of fructose-6-phosphate into fructose-1-6-diphosphate. In the light of the above statements, choose the correct answer from the options given below:

ABoth A and R are true, but R is NOT the correct explanation of A.

BA is true, but R is false.

CA is false, but R is true.

DBoth A and R are true, and R is the correct explanation of A.

Answer key (D) & worked solution

Correct answer: Option D

Both A and R are true, and R is the correct explanation of A.

Q3BotanyNEET UG PYQGlycolysis

What is the role of NAD

^{+}

in cellular respiration?

AIt is a nucleotide source for ATP synthesis

BIt functions as an electron carrier

CIt functions as an enzyme

DIt is the final electron acceptor for anaerobic respiration

Answer key (B) & worked solution

Correct answer: Option B

In cellular respiration, NAD

^{+}

acts as an electron carrier. NAD

^{+}

has two functions- co-enzymes and an electron carrier, which acts as an electron acceptor in the process of glycolysis and Krebs’ cycle and provides this electron in ETC (Electron transport chain) for the production of ATP's.

Q4BotanyNEET UG PYQElectron Transport System and Oxidative Phosphorylation

The complex II of mitochondrial electron transport chain is also known as

ACytochrome c oxidase

BNADH dehydrogenase

CCytochrome bc

_{1}

DSuccinate dehydrogenase

Answer key (D) & worked solution

Correct answer: Option D

Complex II- Succinate dehydrogenase: This enzyme is responsible for oxidizing succinate to fumarate in the citric acid cycle. It also plays a crucial role in the electron transport chain by transferring electrons from succinate to ubiquinone (Q).

Q5BotanyNEET UG PYQTricarboxylic Acid Cycle

Match List I with List II: List I List IIA.Oxidative decarboxylationI.Citrate synthaseB.Glycolysis II.Pyruvate dehydrogenaseC.Oxidative phosphorylationIII.Electron transport systemD.Tricarboxylic acid cycleIV.EMP pathway Choose the correct answer from the options given below:

AA–II, B–IV, C–I, D–III

BA–III, B–I, C–II, D–IV

CA–II, B–IV, C–III, D–I

DA–III, B–IV, C–II, D–I

Answer key (C) & worked solution

Correct answer: Option C

List I List IIA.Oxidative decarboxylationII.Pyruvate dehydrogenaseB.Glycolysis IV.EMP pathway C.Oxidative phosphorylationIII.Electron transport systemD.Tricarboxylic acid cycleI.Citrate synthase

Q6BotanyNEET UG PYQGlycolysis

How many molecules of pyruvic acid are produced at the end of glycolysis from 206 molecules of glucose?

A309

B103

C412

D206

Answer key (C) & worked solution

Correct answer: Option C

Two molecules of pyruvic acid are formed at the end of glycolysis from one molecule of glucose. From 206 molecules of glucose, 412 molecules of pyruvic acid are formed.

Q7BotanyNEET UG PYQTricarboxylic Acid Cycle

The number of substrate-level phosphorylations in one turn of citric acid cycle is

ATwo

BThree

CZero

DOne

Answer key (D) & worked solution

Correct answer: Option D

During Krebs' or citric acid cycle, succinyl-CoA is acted upon by enzyme succinyl-CoA synthetase to form succinate (a 4C compound). The reaction releases sufficient energy to form ATP (in plants) or GTP (in animals) by substrate-level phosphorylation. GTP can then be used to form ATP.

Q8BotanyNEET UG PYQRespiratory Quotient

2 (C_{51} H_{98} C_{6}) + 145 O_{2} \to 102 CO_{2} + 98 H_{2} O +

energy

The Respiratory Quotient (RQ) of a biomolecule used for respiration, as per the above equation would be :

ALess than 0.5

BBetween 0.5 and 0.95

CBetween 1.25 and 2

D1.0

Answer key (B) & worked solution

Correct answer: Option B

R . Q = \frac{Volume of CO _{2} evolved}{Volume of O _{2} consumed}

As per the given equation,

2 (C_{51} H_{98} O_{6}) + 145 O_{2} \to 102 CO_{2} + 98 H_{2} O + Energy

Hence the RQ can be calculated as,

R \cdot Q = \frac{102}{145} = 0.7

This value lies between 0.5 and 0.95.

Which topics in Respiration in Plants carry the most questions?

All 10 topics, by tagged PYQs, then practice questions. Counted from the bank. Updated 19 Oct 2026.

Topic	PYQs	Practice questions
Tricarboxylic Acid Cycle	8	80
Glycolysis	5	78
Electron Transport System and Oxidative Phosphorylation	3	83
Respiratory Quotient	2	35
Fermentation	1	51
Miscellaneous Examples	1	10
Respiration in Plants: Introduction	0	38
Amphibolic Pathway	0	25
The Respiratory Balance Sheet	0	18
Do Plants Breathe?	0	8

Why does Respiration in Plants show "–" until you answer 3 questions?

Unknown is not zero. Until you answer at least 3 graded questions in Respiration in Plants, ViJEEta shows – instead of a zero or a 50% default. Book exercises can raise chapter mastery up to 0.60, adaptive practice up to 0.75, and only a timed chapter test or mock can certify 0.80 and above.

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What happens when you test Respiration in Plants?

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Chapters either side of Respiration in Plants by weight

Environmental Issues Weight 3.9/100 Plant Kingdom Weight 3.7/100 Strategies for Enhancement in Food Production Weight 2.1/100 Transport in Plants Weight 2.0/100

Respiration in Plants: NEET PYQs and weightage

Respiration in Plants: key facts for NEET

Respiration and respiratory substrate

Gas exchange in plants

Glycolysis (EMP pathway)

Entry of sugars into glycolysis

ATP-consuming steps of glycolysis

NADH- and ATP-forming steps of glycolysis

Alcoholic and lactic acid fermentation

Energy yield and limit of fermentation

Oxidative decarboxylation of pyruvate

Krebs' cycle: early steps

Substrate level phosphorylation and yield per turn

Electron transport system (ETS)

Oxidative phosphorylation

ATP synthase (complex V)

Respiratory balance sheet

Amphibolic pathway

Respiratory quotient (RQ)

How does NEET ask Respiration in Plants?

Which topics in Respiration in Plants carry the most questions?

Why does Respiration in Plants show "–" until you answer 3 questions?

What happens when you test Respiration in Plants?

Chapters either side of Respiration in Plants by weight