NEET Biology Respiration in Plants Important Questions Set 01

These Class 11 NEET Biology important questions on Respiration in Plants give 45 questions with step-by-step answers, arranged as very short, short and long answer types, as asked in school and board examinations. They help NEET aspirants revise the definitions, structures, differences and key terms of the chapter.

Very Short Answer Type Questions

Question 1. In which phase of respiration the oxidation of NADH takes place?
Answer: Electron transport system.

Question 2. Name the energy currency of cells.
Answer: ATP

Question 3. What is the substrate of TCA cycle?
Answer: Acetyl CoA

Question 4. Who worked out the detailed steps of citric acid cycle?
Answer: Hans Krebs

Question 5. Write the overall equation of aerobic respiration. C₆H₁₂O₆ + 6O₂ —→ 6CO₂ + 6H₂O + 36/38 ATP
Answer:

Question 6. Name the sugars that normally enter glycolysis.
Answer: Glucose and fructose.

Question 7. How many carbon atoms are present in the following molecules? (A) Pyruvate (B) Acetyl CoA (C) Oxaloacetic acid
Answer: (A) Pyruvate – 3 carbons (B) Acetyl CoA – 2 carbons (C) Oxaloacetic acid – 4 carbons.

Question 8. What is the process in which FADH₂ gives rise to ATP molecules?
Answer: Electron transport system.

Question 9. Expand the following : (A) NAD (B) EMP
Answer: (A) NAD – Nicotinamide Adenine Dinucleotide (B) EMP – Embden Meyerhof and Parnas

Question 10. Which protein acts as a mobile carrier in mitochondrial ETC?
Answer: Cytochrome c

Short Answer Type Questions

Question 11. What is the difference between respiration in plants and respiration in animals?

Answer:

2. All part of the plant perform respiration 2. Lungs, trachea etc. are present for individually. respiration.
3. For respiration (gaseous exchange) 3. Lungs (Alveoli) are present for stomata, lenticels or root hairs are respiration. present.

Question 12. Define glycolysis. Where does it occur?
Answer: Glycolysis a common pathway of aerobic or anaerobic respiration which leads to the breakdown of glucose into 2 pyruvic acid molecules by series of steps catalysed by using various enzymes. It occurs in the cytoplasm of the cell.

Question 13. Name the complex which is associated with F₀ – F₁ in mitochondria. How many molecules of ATP are produced when one molecule of NADH goes through this pathway? What is the role of F₀ – F₁ in this pathway?
Answer: Complex V i.e., ATP synthase is associated with F₀ – F₁ in mitochondria. 3 ATP molecules are produced when one molecule of NADH is oxidised. F₀ part of oxysome function as proton tunnels, stalk part of elementary particles have coupling factors while heads F₁ part have ATP synthase for ATP synthesis.

Question 14. Though we say that aerobic respiration uses oxygen, it is that none of the pathway or cycle (glycolysis, Krebs cycle) utilizes it then, where is oxygen used?
Answer: Oxygen acts as the final₊ hydrogen acceptor and terminal electron acceptor in electron transport system. It combines with the 2H ions to form H₂O molecule. Six oxygen atoms form 6H₂O molecules.

Question 15. Anaerobic respiration has infinite RQ value, why?

Answer:

The ratio of the volume of CO₂ evolved to the volume of O₂ consumed in respiration is called the respiratory quotient (RQ).

RQ = Volume of CO₂ evolved / Volume of O₂ consumed

For anaerobic condition (fermentation): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (glucose to alcohol).

RQ = 2CO₂ / 0 O₂ = ∞

Question 16. Human beings are highly evolved species yet it is seen that they may undergo anaerobic respiration. Explain.

Answer:

Anaerobic respiration refers to the respiration in absence of oxygen. During vigrous exercise when oxygen supply falls short (i.e., lack of oxygen) our skeletal muscle cells they instead of carrying out Krebs cycle start producing lactic acid and supply energy to the body.

CH₃COCOOH —Lactic acid dehydrogenase→ CH₃CHOHCOOH + Energy (Pyruvic acid)

Question 17. Which process of respiration is more efficient aerobic or anaerobic? Explain giving equation.
Answer: Energy released during aerobic respiration is 36 or 38 ATP and that by anaerobic respiration is only 2 ATP. Mitochondria CO₂ + H₂O + 36 or 38 ATP (O2 present) + 2 NADH₊ ₄ + H + ATP 2 NADH + H Glucose Pyruvic acid CO₂ + C₂H₅OH + 2 ATP (absence of O2) 2 ATP + 2 NADH + H Lactic acid + 2 ATP (lack of oxygen)

Question 18. Tree trunk does not have stomata then how do they respire as no respiratory organs are present in the plants.
Answer: (i) In woody stems, the living cells are organised in thin layers inside and beneath the bark.
(ii) They have lenticels.
(iii) Parenchyma cells are loosely arranged.

Question 19. How red muscle fibers in animals work for longer periods of time?
Answer: Red muscle fibres possess a respiratory pigment called myoglobin. This myoglobin is capable of storing and transporting a lot of oxygen inside the muscle fibres. They are associated with many blood capillaries as well as they split ATP at a very slow rate and are resistant to fatigue. Therefore, red muscle fibres can work continuously for long periods without getting fatigued.

Question 20. Though energywise fats give more kilocalories per gram compared to carbohydrates but they have less value of RQ than carbohydrates. Explain.

Answer:

Amount of energy obtained from fat is 9 kcal/gm while that from carbohydrate is 4 kcal/gm but respiratory quotient is defined as the ratio of the volume of CO₂ evolved to the volume of O₂ consumed in respiration. For carbohydrates : 6CO₂ RQ = = 1 6O₂ ∵ C₆H₁₂O₆ + 6O₂ —→ 6CO₂ + 6H₂O + Energy For fats : 102CO₂ RQ = = 0.7 145O₂ 2(C₅₁H₉₈O₆) + 145O₂ —→ 102CO₂ + 98H₂O + Energy Tripalmitin

Thus, the value of RQ for carbohydrates is more though energy given by it is less.

Question 21. Write the difference between floating respiration and protoplasmic respiration.

Answer:

Floating respiration Protoplasmic respiration

1. Here respiratory substrate is fat or 1. Hererespiratory substrateis protein. carbohydrate.

Question 22. What is the anabolic function of respiration?
Answer: Various intermediates of the pathway of respiration are precursors of various compounds.
(i) Acetyl CoA → raw material for carotenoids, gibberellins etc.
(ii) Succinyl CoA → raw material for chlorophyll, cytochrome.
(iii) Oxaloacetic acid → raw material for alkaloids, pyrimidines.
(iv) α-ketoglutaric acid → raw material for amino acid synthesis.

Question 23. Anaerobic respiration is also a source of economic value. Explain.

Answer:

Certain bacteria and yeast show anaerobic respiration.

(i) Yeast when inoculated in the sugar solution helps in the production of alcohol (ethanol). Thus in wine industry it is used to for making wine from sugar present in grapes and in germinating grains of barley.

(ii) Yeast on fermentation it releases CO₂ thus this process is also used in bakeries for production of bakery products.

(iii) Lactobacillus (Lactic acid bacteria) produces lactic acid which is used in various yoghurt companies to form curd and yoghurt.

Question 24. Write a note on oxidative decarboxylation of pyruvate.

Answer:

Pyruvate formed by glycolysis enters mitochondrial matrix from cytoplasm. Pyruvate dehydrogenase catalyzes the conversion of pyruvate to acetyl CoA by removing CO₂ molecules.

+ + + —Mg²+ → + + + + Pyruvic acid CoA NAD Acetyl CoA CO₂ NADH H Pyruvate dehydrogenase (3C)

2 molecules of pyruvic acid formed during glycolysis undergo the formation of acetyl CoA and hence 2 molecules of acetyl CoA, 2CO₂ and 2NADH + 2H⁺ are formed.

Question 25. Only non-green cells undergo respiration is it true or not? Give explanation to your answer.
Answer: Only green plants and cyanobacteria can prepare their own food by the process of photosynthesis by trapping light energy and converting it into chemical energy that is stored in the bonds of carbohydrates like glucose, sucrose and starch, cells that are nongreen need food for oxidation while cells with chloroplast store the food in the cell so it is not true that only non-green cells undergo respiration. Green cells show respiration both during day and night.

Question 26. Where is pyruvic acid synthesized in our body? Write down the step in which pyruvic acid is formed.
Answer: Pyruvic acid is synthesized during glycolysis in our cytoplasm of the cell. Pyruvate kinase 2-phosphoenolpyruvate Pyruvic acid ADP ATP

Question 27. Give a point of difference between obligate and facultative anaerobes.
Answer: Obligate anaerobes Facultative anaerobes These are those which cannot Aerobic organisms which may useoxygen for growth. growwithoutoxygen.

Question 28. Why are the assumptions made for calculation of the net gain of ATP not really valid in a living systems?
Answer: It is because 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 36 ATP molecules during aerobic respiration of one molecule of glucose.

Question 29. Explain the net gain of ATP in aerobic respiration.

Answer:

There is a net gain of 38ATP molecules during aerobic respiration of one molecule of glucose as shown below:

(i) Glycolysis 4 ATP (SLP) = 4 ATP

2 molecules of NADH = 6 ATP

(ii) Pyruvic acid to Acetyl CoA 2 molecules of NADH = 6 ATP

(iii) Krebs cycle 6 molecules of NADH = 18 ATP

2 molecules of FADH₂ = 4 ATP

2 molecules of ATP = 2 ATP

Total 40 ATP ∴ Net gain = 38 or 36 ATP depending on type of shuttle system involved in aerobic respiration.

Question 30. Compare the fermentation and aerobic respiration (w.r.t. net gain of ATP and rate of oxidation of NADH)

Answer:

In fermentation there is a net gain of only two molecules of ATP for each molecule of glucose degraded to pyruvic acid whereas many more molecules of ATP are generated under aerobic conditions.

NADH is oxidised to NAD⁺ rather slowly in fermentation, however the reaction is very vigorous in case of aerobic respiration.

Long Answer Type Questions

Question 31. Plants can get along without respiratory organs. Give reasons.

Answer:

Reasons for Absence of Respiratory Organs in Plants :

(i) Each plant part takes care of its own gas-exchange needs. There is very little transport of gases from one plant part to another.
(ii) Plants do not require much demands for gas exchange. Roots, stems and leaves respire at rates far lower than animals. Only during photosynthesis large volumes of gases are exchanged and each leaf is well adapted to take care of its own needs during theses periods. Moreover, leaves also utilise O₂ released during photosynthesis.
(iii) In plants, cells are closely packed and located quite close to the surface of the plant. Thus, the distance that gases must diffuse is not large. Each living cell in a plant is located quite close (like in leaves) to the surface of the plant. While in stems, the living cells are organised in thin layers inside and beneath the bark and they have lenticells for gas exchange. Loose packing of parenchyma cells in leaves, stems and roots, which provide an interconnected network of air spaces also aids in easy exchange of gases. Thus, most cells of a plant have at least one part of their surface in contact with air.

Question 32. Make the diagram of mitochondrial ETS.
Answer: Draw a neat, fully labelled diagram.

Question 33. Write down the assumptions that are considered to calculate the net gain of ATP from a respiratary substrate.
Answer: It is possible to make calculations of the net gain of ATP for every glucose molecule oxidised; but in reality this can remain only a theoretical exercise. These calculations can be made only on certain assumptions that:
(i) There is a sequential, orderly pathway functioning, with one substrate forming the next and with glycolysis, TCA cycle and ETS pathway following one after another.
(ii) The NADH synthesised in glycolysis is transferred into the mitochondria and undergoes oxidative phosphorylation.
(iii) None of the intermediates in the pathway are utilized to synthesise any other compound.
(iv) Only glucose is being respired - no other alternative substrates are entering in the pathway at any of the intermediary stages.

Question 34. (a) Write down Pfeffer-Kostychev scheme representing interrelationship between aerobic and anaerobic respiration.
(b) How ATP acts as a source of energy?
Carbohydrates

Answer:

(a) Glucose Thisas is a common to both aerobic Glycolysis or EMP Pathway well as anaerobic respiration

Pyruvic acid

Pyruvic acid enters mitochondria,TCA where cycle (Krebs cycle) takes place releasing

C2H5OH + CO + Energy CO2 + H2O + Energy (Ethyloralcohol)² . CH CHOH COOH + Energy 3 (Lactic acid)

(b) ATP is adenosine triphosphate, a nucleotide, which is attached with three high energy rich phosphate bonds which on break down provide energy for performing various activity.

Question 35. Mention the steps for the conversion of pyruvate into C₂H₅OH by yeast.

Answer:

Pyruvic acid on anaerobic respiration is converted to alcohol.

2CH₃COCOOH —Pyruvic decarboxylaseMg++ → 2CH₃CHO + CO₂ (Pyruvic acid)

2CH₃CHO + 2NADH + H+ —Alcohol → 2C₂H₅OH + 2NAD+ dehydrogenase Acetaldehyde (Ethanol)

Question 36. Write a brief note on lactic acid fermentation.

Answer:

Anaerobic respiration where pyruvic acid is converted into lactic acid by using the enzyme lactic acid dehydrogenase.

CH COCOOH —Lactic acid dehydrogenase→ CH CHOHCOOH + Energy 3 2 3 FMN, Zn+ (Pyruvic acid) (Lactic acid)

Example : Lactic acid bacteria and muscle cells during exercise.

During vigrous exercise when oxygen is inadequate muscle cells instead of going to Kreb cycle for getting maximum energy muscle cells start producing lactic acid by using the enzyme lactate dehydrogenase.

Question 37. What happens to the pyruvic acid in aerobic respiration?

Answer:

Pyruvic acid formed during glycolysis enters the mitochondria for aerobic respiration to take place. The crucial events in aerobic respiration are :
(i) The complete oxidation of pyruvate by the stepwise removal of all the hydrogen atoms, leaving three molecules of CO₂. It occurs in two steps :

(a) Formation of Acetyl coenzyme A.

(b) TCA cycle (Tricarboxylic Acid Cycle) or Krebs cycle or Citric Acid Cycle.

This process takes place in the matrix of mitochondria.

(ii) The passing on of the electrons removed as part of the hydrogen atoms to molecular O₂ with simultaneous synthesis of ATP.

This process takes place on the innermembrane of the mitochondria.

Question 38. Write down the steps of TCA cycle.

Answer:

Acetyl CoA then enters a cyclic pathway, tricarboxylic acid cycle, more commonly called as Krebs cycle. Krebs cycle was named after the scientist Hans Krebs who first elucidated in flight muscles of pigeons. In these reactions hydrogen atoms are removed from the acetyl CoA and transferred to the coenzymes for further processing in the electron transport system.

Krebs Cycle proceeds in following steps :

(i) Acetyl group combines with oxaloacetic acid (OAA) and water to yield citric acid and this reaction is catalyzed by citrate synthetase and a molecule of CoA is released.

(ii) Citric acid changes to isocitrate by the action of aconitase.

(iii) Isocitrate dehydrogenase oxidizes isocitrate to oxalosuccinic acid by removing hydrogen and converting NAD⁺ to NADH + H⁺.

(iv) Next step is of decarboxylation where CO₂ is released from six carbon oxalosuccinic acid and results in the formation of α-ketoglutaric acid which is five carbon compound from oxalosuccinic acid.
(v) α-ketoglutaric dehydrogenase complex acts on α-ketoglutaric acid and converts it into a four₊ carbon compound succinyl CoA. During this step CO₂ is released and NAD is reduced to NADH + H .

(vi) In the next step succinate thiokinase catalyzes the conversion of succinyl CoA to succinic acid during this step CoA is released and one molecule of GTP is from GDP. (This is a substrate level phosphorylation. In a coupled reaction GTP is converted to GDP with the simultaneous synthesis of ATP from ADP).

(vii) Fumaric acid is formed in the next step from succinic acid this reaction is catalyzed by succinate dehydrogenase. During this reaction FAD molecule is reduced to FADH₂.

(viii) Malic acid is formed by the action of fumarase on fumaric acid this step involves addition of water molecule.

(ix) Regeneration of oxaloacetic acid is the last step that occurs in this reaction which is catalyzed by malic dehydrogenase which reduces NAD⁺ to NADH + H⁺ by removing hydrogen from malic acid.

Question 39. Describe the pathway that occurs in mitochondrial membrane.

Answer:

The metabolic pathway through which the electron passes from one carrier to another, is called the electron transport system (ETS). This process occurs in inner mitochondrial membrane.

This process proceeds in following steps :

(i) Electrons from NADH produced in the mitochondrial matrix during citric acid cycle are oxidised by an NADH dehydrogenase (Complex I).
(ii) Electrons are then transferred to ubiquinone

located within the inner membrane.

(iii) Ubiquinone also receives reducing equivalents via FADH₂ (complex II) that is generated during oxidation of succinate in the citric acid cycle.

(iv) The reduced ubiquinone (ubiquinol) is then oxidised with the transfer of electrons to cytochrome c via cytochrome bc₁ complex (Complex III).

(v) Cytochrome c is a small protein attached to the outer surface of the inner membrane and acts as a mobile carrier for transfer of electrons between complex III and IV (cytochrome c oxidase complex containing cytochromes a and a₃ and two copper centres is referred as complex IV.

(vi) Oxygen acts as the final hydrogen acceptor and terminal electron acceptor.

Question 40. (a) Write down the two types of respiration on the basis of respiratory substrate.
(b) Draw a diagram of mitochondria showing the position of oxysome.

Answer:

(a) On the basis of respiratory substrate Blackmann introduced two types of respiration :

(i) Floating respiration : When respiratory substrate is fat or carbohydrate.

(ii) Protoplasmic respiration : When respiratory substrate is protein.

Oxysome (F₀ – F₁ particle)

(b)

Mitochondria

Question 41. What is the value of respiratory quotient of tripalmitin, proteins and organic acids?

Answer:

The ratio of the volume of CO₂ evolved to the volume of O₂ consumed in respiration is called the respiratory quotient (RQ) or respiratory ratio.

volume of CO₂ evolved RQ = volume of O₂ consumed

The respiratory quotient depends upon the type of respiratory substrate used during respiration.

(i) When fats are used in respiration, the RQ is less than 1. Calculations for a fatty acid, tripalmitin, if used as a substrate is shown:

2(C₅₁H₉₈O₆) + 145O₂ —→ 102CO₂ + 98H₂O + Energy Tripalmitin

102CO₂ RQ = = 0.7 145O₂

(ii) When proteins are respiratory substrates the ratio would be about 0.9.

(iii) RQ value is 4 for oxalic acid and 1.33 for malic acid.

Question 42. Give the schematic representation of major pathways of anaerobic respiration.
Answer: A well-labelled diagram should show these parts: Glucose; Glyceraldehyde; Lactic; 3-phosphate acid; NAD+; NADH + H+; 3-Phosphoglyceric acid; Pyruvic acid; +; NADH + H; Phosphoenol; NAD pyruvic acid; Ethanol + CO; 2.

Question 43. Mention the steps of decarboxylation in aerobic respiration.

Answer:

(i) Oxidative decarboxylation

2+ Mg Pyruvic acid + CoA + NAD⁺ Acetyl CoA + CO₂ + NADH + H⁺ Pyruvate dehydrogenase

Decarboxylase
(ii) Oxalosuccinic acid α-ketoglutaric acid CO₂

+ NADH + H NAD
(iii) α-ketoglutaric acid Succinyl CoA CO α-ketoglutaric dehydrogenase complex²

Question 44. Write down the step of formation of acetyl CoA from pyruvic acid.

Answer:

Pyruvate which is formed by the glycolytic catabolism of carbohydrates in the cytosol, after it enters mitochondrial matrix undergoes oxidative decarboxylation by a complex set of reactions catalysed by pyruvate dehydrogenase plus it requires some coenzymes like NAD⁺ and coenzyme A.

2+ Mg Pyruvic acid + CoA + NAD⁺ Acetyl CoA + CO₂ + NADH + H⁺ Pyruvate dehydrogenase

Two molecules of pyruvic acid formed during glycolysis undergo the formation of Acetyl CoA and hence two molecules of Acetyl CoA, 2CO₂ and 2NADH + 2H⁺.

Acetyl CoA is often called a link between glycolysis and the Krebs cycle.

Question 45. Show diagrammatic presentation of ATP synthesis in mitochondrial membrane.

Answer:

ATP Outer side

2H⁺ F₀ F₁

ADP Pi Inner mitochondrial membrane