NCERT Solutions for Class 11 Biology Chapter 14 : Respiration in Plants

Q: Q1. Why refer to Class 11 Biology NCERT Solutions Chapter 14 Respiration in Plants?

Answer: Students should refer to the Class 11 Biology NCERT Solutions Chapter 14 to prepare for their exams. The Solutions provide answers to all the questions from the Respiration in Plants Class 11 Notes Biology NCERT textbook in simple language. Hence, students can easily understand the concepts and learn the format of answers to be written in the exam. In NCERT Solutions for Class 11 Biology Chapter 14, you will learn about cellular respiration or the mechanism of breakdown of food materials within the plant cell to release energy, and the trapping of this energy for the synthesis of ATP, various processes within the plant body.

Q: Q2. What concepts can I learn from the NCERT Solutions for Class 11 Biology Chapter 14?

Answer: 14.1 – Do Plants Breathe? 14.2 – Glycolysis 14.3 – Fermentation 14.4 – Aerobic Respiration 14.5 – The Respiratory Balance Sheet 14.6 – Amphibolic Pathway 14.7 – Respiratory Quotient

Q: Q3. What are the uses of referring to the NCERT Solutions for Class 11 Biology Chapter 13?

Answer: 1. All the textbook questions are answered in a descriptive manner. 2. Students will be able to solve complex questions effortlessly using the solutions PDF. 3. By regular practice, students can jot down their areas of weakness and work on them for a better score. 4. Diagrams are present under each concept to help students learn them easily.

Question 1

Differentiate between

(a) Respiration and Combustion

(b) Glycolysis and Kreb's cycle

(c) Aerobic respiration and fermentation

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Answer

(a)

Respiration	Combustion
1. It takes place in living cells only.	1. It does not take place in the living cell.
2. It is carried out with the help of various enzymes.	2. Enzymes are not involved in this process.
3. The oxidation of food and the liberation of energy occur in a step-wise manner.	3. The substances are oxidized spontaneously with sudden release of energy.
4. It occurs at the body temperature of the organism.	4. Sudden release of energy generates high temperature of a fire.
5. 60% of energy escapes as body heat and 40% of energy is packaged directly into new chemical energy (ATP).	5. Energy released in combustion is dissipated as heat and to some extent as light.

(b)

Glycolysis	Krebs cycle
1. It is a linear pathway.	1. It is a cyclic pathway.
2. It occurs in the cell cytoplasm.	2. It occurs in the mitochondrial matrix.
3. It occurs in both aerobic as well as anaerobic respiration.	3. It occurs in aerobic respiration only.
4. Net generation of 2 $N A D H^{+} H^{+}$ and 2 ATP molecules occurs on the breakdown of one glucose molecule.	4. It produces 6 $N A D H^{+} H^{+}$ , 2FADH $_{2}$ , and 2 ATP molecules on the breakdown of two acetyl-CoA molecules generated after glycolysis of one glucose molecule.

(c)

Aerobic respiration	Fermentation
1. Oxygen is used for deriving energy.	1. Occurs in the absence of oxygen.
2. Occurs in the cytoplasm and mitochondria.	2. Occurs in the cytoplasm.
3. End products are carbon dioxide and water.	3. End products are ethyl alcohol and carbon dioxide.
4. Complete oxidation of the respiratory substrate takes place.	4. Incomplete oxidation of the respiratory substrate takes place.
5. About 36 ATP molecules are produced.	5. Only 2 ATP molecules are produced.

Answer

(a)

Respiration	Combustion
1. It takes place in living cells only.	1. It does not take place in the living cell.
2. It is carried out with the help of various enzymes.	2. Enzymes are not involved in this process.
3. The oxidation of food and the liberation of energy occur in a step-wise manner.	3. The substances are oxidized spontaneously with sudden release of energy.
4. It occurs at the body temperature of the organism.	4. Sudden release of energy generates high temperature of a fire.
5. 60% of energy escapes as body heat and 40% of energy is packaged directly into new chemical energy (ATP).	5. Energy released in combustion is dissipated as heat and to some extent as light.

(b)

Glycolysis	Krebs cycle
1. It is a linear pathway.	1. It is a cyclic pathway.
2. It occurs in the cell cytoplasm.	2. It occurs in the mitochondrial matrix.
3. It occurs in both aerobic as well as anaerobic respiration.	3. It occurs in aerobic respiration only.
4. Net generation of 2 $N A D H^{+} H^{+}$ and 2 ATP molecules occurs on the breakdown of one glucose molecule.	4. It produces 6 $N A D H^{+} H^{+}$ , 2FADH $_{2}$ , and 2 ATP molecules on the breakdown of two acetyl-CoA molecules generated after glycolysis of one glucose molecule.

(c)

Aerobic respiration	Fermentation
1. Oxygen is used for deriving energy.	1. Occurs in the absence of oxygen.
2. Occurs in the cytoplasm and mitochondria.	2. Occurs in the cytoplasm.
3. End products are carbon dioxide and water.	3. End products are ethyl alcohol and carbon dioxide.
4. Complete oxidation of the respiratory substrate takes place.	4. Incomplete oxidation of the respiratory substrate takes place.
5. About 36 ATP molecules are produced.	5. Only 2 ATP molecules are produced.

Question 2

What are respiratory substrates? Name the most common respiratory substrate.

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The compounds oxidised during the process of respiration are called as respiratory substrates. Carbohydrates, especially glucose, act as a respiratory substrate. Fats, proteins, and organic acids can also act as respiratory substrates depending upon the physiological condition of the body of an organism.

Answer

The compounds oxidised during the process of respiration are called as respiratory substrates. Carbohydrates, especially glucose, act as a respiratory substrate. Fats, proteins, and organic acids can also act as respiratory substrates depending upon the physiological condition of the body of an organism.

Question 3

Give the schematic representation of Glycolysis

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Glycolysis -

(i) In this process, glucose undergoes partial oxidation to form two molecules of pyruvic acid.

(ii) In plants, this glucose is derived from sucrose which converted into glucose and fructose by the enzyme, invertase and these two monosaccharides readily enter the glycolytic pathway.

(iii) Glucose and fructose are phosphorylated to give rise to glucose-6-phosphate by the activity of the enzyme hexokinase.

(iv) This phosphorylated form of glucose then isomerises to produce fructose-6-phosphate.

(v) A chain of ten reactions, under the control of different enzymes, takes place to produce pyruvate from glucose.

(vi) Utilization of ATP during glycolysis

(a)During the conversion of glucose into glucose-6-phosphate.

(b) During the conversion of fructose-6-phosphate to fructose-1, 6-diphosphate.

Answer

Glycolysis -

(i) In this process, glucose undergoes partial oxidation to form two molecules of pyruvic acid.

(ii) In plants, this glucose is derived from sucrose which converted into glucose and fructose by the enzyme, invertase and these two monosaccharides readily enter the glycolytic pathway.

(iii) Glucose and fructose are phosphorylated to give rise to glucose-6-phosphate by the activity of the enzyme hexokinase.

(iv) This phosphorylated form of glucose then isomerises to produce fructose-6-phosphate.

(v) A chain of ten reactions, under the control of different enzymes, takes place to produce pyruvate from glucose.

(vi) Utilization of ATP during glycolysis

(a)During the conversion of glucose into glucose-6-phosphate.

(b) During the conversion of fructose-6-phosphate to fructose-1, 6-diphosphate.

Question 4

What are the main steps in aerobic respiration? Where does it take place?

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Answer

The major steps in aerobic respiration and the sites where they occur are listed in the given table :

Step	Site of occurrence
Glycolysis	Cytoplasm
Kreb's cycle	Matrix of mitochondria
Electron transport system	Inner mitochondrial membrane
Oxidative phosphorylation	F0 - F1 particles in the inner mitochondrial membrane

Answer

The major steps in aerobic respiration and the sites where they occur are listed in the given table :

Step	Site of occurrence
Glycolysis	Cytoplasm
Kreb's cycle	Matrix of mitochondria
Electron transport system	Inner mitochondrial membrane
Oxidative phosphorylation	F0 - F1 particles in the inner mitochondrial membrane

Question 5

Give the schematic representation of an overall view of Kreb's cycle.

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Question 6

Explain ETS?

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Answer

Explanation:

ETS or electron transport system is located in the inner mitochondrial membrane. It helps in releasing and utilizing the energy stored in NADH $_{2}$ and FADH $_{2}$ .
NADH $_{2}$ which is formed during glycolysis and the citric acid cycle gets oxidized by an NADH dehydrogenase (complex I). The electrons so generated get transferred to ubiquinone through FMN.
In a similar manner, FADH $_{2}$ (complex II) generated during the citric acid cycle gets transferred to ubiquinone. The electrons from ubiquinone are received by cytochrome bc1 (complex III) and further get transferred to cytochrome c.
The cytochrome c acts as a mobile carrier between complex III and cytochrome c oxidase complex, containing cytochrome a and a $_{3}$ , along with copper centres (complex IV).
During the transfer of electrons from each complex, the process is accompanied by the production of ATP from ADP and inorganic phosphate by the action ATP synthase (complex V).
The amount of ATP produced depends on the molecule, which has been oxidized. 3 ATP molecules are produced by the oxidation of one molecule of NADH. One molecule of FADH $_{2}$ , on oxidation, gives 2 ATP molecules.

Answer

Explanation:

ETS or electron transport system is located in the inner mitochondrial membrane. It helps in releasing and utilizing the energy stored in NADH $_{2}$ and FADH $_{2}$ .
NADH $_{2}$ which is formed during glycolysis and the citric acid cycle gets oxidized by an NADH dehydrogenase (complex I). The electrons so generated get transferred to ubiquinone through FMN.
In a similar manner, FADH $_{2}$ (complex II) generated during the citric acid cycle gets transferred to ubiquinone. The electrons from ubiquinone are received by cytochrome bc1 (complex III) and further get transferred to cytochrome c.
The cytochrome c acts as a mobile carrier between complex III and cytochrome c oxidase complex, containing cytochrome a and a $_{3}$ , along with copper centres (complex IV).
During the transfer of electrons from each complex, the process is accompanied by the production of ATP from ADP and inorganic phosphate by the action ATP synthase (complex V).
The amount of ATP produced depends on the molecule, which has been oxidized. 3 ATP molecules are produced by the oxidation of one molecule of NADH. One molecule of FADH $_{2}$ , on oxidation, gives 2 ATP molecules.

Question 7

Distinguish between the following.

(a) Aerobic respiration and Anaerobic respiration

(b) Glycolysis and Fermentation

(c) Glycolysis and Citric acid cycle

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(a)

Aerobic Respiration	Anaerobic Respiration
1. Aerobic respiration takes place in the presence of free oxygen.	1. Anaerobic respiration takes place in the absence of free oxygen.
2. The first step of this process (glycolysis) takes place in the cytoplasm while the second step (Krebs cycle) is carried out in mitochondria.	2.The complete process is carried out outside the mitochondria i.e., in the cytoplasm.
3. Glucose is completely oxidized into carbon dioxide and water.	3. Glucose is incompletely oxidized into carbon dioxide and ethyl alcohol.
4. 38 molecules of ATP are produced by the complete oxidation of one gram-mole of glucose.	4. Only 2 molecules of ATP are formed in this process.

(b)

Glycolysis	Fermentation
1. Glycolysis is a common process during aerobic and anaerobic respiration.	1. Fermentation is a type of anaerobic respiration.
2. Pyruvic acid is produced as its end product.	2. Ethanol or lactic acid is produced as its end product.

(c)

Glycolysis	Citric acid cycle (Krebs cycle)
1. It is a linear pathway.	1. It is a cyclic pathway.
2. It occurs in the cell cytoplasm.	2. It occurs in the mitochondrial matrix.
3. It occurs in both aerobic as well as in anaerobic respiration.	3. It occurs in aerobic respiration only.
4. One glucose molecule breaks down to generate 2 NADH2 and 2 ATP molecules.	4. It produces 6 NADH2, 2 FADH2, and 2 ATP molecules on the breakdown of two acetyl-CoA molecules generated after glycolysis.

Answer

(a)

Aerobic Respiration	Anaerobic Respiration
1. Aerobic respiration takes place in the presence of free oxygen.	1. Anaerobic respiration takes place in the absence of free oxygen.
2. The first step of this process (glycolysis) takes place in the cytoplasm while the second step (Krebs cycle) is carried out in mitochondria.	2.The complete process is carried out outside the mitochondria i.e., in the cytoplasm.
3. Glucose is completely oxidized into carbon dioxide and water.	3. Glucose is incompletely oxidized into carbon dioxide and ethyl alcohol.
4. 38 molecules of ATP are produced by the complete oxidation of one gram-mole of glucose.	4. Only 2 molecules of ATP are formed in this process.

(b)

Glycolysis	Fermentation
1. Glycolysis is a common process during aerobic and anaerobic respiration.	1. Fermentation is a type of anaerobic respiration.
2. Pyruvic acid is produced as its end product.	2. Ethanol or lactic acid is produced as its end product.

(c)

Glycolysis	Citric acid cycle (Krebs cycle)
1. It is a linear pathway.	1. It is a cyclic pathway.
2. It occurs in the cell cytoplasm.	2. It occurs in the mitochondrial matrix.
3. It occurs in both aerobic as well as in anaerobic respiration.	3. It occurs in aerobic respiration only.
4. One glucose molecule breaks down to generate 2 NADH2 and 2 ATP molecules.	4. It produces 6 NADH2, 2 FADH2, and 2 ATP molecules on the breakdown of two acetyl-CoA molecules generated after glycolysis.

Question 8

What are the assumptions made during the calculation of net gain of ATP?

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For theoretical calculation of ATP molecules, various assumptions are made, which are as follows :

(a) It is assumed that various parts of aerobic respiration such as glycolysis, TCA cycle, and ETS occur in a sequential and orderly pathway.

(b) NADH produced during the process of glycolysis enters into mitochondria to undergo oxidative phosphorylation.

(c) A glucose molecule is assumed to be the only substrate while it is assumed that no other molecule enters the pathway at intermediate stages.

(d) The intermediates produced during respiration are not utilized in any other process.

Answer

For theoretical calculation of ATP molecules, various assumptions are made, which are as follows :

(a) It is assumed that various parts of aerobic respiration such as glycolysis, TCA cycle, and ETS occur in a sequential and orderly pathway.

(b) NADH produced during the process of glycolysis enters into mitochondria to undergo oxidative phosphorylation.

(c) A glucose molecule is assumed to be the only substrate while it is assumed that no other molecule enters the pathway at intermediate stages.

(d) The intermediates produced during respiration are not utilized in any other process.

Question 9

Discuss "The respiratory pathway is an amphibolic pathway".

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Explanation:

When a process involves both anabolism and catabolism then the process is known as an amphibolic pathway.
In respiration, various complex molecules like carbohydrates, fatty acids, proteins are broken down into simpler molecules, this is catabolism.
On the other hand, during the formation of fatty acids, acetyl CoA is withdrawn from the respiratory pathway.
Likewise, amino acids also are withdrawn to produce proteins, this being anabolism.

Answer

Explanation:

When a process involves both anabolism and catabolism then the process is known as an amphibolic pathway.
In respiration, various complex molecules like carbohydrates, fatty acids, proteins are broken down into simpler molecules, this is catabolism.
On the other hand, during the formation of fatty acids, acetyl CoA is withdrawn from the respiratory pathway.
Likewise, amino acids also are withdrawn to produce proteins, this being anabolism.

Question 10

Define RQ. What is RQ value for fats?

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Respiratory Quotient ( R. Q) is the ratio of the volume of carbon dioxide release to the volume of oxygen taken in respiration in the given period of time at standard temperature and pressure.

RQof fats- When fats are respiratory substrates, during germination of seeds, the fats are hydrolysed to fatty acids and glycerol. The complete oxidation of glycerol results in the RQ of 0.86. The fatty acids, being poorer in oxygen, require more O2 for complete oxidation as compared to CO2. Therefore, O2 absorption is more and CO2 liberation and RQ becomes less than unity. For example-

RQ is 0.7 during oxidative breakdown of glycerol palmitate-

2 C_{51} H_{98} O_{6} + 145 O_{2} \to 102 C O_{2} + 98 H_{2} O + E n e r g y

RQ= Vol. of CO2\ Vol.of O= 102\145= 0.7

The RQ of fats is mostly less than 1.

Answer

Respiratory Quotient ( R. Q) is the ratio of the volume of carbon dioxide release to the volume of oxygen taken in respiration in the given period of time at standard temperature and pressure.

RQof fats- When fats are respiratory substrates, during germination of seeds, the fats are hydrolysed to fatty acids and glycerol. The complete oxidation of glycerol results in the RQ of 0.86. The fatty acids, being poorer in oxygen, require more O2 for complete oxidation as compared to CO2. Therefore, O2 absorption is more and CO2 liberation and RQ becomes less than unity. For example-

RQ is 0.7 during oxidative breakdown of glycerol palmitate-