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NCERT Solutions for Class 11 Biology Respiration in Plants

1. Differentiate between

(a) Respiration and Combustion

(b) Glycolysis and Krebs’ cycle

(c) Aerobic respiration and Fermentation

Solution:

a) Respiration and Combustion

Respiration

Combustion

It is a biochemical process

It is a physicochemical process.

Temperature stays low

Temperature drastically raises

Occurs in living cells

It is a non-cellular process

Energy entrapped in the form of ATP

ATP is not required for the combustion process

b) Glycolysis and Krebs’ cycle

Glycolysis

Krebs Cycle

The first step in respiration

The second step in respiration

Takes place in cytoplasm

Takes place in mitochondria

Occurs both aerobically and anaerobically

Occurs anaerobically

Two ATPs are consumed

ATPs are not consumed

The net gain is 8 ATP’s

The net gain is 24 ATP’s

It is a linear pathway

It is a circular pathway

c) Aerobic respiration and Fermentation

Aerobic respiration

Fermentation

Included in the exchange of gases

Does not include exchange of gases

Oxygen is necessary for aerobic respiration

Oxygen should be absent for the fermentation process

Respiratory material is completely oxidised

Respiratory material is incompletely oxidised

The end products are inorganic

At least one product is organic

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

Solution:

Organic substrates that are oxidised during respiration to liberate energy inside the living cells are respiratory substrates. Carbohydrates, proteins, fats and organic acids are the most common respiratory substrate.

3. Give the schematic representation of glycolysis?

Solution:

Schematic representation of glycolysis is as follows:

 

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

Solution:

Main steps in aerobic respiration are as follows

  • Glycolysis: Occurs in the cytoplasm(cytosol) where glucose is broken down to pyruvic acid.

  • Oxidative decarboxylation of pyruvic acid to acetyl coenzyme-A: Takes place inside the mitochondrial matrix.

  • TCA or Krebs cycle takes place in Mitochondrial matrix where pyruvic acid is oxidized to transform the energy contained in these molecules into ATP.

  • Electron transport chain occurs in mitochondrial membrane involves ATP synthase complex.

5. Give the schematic representation of an overall view of Krebs’ cycle.

Solution:

The schematic representation of an overall view of Krebs’ cycle is as follows:

 

6. Explain ETS.

Solution:

 

  • Electron transport system(ETS) is found in the inner mitochondrial membrane and aids in liberating and using the energy stored in the NADH+H+ and FADH2

  • NADH+ H+ , formed while citric acid cycle and glycolysis occurs is oxidized by NADH dehydrogenase or complex I

  • Electrons hence produced are conveyed to ubiquinone via FMN

  • Similarly, the complex II or FADH2 synthesized during the citric acid cycle is conveyed to ubiquinone

  • From ubiquinone electrons are accepted by the complex III or cytochrome bc1 which furthermore gets conveyed to cytochrome c which serves as a mobile carrier between the cytochrome c oxidase complex and complex III comprising of cytochrome a and a3 with copper centers (complex IV) additionally

  • When electrons are transferred from each complex, simultaneously other processes occur such as production of the ATP from ADP and the inorganic phosphate through the action of ATP synthase(complex V)

  • This amount of ATP production is dependent on the molecule that has been oxidized. 3 ATP molecules are generated by the oxidation of 1 molecule of NADH while 1 FADH2 molecule upon oxidation produces 2 ATP molecules

7. Distinguish between the following:

(a) Aerobic respiration and Anaerobic respiration

(b) Glycolysis and Fermentation

(c) Glycolysis and Citric acid Cycle

Solution:

a) Aerobic respiration and Anaerobic respiration

Aerobic respiration

Anaerobic respiration

Occurs in the presence of the Oxygen

Occurs in the absence of Oxygen

Involves complete breakdown of respiratory materials.

Involves partial breakdown of the gases.

Carbon-di-oxide and water are the end products

Carbon-dioxide and ethanol are the end products.

Involves the exchange of gases

Does not include the exchange of gases

b) Glycolysis and Fermentation

Glycolysis

Fermentation

It is the first step in aerobic respiration, and it is common to both aerobic and anaerobic modes of respiration

It is anaerobic respiration which does not require Oxygen.

It produces pyruvic acid

It produces lactic acid and ethanol

It produces two molecules of NADH for every glucose molecule.

Uses NADH generated during glycolysis

It forms two ATP for every glucose molecule

It does not produce ATP.

c) Glycolysis and Citric acid Cycle

Glycolysis

Citric acid cycle

Occurs inside cytoplasm

Occurs inside mitochondria

It is a linear pathway

It is a cyclic pathway

In Glycolysis glucose is breakdown to pyruvate

Acetyl group is broken down completely.

The net gain is 8 ATP

Net gain is 24 molecules of ATP

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

Solution:

Assumptions made during the calculation of net gain of ATP are as follows

  • NADH generated inside the mitochondria synthesizes 3 ATP molecules during its oxidation.

  • NADH formed during glycolysis sends its reducing power into mitochondria via the shuttle system.

  • During oxidation of FADH2, 2 molecules of ATP is produced inside mitochondria

  • Formation of 3 ATP in the malate-aspartate shuttle (heart, liver and kidney) and 2 ATP in the glycerol phosphate shuttle (muscles and nerve cells). 

9. Discuss “The respiratory pathway is an amphibolic pathway.”

Solution:

Organic substances such as fats, carbohydrates, proteins etc liberate energy when they are disintegrated in the respiratory pathway. This phenomena is said to be catabolic in nature. The respiratory process that serves as a catabolic pathway for the respiratory substrates also serves as an anabolic pathway to produce different metabolic products and secondary metabolites. Thus, the respiratory pathway serves as a catabolic and anabolic pathway. Therefore, the respiratory pathway is an amphibolic pathway.

10. Define RQ. What is its value for fats?

Solution:

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

 

RQ is less than 1 when the respiratory substrate is either fat or protein

 

11. What is oxidative phosphorylation?

Solution:

Oxidative phosphorylation is the conversion of ADP into ATP by electron transport system. Phosphorylation takes place in the inner mitochondrial membrane via the ATP synthetase complex when the hydrogen protons pass through it. The energy essential for phosphorylation is derived from the oxidation-reduction phenomena in respiration. Thus the process is known as oxidative phosphorylation. 

12. What is the significance of step-wise release of energy in respiration?

Solution:

During respiration single molecule of glucose is disintegrated to generate carbon dioxide and water along with the formation of ATP molecules. If the energy gets released at one go, then most of energy will be lost as heat. In order to synthesize new compounds, the cell should be able to utilize the energy. Hence step-wise release of energy in respiration is most efficient in the conservation of energy.

Frequently Asked Questions on Respiration in Plants

What are respiratory substrates?

Organic substrates that are oxidised during respiration to liberate energy inside the living cells are respiratory substrates. Carbohydrates, proteins, fats and organic acids are the most common respiratory substrate.

What are the main steps in aerobic respiration?

Main steps in aerobic respiration are as follows

  • Glycolysis: Occurs in the cytoplasm(cytosol) where glucose is broken down to pyruvic acid.

  • Oxidative decarboxylation of pyruvic acid to acetyl coenzyme-A: Takes place inside the mitochondrial matrix.

  • TCA or Krebs cycle takes place in Mitochondrial matrix where pyruvic acid is oxidized to transform the energy contained in these molecules into ATP.

  • Electron transport chain occurs in mitochondrial membrane involves ATP synthase complex.

Explain ETS?

Electron transport system(ETS) is found in the inner mitochondrial membrane and aids in liberating and using the energy stored in the NADH+H+ and FADH2

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

Assumptions made during the calculation of net gain of ATP are as follows

  • NADH generated inside the mitochondria synthesizes 3 ATP molecules during its oxidation

  • NADH formed during glycolysis sends its reducing power into mitochondria via the shuttle system. 

  • During oxidation of FADH2, 2 molecules of ATP is produced inside mitochondria 

  • Formation of 3 ATP in the malate-aspartate shuttle (heart, liver and kidney) and 2 ATP in the glycerol phosphate shuttle (muscles and nerve cells).

Define RQ?

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

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