' Respiration in Plants' chapter in NCERT Solutions for class 11 Biology syllabus talks about the mechanism where the food materials breakdown inside the cell to release energy, which is also technically called cellular respiration, and how the energy released is trapped for the Synthesis of ATP. Also elaborated are topics, like Glycolysis, which answers a question - "Do Plants Breathe"?, Aerobic Respiration, Fermentation, Respiratory Quotient, Amphibolic Pathway, and The Respiratory Balance Sheet. Understanding of all these topics is a must for comprehensive learning, So, read below.

• Answering the question - 'Do Plants Breathe'?
• Glycolysis
• Fermentation
• Aerobic Respiration
• The Respiratory Balance Sheet
• Amphibolic Pathway
• Respiratory Quotient

This chapter is the gateway to cellular respiration, which deals with the mechanism of food disintegration inside the cells to discharge energy. ATP, which are the energy boosters for a cell, is synthesized through the released energy, which for this purpose is trapped. The process of breathing, under this topic, has been linked with the cycle of the release of energy from food. The oxidation of certain macromolecules that is known as 'food' is the source of all the energy required to perform any activity.

Q1. Differentiate between

1. Respiration and Combustion

Answer:

2. Glycolysis and Krebs cycle

Answer:

(c) Aerobic respiration and Fermentation

Answer:

Q2. What are respiratory substrates? Name the most common respiratory substrate.

Answer:

Respiratory substrates are those organic substances that are oxidized during respiration to liberate energy inside the living cells. The common respiratory substrates are carbohydrates, proteins, fats, and organic acids.

Q3. Give the systematic representation of glycolysis?

Answer:

Schematic representation of glycolysis is as follows:

Q4. What are the main steps in aerobic respiration? Where does it take place?

Answer:

The main steps of aerobic respiration are as follows:

1. Glycolysis- Cytoplasm
2. Krebs cycle- Matrix of mitochondria
3. Electron transport system- Inner mitochondrial membrane
4. Oxidative phosphorylation- Oxysome in the inner mitochondrial membrane.

Q5. Give the schematic representation of an overall view of Krebs' cycle.

Answer:

Schematic representation of the Krebs cycle

Q7. Distinguish between the following:
 

1. Aerobic respiration and Anaerobic respiration

Answer:

2. Glycolysis and Fermentation

Answer:

c. Glycolysis and Citric acid Cycle

  Answer:

Q8. What are the assumptions made during the calculation of the net gain of ATP?

Answer:

The assumptions made during the calculation of net gain of ATP are as follows:

1. It is assumed that various parts of aerobic respiration such as glycolysis, TCA cycle, and ETS occur in a sequential and orderly pathway.
2. NADH produced during the process of glycolysis enters into mitochondria to undergo oxidative phosphorylation.
3. The glucose molecule is assumed to be the only substrate while it is assumed that no other molecule enters the pathway at intermediate stages.
4.  The intermediates produced during respiration are not utilized in any other process.

Q9. Discuss "The respiratory pathway is an amphibolic pathway."

Answer:

 An amphibolic pathway refers to a pathway in which both catabolic and anabolic reactions take place. The products of some reactions are used to synthesize other products. Carbohydrates are broken down to glucose before entering respiratory pathways. Fats get converted into fatty acids and glycerol whereas fatty acids get converted into acetyl CoA before entering the respiration. Similarly, proteins are converted into amino acids, which enter respiration after deamination. During the synthesis of fatty acids, acetyl CoA is withdrawn from the respiratory pathway. Also, in the synthesis of proteins, respiratory substrates get withdrawn. Thus, respiration involves both anabolism and catabolism in anabolism. Therefore, respiration can be termed as an amphibolic pathway as it involves both anabolism and catabolism.

Q10. Define RQ. What is its value for fats?

Answer:

The respiratory quotient is defined as the ratio of the volume of  evolved to the volume of consumed during respiration. The value of the respiratory quotient depends on the type of respiratory substrate. The value of RQ for various respiratory substrates is as follows:

Carbohydrates- 1

Fat - 0.7

Organic acids- more than 1

 Proteins - less than 1

Q11. What is oxidative phosphorylation?

Answer:

Oxidative phosphorylation is the synthesis of energy-rich ATP molecules with the help of energy liberated during oxidation of reduced coenzymes ( NADH and FADH2 ) produced in respiration. The enzyme required for the synthesis is called ATP synthase. It is the fifth complex of ETS. During this process, several oxidation-reduction reactions occur and lead to the generation of a proton gradient. The enzyme ATP synthase (complex V) consists of and components. The Fl headpiece is a peripheral membrane protein complex and contains the site for ATP synthesis from ADP and inorganic phosphate whereas the the component is a part of the membrane protein complex, which acts as a channel for the crossing of the protons from the inner mitochondrial membrane to the mitochondrial matrix. For every two protons passing through complex synthesis of one ATP molecule takes place.

Q12. What is the significance of the step-wise release of energy in respiration?

Answer:

The process of respiration takes place in a stepwise manner including steps like glycolysis, TCA cycle, ETS, and oxidative phosphorylation. During respiration, the production of ATP also in each phase takes place in a stepwise manner. The products formed in one step of respiration become the substrate of the other pathway. Various molecules produced during respiration are involved in other biochemical processes also. Different respiratory substrates enter and withdraw from the pathway on necessity. The ATP also gets utilized wherever required and the rate of reactions of enzymes are also controlled. Therefore, the stepwise release of energy makes the system more efficient in extracting as well as storing energy.