Biology Class 11 NCERT Solutions: Chapter 14 Respiration in Plants Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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


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) 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.

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


Respiration is generally assumed to be a catabolic process because during respiration, various substrates are broken down for deriving energy. 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 before entering the respiration. In a similar manner, proteins are converted into amino acids, which enter respiration after deamination.

During synthesis of fatty acids, acetyl is withdrawn from respiratory pathway. Also, in the synthesis of proteins, respiratory substrates get withdrawn. Thus, respiration is also involved in anabolism. Therefore, respiration can be termed as amphibolic pathway as it involves both anabolism and catabolism.

Q: 10. Define . What is its value for fats?


The Respiratory Quotient (RQ)

Respiratory quotient or respiratory ratio can be defined as the ratio of the volume of evolved to the volume of consumed during respiration. The value of respiratory quotient depends on the type of respiratory substrate. Its value is one for carbohydrates. However, it is always less than one for fats as fats consume more oxygen for respiration than carbohydrates. It can be illustrated through the example of tripalmitin fatty acid, which consumes molecules of for respiration while molecules of are evolved. The value for tripalmitin is .

The RQ Values for Different Classes of Respiratory

Q: 11. What is oxidative phosphorylation?


Oxidative phosphorylation is a process in which electrons are transferred from electron donors to oxygen, which acts as electron acceptor. The oxidation-reduction reactions are involved in the formation of proton gradient. The main role in oxidative phosphorylation is played by the enzyme ATP synthase (complex V) . This enzyme complex consists of and components. The headpiece is a peripheral membrane protein complex and contains the site for ATP synthesis from ADP and inorganic phosphate. component is a part of membrane protein complex, which acts as a channel for crossing of the protons from inner mitochondrial membrane to the mitochondrial matrix. For every two protons, passing through - complex, synthesis of one ATP molecule takes place.

Oxidative Phosphorylation

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


The process of aerobic respiration is divided into four phases - glycolysis, cycle, , and oxidative phosphorylation. It is generally assumed that the process of respiration and production of in each phase takes place in a step-wise manner. The product of one pathway forms the substrate of the other pathway. Various molecules produced during respiration are involved in other biochemical processes. The respiratory substrates enter and withdraw from pathway on necessity. gets utilized wherever required and enzymatic rates are generally controlled. Thus, the step-wise release of energy makes the system more efficient in extracting and storing energy.

Aerobic Cellular Respiration

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