NCERT Exemplar for Class 11 Biology Chapter-14 (Book Solutions)

1. The ultimate electron acceptor of respiration in anaerobic organism is:

(a) Cytochrome

(b) Oxygen

(c) Hydrogen

(d) Glucose

Ans: (b) Oxygen

Explanation: Electrons that are removed from hydrogen are accepted by O₂ molecules.

2. Phosphorylation of glucose during glycolysis is catalysed by

(a) Phosphoglucomutase

(b) Phosphoglucoisomerase

(c) Hexokinase

(d) Phosphorylase

Ans: (c) Hexokinase

Explanation: Glucose is phosphorylated by hexokinase, and glucose-6-phosphate is produced.

3. Pyruvic acid, the key product of glycolysis, can have many metabolic fates. Under aerobic conditions it forms

(a) Lactic acid

(b) CO₂ + H₂O

(c) Acetyl CoA + CO₂

(d) Ethanol + CO₂

Ans: (c) Acetyl CoA + CO₂

Explanation: Pyruvic acid undergoes dehydrogenation, and the reaction produces Acetyl CoA, CO₂ and NADH.

4. Electron Transport System (ETS) is located in mitochondrial

(a) Outer membrane

(b) Inter membrane space

(c) Inner membrane

(d) Matrix

Ans: (c) The inner membrane

Explanation: ETS can be found in mitochondria's interior membrane.

5. Which of the following exhibits the highest rate of respiration?

(a) Growing shoot apex

(b) Germinating seed

(c) Root tip

(d) Leaf bud

Ans: (b) Germination of seeds

Explanation: Growth is taking place in the case of all the options. But the growth rate is maximum in germinating seeds. So growing seeds exhibit the highest rate of respiration

6. Choose the correct statement:

(a) Pyruvate is formed in the mitochondrial matrix.

(b) During the conversion of succinyl Co-A to succinic acid a molecule of ATP is synthesized.

(c) Oxygen is vital in respiration for removal of hydrogen.

(d) There is complete breakdown of glucose in fermentation.

 Ans: (c) Oxygen is vital in respiration for the removal of hydrogen.

7. Mitochondria are called powerhouses of the cell. Which of the following

observations support this statement?

(a) Mitochondria synthesize ATP

(b) Mitochondria have a double membrane

(c) The enzymes of Krebs cycle and the cytochromes are found in mitochondria

(d) Mitochondria are found in almost all plant and animal cells

Ans: (a) Mitochondrial ATP is synthesized

Explanation: ATP is the energy currency and hence option ‘a’ is correct.

8. The end product of oxidative phosphorylation is

(a) NADH

(b) Oxygen

(c) ADP

(d) ATP + H₂O

Ans: (d) ATP + H₂O

9. Match the following and choose the correct option from those given below:

Options:

(a) A – (ii), B – (iii), C – (iv) D – (i)

(b) A – (iii), B – (iv), C – (ii) D – (i)

(c) A – (ii), B – (i), C – (iii) D – (iv)

(d) A – (iv) B – (iii), C – (i), D – (ii)

Ans: This includes A - (ii), B - (iii), C - (iv), and D - (I)

VERY SHORT ANSWER TYPE QUESTIONS

1. Energy is released during the oxidation of compounds in respiration. How is this energy stored and released as and when it is needed?

Ans: As ATP is synthesized during respiration, it becomes available for storage in mitochondria. The mitochondria release ATP whenever power is needed. ATP is broken down to get the point.

2.   Explain the term “Energy Currency”. Which substance acts as energy currency in plants and animals?

Ans: ATP is a currency that stores energy. ATP can be used as currency when it is needed to power devices. Because ATP has this property, it is sometimes called "energy currency". ATP is used by plants and animals alike as an energy currency.

3. Different substrates get oxidized during respiration. How does Respiratory Quotient (R.Q.) indicate which type of substrate, i.e., carbohydrates, fat or protein is getting oxidized?

R.Q. = A/B

(a) What do A and B stand for?

(b) What type of substrates have R.Q. of 1, < 1 or > 1?

Ans: Ans of (a) It stands for the volume of CO₂ evolved, and B stands for the importance of O₂ consumed.

Ans of (b) Carbohydrates has R.Q. = 1, while protein and fat have R.Q. less than 1. No subtract has

R.Q. > 1.

4. F0 – F1 particles participate in the synthesis of is 

Ans: ATP

5. When does anaerobic respiration occur in man and yeast?

Ans: Anaerobic respiration is carried out by yeast when oxygen isn't available. In a small percentage of muscle cells in people undergo anaerobic respiration. Anaerobic respiration provides extra energy for muscles during strenuous exercise, for example.

6.  Which of the following will release more energy on oxidation? Arrange them in ascending order.

(a) 1 gm of fat

(b) 1 gm of protein

(c) 1 gm of glucose

(d) 0.5 g of protein + 0.5 g of glucose

 Ans: (a) < (b) < (d) < (c)

This means 1 gm of glucose will release more energy compared to any other in this group.

7. The product of aerobic glycolysis in skeletal muscle and anaerobic fermentation in yeast are respectively _____________  and _______________

Ans: Carbon dioxide, ethanol

SHORT ANSWER TYPE QUESTIONS

1. If a person is feeling dizzy, glucose or fruit juice is given immediately but not a cheese sandwich, which might have more energy. Explain.

Ans: What makes glucose a more efficient fuel source than fat is that glucose undergoes aerobic cellular respiration to release energy molecules, carbon dioxide, and water molecules. As a result, glucose is absorbed more quickly than fat by the body. In order to combat dizziness, a person is given glucose or grape juice instead of a cheese sandwich because he needs instant energy.

2. What is meant by the statement “aerobic respiration is more efficient.”?

Ans: When aerobic respiration occurs, the substrate is completely oxidized into energy and carbon dioxide. When anaerobic respiration occurs, the substrate is not oxidized. The result is that more energy is produced in aerobic respiration per gram of substrate consumed than in anaerobic respiration. This is why aerobic respiration is considered to be more efficient than anaerobic respiration.

3. Pyruvic acid is the end product of glycolysis. What are the three s metabolic fates of pyruvic acid under aerobic and anaerobic conditions? Write in the space provided in the diagram.

Ans: (a) Lactic acid

 (b) Ethanol

 (c) Acetyl CoA

4. The energy yield in terms of ATP is higher in aerobic respiration than during anaerobic respiration. Why is there anaerobic respiration even in organisms that live in aerobic conditions like human beings and angiosperms?

Ans: Aerobic respiration yields more energy than anaerobic respiration. Despite this, many organisms (living in aerobic conditions) carry out anaerobic respiration. Anaerobic respiration happens under exigencies. For example, yeast carries out anaerobic respiration when it is faced with a deficiency of oxygen. In humans, anaerobic respiration occurs when the muscles are exhausted, and their cells fulfil sudden excess energy demand.

5. Oxygen is an essential requirement for aerobic respiration but it enters the respiratory process at the end. Discuss. 

Ans: Oxygen is an essential component of aerobic respiration, but its role occurs only at the very end. Through the removal of hydrogen from the system, oxygen directs the whole process. Hydrogen is finally absorbed by oxygen.

6. Respiration is an energy releasing and enzymatically controlled catabolic process which involves a step-wise oxidative breakdown of organic substances inside living cells. In this statement about respiration explain the meaning of (1) Step-wise oxidative breakdown (2) Organic substances (used as substrates).

Ans: It is the stepwise oxidation of the respiratory substrate that results in the breakdown of the substrate over time. Because cells require energy for several other purposes, the breakdown of the respiratory substrate occurs gradually over time. A single step of power release would release a large amount of energy that can be coupled with ATP synthesis. As a result, the cell is able to utilize energy most efficiently.

Organic Substances: Organic substances that are found in living organisms and that obtain energy through respiration are organic substances, for example carbohydrates, fats, and proteins.

7. Comment on the statement - Respiration is an energy producing process but ATP is being used in some steps of the process.

Ans: ATP is sometimes used by respiration as a source of energy for the body. As a result, in the process of ATP synthesis, an important intermediate is produced. During respiration, ATP is utilized twice. Once, it is used to convert glucose into glucose 6-phosphate. ATP is also used to convert fructose 6 - phosphate into fructose 1, 6 - bisphosphate. Finally, when the respiration of one molecule of glucose is complete, there is a net gain of 36 molecules of ATP. The net income of ATP is more important and shows that respiration is an energy-yielding activity.

8. The figure given below shows the steps in glycolysis. Fill the missing steps A, B, C, D and also indicate whether ATP is being used up or released at step E?

Ans:  A = fructose 6 – phosphate 

B = fructose 1, 6 biphosphate

C = triose phosphate

D = triose biphosphate

The energy is expended during the E process.

9. Why is the respiratory pathway referred to as an amphibolic pathway? Explain.

Ans: As a catabolic pathway, the respiratory pathway is traditionally understood to involve decomposing the respiratory substrates. It is energy that is produced by the breakdown of carbohydrates, fats, and proteins. 

The organism must undergo some metabolic intermediates to produce fatty acids and proteins. It is seen that the respiratory pathway participates in both catabolic and anabolic processes; for instance, Acetyl CoA would be withdrawn from the respiratory pathway if fatty acids or proteins are required. Amphibolic pathways are, therefore, respiratory pathways.

10. We commonly call ATP, the energy currency of the cell. Can you think of some other energy carriers present in a cell? Name any two.

Ans: NADP and NADPH are the other energy carriers present in the cell.

11. ATP produced during glycolysis is a result of substrate level phosphorylation. Explain.

Ans: When the formation of ATP happens by direct transfer of a phosphoryl (PO3) group to ADP from a phosphorylated reactive intermediate, this is called substrate-level phosphorylation. During glycolysis, ATP is formed at two stages because of the direct transfer of the phosphoryl group to ADP.

(a) When BPGA (bisphosphoglyceric acid) is converted into PGA (phosphoglyceric acid).

(b) When PEP (phosphoenolpyruvate) is converted into pyruvic acid.

12. Do you know any step in the TCA cycle where there is substrate level phosphorylation? Which one?

Ans: Each time a TCA cycle occurs, a substrate-level phosphorylation occurs. Succinic acid is created when succinyl CoA is converted to succinyl CoA. Consequently, GDP is converted into GTP (guanosine triphosphate).

13. In a way, green plants and cyanobacteria have synthesized all the food on the earth. Comment.

Ans: This is true to a great extent that cyanobacteria and green plants have synthesized all the food on the earth. There are some other autotrophs as well, but their contribution to the food basket of other organisms is negligible. Cyanobacteria are the primary producers in the aquatic environment, while green plants are the primary producers in terrestrial climates. These producers provide food for all other organisms directly or indirectly.

14. When a substrate is being metabolized, why does not all the energy that is produced get released in one step? It is released in multiple steps. What is the advantage of stepwise release?

Ans: Each step of the oxidation process releases energy in the following manner:

This prevents all energy from being used at once.

The body can store ATP for future use when it receives small amounts of energy.

The process can be made more efficient by making intermediaries with some energy.

It is also possible for the organism to use energy to make other substances.

15. Respiration requires O₂. How did the first cells on the earth manage to survive in an atmosphere that lacked O₂?

Ans: Anaerobes were believed to have been the first cells to exist on Earth. There are still many anaerobes on Earth today. Anaerobic respiration is capable of respiring some organisms. Anaerobic respiration can be used by facultative anaerobes when conditions are appropriate, but not by others that cannot. All organisms are able to partially oxidize glucose without oxygen due to this condition. Cells on earth must have been able to survive without oxygen when they were first created.

16. It is known that red muscle fibers in animals can work for longer periods of time continuously. How is this possible?

Ans: The red muscle fibres are thinner than the white muscle fibres. Their functionality can be extended for a longer period of time without becoming fatigued. They can function continuously for a long period of time due to the following factors:

When myoglobin is abundant, oxygen is readily available.

Their energy comes from aerobic respiration. As a result, they do not produce lactic acid in their muscles.

This means there is a large amount of stored ATP in these muscles because there are many mitochondria. Therefore, these muscles are able to work for a longer period of time.

17. The energy yield in terms of ATP is higher in aerobic respiration than during anaerobic respiration. Explain.

Ans: The aerobic respiration of glucose results in complete oxidation, while the anaerobic respiration of glucose results in incomplete oxidation. Anaerobic respiration is less efficient at producing energy than aerobic respiration. Anaerobic respiration produces only two molecules of ATP per molecule of glucose, whereas aerobic respiration produces 36 molecules of ATP per molecule of glucose.

18. RuBP carboxylase, PEP case, Pyruvate dehydrogenase, ATPase, cytochrome oxidase, Hexokinase, Lactate dehydrogenase. Select/choose enzymes from the list above which are involved in

(a) Photosynthesis

(b) Respiration

(c) Both in photosynthesis and respiration 

Ans: (a) RuBP carboxylase, PEP case

(b) Pyruvate dehydrogenase, Hexokinase, Lactate dehydrogenase

(c) ATPase, cytochrome oxidase

19. How does a tree trunk exchange gases with the environment although it lacks stomata?

Ans: A tree trunk is covered with woody bark. The bark is interspersed with lenticels. Exchange of gases takes place through lenticels; in this case.

20. Write two energy-yielding reactions of glycolysis.

Ans: The following are two energy-producing reactions associated with glycolysis:

PGA (phosphoglyceric acid) is created by the transformation of BPGA (bisphosphoglyceric acid)

A process by which PEP is converted into Pyruvic acid (phosphoenolpyruvate)

21. Name the site (s) of pyruvate synthesis. Also, write the chemical reaction wherein pyruvic acid dehydrogenase acts as a catalyst.

Ans: Pyruvate results from the breakdown of glucose in the cytoplasm.

Decarboxylation of pyruvate is carried out by pyruvic acid dehydrogenase. The following equations illustrate the process:

A combination of pyruvic acid, CoA, NAD+, Acetyl CoA, CO₂, NADH, and H+

Acetyl CoA is formed by decarboxylation of pyruvate  

22. Mention the important series of events of aerobic respiration that occur in the matrix of the mitochondrion as well as one that take place in the inner membrane of the mitochondrion.

Ans: Aerobic respiration takes place during the following events:

As pyruvate oxidizes completely in mitochondria, it is converted to pyruvate. As each hydrogen atom is removed one by one, oxidation occurs. Three molecules of carbon dioxide remain when all hydrogen atoms are removed.

During mitochondrial respiration, this event occurs on the inner membrane. A hydrogen atom loses its electrons, and the electrons are transferred to molecular oxygen in an atom exchange process. Adenosine triphosphate is synthesised simultaneously.

23. Respiratory pathway is believed to be a catabolic pathway. However, the nature of the TCA cycle is amphibolic. Explain.

Ans: During the TCA cycle, glucose is broken down, which shows a catabolic pathway. Additionally, FADH₂ and ATP are synthesized during this cycle. Thus, both catabolic and anabolic processes take place during the TCA cycle. Hence, the TCA cycle can say to be amphibolic.

LONG ANSWER TYPE QUESTIONS

1. In the following flow chart, replace the symbols a, b, c and d with appropriate terms. Briefly explain the process and give any two applications of it. 

Ans:

Anaerobic respiration is represented in this figure. The left side of this diagram shows glycolysis, while the right side depicts pyruvic acid's further processing.

Pyruvic acid can be converted into lactic acid by certain organisms. The pyruvic acid in pyruvic acid is converted to ethanol and carbon dioxide by a variety of organisms. Energy is released in this way.

Anaerobic respiration is carried out in two ways:

Cakes and bread are made using yeast from fungal fermentation, which reproduces anaerobically.

As an inoculum, it is necessary to use a small quantity of lactobacillus to make curd.

2. Given diagram shows ATP synthesis during aerobic respiration. Replace the symbols A, B, C, D and E by appropriate terms given in the box.

F1, Particle, Pi, 2H+, Inner mitochondrial membrane, ATP, F0 particle, ADP 

Ans: 

3. Oxygen is critical for aerobic respiration. Explain its role with respect to ETS.

Ans: In the Electron Transport System, NADH + H+ and FADH₂ are energy carriers to produce ATP. Electrons are transferred through a sequence of events and finally to the oxygen molecule. The oxygen molecule works like the final acceptor of hydrogen to form water molecules. Although oxygen comes at the end, it is critical for aerobic respiration. Oxidative phosphorylation involves a chain of events in which electrons are transferred through an electron gradient. Phosphorylation is like the flow of water through a tap. Until the tap is not open to allow the first drop of water, subsequent drops of water cannot flow down.

Oxygen acting as a hydrogen acceptor is like a receptacle collecting the first electron so that.

It is possible to maintain the subsequent flow of electrons through ETS. Hence, oxygen is necessary to create a gradient through which electrons can be transferred passively.

4. Enumerate the assumptions that we undertake in making the respiratory balance sheet. Are these assumptions valid for a living system? Compare fermentation and aerobic respiration in this context.

Ans: The respiratory balance sheet is calculated based on the following assumptions:

Respiration is a sequential process that follows an orderly pattern.

Once NADH has been synthesized through glycolysis, it is oxidatively phosphorylated in the mitochondria.

No intermediate in the pathway can be used to synthesize a compound.

Oxidation of glucose is the only process occurring. Neither intermediate substrates nor intermediate products are utilized.

These assumptions, however, do not apply to a living system. Because pathways operate simultaneously, they are not always sequential. Adenosine triphosphate and ATP are used when needed. Glucose may not be the only fuel available. Although this calculation has practical limitations, it is nonetheless very useful.

5. Give an account of Glycolysis. Where does it occur? What are the end products? Trace the fate of these products in both aerobic and anaerobic respiration.

Ans: Glycolysis involves glucose being broken down into pyruvic acid. Therefore, glucose within the cytoplasm is partially oxidized. Embden, Meyerhof, Pranas (EMP) is also what the scientists who first explained the pathway called it. Glycolysis is composed of the following steps.

• In order to produce glucose-6-phosphate, glucose must first undergo phosphorylation. 

• Fructose-6-phosphate is then converted into PGAL (Phosphoglyceraldehyde). 

• Pyruvic Acid is then formed by breaking down PGAL molecules.

• By converting glucose into ATP, each glucose molecule gains two ATP molecules.

Pyruvate's fate can be summarized as follows:

The oxidation of pyruvic acid produces energy and carbon dioxide during aerobic respiration.

Anaerobic respiration occurs when oxygen is not present in an organism's environment. As a result of inadequate oxygen supply, pyruvic acid can be converted into lactic acid in some organisms.

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About the Chapter

In the chapter Respiration in Plants, the students learn about the definitions of terms like respiration and how it takes place in different organisms. This chapter mostly follows the respiration in plant kingdom and thus, it is necessary for students to know about the various processes plants undergo and how they respire, cellular respiration, respiratory substrates, glycolysis and how plants respire, fermentation, aerobic respiration, tricarboxylic acid cycle, electron transport system (ETS) and oxidative phosphorylation, the respiratory balance sheet, amphibolic pathway, and respiratory quotient. 

Some of the concepts such as cellular respiration refer to the breakdown of glucose at the cellular level. The respiratory substrates are the raw nutrients that get oxidised due to the process of respiration. Glycolysis is the process of conversion of glucose into pyruvic acid. The students will also learn that there are certain cycles that take place for the whole process of respiration of plants to be completed. Aerobic respiration is the breakdown of glucose in the presence of oxygen whereas anaerobic is when respiration happens in the absence of oxygen. Tricarboxylic cycle is also known as the Krebs Cycle. In this topic, the students will study eight different reactions that occur in the powerhouse of a cell or mitochondria to oxidise Acetyl-Coa to carbon dioxide. 

This is an important chapter from botany so all the students of Class 11 should make sure to clear their doubts using the Vedantu study material available for free at Vedantu.com.

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