NCERT Exemplar Class 11 Biology Solutions Chapter 14 Respiration in Plants

Multiple Choice Questions:

Question:1

The ultimate electron acceptor of respiration in an aerobic organism is
(a) cytochrome
(b) oxygen
(c) hydrogen
(d) glucose.

Answer:

The answer is the option b) oxygen
Explanation: the electrons accepted by the oxygen molecules are the ones that are removed from hydrogen, which makes oxygen an electron acceptor.

Question:2

Phosphorylation of glucose during glycolysis is catalysed by
(a) phosphoglucomutase
(b) phosphoglucoisomerase
(c) hexokinase
(d) phosphorylase

Answer:

The answer is the option c) hexokinase
Explanation: hexokinase is responsible for the phosphorylation of glucose which leads to the production of glucose-6-phosphate.

Question:3

Pyruvic acid, the key product of glycolysis, can have many metabolic fates. Under aerobic condition, it forms
(a) lactic acid
(b) CO₂ + H₂O
(c) acetyl CoA + CO₂
(d) ethanol+ CO₂

Answer:

The answer is the option c) Acetyl CoA + CO₂
Explanation: Acetyl CoA, CO₂ and NADH are the products obtained when Pyruvic acid undergoes dehydrogenation reaction.

Question:4

Electron Transport System (ETS) is located in mitochondrial
(a) outer membrane
(b) intermembrane space
(c) inner membrane
(d) matrix.

Answer:

The answer is the option (c) Inner membrane
Explanation: ETS is the electron transport system which as carrier molecules that can act as electron accepters as well as donors, and it is present in the inner membrane of mitochondria.

Question:5

Which of the following exhibits the highest rate of respiration?
(a) Growing shoot apex
(b) Germinating seed
(c) Root tip
(d) Leaf bud

Answer:

The answer is the option (b) Germinating seed

Explanation: germination is the process which has the maximum growth rate as compared to other options and has the highest respiration rate, hence germinating seed is the correct answer.

Question:6

Mitochondria are called powerhouses of the cell. Which of the following observations support this statement?
(a) Mitochondria synthesise ATP.
(b) Mitochondria have a double membrane.
(c) The enzymes of the Krebs’ cycle and the cytochromes are found in mitochondria.
(d) Mitochondria are found in almost all plant and animal cells.

Answer:

The answer is the option (a) Mitochondria synthesise ATP
Explanation: Mitochondria which synthesises ATP (Adenosine triphosphate) is called the powerhouse of the cell as ATP provides the energy to fuel many processes of the cell.

Question:7

The end product of oxidative phosphorylation is
(a) NADH
(b) Oxygen
(c) ADP
(d) ATP + H 2 O.

Answer:

The answer is the option (d) ATP + H₂O
Explanation: this process is mainly used for oxidisation of nutrients by the use of enzymes in order to release energy and molecular oxygen.

Question:8

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

(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

Answer:

The answer is the option (a) A – (ii), B – (iii), C – (iv), D – (i)

Very Short Answer Type Questions:

Question:1

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

Answer:

Career DataDuring the process of respiration, energy is released. This is the energy which gets stored inside the Mitochondria in the form of ATP molecules. Whenever our body needs energy, it is released from the Mitochondria in the form of ATP molecules which are then broken down to release energy.

Question:2

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

Answer:

Energy currency means a reserve of energy which can be used as a currency to obtain something at the required times. ATP is called the energy currency as it acts as an energy source which is released as and when our body requires it. It is present in plants as well as animals as an energy source.

Question:3

Different substrates get oxidised during respiration. How does Respiratory Quotient (RQ) indicate which type of substrate, i.e., carbohydrate, fat or protein is getting oxidised?
R.Q.=A/B
What do A and B stand for?
What type of substrates have R.Q. of 1,< 1 or >1 ?

Answer:

a) The volume of carbon-di-oxide is indicated by A. the volume of oxygen consumed is indicated by B.
b) Respiratory quotient
=1 (equal to 1), for carbohydrates
<1 (Less than 1), for fats and proteins
>1 (greater than 1), No substance

Question:4

F₀ -F₁ particles participate in the synthesis of

Answer:

ATP synthesis is the process in which particles participate.

Question:5

When does anaerobic respiration occur in man and yeast?

Answer:

In the case of yeast, when there is an unavailability of oxygen, anaerobic respiration takes place. However, in the case of man, the anaerobic process takes place in special cases. These include the situations of strenuous physical exercise in which muscle cells require a lot of extra energy.

Question:6

Which of the following will release more energy on oxidation? Arrange them in ascending order,
(a) Igmoffat
(b) 1 gm of protein
(c) 1 gm of glucose
(d) 0.5 g of protein + 0.5g glucose

Answer:

As compared to all the elements in the options, 1 gm of glucose will release the highest amount of energy during the process of oxidation.

Question:7

The product of aerobic glycolysis in skeletal muscle and anaerobic fermentation in yeast are respectively __________and__________

Answer:

Carbon-di-oxide and ethanol are the products when the process of aerobic glycolysis in muscles and anaerobic fermentation in yeast takes place.

Short Answer Type Questions:

Question: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.

Answer:

Glucose and fats both provide energy. However, glucose is a quicker and more instant source of energy than fats as the aerobic cellular respiration releases instant energy from glucose. This process creates CO₂ and water as its by-products. Also, the absorption rate of glucose in our body is faster than fats. Hence when a person is feeling dizzy, he or she should be given glucose at the earliest and a food product containing fats.

Question:2

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

Answer:

Unlike anaerobic respiration, the process of aerobic respiration leads to complete oxidation of substances. This reaction releases energy and carbon-di-oxide. So, in the case of aerobic respiration, a larger amount of energy is produced as compared to anaerobic respiration process as complete oxidation takes place. Hence, aerobic respiration is considered as an efficient process.

Question:3

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

Answer:

(a) Lactic acid
(b) Ethanol
(c) Acetyl CoA

Question: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 condition like human beings and angiosperms?

Answer:

Anaerobic respiration generally does not lead to the production of a higher amount of energy as compared to the aerobic respiration process. But still, in certain circumstances, organisms do undergo anaerobic respiration in the absence of enough supply of oxygen.


Humans undergo anaerobic respiration in muscle cells when they are involved in intense physical activities, and the muscles are exhausted. Also, yeast undergoes anaerobic respiration when there is a dearth of atmospheric oxygen in the surroundings.

Question:5

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

Answer:

The role of oxygen in the process of aerobic respiration is only at the end of the terminal of the process. The vital importance of oxygen is because it drives the hydrogen out of the body by driving the whole process and acting as a final hydrogen acceptor.

Question: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
(i) Step-wise oxidative breakdown
(ii)Organic substances (used as substrates)

Answer:

(i) Step-wise oxidative breakdown
The oxidation of an element does not happen in one single go. It happens in a step by step process known as a step-wise oxidative breakdown. The cells of our body also require some energy to perform other functions. This step by step release of energy would ensure proper utilisation of energy and make it large enough to be associated with the synthesis of ATP molecules.
ii) Organic Substances
Organic substances are the ones which are present in the living organisms. These substances are oxidised in the process of respiration so as to release energy. Examples of organic substances are carbohydrates, proteins and fats.

Question:7

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

Answer:

ATP molecules are also used in the process of respiration which also involves energy production. It is used to fuel energy into the formation of some intermediaries amidst the respiration process. It is used two times in the process of respiration, which includes: conversion of glucose into glucose 6-phosphate and conversion of fructose 6 - phosphate into fructose 1, 6 - biphosphate. There is a gain of 36 ATP molecules when oxidation of one molecule of glucose takes place. Hence the net gain higher than the consumption, and that is why we can label the respiration process as an energy-yielding process.

Question:8

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

Answer:

Step A: fructose 6 – phosphate
Step B: fructose 1, 6 biphosphate
Step C: triose phosphate
Step D: triose biphosphate
And finally, at Step E, we can conclude that the energy is being used up.

Question:9

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

Answer:

Generally, the pathway of respiration is also called the catabolic pathway. This happens as it involves in the release of energy by breaking down substances. Most of the times, organic substances like carbohydrates, proteins and fats are converted into energy by breaking them down but sometimes an intermediate product of this process like Acetyl CoA will be used by the body to synthesise proteins or fats again. Hence the process of respiration is both a catabolic as well as an anabolic pathway.

Question:10

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

Answer:

The other energy carriers present in the cell include NADP (Nicotinamide adenine dinucleotide phosphate) and NADPH (Nicotinamide Adenine Dinucleotide Phosphate Hydrogen).

Question:11

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

Answer:

Substrate level phosphorylation is the stage where the ATP formation is happening by the transferring of the phosphoryl (PO3) group from a phosphorylated reactive intermediate to ADP happens. In the process of glycolysis, ATP formation happens at two main stages which are as follows:
1) Conversion of BPGA (biphosphoglyceric acid) into PGA (phosphoglyceric acid).
2) Conversion of PEP (phosphoenolpyruvate) into pyruvic acid.

Question:12

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

Answer:

There is one stage in the citrus cycle where there is substrate level Phosphorylation. It is the one where succinic acid is produced from succinyl CoA. So, it leads to a conversion of GTP (Guanosine triphosphate) molecule to GDP molecule.

Question:13

ln, a way green plants and cyanobacteria have synthesised all the food on the Earth. Comment.

Answer:

The statement green plants and cyanobacteria have synthesised all the food on the Earth is quite true and can be justified as follows. Since the major producers in the aquatic environment are cyanobacteria and the major producers for terrestrial organisms are plants, all the other organisms are dependent in a direct or indirect manner on these producers.

Question:14

When a substrate is being metabolised, 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 step-wise release?

Answer:

The advantages of stepwise energy release in oxidation are:
- Prevention of all the energy being used up in one go
- Stored energy reserves in the form of ATP can also be used in future
- The making of intermediary products also requires energy
- The stored energy can also be used in other processes in the body

Question:15

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

Answer:

According to the scientists, the category of the cells which were found on the Earth was anaerobes. These cells carried out anaerobic respiration and did not require a continuous supply of oxygen for this process. Also, under special situations, all organisms can respire in an anaerobic manner and partially oxidise the glucose. Owing to this ability, the cells may have survived the atmosphere without oxygen.

Question:16

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

Answer:

The reasons that red muscle fibres in animals can work for longer periods of time Continuously are:

- They are thin muscle fibres
- They get plenty of oxygen supply due to the high amount of myoglobin
- Lactic acid is not formed here as they resort to aerobic respiration
- The number of mitochondria is high in number and hence has a good supply of energy through ATP molecules

Question:17

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

Answer:

In the case of aerobic respiration, the oxidation of glucose happens completely, which leads to a net gain of 36 ATP molecules for one glucose molecule. While, in anaerobic respiration, the oxidation of glucose does not happen in a complete manner, and the number of ATP molecules produced is just 2 for one molecule of glucose.

Question:18

RuBP carboxylase, PEPcase, 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

Answer:

(a) enzymes involved in photosynthesis are: RuBP carboxylase, PEPcase
(b) enzymes involved in respiration are: Pyruvate dehydrogenase, Hexokinase, Lactate dehydrogenase
(c) enzymes involved in photosynthesis as well as respiration are ATPase, cytochrome oxidase

Question:19

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

Answer:

The tree trunk does not have stomata like in the green leaves. But it is covered with a wooden bark which contains lenticels. These lenticels facilitate the exchange of gases in the case of tree trunks.

Question:20

Write two energy-yielding reactions of glycolysis.

Answer:

The two reactions in the glycolysis which yield energy are:
(a) Formation of PGA (phosphoglyceric acid) from BPGA (biphosphoglyceric acid)
(b) Formation of Pyruvic acid (phosphoenolpyruvate) from PEP

Question:21

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

Answer:

The main site for the formation of pyruvate is the cytoplasm of a cell.
pyruvic acid dehydrogenase acts as a catalyst in the decarboxylation of pyruvate, as
shown below:

The reaction of decarboxylation of pyruvate produces Acetyl CoA as a by-product.

Question:22

Mention the important series of events of aerobic respiration that occurs in the matrix of the mitochondrion as well as one that takes place in the inner membrane of the mitochondrion.

Answer:

The important series of events of aerobic respiration that occur in the are as follows:
a) The matrix of mitochondria

1. Complete oxidation of pyruvate. This oxidation is a step by step procedure. It involves the elimination of all the atoms of hydrogen, leaving behind three molecules of CO₂ .

2. The inner membrane of the mitochondrion.

Oxygen acts as an electron accepter here. As the hydrogen atoms are passed to oxygen atoms, removal of electrons take place along with the formation of ATP molecules.

Respiration in Plants Excercise: 1.4

Question:23

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

Answer:

The citrus cycle involves breaking down of the glucose molecules depicting catabolic behaviour. And it also involves the formation of FADH2 and ATP molecules which depict its anabolic behaviour. Hence both these process takes place in the TCA cycle, and this is the reason because of which it can be labelled as amphibolic.

Long Answer Type Questions:

Question: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 application of it.

Answer:

The major pathways or the sequence of the steps are shown in the image above. The left flowchart depicts the process of glycolysis. The right flow chart depicts the processing of pyruvic acid, which then leads to the formation of lactic acid. In some
organisms to produce CO 2 and ethanol, pyruvic acid is processed to release some amount of energy. The applications of anaerobic respiration are:
- To bring the rise in bread and cakes and make it fluffy, the yeast undergoes anaerobic reproduction.
- In the formation of curd, when inoculum is lactobacillus

Question:2

Given below is a diagram showing ATP synthesis during aerobic respiration, replace the symbols A, B, C, D and E by appropriate terms given in the box.

F₁ , Particle, P_i , 2H ⁺ , Inner mitochondrial membrane, ATP, F 0 particle, ADP.

Answer:

Question:3

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

Answer:

NADH⁺ , H⁺ and FADH₂ are the carriers of energy in the electron transport system. These carriers are utilised to produce ATP during this process. Oxygen molecules accept electrons which are transferred to them through a series of reactions. Oxygen molecules accept the hydrogen molecules and lead to the formation of water molecules. This process is important for the aerobic respiration process.

The process of Oxidative phosphorylation involves the transfer of electrons which can be related to the flow of water through a tap. Just as in that case the droplets cannot flow down until the first drop is allowed to pass through, after the first electron is allowed, others follow when the oxygen starts accepting electrons as a hydrogen acceptor. That is the reason due to which the presence of oxygen is necessary for the electron transfer to be made possible by the creation of a gradient.

Question: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.

Answer:

The assumptions that are made during the calculation of a respiratory balance sheet are:

- An orderly and sequential pathway is followed in the process of respiration.
- During the process of glycolysis, NADH is produced. This undergoes oxidative phosphorylation inside the mitochondria.
- No intermediate products are utilised in the formation of other products
- Glucose is oxidised only, and no other substance is utilised at any in-between stages The above assumptions are invalid for a living organism. The processes need to take place in a simultaneous manner and not following a strict sequential path.

Question: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.

Answer:

Pyruvic acid is formed in the process of glycolysis due to the breakdown of glucose which takes place in the cytoplasm of the cell. This process also involves partial oxidation of glucose molecules known as the EMP pathway. The important steps involved in the process of glycolysis are as follows:

- Phosphorylation of glucose for the production of glucose-6-phosphate
- Formation of PGAL (Phosphoglyceraldehyde) through the conversion of Fructose-6-phosphate
- The molecules of PGAL are further processed for the production of Pyruvic acid.
- Two molecules of ATP are gained in the process of glycolysis of one glucose molecule
Aerobic Respiration of Pyruvate:
Complete oxidation of Pyruvic acid takes place and carbon dioxide and Energy is produced as a result of this reaction.

Anaerobic Respiration Pyruvate:
In the absence of oxygen Anaerobic Respiration takes place, and ethanol and CO₂ are produced from the conversion of pyruvic acid. In some organisms who face a complete absence of oxygen, the pyruvic acid can also be converted to lactic acid.