CBSE Class 11 Biology Chapter 17 Question Answer

Class 11 Biology Chapter 17 Important Questions – Breathing and Exchange of Gases

Biology is called the science of life. The biological world is all around us, so studying its diverse fields and newly introduced modern techniques are important. The subject of biology in Class 11 introduces a wide variety of important topics crucial for understanding higher-level concepts in Class 12. Topics and questions related to Class 11 Biology hold good weightage in competitive examinations like NEET, MH-CET and others.

Chapter 17 of Class 11 is about breathing and the exchange of gases. It is a crucial chapter in Class 11 Biology and explains the breathing mechanism and absorption of gases like O2 and CO2 in humans. Students must note that the questions from this chapter are frequently asked in board exams and other competitive examinations. 

Students can solve exercise questions provided in the NCERT textbook and other exemplar questions to prepare themselves well for their examinations.

Extramarks is one of the most trusted online learning platforms for students studying from Class 1 to Class 12. Extramarks helps students create a strong foundation for future studies across various streams. Registered students can easily understand different concepts from various chapters by referring to NCERT solutions, CBSE revision notes, CBSE sample papers, CBSE previous year question papers and other study materials prepared by the Extramarks. These study materials are developed by the experienced science faculty appointed by Extramarks. 

The biology faculty have prepared this set of Important Questions Class 11 Biology Chapter 17 after thoroughly analysing the entire syllabus and subject. Each question is followed by stepwise solutions that will assist students in understanding the concept more clearly and clarify any previous doubts. 

It is essential to regularly review the topics and solve multiple questions to understand the different concepts introduced in the chapter. The Extramarks team understands the importance of chapter revision, which is the reason behind creating various questions and their solutions for students and making it available in the form of Important Questions Class 11 Biology Chapter 17.

Breathing and Exchange of Gases Questions and Answers for the Academic Year 2022-23.

Class 11 Biology Chapter-wise important questions are available for free to students, and these questions are perfect for self-study.

Check out CBSE Class 11 Biology Important Questions for other chapters as well:

CBSE Class 11 Biology Important Questions

Sr No. Chapters Chapters Name
1 Chapter 1 The Living World
2 Chapter 2 Biological Classification
3 Chapter 3 Plant Kingdom
4 Chapter 4 Animal Kingdom
5 Chapter 5 Morphology of Flowering Plants
6 Chapter 6 Anatomy of Flowering Plants
7 Chapter 7 Structural Organisation in Animals
8 Chapter 8 Cell the Unit of Life
9 Chapter 9 Biomolecules
10 Chapter 10 Cell Cycle and Cell Division
11 Chapter 11 Transport in Plants
12 Chapter 12 Mineral Nutrition
13 Chapter 13 Photosynthesis in Higher Plants
14 Chapter 14 Respiration in Plants
15 Chapter 15 Plant Growth and Development
16 Chapter 16 Digestion and Absorption
17 Chapter 17 Breathing and Exchange of Gases
18 Chapter 18 Body Fluids and Circulation
19 Chapter 19 Excretory Products and their Elimination
20 Chapter 20 Locomotion and Movement
21 Chapter 21 Neural Control and Coordination
22 Chapter 22 Chemical Coordination and Integration

CBSE Class 11 Biology Chapter 17 Question Answer 

The chapter covers the difference between breathing and respiration, respiratory organs in different organisms, and the human respiratory system that includes parts like the nasal chamber, pharynx, larynx, trachea, primary, secondary and tertiary bronchi, alveoli, etc. It also explains the mechanism of breathing, respiration steps, respiratory volume and its capacities, exchange and transport of gases like oxygen, carbon dioxide, haemoglobin, regulation of respiration, disorders of the respiratory system and so on. 

The solutions from our Important Questions Class 11 Biology Chapter 17 explains all these different concepts that are important to understand and clear the examination. 

The set of Biology Class 11 Chapter 17 important questions will cover most of the topics mentioned in the chapter and help students easily revise their concepts and theories. After going through these question-answer sets, students will know their strengths and weaknesses among the various topics covered in the chapter. This will help students develop a core foundation and build more knowledge.

Given below is a list of questions from the Class 11 Biology Chapter 17 important questions and their solutions:

Question 1. It is known that exposure to carbon monoxide is harmful to animals because

  • It destroys haemoglobin.
  • It reduces CO2 transport.
  • It increases O2 transport.
  • It increases CO2 transport.

Answer 1: The correct option is B

Explanation of the correct option:

  1. Carbon monoxide destroys haemoglobin.
  2. Carbon monoxide is known to combine more readily with haemoglobin than with oxygen.
  3. It forms the stable compound carboxyhemoglobin.
  4. Thus, fewer molecules of free haemoglobin become available for oxygen transport.

Question 2. Define vital capacity. What is its significance?

Answer 2: Vital capacity is the maximum volume of air that can be exhaled after a maximum inspiration. It is around 3.5 – 4.5 litres in the human body. It allows the intake of maximum fresh air and removes the foul air within a single stroke of respiration. Hence, it causes an increase in gaseous exchange between the various tissues of the body, which leads to increased energy available for body functioning.

Question 3. Write a note on the mechanism of breathing.

Answer 3: The breathing process is carried out through different respiratory organs such as the nose, pharynx, larynx, trachea, bronchi, and lungs. The action of breathing in and out is because of the pressure changes within the thorax compared to the pressure in the outside environment. This action is also called external respiration. When we inhale, our diaphragm muscles contract downward, and rib muscles pull upward. This action causes an increase in the thoracic cavity. The pulmonary volume of the lungs also increases. Due to the increase in the size of the thoracic cavity, the internal air pressure decreases. As a result, air from the outside rushes into the lungs to equalise the pressures on both sides. This is known as inspiration.

While exhaling, the diaphragm and intercostal muscles relax and return to their resting positions. The diaphragm regains its dome shape. Due to this relaxation, the size of the thoracic cavity reduces. This reduction increases the pressure in the lungs, and the air is pushed from the lungs to the outside through the nose. This is called expiration. Inspiration and expiration are the two main mechanisms of breathing.

Question 4. What are the major transport mechanisms for CO2? Explain.

Answer 4: Carbon dioxide is said to be liberated by a vigorously active tissue in the blood. On average, 100ml of blood accepts approximately 3.7ml of carbon dioxide from tissues. In blood, CO2 is carried in three forms:

  1. Carbon dioxide as a simple solution:

Nearly 5-10% of carbon dioxide in the total volume of blood is dissolved in plasma. Carbon dioxide is transported as a simple physical solution.

  1. Carbon dioxide as a bicarbonate ion:

The partial pressure of carbon dioxide at the tissue site is high due to catabolism. Carbon dioxide diffuses in the blood and forms carbonic acid after reacting with water. This reaction occurs in the presence of the carbonic anhydrase enzyme. 

The reaction is as follows:

carbon dioxide

Carbonic acid dissociates into H+ ions and bicarbonate. Some amount of bicarbonate ions is required to sustain the pH of the blood. The proteins use the hydrogen ions; the plasma picks up the remaining bicarbonate ions.

  1. Carbon dioxide as carbamino-haemoglobin:

In tissues, when the partial pressure of oxygen is observed to be lower, and the pressure of carbon dioxide is higher, the CO2 loosely combines with the globin section of the reduced haemoglobin. As a result of this combination, carbamino-haemoglobin is formed. 

The reaction is as follows:


When pO2 is higher, and the pCO2 is lower at the alveolar level, the CO2 dissociates from carbamino-haemoglobin. Therefore, carbon dioxide bound to haemoglobin is liberated in the alveoli.

Question 5. The incidence of emphysema, a respiratory disorder, is high in cigarette smokers. In such cases:

  1. the bronchioles are found damaged.
  2. the alveolar walls are found damaged.
  3. the plasma membrane is found damaged.
  4. the respiratory muscles are found damaged.

Answer: The correct option is B

Explanation of the correct option:

  1. Emphysema is a chronic disorder. 
  2. The alveolar walls are damaged in emphysema due to infection or abnormal dispersion.
  3. It is a respiratory disorder caused primarily by cigarette smoking. 
  4. It can also be caused by inhalation of other smoke or toxic substances over a while.

Explanation of the incorrect option:

Options A, C and D did not satisfy the appropriate explanation of the given question.

Question 6. What happens to the respiratory process in someone going uphill?

Answer 6: When a man goes uphill, the altitude keeps increasing. As there is an increase in altitude, the oxygen level in the atmosphere decreases. Therefore, as a man goes uphill, he gets less oxygen with each breath. This uphill movement causes the amount of oxygen in the blood to decline—the respiratory rate increases in response to the decrease in blood oxygen content. Simultaneously, the heartbeat rate increases the supply of oxygen to the blood.

Question 7. What is the role of the neural system in controlling respiration?

Answer 7: The neural system plays an important role in regulating respiration. The neural system helps maintain and moderate the respiratory rhythm as per the demands of the body tissues. Regulation of respiration depends on various intrinsic and extrinsic factors. The respiratory rhythm centre is located in the medulla region. This is a specialised centre and is primarily responsible for the regulation of respiration. The pneumatic centre is located in the pons region of the brain. It can moderate the functions of the respiratory rhythm centre. Nerve signals from the pneumatic centre can reduce the duration of inspiration and can thus alter the respiratory rate. A chemosensitive section adjacent to the rhythm centre is very sensitive to hydrogen ions and CO2, which activates this centre by increasing these substances. Then, the chemosensitive area can signal the rhythm centre to make necessary adjustments to eliminate these substances. There are receptors associated with the aortic arch and carotid artery. These receptors can also recognise changes in CO2​ and H+ concentration. After that, they send necessary signals to the rhythm centre to take corrective actions. The presence of oxygen is quite insignificant in regulating the respiratory rhythm centre. 

Question 8. Explain the transport of O2 and CO2 between alveoli and tissue with a diagram.

Answer 8:

Exchange of gases between alveoli and tissues:

The primary site for the process of exchange between gases is alveoli. The exchange of gases between alveoli and tissue takes place through simple diffusion, which depends upon the following factors:

  • A partial pressure gradient of gases across alveoli and tissues
  • Solubility of the gases
  • Diffusion membrane
  • Diffusion of O2 across alveo

The partial pressure of O2 is higher in the alveoli, i.e., 104 mmHg, compared to the deoxygenated blood (40 mHg). Therefore, O2 diffuses into the blood through the diffusion membrane. 

Transport of O2 to various body parts: 

O2 is transported by blood in the following ways:

  • Transport via RBCs (in the form of oxyhaemoglobin): About 97% of O2.
  • Transport via plasma (in the dissolved state): Remaining 3% of oxygen-rich blood reaches the left atrium from the lungs via the pulmonary veins. The left ventricle is carried by the systemic arteries, reaching the body tissues.
  • Diffusion of O2 across tissue pO2 is more in the oxygenated blood (95 mmHg) than in the tissues (40 mmHg). Hence, O2 diffuses into the tissues from the blood.

alveoli and tissue

Benefits of Solving Breathing and Exchange of Gases Important Questions

If you like learning about different living organisms and how they relate to each other and their environment, then studying biology is the right fit for you. A biology major can give an in-depth understanding of the natural biological world surrounding us. It allows you to learn and understand the importance of researching various topics, problem-solving, organising a piece of the given information and thinking critically and logically. 

Conceptual learning is one of the key factors in studying biology. Students must actively participate and try to solve maximum questions and books available to students to help them excel in their academics.

We recommend students register at the Extramarks website and access all the study materials besides Important questions Class 11 Biology Chapter 17.

With regular revision and question-solving, students can quickly cover different topics throughout their course.

These are the benefits of solving important questions Class 11 Biology Chapter 17: 

  • The solutions to important questions Class 11 Biology Chapter 17 are prepared with the latest syllabus and guidelines the CBSE board has been given.
  • Extramarks has compiled the solutions to the questions after running a thorough analysis on the NCERT textbook and various other sources. We assure that students can rely on these solutions without a doubt.
  • Experienced biology experts have curated these questions.
  • It will help students get an idea of the chapter, learn the syllabus, and revise the lessons, concepts, and theories in just a few days.
  • Students start to develop the quality of strategic scheduling. They learn to prioritise various important activities and start working on the principle of time management. Hence students can strive efficiently toward their goals. 
  • The questions given are for extra practice and to help understand the complex concepts and solve related questions. 
  • The list of complete Chapter 17 Class 11 Biology important questions offers detailed information on the practicalities of clearing the question paper.  

Extramarks assist students by providing a wide range of study materials to work on their doubts and clear them.

Click below to access different other materials on the Extramarks website. 

Q.1 A complete respiratory cycle involves:



A complete respiratory cycle involves three phases:

i) Inspiration ? breathing in air

ii) Rest period ? short pause

iii) Expiration ? breathing out air

Q.2 Alisa recorded the following data by measuring her breathing rate and heart rate under these two conditions:
a) At rest
b) During exercise

Rate (Per min) At Rest During exercise
Breathing Rate (breaths/ min) 17 54
Heart Rate (beats/ min) 72 144

What should be the correct analysis of the data?



Both breathing rate and heart rate are normal when our body is at the state of rest.


Both breathing rate and heart rate are normal when our body is at the state of rest, increase at the time of exercise and then become back to normal at the state of recovery.

Q.3 Cherry?s father is suffering from asthma due to which he is facing difficulty in breathing.
Which factor has caused the blockage in the bronchioles and thus; reduced the airflow?



The major factor that caused blockage in the bronchioles and thus; reduced the air flow is the deposition of mucus due to its excess production.

Q.4 Carefully analyse the data given below. 

Name No. of Breaths/ Minute
Walking Jogging Running
Peter 16 25 34
Harry 15 19 25
Tom 15 26 33
David 19 29 37

Among them, who is an athlete?



Harry is an athlete because his heart has become more efficient to pump a large amount of blood.

Q.5 Recall the diagram of the human respiratory system and compare it with the given model. Choose the correct option with the parts that are analogous to the parts of the human respiratory system.



Tube-Trachea, Bell jar-Chest cavity, Balloon-Lung, Rubber sheet-Diaphragm

In the given diagram, the tube is analogous to the trachea, bell jar is analogous to the chest cavity, the balloon is analogous to the lung, while the rubber sheet is analogous to the diaphragm.

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FAQs (Frequently Asked Questions)

1. Why is it important for a student to revise the concepts of the previous class?

Some students find the subject of biology hard and challenging; like in mathematics and other subjects, learning biology is a cumulative process. Before one can understand complex biological concepts and theories, one must first comprehend the basics. If you just read your biology textbook or copy your classmate’s notes, it will not compensate for missing the class. Biology is a complex hands-on subject. It involves understanding different biological systems for which explanation and experimentation are required. What you learn from each class creates a building block for learning different topics in the future. 

Read the textbook before each lecture and complete your lab assignments on time. While preparing for the next class, revising the initial concepts is necessary. Biology is filled with several complex systems and processes that you must understand, memorise, apply and reproduce in your exam, for assignments assigned by your teacher, and quite possibly for your future career. 

Imagery, particularly drawings and diagrams, can make even the most challenging biological processes easy to understand and remember. It is observed that students who attend biology class regularly and are in touch with previous concepts along with the ongoing ones are more likely to perform better and score higher grades in exams.

2. Which are the chapters included in the Class 11 Biology syllabus?

Below is a list of all chapters from CBSE Class 11 Biology:

  • Chapter 1 The Living World
  • Chapter 2 Biological Classification
  • Chapter 3 Plant Kingdom
  • Chapter 4 Animal Kingdom
  • Chapter 5 Morphology of Flowering Plants
  • Chapter 6 Anatomy of Flowering Plants
  • Chapter 7 Structural Organisation in Animals
  • Chapter 8 Cell the Unit of Life
  • Chapter 9 Biomolecules
  • Chapter 10 Cell Cycle and Cell Division
  • Chapter 11 Transport in Plants
  • Chapter 12 Mineral Nutrition
  • Chapter 13 Photosynthesis in Higher Plants
  • Chapter 14 Respiration in Plants
  • Chapter 15 Plant Growth and Development
  • Chapter 16 Digestion and Absorption
  • Chapter 17 Breathing and Exchange of Gases
  • Chapter 18 Body Fluids and Circulation
  • Chapter 19 Excretory Products and their Elimination
  • Chapter 20 Locomotion and Movement
  • Chapter 21 Neural Control and Coordination
  • Chapter 22 Chemical Coordination and integration


3. How are Important Questions Class 11 Biology Chapter 17 available on the Extramarks website helpful for students in scoring good marks?

Extramarks is one of the most trusted online learning platforms for students from Class 1 to Class 12. We provide a comprehensive suite of study materials, including NCERT solutions and chapter notes, CBSE revision notes, solutions to past exam questions, etc. Our question bank of Important Questions Class 11 Biology Chapter 17 is crucial study material for students to practise exam-oriented questions. While solving the questions, students will be able to self-assess their weak areas. Expert science teachers prepare our solutions. They are available with step-by-step guidance, making it easy for students to understand and even revise the concepts used in the answers.

So our question bank of Chapter 17 Class 11 Important Biology Questions ensures that all core topics of the chapter are covered while solving these questions. 

4. Can I score full marks in Class 11 Biology?

 Yes, you can score full marks in Class 11 Biology if you study the subject consistently, learn questions and answers given in the textbook thoroughly, take experts guidance, practice problems from different sources like NCERT textbook, NCERT solutions, NCERT exemplar, etc. Class 11 Biology has an extensive syllabus with 22 chapters so it’s important for students to start studies from the start. And then regularly keep revising the chapters during the entire year while they prepare for the exams.