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Breathing and Exchange of Gases Class 11 Important Questions And Answers MCQ PDF

Breathing and Exchange of Gases Class 11

 Breathing and Exchange of Gases Class 11 – Introduction –

Breathing and Exchange of Gases Class 11:- The process of breathing is a fundamental characteristic  feature that is exhibited by all the living organisms. The  cells needs to be continuously administered with the oxygen to carry out functionality. The cells in returns produces carbon dioxide gas . The exchange of oxygen from atmosphere with carbon dioxide generated by the cells is called breathing. It is also known as respiration. The two processes occurring in process of respiration are Inspiration and Expiration that are carried out by creating the pressure gradients between the alveoli and the atmosphere through specialized muscles. Through this chapter, we will  understand the various respiratory organs and the different mechanisms that we go through in order to breathe.

Breathing and Exchange of Gases Class 11
Breathing and Exchange of Gases Class 11

Biology Chapter 17 Breathing and Exchange of Gases Class 11 – Very Short Answer Type Questions

Q.1. Explain –

a) The tidal volume

b)  The residual volume

c) Asthma disease 

A.1. a) Tidal volume (TV) is defined as the air volume expired or inspired during process of respiration. In a healthy individual person , TV is about 500ml. So in a minute, TV is about 6000-8000ml of air.

b) Residual volume (RV) is defined as the air volume left in  lungs after a forcible expiration .RV is about 1100-1200ml.

c) Asthama is a disease which is caused due to  an allergic reactions to the  foreign particles. Inflammations of the bronchi causes breathing difficulties and hence results in coughing and wheezing.

Q.2. Give names and the important functions of the fluid-filled double membranous layer surrounding  lungs.

A.2. It is known as pleura and the fluid is known as the pleural fluid. The outer and the inner pleural membrane both together reduces the friction or the resistance on lungs.

Q.3. Say where the exchange of gases in our body takes place?

A.3.  It takes place in the Alveoli of the lungs.

Q.4. Smoking cigarette cause emphysema.comment.

A.4. Emphysema is a chronic disease of respiratory system. Here inflations of the alveolar region occurs. Over a period of time, cigarette smoking or even the inhalation of the smoke causes damage in the septa region between the alveoli and of its elastic tissue is replaced by the connective tissues i in the lungs. Emphysema results in the decrease of the respiratory surface.

Q.5. Write the following in increasing order of their volumes .

a) Tidal volume,TV

b) Residual volume,RV

c) Inspiratory reserve volume,IRV

d) Expiratory capacity,EC


a) Tidal Volume is about 500ml.

b) Residual Volume  is about 1100-1200 ml.

c) Inspiratory reserve volume is about 2500-3000ml.

d) Expiratory capacity is about 1500-1600ml

The increasing order of volumes are-

 Tidal Volume< Residual Volume<Expiratory Capacity<Inspiratory Reserve Volume.

Q.6. Give names of the organs of respiration in the following organisms:

a) flatworm

b)  birds 

c) frog 

d) cockroach


      Organisms           Respiratory organ 

a)  Flatworm                  Body surface.

b)  Birds                        Lungs 

c)  Frog                           Moist skin and lungs 

d) Cockroach                Tracheal tubes.

Breathing and Exchange of Gases Class 11 Quiz

Q.7.Write the names of the main parts involved in initiating a pressure gradient between lungs and the atmosphere during the normal respiration process 

A.7. Diaphragm and a specialized set of the external and the intercostal muscles between ribs aids in the generation of the pressure gradient during the  respiration process.

Q.8. What do u mean by the process of  Breathing?

A.8. It  is defined as biological process in where the air moves in and out of the lungs. Breathing is carried out by the various organs of the Human Respiratory System.

Q.9.Write the formulae of Respiratory Quotient (RQ)?

A.9.  The formulae of RQ is-

RQ =  Vol of the CO2 eliminated / vol of the O2 consumed

Q.10. Define exchange of the gases?

A.10. Exchange of gases refers to the physical process, through which gases moves passively by the process diffusion across a surface.

Breathing and Exchange of Gases Class 11 – Short Answer Types Questions-

Q.1. What are  the various modes of transportation of the carbon dioxide gas in the blood?

A.1. CO2 is carried in the blood in three different forms:

  • In the dissolved state under the  normal pressure and the normal temperature, 7% of CO2 is transported by the physical solution.
  • In the form of  carbamino compounds, carbon dioxide combines with the heamoglobin,Hb to form an unstable compound, called carbamino compounds.
  • In the form of bicarbonate ions.

Q.2. Why the diffusion of carbon dioxide,CO2  by the diffusion membrane per unit differs in the partial pressure and is much greater compared to the oxygen.

A.2. The rate of solubility of CO2 is 22-25 times more than the rate of solubility of oxygen.

Q.3.  Write the steps in a sequential manner for the respiration process to get complete.

a) Diffusion of the  oxygen and CO2 across alveolar membrane if the lungs.

b) Transportation of the gases by the blood.

c) Utilization of the oxygen for the catabolic reactions by the cells which results in the  release of CO2 gas.

d) Pulmonary ventilation through which the atm air is drawn in and carbon dioxide-rich alveolar air is given out of the lungs.

e) Diffusion of the oxygen gas  and the carbon dioxide gas  between the tissues and the blood


a) Diffusion of the  oxygen and the CO2 gas across the alveolar membrane.

b) Transportation of the gases by the blood.

c) Utilization of oxygen for the catabolic reactions by cells and hence results in the release of CO2 gas.

d) Pulmonary Ventilation through which atm air is drawn in and carbon dioxide,CO2 rich alveolar air is given out.

e) Diffusion of the oxygen and the CO2 gas between the tissues and the blood.

Q .4. Write the differences between following:

a)  the expiratory, ERVand  the inspiratory reserve volume,IRV

b) The total lung capacity, TLC and the vital capacity,VC

c) The occupational respiratory disorder and the Emphysema.

A.4. The differences are as follows:


Inspiratory reserve volume,IRVExpiratory reserve volume,ERV
It is the  additional volume of the air that can be inspired by a person by the forcible inspiration which has a  range between – 2500ml – 3000ml.It is the additional volume of air that can be expired forcibly by  a forcible expiration which ranges between 1000ml-110ml.
Breathing and Exchange of Gases Class 11


Vital Capacity,VCTotal lung capacity, TLC 
The maximum capacity in volume of air that a person can breathe in ,after a forceful expiration.It is the  total volume of air accommodated in lungs at  end of forceful inspiration.
Breathing and Exchange of Gases Class 11


EmphysemaOccupational Respiratory Disorder
It  is a chronic disease of the respiratory system, wherein the alveolar cells are damaged due to which the regulatory surface is being decreased.It is caused due to the  long exposure of dust that is generated by the breaking or stone grinding and causes the inflammation that leads to the fibrosis and hence damages the lungs.
Breathing and Exchange of Gases Class 11

Q.5. Write the name of the organs of respiration in cockroach, earthworm and birds?


  1. Cockroaches respires hrough the small openings on the sides of its body called the  spiracles.
  2. Earthworm respires through the skin.
  3. The birds respires through  lungs.

Breathing and Exchange of Gases Class 11 study materials.

Q.6.Define Respiratory Quotient?

A.6. It is defined as the actual ratio of volume of carbon dioxide,CO2  eliminated to the volume of oxygen,O2 consumed during  act of the cellular respiration, it is called the respiratory quotient,RQ . It  is also referred to as the respiratory ratio and is indicated as RQ.

The formulae of Respiratory Quotient is-

RQ = vol of Carbon dioxide,CO2  eliminated / vol of Oxygen,O2  consumed

Breathing and Exchange of Gases Class 11 – Long Answer Types Questions

Q.1. Give a note on the mechanism of breathing process.


a) Inspiration – This proces is induced by the diaphragm contraction that raises vol of the thoracic chamber in the antero -posterior axis. The inter-costal muscles starts contracting causing the external protrusion of  sternum and ribs resulting in an increment in the vol of  thoracic chamber in the dorso -ventral axis. This increase in thoracic volume results in a similar increase in the  pulmonary volume causing the reduced intrapulmonary pressure to lesser than the atmospheric pressure which results in inspiration. 

b) Expiration –  Here the inter-costal muscles reverses sternum and the diaphragm to their original positions with the diaphragm relaxing, which decreases the thoracic volume and hence results in the decrease of the pulmonary volume. Expulsion of the air occurs as the intra-pulmonary pressure increases to a level somewhat above the atmospheric pressure causing the expiration.

Q.2. Explain the role of  Neural System in controlling the process of  Respiration.

A.2. Neural System maintains and moderates the respiratory rhythm as per the demands of the body tissue requirements.. The respiratory rhythm centre present in brain is responsible for the regulation process. The pneumotaxic centre, another region in  pons of the brain, moderates the functions of the respiratory rhythm centre.

 The neural signals from this centre have ability to reduce  duration of the  inspiration hence altering the rate of the respiration. A chemosensitive area present adjacent to rhythm centre is very sensitive to the hydrogen ions and CO2 gas which activates this centre by an increase of these substances. These senda down a signal to the rhythm centre of the brain to cause essential adjustments in the process which can cause the elimination of these substances. Changes in CO2 and the hydrogen ions are recognized by the receptors linked with the aortic arch and carotid artery,and  thereby sending signals for corrective actions to rhythm centre.

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