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Breathing And Exchange Of Gases


  • We all need energy to perform different activities.
  • This energy requirement is served by glucose.
  • Glucose is broken down to produce carbon dioxide, water and energy (in the form of ATP).
  • Carbon dioxide produced needs to be removed continuously.
  • Hence, a continuous exchange of gases (O₂ and CO₂) is required.
  • Breathing and gaseous exchange are steps involved in a complex process called respiration, which makes use of a physiological system called the respiratory system.


Breathing: “The process of exchange of O₂ from the atmosphere with CO₂ produced by the body of the organism.”
Respiration: It is the biochemical process where food material, i.e. glucose is oxidised to produce energy in the form of ATP.

Steps of Respiration
1. Breathing or pulmonary ventilation - Atmospheric air is drawn in and carbon dioxide-rich alveolar air is released out.
2. Diffusion of oxygen and carbon dioxide across the alveolar membrane.
3. Transport of gases by the blood.
4. Diffusion of oxygen and carbon dioxide between blood and tissues.
5. The utilisation of oxygen by the cells for catabolic reactions and resultant release of carbon dioxide gas.

Topics covered:


Q1. Which one of the following statements is incorrect?
(1) The residual air in lungs slightly decreases the efficiency of respiration in mammals.
(2) The presence of non respiratory air sacs increases the efficiency of respiration in birds.
(3) In insects, circulating body fluids serve to distribute oxygen to tissues.
(4) The principle of countercurrent flow facilitates efficient respiration in fishes.

Q2. The majority of carbon dioxide produced by ourBody cells is transported to the lungs:
(1) Dissolved in blood
(2) As bicarbonates
(3) As carbonates
(4) Attached to haemoglobin

Q3. Bowman’s glands are found in?
(1) Olfactory epithelium
(2) External auditory canal
(3) Cortical nephrons only
(4) Juxtamedullary nephrons

Q4. Arrange the following in order of increasing volume:
(A) Tidal volume
(B) Residual volume
(C) Inspiratory volume
(D) Vital capacity
(1) A < B < C < D
(2) A < C < B < D
(3) A < D < C < B
(4) A < D < B < C

Q5. What is vital capacity of our lungs?
(1) Inspiratory reserve volume plus expiratory reserve volume
(2) Total lung capacity minus schedule
(3) Inspiratory volume plus tidal volume
(4) Total lung capacity minus expiratory reserve volume

Q6. What is true about RBC in humans?
(1)They do not carry carbon dioxide at all
(2) They carry about 20 to 25% of carbon dioxide
(3) They transport 99.5% of oxygen
(4) They transport about 80% oxygen only and the rest 20% of it is transported in dissolved state in blood plasma.

Q7. Two friends eating together on a dining table one of them start and restarts coffee while solving some food this coffee would have been due to improper movement of?
(1) Epiglottis
(2) Diaphragm
(3) Neck
(4) Tongue

Q8. Bowman’s glands are located in the:
(1) Olfactory epithelium of our nose
(2) Proximal end of uriniferous tubules
(3) Anterior pituitary
(4) Female reproductive system of cockroach

Q9. A large proportion of oxygen is left unused in human blood even after its uptake by the blood tissues. This oxygen:
(1) Acts as a reserve during muscular exercise
(2) Raises the pCO₂ of blood to 75 mm of Hg
(3) Is enough to keep oxyhaemoglobin saturation at 96%
(4) Helps in releasing more oxygen to epithelial tissues

Q10. Lungs are made of air-filled sacs, alveoli. They do not collapse even after forceful expiration, because of?
(1) Inspiratory Reserve Volume
(2) Tidal Volume
(3) Expiratory Reserve Volume
(4) Residual Volume

Answer Key:
1. (3)
2. (2)
3. (1)
4. (1)
5. (2)
6. (2)
7. (1)
8. (1)
9. (1)
10. (4)

Related Topics to Breathing and Exchange of Gases in Biology

NCERT Class 11 Biology Chapters

The Living World Biological Classification Plant Kingdom
Animal Kingdom Morphology of Flowering Plants Anatomy of Flowering Plants
Structural Organization in Animals Cells: The Unit of Life Biomolecules
Cell Cycle and Division Transport in Plants Mineral Nutrition
Photosynthesis in Higher Plants Respiration in Plants Plant Growth and Development
Digestion and Absorption Breathing and Exchange of Gases Body Fluids and Circulation
Excretory Products and their Elimination Locomotion and Movement Neural Control and Coordination
Chemical Coordination and Integration


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