CBSE Class 11 Biology HOTs Breathing and Exchanger of gases

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MCQ Questions for NCERT Class 11 Biology Breathing and Exchange of Gases

Question. For the occurrence of expiration,intrapulmonary pressure should be
(a) equal to atmospheric pressure
(b) more than atmospheric pressure
(c) less than atmospheric pressure
(d) either (a) or (c).

Answer : B

Question. Hering-Breuer reflex is related to
(a) effect of pH on respiratory centre
(b) effect of CO2 on respiratory centre
(c) effect of nerves on respiratory centre
(d) effect of temperature on respiratory centre.

Answer : C

Question. Refer to the given figure and select option which correctly identifies the labels.
(a) A-Alveolar ducts, B-Alveoli, C-Venule,D-Arteriole, E-Blood capillaries
(b) A-Alveoli, B-Alveolar ducts, C-Arteriole, D-Blood capillaries, E-Venule
(c) A-Arteriole, B-Alveoli, C-Alveolar ducts, D-Venule, E-Blood capillaries
(d) A-Alveoli, B-Arteriole, C-Venule, D-Blood capillaries, E-Alveolar ducts

Answer : B

Question. Oxygen and carbon dioxide is transported in the blood with the help of
(a) RBCs and blood plasma
(b) RBCs and WBCs
(c) WBCs only
(d) platelets only.

Answer : A

Question. In the graphical representation of pulmonary volumes and capacities, ‘X’ denotes
(a) Inspiratory reserve volume
(b) Total lung capacity
(c) Expiratory capacity
(d) Inspiratory capacity.

Answer : D

Question. Extra amount of air inspired forcibly after normal inspiration is approximately
(a) 4.5 L
(b) 3.5 L
(c) 1.5 L
(d) 2.7 L.

Answer : D

Question. Read the given statements and select the correct option.
Statement 1 : CO2 passes from the blood to the alveoli.
Statement 2 : pCO2 is higher in deoxygenated blood than in alveoli.
(a) Both statements 1 and 2 are correct and 2 is the correct explanation of 1.
(b) Both statements 1 and 2 are correct but 2 is not the correct explanation of 1.
(c) Statement 1 is correct but statement 2 is incorrect.
(d) Both statements 1 and 2 are incorrect.

Answer : A

Question. Identify the correct statement with reference to transport of respiratory gases by blood.
(a) Haemoglobin is necessary for transport of carbon dioxide and carbonic anhydrase for transport of oxygen.
(b) Haemoglobin is necessary for transport of oxygen and carbonic anhydrase for transport of carbon dioxide.
(c) Only oxygen is transported by blood.
(d) Only carbon dioxide is transported by blood.

Answer : B

Question. Neither the trachea nor the bronchi contain
(a) hyaline cartilage
(b) ciliated columnar epithelium
(c) goblet cells
(d) simple squamous epithelium.

Answer : D

Question. Which of the following is correct for bronchioles?
(a) They are filled with pleural fluid.
(b) They are closed at the tip.
(c) They are branches of tertiary bronchi.
(d) They penetrate the body cells.

Answer : C

Question. Select the correct statement.
(a) H+ ions released from carbonic acid combine with haemoglobin to form haemoglobin acid.
(b) Oxyhaemoglobin of erythrocytes is alkaline.
(c) More than 70% of carbon dioxide is transferred from tissue to lungs as carbamino compounds.
(d) In healthy person, haemoglobin content is more than 25 g / 100 mL .

Answer : A

Question. The figure given below shows a small part of human lung where exchange of gases takes place. Select the option which represents labelled part (A, B, C or D) correctly
identified along with its function.
(a) C : arterial capillary - passes oxygen to tissues
(b) A : alveolar cavity - main site of exchange of respiratory gases
(c) D : capillary wall - exchange of O2 and CO2 takes place here
(d) B : red blood cells - transport of CO2 mainly 

Answer : B

Question. Which of the following events does not occur during internal respiration?
(a) Blood becomes deoxygenated and is carried to the heart.
(b) Carbon dioxide diffuses from the body cells to capillary blood via tissue fluid.
(c) Oxygen diffuses from the capillary blood to the body cells through tissue fluid.
(d) Oxygen binds with haemoglobin under low partial pressure of oxygen to form oxyhaemoglobin.

Answer : D

Question. Which of the following factors will increase the Bohr’s effect?
(i) Increase in partial pressure of oxygen
(ii) Decrease in partial pressure of carbon dioxide
(iii) Increase in H+ ion concentration
(iv) Increase in body temperature
(v) High pH
(a) (i), (ii), (iii) and (iv)
(b) (i), (ii), (iv) and (v)
(c) (iii), (iv) and (v)
(d) (iii) and (iv)

Answer : D

Question. The figure shows a diagrammatic view of human respiratory system with labels A, B, C and D. Select the option which gives correct identification and main function and / or characteristic.
(a) C - Alveoli - Thin walled vascular bag-like structures for exchange of gases.
(b) D - Lower end of lungs - Diaphragm pulls it down during inspiration.
(c) A - Trachea - Long tube supported by complete cartilaginous rings for conducting inspired air.
(d) B - Pleural membrane - Surrounds ribs on both sides to provide cushion against rubbing.

Answer : A

Case II : Read the following passage and answer questions from 46 to 50 given below: A human lung can hold a maximum of six litres of air. The volume of air involved in the process of breathing can be evaluated with the help of an equipment, used to examine the total volume of air inhaled and exhaled by the lungs. It is also used in testing the pulmonary functions. The air in the lungs is measured in terms of lung volume of air breathed by an individual and are of four types : Tidal volume, Inspiratory reserve volume, Expiratory reserve volume and Residual volume.

Question. What instrument is used for measuring the volume of air inspired and expired by the lungs?
(a) Drinker’s respirator
(b) Spirometer
(c) Barometer
(d) Calorimeter

Answer : B

Question. Which lung capacity involves about 3500-4700 mL of air?
(a) Inspiratory capacity
(b) Functional residual capacity
(c) Vital capacity
(d) Total lung capacity

Answer : C

Question. Which of the following statements is correct regarding inspiratory reserve volume?
(a) Volume of air inspired or expired during normal breathing
(b) Extra amount of air inspired forcibly after normal inspiration.
(c) Volume of air that remains in the lungs even after a forcible expiration.
(d) Extra amount of air exhaled forcibly after normal expiration.

Answer : C

Question. What volume of air can be expired forcibly after normal expiration?
(a) 500 mL
(b) 2600 mL
(c) 1100 mL
(d) 1300 mL

Answer : C

Question. Which respiratory volume has highest value?
(a) Tidal volume
(b) ERV
(c) RV
(d) IRV

Answer : D

Important Questions for NCERT Class 11 Biology Breathing and Exchange of Gases

Very Short Answer Type Questions

Question. Name the respiratory disorders that are referred to as chronic obstructive pulmonary disease.
Answer. Bronchitis, emphysema and bronchial asthma.

Question. How cutaneous respiration is different from pulmonary respiration?
Answer. Cutaneous respiration is exchange of gases through skin, e.g., in earthworm. Pulmonary respiration occurs through lungs as in humans.

Question. Name the phenomenon that encourages CO2 exchange in both the tissues and lungs. 
Answer. Haldane effect

Question. Name the aperture by which pharynx opens into the larynx.
Answer. The pharynx opens into the larynx by the slit-like aperture called glottis.

Question. What is diffusing capacity of respiratory membrane?
Answer. Diffusing capacity is the volume of gas that diffuses through membrane per minute for a pressure difference of 1 mmHg. It depends on solubility of the diffusing gases.

Short Answer Type Questions 

Question. Name parts of human respiratory system that constitute conducting portion of respiratory system. What are its functions? 
Answer. The parts starting with external nostrils upto the terminal bronchioles constitute the conducting parts of human respiratory system. It includes nose, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles. The main functions of the conducting parts of the respiratory tract are: (i) Transport atmospheric air to alveoli. (ii) They filter the air from dust and foreign particles. (iii) Humidify and bring air to body temperature.

Question. How is O2 transported in the blood and released in the tissues?
Answer. Blood carries O2 from lungs to the heart and from the heart to the various parts of the body. About 3% of O2 in the blood is dissolved in plasma which carries O2 to the body cells and 97% of O2 is carried in combination with haemoglobin of the erythrocytes. Haemoglobin (Hb) consists of a protein portion called globin and a pigment portion called heme. The heme portion contains four atoms of iron, each capable of combining with a molecule of oxygen. Four molecules of oxygen bind one molecule of haemoglobin. Oxygen and haemoglobin combine in an easily reversible reaction to form oxyhaemoglobin. (Img 108) Under high partial pressure, oxygen easily binds with haemoglobin in the pulmonary blood capillaries. When this oxygenated blood reaches the different tissues, the partial pressure of O2 declines and the bonds holding oxygen to haemoglobin become unstable and O2 is released from the blood capillaries.

Question. What are occupational respiratory disorders? Give two examples of such disorders.
Answer. Occupational respiratory disorders are due to the occupation of the individual. These are caused by the harmful substances, such as fumes or dusts, present in the environment where an individual works. Two examples of such disorders are : silicosis and asbestosis which occur due to chronic exposure of silica and asbestos dust in the mining industry respectively. These are characterised by proliferation of fibrous connective tissue of upper part of lung, causing inflammation.

Question. Describe the process of inspiration under normal conditions. 
Answer. Inspiration is the process of intake of fresh air into lungs. It is caused by contraction of diaphragm and intercostal muscles. Inspiration is initiated by contraction of diaphragm, as it becomes flat and gets lowered, thereby increasing the volume of thoracic cavity. Ribs and sternum move upward and outward due to contraction of external intercostal muscles. The increase in thoracic volume increases pulmonary volume, that decreases intra-pulmonary pressure to less than the atmospheric pressure. This forces air from outside to move into the lungs, i.e., inspiration.

Question. Describe the role of intercostal muscles in respiration. 
Answer. Inspiration and expiration both are affected by contraction and relaxation of muscles of diaphragm and intercostal muscles. Inspiration is caused by contraction of external intercostal muscles, it pulls ribs and sternum upward and outward, increasing the volume of thoracic cavity and forcing the air to move into lungs. Expiration is caused by contraction of internal intercostal muscles, as it pulls ribs downward and inward decreasing the size of thoracic cavity and thus forcing the air out of lungs.

Question. How right lung can be differentiated from left lung?
Answer. Differences between right lung and left lung are: (Table 107)

Question. Describe the following terms: (a) Inspiratory capacity (b) Residual volume and (c) Functional residual capacity.
Answer. (a) Inspiratory capacity (IC) is the total volume of air that can be inhaled after a normal expiration. It includes tidal volume and inspiratory reserve volume (IC = TV + IRV). It is about 2500 – 3000 mL. (b) Residual volume (RV) is the volume of air that always remains in the lungs after forcible expiration. It enables the lungs to continue the exchange of gases even after maximum exhalation or on holding the breath. It is nearly 1500 mL. (c) Functional residual capacity (FRC) is the volume of air that will remain in the lungs after a normal expiration. It is the sum total of residual volume and expiratory reserve volume (FRC = RV + ERV). It is about 2500 to 3000 mL.

Long Answer Type Questions

Question. Explain the various factors affecting the oxygen dissociation curve.
Answer. The oxygen haemoglobin dissociation curve is shifted either to right or left by various factors, like pCO2, H+ concentration, temperature.
(i) Shift to right : The shift to the right indicates dissociation of oxygen from haemoglobin in the following conditions :
(a) Decrease in pO2 (b) Increase in pCO2 (c) Increase in hydrogen (H+) ion concentration and decrease in pH (acidity)
(d) Increase in body temperature (e) Excess of 2,3 DPG (2, 3 – Diphosphoglycerate, a by product of glycolysis) (ii) Shift to left : The shift to left indicates association of oxygen with haemoglobin in the following conditions : (a) In the fetal blood, because fetal haemoglobin has more affinity for oxygen than the adult haemoglobin.
(b) Decrease in hydrogen ion concentration and increase in pH (alkalinity).
(c) Decrease in partial pressure of CO2.

Question. Explain the role of neural system in regulation of respiration.
Answer. Neural system plays a significant role in maintaining and moderating the respiratory rhythm. Medulla oblongata has a specialised centre called respiratory rhythm centre, that regulates the respiration. The functions of the respiratory rhythm centre are controlled by another centre present in the pons varolii, called pneumotaxic centre. Neural signals from this centre can reduce the duration of inspiration and thereby alter the respiratory rate. Adjacent to the rhythm centre is situated a chemosensitive area which is highly sensitive to CO2 and H+ ions. Increase in these substances can activate this centre, which in turn can signal the rhythm centre to make necessary adjustments in the respiratory process by which these substances can be eliminated. Receptors present on aortic arch and carotid artery also can recognise changes in CO2 and H+ concentration and send necessary signals to the rhythm centre for remedial actions.

Breathing and Exchanger of gases

Question. What is the role of oxyhaemoglobin after the release of molecular oxygen in the tissue?

Answer. Combines with carbon dioxide to form carbamino-haemoglobin.

Question. Differentiate between haemoglobin of human and earthworm?

Answer. Human: RBC; Earthworm : dissolved in plasma( location based)

Question. Why cartilaginous rings on trachea are C-shaped?

Answer. For shock absorption and expansion / contraction while breathing in / out.

Question. Define partial pressure of gases?

Answer. Pressure exerted by the molecules of a gas in a mixture of gases.

Question. If deoxygenated blood in the lungs has PCO2= 46 mmHg, what should be the alveolar PCO2,for CO2 to diffuse into alveoli from blood.

Answer. Less than 46mmHg.

Question. A blood vessel in kidney has PO2 =90mmHg, while that in the tissue is 76mmHg. What will be the direction of diffusion of O2.

Answer. O2 will diffuse from blood into the tissues of kidney.

Question. What is chloride shift? What is its importance?

Answer. Diffusion of Cl- from blood plasma into RBC. To maintain ionic balance & electrochemical neutrality.

Question. Arrange in increasing order of their volume: TV, IRV, RV, ERV, VC,TLC.


Question. Discuss the role of “Carbonic Anhydrase”.

Answer. CO2 + H2O ---CARBONIC ANHYDRASEà H2CO3 (Carbonic acid) 

          H2CO3 ------ H+ + HCO3-

Question. Discuss Bohr’s effect.

Answer. Increase in concentration of CO2 shifts its dissociation curve towards right.

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