Chapter 14: Breathing and Exchange of Gases Assertion-Reason Questions | biology Class 11 CBSE

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): Breathing is commonly known as respiration and involves exchange of O2 from atmosphere with CO2 produced by cells. Reason (R): O2 is utilised by cells to break down molecules like glucose and release energy, producing CO2 as a by-product.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 2

Logic Check

Assertion (A): Lower invertebrates like sponges and flatworms exchange O2 and CO2 by simple diffusion over their entire body surface. Reason (R): These animals have specialised gills and lungs that are more efficient than simple body surface diffusion.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 3

Logic Check

Assertion (A): The trachea, primary, secondary and tertiary bronchi are supported by incomplete cartilaginous rings. Reason (R): Cartilaginous support prevents the collapse of these airways during the negative pressure phase of inspiration.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 4

Logic Check

Assertion (A): The alveoli and their ducts form the exchange part of the respiratory system. Reason (R): Alveoli are thin-walled, vascularised structures where actual diffusion of O2 and CO2 between blood and atmospheric air takes place.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 5

Logic Check

Assertion (A): Inspiration occurs when intra-pulmonary pressure is higher than atmospheric pressure. Reason (R): A positive pressure gradient from lungs to atmosphere forces air into the lungs during inspiration.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 6

Logic Check

Assertion (A): Contraction of the diaphragm increases thoracic volume in the antero-posterior axis. Reason (R): Contraction of external intercostal muscles lifts the ribs and sternum, increasing thoracic volume in the dorso-ventral axis.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 7

Logic Check

Assertion (A): Residual Volume cannot be measured directly by a spirometer. Reason (R): Residual Volume is the air remaining in the lungs even after a forcible expiration and cannot be voluntarily expelled.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 8

Logic Check

Assertion (A): Vital Capacity is always greater than Total Lung Capacity. Reason (R): Total Lung Capacity equals Vital Capacity plus Residual Volume.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 9

Logic Check

Assertion (A): O2 moves from alveolar air into deoxygenated blood at the alveoli. Reason (R): pO2 in alveolar air (104 mm Hg) is higher than pO2 in deoxygenated blood (40 mm Hg), creating a concentration gradient for diffusion.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 10

Logic Check

Assertion (A): CO2 diffuses efficiently across the alveolar diffusion membrane despite a smaller partial pressure gradient compared to O2. Reason (R): The solubility of CO2 is 20–25 times higher than that of O2, allowing more CO2 to diffuse per unit pressure difference.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 11

Logic Check

Assertion (A): The diffusion membrane has a total thickness much less than a millimetre. Reason (R): The diffusion membrane consists of the thin squamous epithelium of alveoli, the basement substance, and the endothelium of alveolar capillaries.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 12

Logic Check

Assertion (A): About 97% of O2 is transported in dissolved state through plasma. Reason (R): Haemoglobin has limited capacity to bind O2 and can carry only a small proportion of the body's O2 requirement.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 13

Logic Check

Assertion (A): In the alveoli, conditions are favourable for the formation of oxyhaemoglobin. Reason (R): The alveoli have high pO2, low pCO2, lesser H+ concentration, and lower temperature compared to tissues.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 14

Logic Check

Assertion (A): The oxygen dissociation curve is sigmoid in shape. Reason (R): Binding of O2 to haemoglobin is primarily related to the partial pressure of O2, and pCO2, H+ and temperature also affect this binding.

Reasoning Options

ByteNotes

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 15

Logic Check

Assertion (A): About 70% of CO2 is transported as bicarbonate in the blood. Reason (R): Carbonic anhydrase in RBCs catalyses the reversible conversion of CO2 and H2O to HCO3– and H+.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 16

Logic Check

Assertion (A): At tissue sites, CO2 diffuses into blood and forms HCO3– and H+. Reason (R): At tissue sites, partial pressure of CO2 is high due to catabolism, driving CO2 into blood where carbonic anhydrase facilitates HCO3– formation.

Reasoning Options

ByteNotes

Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 17

Logic Check

Assertion (A): CO2 is carried by haemoglobin as carbamino-haemoglobin in greater proportion than as bicarbonate. Reason (R): At tissue sites where pCO2 is high and pO2 is low, more CO2 binds to haemoglobin to form carbamino-haemoglobin.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 18

Logic Check

Assertion (A): The respiratory rhythm centre in the medulla oblongata is primarily responsible for regulating breathing. Reason (R): The pneumotaxic centre in the pons can reduce the duration of inspiration and alter the respiratory rate.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 19

Logic Check

Assertion (A): The role of oxygen in the regulation of respiratory rhythm is quite insignificant. Reason (R): The chemosensitive area in the medulla is highly sensitive to CO2 and H+ ions, which primarily drive changes in ventilation rate.

Reasoning Options

ByteNotes

Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 20

Logic Check

Assertion (A): Receptors associated with aortic arch and carotid artery can recognise changes in CO2 and H+ concentration. Reason (R): These peripheral receptors send signals to the respiratory rhythm centre for remedial actions.

Reasoning Options

ByteNotes

Chapter sections

Chapter 14: Breathing and Exchange of Gases | Assertion-Reason

Assertion (A): Breathing is commonly known as respiration and involves exchange of O2 from atmosphere with CO2 produced by cells. Reason (R): O2 is utilised by cells to break down molecules like glucose and release energy, producing CO2 as a by-product.

Assertion (A): Lower invertebrates like sponges and flatworms exchange O2 and CO2 by simple diffusion over their entire body surface. Reason (R): These animals have specialised gills and lungs that are more efficient than simple body surface diffusion.

Assertion (A): The trachea, primary, secondary and tertiary bronchi are supported by incomplete cartilaginous rings. Reason (R): Cartilaginous support prevents the collapse of these airways during the negative pressure phase of inspiration.

Assertion (A): The alveoli and their ducts form the exchange part of the respiratory system. Reason (R): Alveoli are thin-walled, vascularised structures where actual diffusion of O2 and CO2 between blood and atmospheric air takes place.

Assertion (A): Inspiration occurs when intra-pulmonary pressure is higher than atmospheric pressure. Reason (R): A positive pressure gradient from lungs to atmosphere forces air into the lungs during inspiration.

Assertion (A): Contraction of the diaphragm increases thoracic volume in the antero-posterior axis. Reason (R): Contraction of external intercostal muscles lifts the ribs and sternum, increasing thoracic volume in the dorso-ventral axis.

Assertion (A): Residual Volume cannot be measured directly by a spirometer. Reason (R): Residual Volume is the air remaining in the lungs even after a forcible expiration and cannot be voluntarily expelled.

Assertion (A): Vital Capacity is always greater than Total Lung Capacity. Reason (R): Total Lung Capacity equals Vital Capacity plus Residual Volume.

Assertion (A): O2 moves from alveolar air into deoxygenated blood at the alveoli. Reason (R): pO2 in alveolar air (104 mm Hg) is higher than pO2 in deoxygenated blood (40 mm Hg), creating a concentration gradient for diffusion.

Assertion (A): CO2 diffuses efficiently across the alveolar diffusion membrane despite a smaller partial pressure gradient compared to O2. Reason (R): The solubility of CO2 is 20–25 times higher than that of O2, allowing more CO2 to diffuse per unit pressure difference.

Assertion (A): The diffusion membrane has a total thickness much less than a millimetre. Reason (R): The diffusion membrane consists of the thin squamous epithelium of alveoli, the basement substance, and the endothelium of alveolar capillaries.

Assertion (A): About 97% of O2 is transported in dissolved state through plasma. Reason (R): Haemoglobin has limited capacity to bind O2 and can carry only a small proportion of the body's O2 requirement.

Assertion (A): In the alveoli, conditions are favourable for the formation of oxyhaemoglobin. Reason (R): The alveoli have high pO2, low pCO2, lesser H+ concentration, and lower temperature compared to tissues.

Assertion (A): The oxygen dissociation curve is sigmoid in shape. Reason (R): Binding of O2 to haemoglobin is primarily related to the partial pressure of O2, and pCO2, H+ and temperature also affect this binding.

Assertion (A): About 70% of CO2 is transported as bicarbonate in the blood. Reason (R): Carbonic anhydrase in RBCs catalyses the reversible conversion of CO2 and H2O to HCO3– and H+.

Assertion (A): At tissue sites, CO2 diffuses into blood and forms HCO3– and H+. Reason (R): At tissue sites, partial pressure of CO2 is high due to catabolism, driving CO2 into blood where carbonic anhydrase facilitates HCO3– formation.

Assertion (A): CO2 is carried by haemoglobin as carbamino-haemoglobin in greater proportion than as bicarbonate. Reason (R): At tissue sites where pCO2 is high and pO2 is low, more CO2 binds to haemoglobin to form carbamino-haemoglobin.

Assertion (A): The respiratory rhythm centre in the medulla oblongata is primarily responsible for regulating breathing. Reason (R): The pneumotaxic centre in the pons can reduce the duration of inspiration and alter the respiratory rate.

Assertion (A): The role of oxygen in the regulation of respiratory rhythm is quite insignificant. Reason (R): The chemosensitive area in the medulla is highly sensitive to CO2 and H+ ions, which primarily drive changes in ventilation rate.

Assertion (A): Receptors associated with aortic arch and carotid artery can recognise changes in CO2 and H+ concentration. Reason (R): These peripheral receptors send signals to the respiratory rhythm centre for remedial actions.

Unlock all Assertion-Reason Questions

Practice in Quiz Mode