NCERT Solutions for Class 11 Science Biology Chapter 17 - Breathing And Exchange Of Gases

Answer:

In insects, a network of tubes called tracheal tubes is used for the transportation of atmospheric air within the body. 

Hence, the correct answer is option d.

Answer:

The respiratory system transports the atmospheric air to the alveoli, then clears it from foreign particles, humidifies, and also brings the air to body temperature. 

Hence, the correct answer is option d. 

Answer:

There is a pressure difference in the lungs for inhalation and exhalation of air. For example- During inhalation, a negative pressure gradient is formed in the lungs while during exhalation, a positive pressure gradient is a buildup inside the lungs. If a person suffers from a puncture in their chest cavity, then their will be very less or no pressure gradient in the lungs, and because of this their breathing ceases.
​Hence, the correct answer is option d.

Answer:

Exposure to carbon monoxide is harmful to animals because inhalation of carbon monoxide results in CO poisoning. It binds with the haemoglobin and forms carboxyhaemoglobin. It reduces the transportation of oxygen to the tissues. 

Hence, the correct answer is option b. 

Answer:

The process of breathing involves two stages such as inspiration and expiration. In inspiration, the atmospheric air is drawn inside the lungs while in expiration, the alveolar air is released out from the lungs. So, inspiration is an active process while expiration is a passive process. 

Hence, the correct answer is option b. 
 

Answer:

Vital capacity is the maximum amount of air a person can breathe in after a forced expiration. The value varies from 3400 to 4800ml.
VC = IRV + ERV + TV

Hence, the correct answer is option c. 

Answer:

For the formation of oxyhemoglobin in the alveoli, some factors such as high pO₂, low pCO₂, lesser H⁺ concentration, and lower temperature play an important role. 

Hence, the correct answer is option d. 
 

Answer:

Two lungs - left and right lungs are present in humans that are covered by double-layered pleura. Pleural fluid is present between the two layers and it reduces the friction on the lung surface. Trachea is a straight tube extending up to primary bronchi. Each bronchi undergoes repeated divisions to form the secondary and tertiary bronchi and bronchioles ending up in very thin terminal bronchioles.

Hence, the correct answer is option a. 

Disclaimer: The solution given in the NCERT exemplar is incorrect. The correct answer is option a.

Answer:

Emphysema is a chronic respiratory disorder. It is caused due to the decrease in respiratory surface results in damage of alveolar walls. It is majorly caused due to cigarette smoking. 

Hence, the correct answer is option b. 

Answer:

The pneumotaxic centre is a specialised centre present in the pons region of the brain. This centre can moderate the functions of the respiratory rhythm centre. 

Hence, the correct answer is option b. 

 

Answer:

The dissociation of CO₂ from carbamino-hemoglobin occurs when the pCO₂ is low and pO₂ is high as in the alveoli. In this condition, carbon dioxide is dissociated from the tissue and is delivered to the alveoli. 

Hence, the correct answer is option b. 

Answer:

A spirometer is a device used for the estimation of the volume of air that is involved in breathing movements. This instrument is used for the clinical assessment of pulmonary functions. 

Hence, the correct answer is option d. 

 

Answer:

i. Inspiratory capacity (IC) = Tidal volume (TV) + Inspiratory reserve volume (IRV)
ii. Vital Capacity (VC) = Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV)
iii. Residual volume (RV) = It is the volume of air remaining in the lungs even after a forcible expiration.
iv. Tidal volume (TV)= Inspiratory Capacity (IC) – Inspiratory Reserve Volume (IRV)

Hence, the correct answer is option b. 

Answer:

Factors such as low  pO₂, high pCO₂, high H⁺ concentration, and higher temperature all are favourable for the dissociation of oxygen from oxyhaemoglobin. So, the oxygen - haemoglobin dissociation curve will show a right shift when their is high pCO_2. 

Hence, the correct answer is option a. 

 

Answer:

Correct match:
 

Answer:

a. Tidal Volume (TV): It is the volume of air inspired or expired during normal respiration. It is approx. 500 mL., i.e., a healthy man can inspire or expire approximately 6000 to 8000 mL of air per minute. 

b. Residual volume (RV): It is the volume of air that remains in the lungs even after a forcible expiration. This averages 1100 mL to 1200 mL. 

c. Asthma: It is a respiratory disorder that results in difficulty in breathing caused due to wheezing. It is caused because of the inflammation of the bronchi and bronchioles. 
 

Answer:

Pleura is the fluid-filled double membranous layer that surrounds the lungs. Pleural fluid is present in between the two layers that reduce the friction on the lung surface.

Answer:

Alveoli are bag-like structures present in the lungs and are the primary site for gaseous exchange in the body. 

Answer:

Emphysema is a chronic respiratory disorder majorly caused due to cigarette smoking. It contains harmful chemicals like tar, nicotine, sulfur that damages the alveolar walls and also decreases the respiratory surface. 

 

Answer:

Every 100 ml of oxygenated blood can deliver around 5 ml of oxygen to the tissues under normal physiological conditions.

Answer:

Blood is a specialized fluid responsible for the transportation of oxygen and carbon dioxide. Approximately 97 % of oxygen is transported by RBCs in the blood and the remaining 3% of oxygen is carried in a dissolved state through plasma. 

Answer:

a. Tidal Volume (TV)- It is the volume of air that is inspired or expired during normal respiration. It is approx. 500 mL., i.e., a healthy man can inspire or expire approximately 6000 to 8000 mL of air per minute. 

b. Residual Volume (RV)- It is the volume of air that remains in the lungs even after a forcible expiration. This averages 1100 mL to 1200 mL.

c. Expiratory Capacity (EC)-  It is the total volume of air a person can expire after a normal inspiration.
    EC=  Tidal Volume (TV) +Expiratory Reserve Volume (ERV)

d. Inspiratory Reserve Volume (IRV)-  It is the additional volume of air, a person can inspire by a forcible inspiration. This averages 2500 mL to 3000 mL.

The correct ascending order based on their volumes is:

TV(500ml) < RV(1100-1200ml) < EC(1500-1600ml) < IRV(2500-3000ml)

 

Answer:

a. Inspiratory Capacity (IC) =  TV+IRV
b. Expiratory capacity (EC) = TV + ERV
c. Functional Residual Capacity (FRC) = ERV + Residual volume (RV)

Answer:

a. Flatworm - Gaseous exchange occurs through the entire body surface. 
b. Birds - They respire through the lungs.
c. Frog- They respire through their lungs and moist skin (cutaneous respiration). 
d. Cockroach - They have a network of tubes called tracheal tubes involved in the transportation of atmospheric air within the body. 
 

Answer:

The diaphragm and a specialized set of muscles such as external and internal intercostals present between the ribs, help in the generation of pressure gradients between the lungs and the atmosphere during normal expiration. 

Answer:

CO₂ is transported in the blood by following ways:

1. About 20-25% of carbon dioxide is transported by RBCs. CO₂ is carried by haemoglobin as carbamino-haemoglobin.

2. The remaining 70% is transported as bicarbonate ions. Carbon dioxide reacts with water to form carbonic acid (H₂CO₃) in the presence of enzyme carbonic anhydrase in RBCs. H₂CO₃ dissociates into hydrogen and bicarbonate ion.


3. Approximately 7% is transported by plasma in a dissolved state. 
 

Answer:

The solubility of carbon dioxide is 20-25 % higher than the solubility of oxygen and because of this, the diffusion rate for carbon dioxide through the diffusion membrane per unit difference in partial pressure is higher than that of the diffusion rate of oxygen. 

Answer:

a. Pulmonary ventilation by which the atmospheric air is drawn in and CO₂ rich alveolar air is released out.
b. Diffusion of gases (O₂ and CO₂) across the alveolar membrane.
c. Transport of gases by blood
d.  Diffusion of O₂ and CO₂ between blood and tissues.
e. Utilisation of O₂ by the cells for catabolic reactions and resultant release of CO_2.

Answer:

a. 

Answer:

Transport of oxygen- 
1. The formation of oxyhemoglobin occurs in the alveoli when factors such as high pO₂, low pCO₂, lesser H⁺ concentration, and lower temperature all are favourable. 
2. Oxygen is dissociated from the oxyhaemoglobin that occurs in the tissue when factors such as pO₂, high pCO₂, high H⁺ concentration, and higher temperature are favourable.

Transport of carbon dioxide: 
1. About 20-25 % of carbon dioxide is carried by haemoglobin as carbamino-haemoglobin and is related to the partial pressure of carbon dioxide (pCO₂). The binding of carbon dioxide occurs when pCO₂ is high and pO₂ is low in the tissues. While, the dissociation of carbon dioxie from carbamino- haemoglobin occurs when the pCO₂ is low and pO2 is high in the alveoli. 

2. RBCs have high enzyme (carbonic anhydrase) concentration and the small quantities of this enzyme is present in the plasma. Carbonic anhydrase enzyme facilitates the reaction in both directions- 


$C{O}_2+ H_{2}O \stackrel{Carbonic anhydrase}{\rightleftarrows } H_{2}C{O}_3\stackrel{Carbonic anhydrase}{\rightleftarrows }HC{O_3}^{-}+H^{+}$

The pCO₂ is high due to catabolism at the tissue site, the carbon dioxide diffuses into blood (RBCs and plasma) and forms HCO₃ - and H⁺.  The pCO₂ is low at the alveolar site and this reaction proceeds in the opposite direction results in the formation of Carbon dioxide and water. The carbon dioxide is trapped as bicarbonate at the tissue level and transported to the alveoli is released out as CO₂. 









 

Answer:

The mechanism of breathing involves two stages- inspiration and expiration. 

Inspiration-
1. In this, the atmospheric air is drawn inside the lungs. 
2. It occurs when the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure. 
3. This process is initiated by the contraction of the diaphragm that increases the volume of the thoracic chamber in the anteroposterior axis.
4. The contraction of external intercostal muscles lifts up the ribs and the sternum results in an increase in the volume of the thoracic chamber in the dorso-ventral axis.
5. The overall increase in the thoracic volume increase in pulmonary volume.
6. An increase in pulmonary volume decreases the intra-pulmonary pressure to less than the atmospheric pressure that forces the air from outside to move into the lungs. 


Expiration: 
1. In expiration, the alveolar air is released out and it takes place when the intra-pulmonary pressure is higher than the atmospheric pressure. 
2. Relaxation of the diaphragm and the inter-costal muscles returns the diaphragm and sternum to their normal positions.
3. This reduce the thoracic volume and thereby the pulmonary volume.
4. It leads to an increase in intra-pulmonary pressure to slightly above the atmospheric pressure causing the expulsion of air from the lungs. 





 

Answer:

The neural system plays an important role in maintaining the respiratory rhythm as per the demand of body tissues. The respiratory rhythm centre is a specialised centre present in the medulla region of the brain. It is responsible for maintaining the respiratory rhythm of the body.  The Pneumotaxic centre is another specialised centre located in the pons region of the brain. This centre moderates the functions of the respiratory rhythm centre. A neural signal sent from the pneumotaxic centre reduces the duration of inspiration and alter the respiratory rate. 
The Chemosensitive area is present adjacent to the rhythm centre and is highly sensitive to carbon dioxide and hydrogen ions. An increase in CO₂ and hydrogen ions can activate the chemotaxic centre that in turn sent a signal to the rhythm centre to adjust the respiratory process. The receptors associated with the aortic arch and carotid artery can also recognise the changes in the concentration of carbon dioxide and hydrogen ions and send required signals to the rhythm centre for necessary actions.