NCERT Exemplar Class 11 Biology Solutions Chapter 17 Breathing and Exchange of Gases

Breathing and Exchange of Gases Exercise:

Multiple Choice Question:

Question:1

Respiration in insects is called direct because
(a) The cells exchange O₂ / CO₂ directly with the air in the tubes
(b) The tissues exchange O₂ / CO₂ directly with coelomic fluid
(c) The tissues exchange O₂ / CO₂ directly with the air outside through body surface
(d) Tracheal tubes exchange O₂ / CO₂ directly with the haemocoel which then exchange with tissues

Answer:

Question:2

Regarding the functions of our respiratory system, mark the wrong entry.

a. Humidifies the air

b. Warms up the air

c. Exchange of gases

d. Cleans up the air

Answer:

The answer is the option (d) cleans up the air, because all other functions are performed by the respiratory system.

Question:3

A person suffers punctures in his chest cavity in an accident, without any damage to the lungs, its effect could be
(a) Reduced breathing rate
(b) Rapid increase in breathing rate
(c) No change in respiration
(d) Cessation of breathing

Answer:

The answer is the option (d) Cessation of breathing

Explanation: - The process of breathing includes the diffusion of gases. A person with chest cavity caused due to an accident without any damage is the cessation of breathing. This might be due to inflation or deflation of the air-tight chest cavity.

Question:4

It is known that exposure to carbon monoxide is harmful to animals because
(a) It reduces CO₂ transport
(b) It reduces O₂ transport
(c) It increases CO₂ transport
(d) It increases O₂ transport

Answer:

Question:5

Mark the true statement among the following with reference to normal breathing.

(a) Inspiration is a passive process whereas expiration is active

(b) Inspiration is an active process whereas expiration is passive

(c) Inspiration and expiration are active processes

(d) Inspiration and expiration are passive processe

Answer:

Question:6

A person breathes in some volume of air by forced inspiration after having a forced expiration. This quantity of air taken in is

a. Total lung capacity
b. Tidal volume
c. Vital capacityd.
d. Inspiratory capacity

Answer:

Question:7

Mark the incorrect statement in context to O2 binding to Hb.

(a) Lower pH

(b) Lower temperature

(c) Lower pCO2

(d) Higher pO2

Answer:

Question:8

Mark the correct pair of muscles involved in the normal breathing in humans
(a)External and internal intercostal muscles
(b)Diaphragm and abdominal muscles
(c)Diaphragm and external intercostal muscles
(d) Diaphragm and intercostal muscles

Answer:

Question:9

Incidence of Emphysema-a respiratory disorder is high in cigarette smokers. In such cases

(a) The bronchioles are found damaged

(b) The alveolar walls are found damaged

(c) The plasma membrane is found damaged

(d) The respiratory muscles are found damaged

Answer:

Question:10

Respiratory process is regulated by certain specialised centres in the brain. One of the following listed centres can reduce the inspiratory duration upon stimulation

(a) Medullary inspiratory centre
(b) Pneumotaxic centre
(c) Apneustic centre
(d) Chemosensitive centre

Answer:

(b) Pneumotaxic centre is the correct answer.

Question:11

CO₂ dissociates from carbamino haemoglobin when
(a) pCO₂ is high and pO₂ is low
(b) pO₂ is high and pCO₂ is low
(c) pCO₂ and pO₂ are equal
(d) None of the above

Answer:

Question:12

In breathing movements, air volume can be estimated by
(a) Stethoscope
(b) Hygrometer
(c) Sphygmomanometer
(d) Spirometer

Answer:

Question:13

From the following relationships between respiratory volumes and capacities, mark the correct option.

(i) Inspiratory capacity (IC) = Tidal Volume + Residual Volume
(ii) Vital Capacity (VC) = Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV)
(iii) Residual Volume (RV) = Vital Capacity (VC) – Inspiratory Reserve Volume (IRV)
(iv) Tidal Volume (TV) = Inspiratory Capacity (IC) – Inspiratory Reserve Volume (IRV)

(a) (i) Incorrect (ii) Incorrect (iii) Incorrect (iv) correct
(b) (i) Incorrect (ii) correct (iii) Incorrect (iv) correct
(c) (i) correct (ii) correct (iii) Incorrect (iv) correct
(d) (i) correct (ii) Incorrect (iii) correct (iv) Incorrect

Answer:

Question:14

The oxygen-haemoglobin dissociation curve will show a right shift in case of
(a) High pCO₂
(b) HighpO₂
(c) Low pCO₂
(d) Less H + concentration

Answer:

Question:15

Match the following and mark the correct options

Answer:

The answer is the option (d) A—(i), B—(iv), C—(ii), D—(iii)

Very Short Answer Type Questions:

Question:1

Define the following terms
a. Tidal volume
b. Residual volume
c. Asthma

Answer:

Question:2

A fluid-filled double membranous layer surrounds the lungs. Name it and mention its important function.

Answer:

Question:3

Name the primary site of exchange of gases in our body?

Answer:

Question:4

Cigarette smoking causes emphysema. Give reason.

Answer:

Question:5

What is the amount of O₂ supplied to tissues through every 100 mL of oxygenated blood under normal physiological conditions?

Answer:

Question:6

A major percentage (97%) of O₂ is transported by RBCs in the blood. How does the remaining percentage (3%) of O₂ transported?

Answer:

Question:7

Arrange the following terms based on their volumes in an ascending order
a. Tidal Volume (TV)
b. Residual Volume (RV)
c. Inspiratory Reserve Volume (IRV)
d. Expiratory Capacity (EC)

Answer:

Question:8

Complete the missing terms
a. Inspiratory Capacity (IC) = _____+ IRV
b. _____ = TV + ERV
c. Functional Residual Capacity (FRC) = ERV + _____

Answer:

Question:9

Name the organs of respiration in the following organisms:
a. Flatworm
b. Birds
c. Frog
d. Cockroach

Answer:

Question:10

Name the important parts involved in creating a pressure gradient between the lungs and the atmosphere during normal respiration.

Answer:

Diaphragm and Intercostal muscles are involved in creating a pressure gradient between the lungs and the atmosphere during normal respiration.

Short Answers Type Questions:

Question:1

State the different modes of C0₂ transport in the blood.

Answer:

• About 20 – 25% of CO₂ is carried by RBCs
• About 70% of CO² is transported as a bicarbonate
• About 7% of CO₂ is carried in the dissolved state through the plasma

Question:2

Compared to O₂, the diffusion rate of CO₂ through the diffusion membrane per unit difference in partial pressure is much higher. Explain.

Answer:

Question:3

For completion of respiration process, write the given steps in sequential manner.
1. Diffusion of gases (O₂ and CO₂ ) across alveolar membrane.
2. Transport of gases by blood.
3. Utilisation of O₂ by the cells for catabolic reactions and resultant release of CO₂ .
4. Pulmonary ventilation by which atmospheric air is drawn in and CO₂ rich alveolar air is released out.
5. Diffusion of O₂ and CO₂ between blood and tissues.

Answer:

Question:4

Differentiate between

A) Inspiratory and Expiratory Reserve Volume

B) Vital Capacity and Total Lung Capacity

C) Emphysema and occupational respiratory disorder

Answer:

Long Answer Type Question:

Question:1

Explain the transport of O₂ and CO₂ between alveoli and tissue with a diagram.

Answer:

In alveoli, the partial pressure of O₂ is 104 mm Hg, and that of CO₂ is 40 mm Hg. While the blood is deoxygenated, pO₂ is 40 mm Hg. This is much less than the pO₂ in alveoli.
Thus oxygen enters the blood in alveoli. In deoxygenated blood, the partial pressure of CO₂ is 45 mm Hg. This is much more than the partial pressure of CO₂ in alveoli. Thus, carbon dioxide exits from tissue cells and enter the alveoli.

Once the blood reaches the tissues, the partial pressure of oxygen present in the oxygenated blood is 95 mm.
Thus, oxygen from the blood enters the tissues. At the tissue level, the partial pressure of carbon dioxide in deoxygenated blood is more than that in oxygenated blood. Hence, carbon dioxide exits from the tissues.

Question:2

Explain the mechanism of breathing with neat labelled sketches.

Answer:

• The intercostal muscles initiate contraction of the diaphragm. This increases the volume of the thoracic chamber.
• Ribs and diaphragm are moved upwards. As a result, the pressure inside the lungs becomes less than atmospheric pressure. This difference in pressure causes air to move inside the lungs.

• The intercostal muscles and the diaphragm relax and move to their original position.
• Ribs and sternum return to their original position.
• The volume inside the thoracic chamber reduces. As a result, the pressure inside the lungs becomes more than the atmospheric pressure and the air is forced out of the lungs.

Question:3

Explain the role of the neural system in the regulation of respiration

Answer:

• The respiratory rhythm centre is present in the medulla. It is a specialised centre and is responsible for the regulation of respiration.
• The pneumotaxic centre is present in the pons of the brain. It moderates the functions of the respiratory rhythm centre. Nerve signals present in pneumotaxic centre reduces the duration of inspiration thus altering the respiratory rate.
• A chemosensitive area is also there adjacent to the rhythm centre. This is highly sensitive to CO₂ and hydrogen ions. An increase in these substances can activate this centre.
• The chemosensitive area gives a signal to the rhythm centre to make adjustments to eliminate these substances. There are receptors that are associated with the aortic arch and the carotid artery. They also recognise changes in CO₂ and H+ concentration.
• After that, they send necessary signals to the rhythm centre so that corrective actions can be taken. The role of oxygen is quite insignificant in the regulation of the respiratory rhythm centre.