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

Breathing is a fundamental characteristic that is exhibited by all living entities. Our cells need to be continuously administered with oxygen to carry out their functionality. The cells in return release carbon dioxide. This exchange of oxygen from the atmosphere with carbon dioxide generated by the cells is called breathing. It is also referred to as respiration. The two main processes occurring in respiration are inspiration and expiration that are carried out by creating pressure gradients between the alveoli and atmosphere through specialized muscles. Through this chapter, we understand the various respiratory organs and the different mechanisms that we go through in order to breathe.

Very Short Answer Type Questions

Q.1. Define:
a) Tidal volume
b) Residual volume
c) Asthma
A.1. a) Tidal volume (TV) is the air volume expired or inspired during respiration. In a healthy individual, it is about 500ml. Hence per minute, it is about 6000-8000ml of air. b) Residual volume (RV) is the air volume left in the lungs following a forcible expiration which is about 1100-1200ml. c) It is a disease that is caused because of an allergic reaction to foreign particles. Inflammation of the bronchi causes breathing difficulty and hence coughing and wheezing.
Q.2. Write the name and important function of the fluid-filled double membranous layer surrounding the lungs.
A.2. It is pleura and the fluid is pleural fluid. The outer and inner pleural membrane collectively reduce friction or resistance on the lungs.
Q.3. Which is the prime site for the exchange of gases in our body?
A.3. Alveoli
Q.4. Why does smoking cigarette cause emphysema?
A.4. It is a chronic disease of the respiratory system where inflation of the alveolar occurs. Over a period of time, cigarette smoking or even inhalation of smoke causes damage of septa between the alveoli and of its elastic tissue is substituted by the connective tissue in the lungs. The respiratory surface decreases which cause emphysema.
Q.5. Organize the following in ascending order
a) Tidal volume
b) Residual volume
c) Inspiratory reserve volume
d) Expiratory capacity
A.5. a) Tidal Volume – 500ml b) Residual Volume – 1100-1200 ml
c) Inspiratory reserve volume – 2500-3000ml
d) Expiratory capacity – 1500-1600ml Tidal Volume, Residual Volume, Expiratory Capacity, Inspiratory Reserve Volume
Q.6. Write the organs of respiration in the entities given below:
a) Flatworm
b) Frog
c) Birds
d) Cockroach
A.6. a) Flatworm – Body surface b) Frog – Moist skin and lungs c) Birds – Lungs d) Cockroach – Tracheal tubes
Q.7. Mention the main parts involved in the initiating a pressure gradient between the lungs and the atmosphere during normal respiration.
A.7. The diaphragm and a specialized set of external and intercostal muscles between the ribs aid in the generation of pressure gradient during respiration.

Short Answer Type Questions

Q.1. Write the various modes of transportation of carbon dioxide in the blood.
A.1. It is carried in the blood in three forms:

  • Dissolved state under normal pressure and temperature, 7% of CO2 is transported by physical solution
  • As carbamino compounds, carbon dioxide directly combines with Hb to form an unstable compound, the carbamino compounds
  • As bicarbonate ions

Q.2. Explain why the diffusion of carbon dioxide by the diffusion membrane per unit difference in partial pressure is much greater compared to oxygen.
A.2. The solubility rate of CO2 is 22-25 times more than oxygen.
Q.3. List the following steps in a sequential manner for the completion of the respiration process.
a) Diffusion of oxygen and CO2 across the alveolar membrane
b) Transportation of gases by blood
c) Utilization of oxygen for catabolic reactions by the cells and hence the resultant release of CO2
d) Pulmonary ventilation through which atmospheric air is drawn in and carbon dioxide-rich alveolar air is given out
e) Diffusion of oxygen and carbon dioxide between tissues and blood
A.3.

d) Pulmonary ventilation through which atmospheric air is drawn in and carbon dioxide-rich alveolar air is given out

a) Diffusion of oxygen and CO2 across the alveolar membrane

b) Transportation of gases by blood

e) Diffusion of oxygen and CO2 between tissues and blood

c) Utilization of oxygen for catabolic reactions by the cells and hence the resultant release of CO2

Q.4. State the differences between the following:
a) Expiratory and inspiratory reserve volume
b) Total lung capacity and vital capacity
c) Occupational respiratory disorder and Emphysema
A.4. The differences are as follows: a)

Inspiratory reserve volume Expiratory reserve volume
The additional volume of air that can be inspired by a person forcible inspiration which can range between – 2500ml – 3000ml The additional volume of air that can be expired forcibly through a forcible expiration, ranges between 1000ml-110ml

b)

Vital Capacity Total lung capacity
It is the maximum volume of air that a person can breathe in after forced expiration. The total volume of air accommodated in the lungs at the end of a forced inspiration

c)

Emphysema Occupational Respiratory Disorder
Emphysema is a chronic disease of the respiratory system wherein the alveolar cells are damaged due to which regulatory surface is decreased. Caused due to long exposure of dust that is generated by breaking or stone grinding and causes inflammation that leads to fibrosis and hence lung damage.

Long Answer Type Questions

Q.1. Write a note on the mechanism of breathing
A.1. a) Inspiration – It is inducted by the diaphragm contraction that raises the volume of the thoracic chamber in the anteroposterior axis. The inter-costal muscles contracts causing external protrusion of the sternum and ribs resulting in an increment in the volume of the thoracic chamber in the dorsoventral axis. This increase in the thoracic volume results in a similar increase in pulmonary volume causing reduced intra-pulmonary pressure to lesser than the atmospheric pressure which results in inspiration. b) Expiration – The inter-costal muscles reverse the sternum and diaphragm to their original positions with the diaphragm relaxing, which decreases the thoracic volume and hence the pulmonary volume. Expulsion of air occurs as the intra-pulmonary pressure increases to a level somewhat above the atmospheric pressure causing expiration.
Q.2. Describe the role of the neural system in controlling respiration.
A.2. The neural system maintains and moderates the respiratory rhythm as per the demands of the body tissues. The respiratory rhythm centre present in the brain is responsible for regulation. The pneumotaxic centre, another region in the pons of the brain, moderates the functions of the respiratory rhythm centre. The neural signals from this centre have the ability to reduce the duration of inspiration hence altering the rate of respiration. A chemosensitive area present adjacent to the rhythm centre is very sensitive to hydrogen ions and CO2 which activate this centre by an increase of these substances. These send down a signal to the rhythm centre to cause essential adjustments in the process which can cause the elimination of these substances. Changes in CO2 and hydrogen ions are recognized by receptors linked with aortic arch and carotid artery, thereby sending signals for corrective actions to the rhythm centre. Know more about the exchange of gases and other related biological concepts by registering at BYJU’S.

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