Important Questions Class 11 Biology Chapter 14 Breathing and Exchange of Gases

Important Questions Class 11 Biology Chapter 14 Breathing and Exchange of Gases

Breathing and Exchange of Gases is Chapter 14 of Class 11 Biology. Breathing is the process of taking in oxygen-rich air and giving out air rich in carbon dioxide. The chapter explains the human respiratory system, the mechanism of breathing, exchange of gases in the alveoli (tiny air sacs of the lungs), transport of oxygen and carbon dioxide in the blood, regulation of respiration and common respiratory disorders.

This page gives 12 important questions from Breathing and Exchange of Gases with clear answers prepared by Extramarks experts. The questions cover the role of the diaphragm, inhalation and exhalation, the function of alveoli and pleural fluid, transport of carbon dioxide, asthma, emphysema and the structure of the respiratory system. Students can use them for school tests and CBSE (Central Board of Secondary Education) exam revision, and teachers and parents can use them for quick practice.

Important Questions Class 11 Biology Chapter 14 Breathing and Exchange of Gases

Breathing and Exchange of Gases
Easy
Q.
Define vital capacity. What is its significance?
Breathing and Exchange of Gases
Medium
Q.
State the volume of air remaining in the lungs after a normal breathing.
Breathing and Exchange of Gases
Medium
Q.
Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why?
Breathing and Exchange of Gases
Medium
Q.
What are the major transport mechanisms for CO2? Explain.
Breathing and Exchange of Gases
Easy
Q.
What will be the pO2 and pCO2 in the atmospheric air compared to those in the alveolar air?
 
(i) pO2 lesser, pCO2 higher
 
(ii) pO2 higher, pCO2 lesser
 
(iii) pO2 higher, pCO2 higher
 
(iv) pO2 lesser, pCO2 lesser
Breathing and Exchange of Gases
Medium
Q.
Explain the process of inspiration under normal conditions.
Breathing and Exchange of Gases
Medium
Q.
How is respiration regulated?
Breathing and Exchange of Gases
Medium
Q.
What is the effect of pCO2 on oxygen transport?
Breathing and Exchange of Gases
Medium
Q.
What happens to the respiratory process in a man going up a hill?
Breathing and Exchange of Gases
Easy
Q.
What is the site of gaseous exchange in an insect?
Breathing and Exchange of Gases
Medium
Q.
Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?
Breathing and Exchange of Gases
Medium
Q.
Have you heard about hypoxia? Try to gather information about it, and discuss with your friends.
Breathing and Exchange of Gases
Medium
Q.
Distinguish between
 
(a) IRV and ERV
 
(b) Inspiratory capacity and expiratory capacity.
 
(c) Vital capacity and Total lung capacity.
 
Breathing and Exchange of Gases
Medium
Q.
What is Tidal volume? Find out the Tidal volume (approximate value) for a healthy human in an hour.

Q1. Why is alveoli important in human respiratory system?

Answer: Alveoli provide a surface for the exchange of gases. An extensive network of blood vessels is present in the wall of the alveoli. By lifting our ribs and flattening the diaphragm, the chest cavity becomes spacious. Air is sucked into the lungs and alveoli.

The oxygen from the breath, diffuses into the blood and CO2 from the blood brought from the body, diffuses out into the air.

Q2. Mention the role of diaphragm with the help of a flow chart.

Answer: The role of the diaphragm during inhalation and exhalation is shown in the flow chart below:

Flow chart showing the role of diaphragm during inhalation and exhalation

Q3. What is the difference between inhalation and exhalation?

Answer:

Inhalation Exhalation
The process of taking in of air is called inhalation. The process of releasing out air rich in carbon dioxide is called exhalation.
During inhalation, diaphragm moves downwards. During exhalation, diaphragm moves upwards.

Q4. Describe the role of the inner lining of nasal chambers in breathing.

Answer: The inner lining of nasal chambers helps in breathing by –

i. warming the air passed through

ii. adding moisture to the air

iii. entrapping the harmful particles

Q5. How does the ciliated lining protect the respiratory tract?

Answer: The cilia of the respiratory tract keeps on moving constantly, driving the mucous secreted by the goblet cells and particles entrapped in it towards the throat. Thus, it prevents the particles to enter the lungs.

Q6. What is pleural fluid? Describe its function.

Answer: Pleural fluid is the watery fluid filled within the pleural cavity of the two membranes enclosing the lungs. The pleural fluid lubricates free movement of the lungs.

Q7. How are respiratory movements controlled in humans?

Answer: The respiratory movements are involuntary and not under our will. They are controlled by a respiratory centre, located in the medulla oblongata of the human brain.

Q8. Discuss the fate of carbon dioxide after entering in blood of the human body.

Answer: Carbon dioxide, after entering the blood of the human body, is transported in 3 forms:

1. About 5-7% of carbon dioxide is transported in dissolved form in the plasma of the blood.

2. 20-25% CO2 is carried by haemoglobin as carbamino-haemoglobin. Carbon dioxide on reaction with amine radicals of haemoglobin form carbaminohaemoglobin.

3. About 70% of the carbon dioxide enters the erythrocytes, where it reacts with water to form carbonic acid (H2CO3). This reaction is facilitated in blood by enzyme carbonic anhydrase present in red blood cells. Carbonic acid immediately dissociates into bicarbonate and hydrogen ions. Hydrogen ions combine with haemoglobin to form haemoglobinic acid and bicarbonate ions diffuses out in the plasma to combine with Na+ and K+ to maintain the pH of blood.

CO2 trapped as bicarbonate ions at the tissue level is transported to the alveoli and is released out as CO2.

Q9. Haemoglobin performs twin functions of combining with oxygen and carbon dioxide. What is the advantage of binding of these gases with Hb?

Answer: Haemoglobin combines with carbon dioxide, preferentially before oxygen, since it can store oxygen or saturate itself with oxygen to be used later. For haemoglobin, oxygen is for storage, whereas carbon dioxide is for removal. This adaptation can be useful in removing the "harmful" carbon dioxide first, otherwise the blood pH will drop to make blood too acidic. Blood is more prone to being too acidic than being too alkaline.

Q10. In the given diagram, label the parts that signify:
(i) Network of branches present inside lungs
(ii) Sound-producing organ
(iii) A common passage for food and air
(iv) The structure supporting lungs

Diagram of the human respiratory system to be labelled

Answer: (i) Network of branches present inside lungs : Bronchioles

(ii) Sound-producing organ : Larynx

(iii) A common passage for food and air : Pharynx

(iv) The structure supporting lungs : Diaphragm

Human respiratory system showing pharynx, larynx, bronchioles and diaphragm

Q11. Briefly explain the following terms:
(i) Asthma
(ii) Emphysema
(iii) Occupational Respiratory Disorders

Answer: (i) Asthma is the inflammation of bronchi and bronchioles causing difficulty in breathing and wheezing.

(ii) Emphysema is a chronic disorder in which alveolar walls are damaged and hence the respiratory surface is reduced. Cigarette smoking is one of the major causes of this disorder.

(iii) Occupational Respiratory Disorders are the inflammation of respiratory system occurring in those persons who work in certain industries like grinding or stone-breaking. So much of dust is produced due to which the defense mechanism of the body cannot fully cope with the situation. Long exposure can give rise to inflammation leading to fibrosis (proliferation of fibrous tissues) and thus causing serious lung damage.

Q12. Describe the structure of human respiratory system.

Answer: Human respiratory system consists of a pair of external nostrils, nasal cavity chamber, nasopharynx, larynx, trachea, bronchioles and alveoli. The external nostrils present just above the upper lip lead into the nasal chamber through the nasal passage.

The nasal chamber opens into nasopharynx, which is a portion of pharynx, the common passage for food and air.

Larynx is a cartilaginous box like structure that helps in sound production; it leads into the trachea.

Trachea is a straight tube extending up to the mid-thoracic cavity, which divides at the level of 5th thoracic vertebra into right and left primary bronchi.

Each bronchus undergoes repeated divisions to form the secondary and tertiary bronchi and bronchioles ending up in very thin terminal bronchioles.

The trachea, primary, secondary and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings. Each terminal bronchiole gives rise to a number of very thin, irregular walled and vascularised bag-like structures called alveoli. The branching network of bronchi, bronchioles and alveoli constitutes the lungs.

The lungs are located in the thoracic chamber which are covered by a double layered membrane called pleura, with pleural fluid between them.

The outer pleural membrane is in close association with the thoracic cavity whereas the inner pleural membrane is in contact with the lung surface.

Related Study Material on Extramarks

Q.1 Which of the following substrates will have maximum respiratory quotient?

Marks:1

Ans

The respiratory quotient of barley (carbohydrate) is 1 and that of soybean (protein) is 0.9. While the respiratory quotient of almonds and chia seeds (fat) is less than 1.

Q.2 One molecule of glucose requires 2 ATP to get phosphorylated to form fructose 1-6 Biphosphate in glycolysis. The ATP which are used in the same process if the substrate is fructose is

Marks:1

Ans

2.

Whether it is glucose or fructose, reactions are same.

Q.3 In Krebs cycle, the number of reduced coenzymes formed is

Marks:1

Ans

One turn of Krebs cycle produces four reduced coenzymes (2NADH2, 1NADH2 and 1FADH2) and 2CO2. In all, there are two turns of Krebs cycle for the oxidation of 1 molecule of glucose.

Q.4 One turn of Krebs cycle for the oxidation of 1 mol of sucrose produces

Marks:1

Ans

Whether it is glucose/sucrose, one turn of Krebs cycle produces 12 ATP. In sucrose, there will be in all four turns of Krebs cycle instead of two, as in case of glucose, and therefore, total ATP production will be two times more than glucose, that is 76 ATP.

Q.5 The step of glycolysis where NADH+H+ is formed:

Marks:1

Ans

The step of glycolysis where NADH+H+ formed is 3-PGA to 3-biphosphoglycerate.

 

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