Chapter 17 Breathing and Exchange of Gases

Class 11 Biology Chapter 17 Important Extra Questions Breathing and Exchange of Gases

Breathing and Exchange of Gases Important Extra Questions Very Short Answer Type

Question 1.
Name the site of the exchange of gases in man.
Answer:
Alveoli in the lungs.

Question 2.
Name the respiratory organs in insects.
Answer:
Tracheae and spiracles.

Question 3.
Name the respiratory pigment of the blood of mammals.
Answer:
Haemoglobin.

Question 4.
What makes the exchange of gases in gills and lungs possible?
Answer:
Thin-walled blood capillaries.

Question 5.
Why are erythrocytes unable to carry out cellular oxidation?
Answer:
They lack mitochondria.

Question 6.
What is the main source of energy?
Answer:
Carbohydrates lipids and proteins.

Question 7.
Why energy obtained from ATP molecules is called biologically useful energy?
Answer:
Because it drives the life processes.

Question 8.
How does the exchange of gases across a respiratory membrane occur?
Answer:
By diffusion and circulatory system.

Question 9.
What holds the energy in the body?
Answer:
Molecules of food hold energy in their chemical bonds.

Question 10.
What is external respiration?
Answer:
It is the intake of oxygen by the blood from air or water to the respiratory organs and the elimination of CO₂.

Question 11.
Name the parts of the human respiratory system in a sequence starting from the nose.
Answer:
External nostrils, nasal cavity, internal nostrils, pharynx, trachea, bronchi, lungs.

Question 12.
What is glottis?
Answer:
The opening of the pharynx into the trachea is called the glottis.

Question 13.
What is breathing?
Answer:
Breathing is one phase of respiration. During breathing, we get oxygen from the atmosphere inside our body.

Question 14.
How breathing is different from circulation give a reason?
Answer:
Breathing is a phase of respiration. It is a physical process.

Question 15.
Which gases take part in breathing?
Answer:
Carbon dioxide, oxygen, nitrogen and mixture.

Question 16.
What is glomerulus?
Answer:
The glomerulus is a lift of blood capillaries in a cup-shaped Bowman’s capsule.

Question 17.
What is tidal volume?
Answer:
It is the volume of air breathed in and out normally.

Question 18.
Why gaseous exchange continues in the lungs even after expiration?
Answer:
Because of the presence of residual volume.

Question 19.
Where does the exchange of gases occur in our body?
Answer:
In lung alveoli and tissue cells.

Question 20.
What is vital capacity in regard to breathing?
Answer:
Vital capacity is the volume of air that can be inspired and expired with maximum efforts.

Question 21.
Name excretory organs of earthworm.
Answer:
Nephridia.

Breathing and Exchange of Gases Important Extra Questions Short Answer Type

Question 1.
Define partial pressure of a gas.
Answer:
It is the pressure exerted in a mixture of gases and is equal to the total pressure of the mixture of gases divided by the percentage of that gas in a mixture. The atmospheric air pressure at sea level is 760mm of Hg. Oxygen forms 35% of the air. The partial pressure of oxygen is 760 × 35/ 100 = 266 mmHg.

Question 2.
How would you differentiate between tidal volume and residual volume?
Answer:

1. Tidal volume is the amount of air inhaled or exhaled in one complete breathing. It is about 500 ml.
2. Residual volume is the volume of air that remained in the lungs after the maximum effort of exhalation. It is about 1500ml.

Question 3.
What is the need for a circulatory system in a bigger animal?
Answer:
In larger animals the deeper cells cannot obtain oxygen directly from the atmosphere simply through the process of diffusion or eliminate CO₂. In such a case, the respiratory system transports the respiratory gases from the respiratory’ surface to the deep-lying tissues.

Question 4.
Why does one experience difficulty at a high altitude?
Answer:
At high altitude, the pressure of air falls and the person cannot get enough oxygen in the lungs for diffusion in the blood. Due to insufficient O_2, the person has difficulty breathing at high altitude. The person feels difficulty such as breathlessness, headache, dizziness, irritability, nausea, vomiting, mental fatigue and a blush (///) on the skin, nails and lips.

Question 5.
What are the conditions essential for effective respiration?
Answer:
Conditions essential for effective respiration:

1. The respiratory surface should be thin and permeable to O₂ and CO₂
2. The rich supply of blood to the respiratory surface.
3. Passage for bringing oxygen to the respiratory surface and removing CO₂ through the same passage.
4. The respiratory surface should be moist.
5. Presence of a circulatory system.
6. Presence of a respiratory pigment to carry out the respiratory gases (CO₂ and O₂)

Question 6.
What is a specialized respiratory surface and what are its advantages?
Answer:
A specialized respiratory surface is thin, moist and highly vascular. It remains in contact with the environment outside the body and tissues inside the body. Diffusion of gases takes place from the respiratory surface between the body and outside the environment. The epidermal capillaries release carbon dioxide and take up oxygen dissolved in the film of surface moisture.

Question 7.
What is respiration?
Answer:
A process of physiochemical change by which environmental oxygen is taken in to oxidise the stored food to release CO₂ water and energy; the energy released is used for doing various life activities whereas CO₂ being foul gas is thrown out from the body. The main source of energy are carbohydrates, lipids and proteins. Respiratory mediums are air and water.

Question 8.
Define the
(a) Inspiratory reserve volume (IRV)
Answer:
Inspiratory reserve volume: It is the amount of air that can be inhaled forcibly after a normal inspiration. It is about 200 – 250 ml.

(b) Expiratory reserve volume (ERV)
Answer:
Expiratory reserve volume: It is the volume of ah, which can be exhaled forcibly after a normal expiration. It is about 1000 – 1500 ml.

(c) Vital capacity of lungs (VC)
Answer:
Vital capacity of lungs: It is the amount of air that one can exhale with maximum effort. It is about 3500-4500 ml.

(d) Residual volume. (RV)
Answer:
Residual volume: The amount of air left in the lungs after forcible expiration is called residual volume. It is about 1500ml.

Question 9.
What is Bronchial Asthma? How it is caused? What are the symptoms of this disease?
Answer:
It is characterised by the spasm of the smooth muscles present in the walls of the bronchiole. It is generally caused due to the hypersensitivity of the bronchiole to the foreign substances present in the air passing through it.

The symptoms of this disease are coughing, difficulty in breathing mainly due to expiration, the mucous membrane starts secreting an excess amount of mucous.

Question 10.
What is the preventive measure of the disease Bronchitis?
Answer:
Bronchitis is caused by cigarette smoking and exposure to air pollutants like carbon monoxide. It can be prevented and cured by avoiding exposure to the cause i.e. smoke, chemicals and pollutants. The underlying infection of the disease is treated with suitable antibiotics Bronchodilator drugs (for widening the constriction of bronchial passage by relaxing the smooth muscles) provide symptomatic relief.

Question 11.
How respiration fulfil the energy requirement of an organism?
Answer:
Respiration is a catabolic process. A catabolic biochemical process of exchange of gases by which atmospheric oxygen is taken in to oxidise the stored food to liberate energy, CO2 and water. Energy set free is used for doing life activities. For oxidation usually, oxygen is used. The energy is released in steps from the continuous breakdown of foodstuffs and is stored in the high energy bonds of ATP molecules. This energy obtained from ATP molecules is termed biologically useful energy as it allows the working of all life processes.

Question 12.
What is chloride shift? Write its significance during respiration.
Answer:
The chloride ions (CI^–) inside RBC combine with potassium ion (K⁺) to form potassium chloride (KCL), whereas hydrogen carbonate ions (HCO^–₃) in the plasma combine with Na’ to form sodium hydrogen carbonate (NaHCO₃) Nearly 70% of carbon dioxide is transported from tissues to the lungs in this form.

In response to chloride ions (CI^–) diffuse from plasma into erythrocytes to maintain the ionic balance. This is called the chloride shift.

Significance: It maintains electrochemical neutrality during respiration.

Question 13.
Write true or false.
(a) Inspiratory reserve volume is the volume of air, which can be inspired in addition to the normal inspiration.
Answer:
False

(b) Vital capacity is a measure of maximum inspiration.
Answer:
true

(c) During the gaseous exchange the gases diffuse from high partial pressure to low partial pressure.
Answer:
true

(d) Carbon dioxide cannot be transported with haemoglobin.
Answer:
true

(e) Earthworm respires through parapodia.
Answer:
false.

Question 14.
What is the role of the carbonic anhydrase enzyme in the transport of gases during respiration?
Answer:
Carbon dioxide produced by the tissues diffuses passively into the bloodstream and passes into the red blood corpuscles where it reacts with water to form carbonic acid (H₂CO₃). This reaction is catalysed by the enzyme, carbonic anhydrase found in the erythrocytes and takes less than one second to complete the process. Immediately after its formation, carbonic acid dissociates into hydrogen (H⁺) and bicarbonate (HCO₃^–) ions. The majority of bicarbonate ions (HCO₃^– ) formed within the erythrocytes diffuse out into the plasma along a concentration gradient. These combine with haemoglobin to form the haemoglobin acid (H.Hb).

Question 15.
What is partial pressure? How does it help in gaseous exchange during respiration?
Answer:
During inspiration and expiration, gases move freely by the process of diffusion. Diffusion of any molecule takes place from high to low concentration. The process of diffusion is directly proportional to the pressure caused by the gas alone. The pressure exerted by an individual gas is called partial pressure. It is represented as PO₂, PCO₂, and PN₂, for oxygen, carbon dioxide and nitrogen respectively.

The inspired air ultimately reaches the alveoli of the lung, which in turn receives the blood supply of the pulmonary circulation. At this stage the oxygen of the inspired air is taken in by the blood and carbon dioxide is released into the alveoli for expiration.

In this way, the gases exchange takes place due to partial pressure.

Question 16.
How does haemoglobin help in the transport of oxygen from the lung to tissues?
Answer:
Blood is the medium for the transport of oxygen from the respiratory organ to the different tissues and carbon dioxide from tissues to the respiratory organs. 97% of the oxygen is transported from the lungs to the tissues in combination with haemoglobin (Hb + O₂ — HbO₂), oxyhaemoglobin and 3% is transported in dissolved condition by the plasma.

Under high partial pressure oxygen easily binds with haemoglobin in the pulmonary capillaries. When this oxygenated blood reaches the different tissues, the partial pressure of oxygen declines and the bonds holding oxygen to haemoglobin become unstable. As a result, oxygen is released from the capillaries.

Question 17.
Write the names of the respiratory organs present in human.
Answer:
The human respiratory system consists of external nares or nostrils, nasal cavity, nasopharynx, larynx, trachea, bronchi, bronchiole and lungs.

Question 18.
How skin of the earthworm helps in respiration?
Answer:
Earthworms exchange O₂ and CO₂ between their looped epidermal blood capillaries and their body surface have a moist film. The epidermal capillaries release carbon dioxide; take up the oxygen dissolved in the film of surface moisture.

Question 19.
Fill in the blanks.
Answer:
(a) 15ml of oxygen is transported per decilitre of blood,
(b) Total lung capacity is 3400 to 4800 ml.
(c) There are 10 pairs of spiracles in the cockroach.
(d) Lung is enclosed by a pleural membrane
(e) Streptococcus bacteria causes pneumonia.

Question 20.
Explain breathing disorders in brief.
Answer:

1. Asthma is caused by an allergic reaction. There is difficulty in breathing.
2. Pneumonia is caused by bacterial infection. There are fever, pain and severe cough.
3. Tuberculosis is an infectious bacterial disease of the lungs and in serious cases, blood may come out while coughing.

Question 21.
With the help of arrow marks show1 the sequence of airflow up to lungs.
Answer:
Air → Nostrils → Nasal cavity → Pharynx → Larynx → Bronchi Bronchioles → Lung, alveoli

Question 22.
In what form O₂ is carried in blood? What happens to it when blood reaches the tissue?
Answer:
O₂ is carried in combination with the haemoglobin of RBCs and forms oxyhaemoglobin.

In tissues, there is the dissociation of oxyhaemoglobin and release of Or It diffuses into the tissue cells where it is used in oxidation.

Breathing and Exchange of Gases Important Extra Questions Long Answer Type

Question 1.
Explain gas transport in the blood.
Answer:
It may be explained in two steps.
(a) Transport of O₂ from lungs to tissues.
(b) Transport of CO₂ from tissues to lungs.

A. Oxygen Transport

1. O₂ is transported in the blood via haemoglobin.
2. O₂ diffuses into RBC and combines with haemoglobin to form oxyhaemoglobin.
3. Oxyhaemoglobin breaks into haemoglobin and oxygen at the tissues, where there are high PCO₂ and PO₂.
4. In the lungs, oxyhaemoglobin is formed due to high PO₂ and low PCO₂.

B. CO₂ Transport: CO₂ is transported in 3 ways with blood.

1. 70% of CO₂ in RBC reacts with H₂O to form H₂CO₃
   
2. The rest 30% CO₂ combining with Hb to form carbon haemoglobin. (HCO₃^– carried by RBC and plasma)
3. Some CO₂ dissolves in plasma on reaching the lungs.
   HCO₃^– + H + H₂CO₃
   H₂CO₃ CO₂ + 2H₂O
   And this CO₂ is expelled out through the lungs.

Question 2.
Name and explain the respiratory organs of the following,
(i) Insect
Answer:
Insect: The integument of insects is thick and highly impermeable to minimise the loss of water through the environment. The exchange of gases cannot take place through the skin covering of these insects. These insects have a highly developed complex system called the tracheal. This mode of respiration is called tracheal respiration.

(ii) Neries
Answer:
Neries: Parapodia is the respiratory oxygen in neries. In this organism respiratory occurs through the skin covering the parapodia (Locomotory organs), which is again very thin, moist, permeable and highly vascular.

(iii) Prawn
Answer:
Prawn: Gills, in the animals like prawns, certain molluscs, fishes, tadpoles, the process of gaseous exchange occur by special respiratory organs called gills. These are richly supplied with blood and readily absorb oxygen found dissolved in water and release CO₂ back into the water.

(iv) Birds
Answer:
Birds: (lungs). In birds and mammals, the skin is impermeable. These have a high metabolic rate and their oxygen requirement is very high. Birds have spongy lungs to have a more extensive respiratory surface. These lungs always remain in the body to keep the respiratory surface moist, which is necessary for the exchange of respiratory gases.

(v) Fishes
Answer:
Oxygen and carbon dioxide dissolves in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills.

(iv) Earthworm.
Answer:
Earthworms do not have lungs. They breathe through their skin. Oxygen and carbon dioxide pass through the earthworm’s skin by diffusion

Question 3.
Define the following terms:
(a) Anaerobic respiration,
Answer:
Anaerobic respiration: It is a process that does not involve the use of molecular oxygen. Food is not completely oxidised to CO₂ and water. Less energy is present in anaerobic respiration.

(b) Breathing,
Answer:
Breathing: It is a physical process, which brings in fresh air to the respiratory surface and removes foul impure airs from the outside. It occurs outside the cells and is thus an extracellular process.

(c) Vital capacity,
Answer:
Vital capacity: It is defined as an important measure of pulmonary capacity. It is the maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent.

Vital capacity is the sum total of inspiration reserve volume, tidal volume and expiratory reserve volume.
(1 + 1 + VC = IRV = TV/ERV)

(d) Tidal volume,
Answer:
Tidal volume: It is defined as the volume of air normally inspired or expired in one breath without doing any effort. It is about 500 ml in an adult person. It represents the volume of air, which is renewed in the respiratory system during every breathing.

(e) Respiratory centre.
Answer:
Respiratory centre: A number of groups of neurons located bilaterally in the medulla oblongata control the respiratory. These are called respiratory centres. These centres are named the dorsal respiratory group. Ventral respiratory group and pneumatic centre.

Question 4.
Write the role of the diaphragm and its Costals muscles in the breathing process.
Answer:
During breathing, when the lungs contract their volumes decrease resulting in the increase of air pressure in the lungs. Hence, the air is exhaled from the lungs. These two processes are called inspiration and expiration. During normal breathing, the downward and upward movement of the diaphragm takes place. When the diaphragm, contracts, the lower surface of the lung is pulled downward consequently the volume of the lungs increases.

This causes the inhalation of air or inspiration. When the diaphragm relaxes, lungs are compressed and air exhaled, expiration takes place. The demand for extra oxygen is fulfilled by the expansion of the rib cage, during exercise when the rate of breathing increases.

During expiration, high pressure is generated in the lungs and air moves out. The upward movement of the rib cage is caused mainly by the external intercostals muscles present between the ribs along with the assistance of few other adjacent muscles.

Similarly, the downward movement of the rib cage is facilitated by the internal intercostals, external oblique and internal oblique muscles, position of the diaphragm, ribs and sternum during breathing as shown in the diagram

Position of diaphragm, ribs and sternum during breathing