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Question-1

What are the two factors that contribute towards the dissociation of oxyhaemoglobin in the arterial blood to release molecular oxygen in an active tissue?

Solution:
The two factors that contributes towards the dissociation of oxyhaemoglobin in the arterial blood to release molecular oxygen in an active tissue are,

(i) The lower concentration of PO2 and

(ii) Higher concentration of PCO2.

Question-2

What do you understand by forceful expiration?

Solution:
Vital capacity is the volume of air breathed out by a maximum forceful expiration.

Question-3

What is the role of carbonic anhydrase in RBCs?

Solution:
About 70% of CO2 reacts with water to form carbonic acid in RBCs in the presence of the enzyme, carbonic anhydrase.

Question-4

Blood vessel in the liver has blood with PO2 of 95 mm Hg that is much higher than the PO2 of the tissue in the liver. Does O2 diffuses in the blood from the tissue or diffuse from blood into the tissue.

Solution:
O2 will diffuse from the blood into the tissue.

Question-5

In mammals, the lungs replace the skin very effectively as a respiratory organ. Explain giving three reasons.

Solution:
(i) Lungs provide a very large surface area for the exchange of gases. The total alveolar surface area is nearly 100 m2 whereas the total surface area of the skin is around 1.6m2 only.

(ii) Alveoli are lined by thin highly permeable membranous wall. These are surrounded by many blood capillaries. They are, therefore more richly connected with blood capillaries than the skin.

(iii) Endothelium of blood capillaries and membranous walls of the alveoli are highly permeable to respiratory gases.
Therefore, the lungs replace the skin very effectively as a respiratory organ.

Question-6

What is tidal volume?

Solution:
The volume of air breathed in and out during effortless respiration.

Question-7

Why does it become difficult to breathe at high altitudes?

Solution:
At high altitudes, the concentration of oxygen becomes less. At a height of about 15,000 feet or more, the pressure also decreases along with a decrease in the oxygen content. Persons reaching such heights are unable to get the amount of oxygen required for proper functioning of their body. Due to this, sufficient oxygen does not diffuse into the blood, as a result of which the person suffers from nausea, headache and delusion. As a result he finds it difficult to breathe.

Question-8

The maximum number of molecules of oxygen which one molecule haemoglobin can carry?

Solution:
Four.

Question-9

What is pneumonia?

Solution:
Pneumonia is the disease of lungs characterized by accumulation of mucous in lungs.

Question-10

Explain how CO2 produced during oxidation of carbohydrate in the muscles of our heart is released into the atmosphere.

Solution:
CO2 in the plasma is absorbed by RBC as a physical solution. It is transported as carbonic acid, bicarbonates and carbonic haemoglobin. It is then carried to the heart and from there it is taken to the pulmonary artery and then to the lungs. Dissociation takes place in the alveoli and the CO2 is finally, exhaled through the nostrils.

Question-11

Give two symptoms of bad cold.

Solution:
(i) Inflammation of mucous membrane in Rhinitis.

(ii) Enlargement of tonsils.

Question-12

What is the dissociation curve? Explain.

Solution:
The relationship between O2 tension and its absorption by haemoglobin produces a graph called the oxygen dissociation curve. At about 100mm Hg, O2 tension in Hb is 98% saturated. As it falls, the saturation of Hb decreases slowly. When O2 tension is about 40mm Hg, oxyhaemoglobin dissociates and O2 is available to the tissues.

Question-13

What is formed when CO2 combines with globin of reduced haemoglobin?

Solution:
Carbaminohaemoglobin is formed when CO2 combines with globin of reduced haemoglobin.

Question-14

How does exchange of respiratory gases take place in the alveoli of lungs?

Solution:
During intake of air, the partial pressure of oxygen (PO2) and partial pressure of carbon dioxide (PCO2) are 158mm Hg and 0.3mm Hg respectively. There is already a small amount of alveolar air in the lungs. This air contains less amount of oxygen and more amount of CO2 than the inspired air. As this alveolar air mixes with the inspired air, the O2 content and PO2 of the alveolar air increase to about 13.1% and 100mm Hg. Whereas, CO2 content and PCO2 are about 5.3% and 40mm Hg.

The pulmonary artery brings the deoxygenated blood from the heart to the lungs. The blood consists of lower PO2 than the alveolar PO2. In the lungs, O2 diffuses into the blood from the alveolar air and now PO2 is about 95mm Hg. Now the O2 content is 19.8%. This oxygenated blood is taken away by the pulmonary vein. The mixed venous blood present in the alveolar capillaries contains PCO2 of 40mm Hg. So the CO2 diffuses from the alveolar capillaries to the alveolar air and PCO2 falls to 40mm Hg. In the alveoli of the lungs, O2 is taken up by the pulmonary vein and CO2 is given out from the blood of the pulmonary artery.

Question-15

How much is the "vital capacity" of human? Do people living on mountains have the same, less or more vital capacity as those living in the plains?

Solution:
About 3.5 – 4.5 litres. Vital capacity is higher in people living on mountains than living in the plains.

Question-16

Why is haemoglobin called conjugated protein? What happens to the molecule at high and low partial pressure of oxygen?

Solution:
Haemoglobin is called conjugated protein because it consists of a basic protein globulin and a non-protein called haem. The haemoglobin, when exposed to high partial pressure of oxygen, combines with it to form oxyhaemoglobin, which carries four molecules of oxygen loosely bound to the four Fe2+ ions. When this oxyhaemoglobin reaches the tissues where there is low oxygen pressure, oxyhaemoglobin dissociates into oxygen and deoxyhaemoglobin.

Question-17

Write an equation to represent an aerobic respiration.

Solution:
C6H12O6 + enzymes ###ERROR###à 2C2H5OH + 2CO2 + 54 Kcals energy

Question-18

Give at least four points of difference between aerobic and anaerobic respiration.

Solution:
The four points of difference between aerobic respiration and anaerobic respiration are as follows:

Aerobic respiration

Anaerobic respiration

(i) It takes place in the presence of oxygen. (i) It takes place in the absence of oxygen.
(ii) It takes place in two steps - the first step is glycolysis, which is carried out in the cytoplasm and the second step is the Kreb’s cycle, which takes place in the mitochondria. (ii) The complete process takes place outside the mitochondria, in the cytoplasm.
(iii) Complete oxidation of glucose takes place. (iii) Incomplete oxidation of glucose takes place.
(iv) During this process, 38 ATP molecules per gram mole of glucose are formed. (iv) During this process, 2 ATP molecules per gram mole of glucose are formed.

 

Question-19

Which organelle in the cell is associated with the production of energy?

Solution:
Mitochondrion is the organelle in the cell which is associated with the production of energy.

Question-20

Write the difference between carbamino-haemoglobin and oxyhaemoglobin.

Solution:
Carbamino-haemoglobin Oxyhaemoglobin
Carbon dioxide when enters the erythrocytes combines with globin, part of deoxy haemoglobin as a result of which carbamino- haemoglobin is formed. Oxygen diffuses into erythrocytes and combines with the Fe2+ ions of haemoglobin and forms oxyhaemoglobin

 

Question-21

Why is it not healthy to breath in a closed room for a very long time?

Solution:
In a closed room there is no provision of fresh air coming into the room. The oxygen already present in the air of that room shall be gradually consumed. If more number of people are sitting in a room the percentage of oxygen will go on decreasing and the percentage of carbon dioxide would go on increasing by continuous use of oxygen during respiration. Thus it is not a healthy sign to breath in a closed room for a very long time.

Question-22

What happens to the leg muscle of an athlete who runs a marathon race?

Solution:
While running a marathon race, the internal muscle respires anaerobically as they do not get the required increased supply of oxygen at that time. This results in the deposition of lactic acid in them. As a result of the lactic acid deposition, the leg muscles feel cramps. Lactic acid, thus produced will be oxidised later by other tissues.

Question-23

The venous blood in the lungs has a PCO2 of 46mm Hg. Should the alveolar PCO2 exceed or be less than 46mm Hg to result in diffusion of CO2 from the blood into the alveolus?

Solution:
Less (40 mm Hg).

Question-24

Why is haemoglobin called conjugated protein?

Solution:
Haemoglobin is called conjugated protein because it consists of a basic protein globin and a non-protein haem.

Question-25

Write any three differences between larynx and pharynx.

Solution:
Larynx Pharynx
It produces sound. It does not produce sound.
It has a cartilaginous framework. It has no cartilaginous framework.
It is a passage for air only. It is a passage for both food and air.

 

Question-26

Define external respiration.

Solution:
External respiration is the biophysical process where uptake of oxygen and elimination of carbon dioxide takes place.

Question-27

Differences between aquatic and terrestrial respiration.

Solution:
Aquatic respiration Terrestrial respiration
It occurs mainly through gills and moist body wall. It occurs mainly through the lungs.
The oxygen is absorbed from the water. The inhalation of oxygen occurs from the atmosphere.
Respiratory pigments and process of respiratory exchange between the internal medium and tissue are not well developed. The respiratory pigments and the process of respiratory exchange between the internal medium and tissues are well developed.

 

Question-28

What is the role of carbonic anhydrase in RBC’s?

Solution:
About 70% of CO reacts with water to form carbonic acid in RBCs in the presence of enzyme carbonic anhydrase.

Question-29

Why do you breathe faster while running?

Solution:
The metabolism of food increases due to the supply of more energy to the body, while running. Due to this process more carbon dioxide is added into the blood and its concentration in the blood is increased above normal, which stimulates the respiratory center in the brain. The respiratory center sends the stimulus to the muscles of ribs and diaphragm through the nerves for faster and deeper respiration. Thus we breathe faster during running or hard physical work.

Question-30

Name the artery, which supplies blood to the alveolar capillaries.

Solution:
Pulmonary artery.

Question-31

What is pulmonary respiration?

Solution:
Respiration by lungs is termed as pulmonary respiration.

Question-32

Which part of the brain controls the respiratory process in the vertebrates.

Solution:
Respiratory center which is situated in the floor of medulla oblongata is the part of brain that controls the respiratory process in the vertebrates.

Question-33

What is epiglottis?

Solution:
Epiglottis is the structure situated in the pharyngeal region, the function of which is to close the open larynx during food swallowing so that food particles do not enter the respiratory tract.

Question-34

When haemoglobin content is less what disease occurs?

Solution:
Anaemia.

Question-35

By what process does yeast derive energy from food?

Solution:
Yeast derives energy by the anaerobic fermentation of glucose into ethanol.

Question-36

What is normal rate of breathing in man?

Solution:
15 to 20 times per minute.

Question-37

What is the percentage of O2 in the inspired and expired air?

Solution:
Inspired air – 21 % of oxygen and expired air - 16 % of oxygen.

Question-38

Name the structure, which prevent the collapsing of trachea.

Solution:
Cartilaginous rings.

Question-39

Name the process of respiration, which takes place in the absence of oxygen.

Solution:
Anaerobic respiration.

Question-40

Is the energy released during respiration liberated immediately or is it stored somewhere and utilized as and when required?

Solution:
The energy released during respiration is stored in small chemical compounds known as ATP.

Question-41

What is the residual volume? What is its role?

Solution:
Even after maximum forced exhalation some air remains in the lungs. This is called residual volume of the air. It is there to prevent collapse of the lungs.

Question-42

Name the substance, which are readily oxidized during respiration to produce energy.

Solution:
Carbohydrates (Glucose and fructose).

Question-43

How does the diaphragm help in respiration?

Solution:
The diaphragm increases the volume of thoracic cavity during inspiration and decreases the volume of thorax during expiration.

Question-44

Name the blood vessel, which supplies blood to alveolar capillaries. What are the values of PO2 and PCO2 in the blood of the vessel?

Solution:
Pulmonary artery carrying blood with PO2 equal to 40mm Hg and PCO2 to 46 mm Hg.

Question-45

Name the other pigments, which are present in animals besides haemoglobin.

Solution:
Haemocyanin and haemoerythrin.

Question-46

What is the normal value of tidal volume in adult person?

Solution:
The normal value of tidal volume in adult person is 500ml.

Question-47

What is the total alveolar surface area in the lungs of human beings?

Solution:
100m2 (which is about 62 times more than the surface area of skin).

Question-48

What are the difference between breathing and respiration?

Solution:
Breathing is a physical process in which O2 is taken in and CO2 is given out.
Respiration is a biochemical process in which energy is liberated along with CO2 and water vapour due to oxidation of food.

Question-49

What is apnea?

Solution:
When breathing rate is decreased we called it as apnea.

Question-50

State two types of TB.

Solution:
The two types of TB are

(i) Pulmonary TB and

(ii) Lymph gland TB

Question-51

Name a respiratory disease.

Solution:
Emphysema

Question-52

Describe how our brain gets a continuous supply of oxygen from the atmosphere.

Solution:
The passage of air which contains oxygen: Inhalation of fresh air ###ERROR###à trachea ###ERROR###à bronchi ###ERROR###à lungs ###ERROR###à alveoli ###ERROR###à diffusion of O2 into blood (RBC) ###ERROR###à formation of oxyhaemoglobin ###ERROR###à some in plasma ###ERROR###à pulmonary vein ###ERROR###à carry it to heart ###ERROR###à left auricle +left ventricle ###ERROR###à dorsal aorta ###ERROR###à carotid artery to the brain dissociation of oxyhaemoglobin, O2 supplied to the tissue, partial pressure of oxygen facilitates diffusion.

Question-53

Write short note on inspiratory capacity and vital capacity.

Solution:
Inspiratory capacity is represented as IC. It is the volume of air that can be taken into lungs after a normal inspiration through a maximum inspiration. Its value is the sum of tidal volume (VT) and inspiratory reserve volume (IRV)
IC = VT + IRV
= 500 to 2000 to 2500
= 2500 to 3000 c.c

Vital capacity is written as VC. It is the total volume of air that can be expelled from the lungs after first filling the lungs to the maximum and then exhaling the same to the maximum. It is equal to the sum total of tidal volume, inspiratory reserve volume and expiratory reserve volume.
VC = VT + IRV + ERV
= 500 +2000 to 2500+1000 to 1500
= 3500 to 4500 c.c

Sports or mountain dwellers have higher vital capacity. Younger people, possess more vital capacity than older people. Males show higher vital capacity than the females. Hence it (VC) differs with the activities of a person.

Question-54

Distinguish between external respiration and internal respiration.

Solution:
External respiration Internal respiration
It is the process in which oxygen is taken up by the organism from the surrounding medium and carbon dioxide is thrown out into the surrounding medium. It is the process in which oxygen is taken up by the tissue cells and the elimination of carbon dioxide from the tissue cells and this oxygen brings about oxidation of food within the cell to liberate energy.

 

Question-55

Distinguish between inspiratory muscles and expiratory muscles.

Solution:
Inspiratory muscles Expiratory muscles
These are the muscles which bring about increase in the chest cavity or body cavity so that the volume of the thoracic cavity increases. This allows air to enter the lungs or trachea. These are the muscles which bring about the reverse position allowing the air to leave the respiratory system.

 

Question-56

Write the difference between photosynthesis and respiration.

Solution:
             Photosynthesis         Respiration
Photosynthesis is an anabolic process in which synthesis of organic molecules takes place in the presence of solar energy. Respiration is a catabolic process in which there is oxidation of organic molecules to release their bond energy.

 

Question-57

Distinguish between alveolar air and inspired air.

Solution:
               Alveolar air                     Inspired air
The air present in the alveoli. The amount of air inspired at a time.

 

Question-58

Write the difference between Anaerobic metabolism and aerobic respiration.

Solution:
Anaerobic metabolism Aerobic respiration
In some organism food is oxidized in the absence of oxygen. Such process is called fermentation or anaerobic metabolism e.g. yeast ferments glucose to ethanol. In most animals oxidation of food takes place in the presence of oxygen. Carbon dioxide is produced as a result of such oxidation.

 

Question-59

Write the difference between Tracheoles and bronchioles.

Solution:
Tracheocles Bronchioles
It is terminal branch of trachea of insects pervading tissues in a very large number. In the tracheolar branches interchange of respiratory gases (CO2 and O2) takes place. Each bronchi in mammals divides into smaller branches which are called as bronchioles. Exchange of gases does not take place in bronchioles.

 

Question-60

Write short notes on FRC.

Solution:
Functional residual capacity is written as FRC. It is the amount of air that remains inside the lungs at the end of the tidal expiration. It is equal to the sum of the expiratory reserve volume and the residual volume.

FRC = ERV + RV = 1000 to 1500 + 1500 = 2500 to 3000 c.c approx.

Question-61

Define aerobic respiration.

Solution:
When respiration takes place in the presence of oxygen, it is termed as aerobic respiration. In other words respiratory substrates are broken down in the presence of oxygen. In this process 38 ATP molecules are produced.

Question-62

Why is it not healthy to breath in a closed room in winters where a large number of persons are sitting near an angithi?

Solution:
In a closed room there is no provision of fresh air coming into the room. The oxygen already present in the air of that room shall be gradually consumed. Moreover if more number of people are sitting in that room the percentage of oxygen will go on decreasing and the percentage of carbon dioxide will go on increasing by continuous use of oxygen during respiration. If in such a room there is angithi also then it is positively harmful for the persons sitting in the room. We know that the burning of coal or wood in the angithi we know would consume oxygen very rapidly. Burning also produce poisonous gases like carbon monoxide in addition to carbon dioxide.

Question-63

Define inspiratory reserve volume.

Solution:
Inspiratory reserve volume is the additional volume of air that can be inhaled over and above the tidal volume by the deepest possible inspiration. It can be about 2-3 litres of air.

Question-64

Define expiratory reserve volume.

Solution:
Expiratory reserve volume is the extra volume of air that can be exhaled out with each tidal volume of expiration by the most forceful expiration. It is about 1100 ml of air.

Question-65

Define total lung capacity.

Solution:
Total lung capacity is the volume of air in the lungs and respiratory passage after a maximum inhalation effort. It is equal to the vital capacity plus the residual volume. It is about 5000 to 6000ml in adult males.

Question-66

Write short notes on mountain sickness.

Solution:
On mountain-tops about 8000ft. above from the sea level, one has difficulty in breathing due to considerable decrease in the oxygen in the air. Consequently, the alveolar PO2 reduces and oxygen cannot be diffused into the blood. Thus, the process of oxygenation of blood is progressively gets decreased to such an extent that the person becomes mountain sickness. It produces a number of symptoms like breathlessness, headache, dizziness, nausea, vomiting and a bluishness of skin, nails and lips. This is because of lack of adequate oxygen. People suffering from heart ailment or blood pressure should not go to such a height.

Question-67

Explain the mechanism of breathing in humans.

Solution:
The mechanisms of breathing in human involve breathing in of air into the lungs and breathing out of air from lungs. The former is called inspiration and later expiration. The lungs are located in the closed thoracic cavity. The lateral walls of thorax are made up of ribs and intercostal muscle which are attached to the ribs. A muscular partition called the diaphragm separates the thoracic cavity from the abdominal cavity.

During inspiration the diaphragm is lowered due to the contraction of its muscles and the lateral thoracic walls move outwards and upwards due to the contraction of internal intercostal muscle. This result into the increase of volume of thorax causing fall of air pressure in the closed thoracic cavity. This lowers the pressure in the lungs and the air rushes from outside into lungs through external nares, trachea and bronchi.

During expiration the diaphragm move upwards and the lateral thoracic walls move inwards due to the relaxation of muscles of diaphragm and the intercostals muscles. This decrease the volume of thorax and the pressure inside the thorax and lungs is increased which results in the expulsion of air from the lungs to the atmosphere outside the body.

Question-68

Describe in brief the respiratory organs of man.

Solution:
The following are the main respiratory organs which are involved actively during respiration:

Nostrils - These are the paired openings situated at the anterior and posterior ends of the nasal chambers. The nasal chambers are lined by cells that prevent the entrance of dust into the lungs and help in warming and moistening the air. The nasal chamber opens anteriorly by external nostril and posteriorly by internal nostril into the pharynx. Through the nostrils air enters and leaves the respiratory organs.

Larynx – It is situated at the anterior part of trachea and communicates with the pharynx. The glottis is protected by a stiff cartilage called epiglottis. The larynx contains pairs of vocal cords which are set into vibrations when the air enters into it and produces the sound.

Trachea - It is a long ringed tube which extends throughout the neck and enters the thoracic cavity. It is supported by c-shaped elastic cartilaginous rings to prevent its collapsing. It is lined internally with mucous membrane to hold the dust particles, bacteria and other foreign bodies. It also warms the air.

Bronchi – Inside the thorax, the trachea bifurcates into two bronchi and each of which enters into one lung. In each lung, the bronchus redivides into numerous small branches known as bronchioles. These bronchioles further redivide at its ends to form respiratory bronchioles.

Lungs- These are two large bags like spongy structures which are the main respiratory organs. These are enclosed by double pleural membranes. The lungs are divided externally by lobes. The right lung consists of three lobes and left by two lobes. Inside the lungs, the respiratory bronchioles give rise to alveolar ducts, alveolar sac and finally smaller alveoli. Each lung contains millions of alveoli. Each alveolus is exceptionally thin walled. It walls are highly permeable and richly supplied with blood capillaries.
The blood is supplied to the lungs by a pair of pulmonary arteries. These bring blood which is poor in oxygen and rich in CO2. The exchange of gases occurs in the alveoli of the lungs. The oxygenated blood from alveolar capillaries is collected by pair of pulmonary veins to be conveyed to the heart.

Question-69

Describe only with suitable diagram the tracheal division upto tertiary bronchi.

Solution:

Question-70

Show only the diagram of larynx of man.

Solution:

Question-71

Explain how CO2 produced during oxidation of carbohydrates in the muscles of our heart is released into the atmosphere.

Solution:
CO2 in plasma as physical solution is absorbed by RBC. It is transported as carbonic acid, as bicarbonates and as carbonic haemoglobin. It is then carried through the heart from there to pulmonary artery then to the lungs. Dissociation takes place in alveoli. Finally, exhaled through the nostrils.

Question-72

Why is haemoglobin called conjugated protein? What happen to the molecule at high and low partial pressure of oxygen?

Solution:
Haemoglobin is called conjugated protein because it consists of a basic protein globin and a non-protein heme. The haemoglobin when exposed to high partial pressure of oxygen combines with oxygen to form Oxyhaemoglobin which carries four molecules of oxygen loosely bound to the four Fe2+ ions. When this Oxyhaemoglobin reaches the tissues there is low oxygen pressure. Oxyhaemoglobin dissociates into oxygen and deoxyhaemoglobin.

Question-73

Explain residual volume.

Solution:
Residual volume is the volume of air that remains inside the lungs at the end of maximum forceful expiration. Its value is 1500 cc. Residual air continues to exchange gases with the blood in the interval between expiration and inspiration process. It is represent by RV.

Question-74

Explain how your heart muscles receive continuous supply of atmospheric oxygen.

Solution:
Continuous supply of oxygen in the body is maintained by the agency of blood. The blood contains haemoglobin, an iron compound which has great affinity for the oxygen. Oxygen continuously comes into the lungs during inspiration. Here the oxygen meets with the blood and the haemoglobin of the blood takes up oxygen to form Oxyhaemoglobin. This Oxyhaemoglobin is sent to heart by pulmonary veins. These veins contain oxygenated blood and open into the left ventricle. From left ventricle the blood goes to the left auricle. From here the blood goes to the various parts of the body through aorta. From here small arteries take the oxygenated blood to the heart muscles, which continuously work. In the muscles the capillaries break up and the oxyhaemoglobin releases the oxygen. The CO2 from the cells is absorbed by the blood, which is returned back to the lungs. Some CO2 gets dissolved in the plasma. This cycle goes on and the regular supply of oxygen is maintained in the heart muscles, so that heart beats continuously.

Question-75

Point out the differences between respiration and combustion.

Solution:
Characters Respiration Combustion
Nature of process A biochemical and stepped process. A physico- chemical and spontaneous process.
Release of energy Energy released stepwise. Energy released simultaneously.
Temperature Remains within limits. Increased very high.
Intermediate produced Many intermediates are produced. No intermediates are produced.
Light formation No light is formed. Light can be produced.
Enzymes involved It is controlled by enzymes. It is not controlled by enzymes.
Site of occurrence It occurs inside the cells. It is not a cellular process.
Control It is controlled biologically. It is an uncontrolled reaction.

 

Question-76

What is a respiratory centre? What is its use in the process of respiration?

Solution:
Respiration is controlled by a respiratory centre located in the floor of the medulla oblongata of the brain. The centre is bilateral and its two halves which are connected together by commiseural neurons. The sides of this centre are connected with motor respiratory neurons. The nerve cells of the centre are connected with the breathing apparatus forming a reflex arc. These nerve cells are sensitive to chemical composition of blood. Half of the respiratory centre is an inspiratory centre and the other half is an expiratory centre. It is belived that the expiratory centre during other conditions like coughing, sneezing and laughing. These two centres control the entire breathing in man with his knowing about it. Dorsal respiratory group, ventral respiratory group and pneumatoxic groups act as respiration centres in the brain.

Question-77

Why does exchange of respiratory gases continue in the lungs even after a maximum expiration?

Solution:
(i) The more oxygen is released from Oxyhaemoglobin in a more active tissue because its partial oxygen pressure is lower than the least active tissue. The lower PO2 in the active tissue causes the dissociation of Oxyhaemoglobin to release sufficient oxygen required by the tissues.

(ii) The CO2 from the tissue is carried in the blood in three different forms, bicarbonate in plasma and erythrocytes, carbaminohaemoglobin in erythrocytes and small amounts of dissolved carbon dioxide in plasma. On reaching the lungs blood is oxygenated. It donates H+ which joins bicarbonate to form carbonic acid. This carbonic acid cleaves into water and carbon dioxide by carbonic anhydrase. In this way, the carbon dioxide is released from the carbaminohaemoglobin. The oxygen affinity of haemoglobin also gets enhanced with the fall in the blood PCO2 resulting from the elimination of carbon dioxide from the blood in the lungs.

(iii) The blood in the tissue capillaries contains higher PO2 than the tissue fluid. So, oxygen is released from Oxyhaemoglobin diffuses from the capillary blood to the tissue fluid and finally to the cells of the tissues. The CO2 diffuses from the cells to the tissue fluid to raise its PCO2 than the capillary blood. This enables carbon dioxide to diffuse from the tissue fluid to the capillary blood.

(iv) Erythrocytes lack mitochondria and respiratory enzymes to perform the process of aerobic respiration. Therefore, they undergo aerobic respiration to carry out anaerobic metabolism only.

(v) Gaseous exchange continues in the lungs continuously because some air remains inside the lungs even after deepest exhalation. This air is called as residual volume, which is never driven out, and this is sufficient to precede gaseous exchange without any interruption.

(vi) The contraction of the external intercostals muscles and diaphragm increases the volume of the thoracic cavity and lowers the pressure in the lungs. To fill up this gap fresh air rushes to the lungs resulting in the inspiration.

The relaxation of the inspiratory muscles decreases the volume of the thoracic cavity and subsequently, pressure in the lungs increase. To equalize this pressure, the air from the lungs rushes out through the respiratory passage to bring about expiration.

(vii) The pulmonary artery contains deoxygenated blood and this has PO2 much lower than that of alveolar PO2. So, oxygen from the alveolar air diffuses into the blood capillaries. Similarly, CO2 leaves the blood and enters the alveolar air because PCO2 of blood is higher than the alveolar PCO2.

Question-78

Describe the role of red blood cells in the transport of oxygen and carbon dioxide by blood.

Solution:
Red blood cells are known as erythrocytes. They carry oxygen in the form of an unstable, easily dissociable chemical combination with haemoglobin. Oxygen diffuses into RBCs and combines usually with haemoglobin to form Oxyhaemoglobin. In tissue Oxyhaemoglobin dissociates into oxygen and deoxyhaemoglobin at low partial pressure. The blood carries its full load to oxygen until it enters the capillaries in tissues to the lungs.

Role of red blood cells in the transport of carbon dioxide is carried by RBCs. About 30% of carbon dioxide on entering the red blood cell loosely combines with the amino group of reduced Hb and forms carbaminohaemoglobin. Oxygenation of haemoglobin also releases CO2 from carbaminohaemoglobin.

Question-79

How is carbon dioxide taken up from tissues and transported to lungs?

Solution:
Transport of carbondioxide – During respiration oxygen is taken in and carbon dioxide is given out. This exchange of gases takes place by diffusion in the lungs and also in the tissues. Most of the carbon dioxide produced in the tissue diffuses into the blood, some amount of CO2 gets dissolved in the blood plasma and a greater amount of carbon dioxide combines with haemoglobin to form carbaminohaemoglobin inside the RBC and then it goes to the lungs in this form. About 70% of carbon dioxide reacts with water to form carbonic acid particularly inside RBC.

This reaction takes place in the presence of enzyme carbonic anhydrase. This carbonic acid gets dissociated into bicarbonate and H+ ions.

Since all the carbon dioxide which is absorbed by the RBC gets converted into carbonic acid, the CO2 concentration in the RBC is reduced to zero. As a result of this process more and more of HCO3 ions starts diffusing into the blood plasma. There HCO3 ions when combines with H+ ions from Oxyhaemoglobin on reaching the lungs forms carbonic acid which is cleaved into water and carbon dioxide in the presence of carbonic anhydrase. Rest of the 30% of the carbon dioxide combines with the globin of the deoxygenation of haemoglobin also releases carbon dioxide from carbaminohaemoglobin. Carbon dioxide is thus carried in the blood in three major forms:

(i) Bicarbonates in plasma and erythrocytes.

(ii) Carbaminohaemoglobin in erythrocytes.

(iii) Small amount of dissolved carbon dioxide in blood plasma.

Question-80

Distinguish between photosynthesis and respiration.

Solution:
Photosynthesis Respiration
Photosynthesis is the sole mechanism for the conversion of solar energy into other utilizable forms of energy. Respiration is common to all plants and animals. It provides energy to the organisms for carrying out various life activities.
Leaves and other green parts of the plant carry out photosynthesis. Respiration is an intracellular process.
Photosynthesis occurs in the chloroplasts of the cell, which contains chlorophyll. Respiration takes place in the cells.
Carbon dioxide and water are the two basic raw materials of photosynthesis. Oxygen is required for the respiration. The energy released by respiration is trapped in small chemical compounds called ATP.
Oxygen evolves as a by-product of photosynthesis. Carbon dioxide is evolved as a product of respiration.

 

Question-81

Why is smoking bad for health?

Solution:
Smoking is bad for health because,

(i) Smoking causes irritation of throat and respiratory passages leading to cough.

(ii) Prolonged smoking impairs the efficient working and functioning of various respiratory organs and makes them susceptible to diseases.

(iii) Nicotine present in the tobacco has harmful effect on blood vessels, nervous system digestive organs and lungs.

(iv) Smoking is also known to cause cancer and the incidence of cancer, bronchitis, laryngitis, tonsilities and other diseases of respiratory system is high.

(i) Smoking also contributes to emphysema.

(ii) It is bad for heart.

(iii) It is also bad for eyes.

(iv) It affects appetite.

Question-82

Describe how the respiratory gases are exchanged between the blood and the alveolar air.

Solution:
Exchange of oxygen and carbon dioxide takes place between the blood and alveolar air. In air about 21% oxygen, 0.4% carbon dioxide, 40.6% of other gases and water vapour are present. When air is taken in during respiration the partial pressure of oxygen and carbon dioxide are 158mm Hg and 0.3mm Hg respectively. In lungs where the inspired air gets collected already small amount of alveolar air is already present. This contains less oxygen and more carbon dioxide than the inspired air. When this alveolar air mixes with the inspired air then the oxygen content and PO2 of the alveolar air increases to about 13.1% and 100 mm Hg while as carbon dioxide content and PCO2 are about 5.3% and 440 mm Hg.

The blood coming from the heart to the lungs through pulmonary artery is venous blood. This blood has PO2 which is lower than the alveolar PO2. In the lungs O2 diffuses into the blood from the alveolar air and now PO2 is about 95mm Hg. At this stage oxygen content is 19.8%. Thus oxygenated blood is now taken away by the pulmonary veins.
The mixed venous blood which is present in the alveolar capillaries, has PCO2 of 46mm Hg which is more than the alveolar PCO2 of 40mm Hg. So the carbon dioxide diffuses from the alveolar capillaries to the alveolar air until the PCO2 falls to 40mm Hg. Thus, in the alveoli of the lungs, O2 is taken up by the pulmonary vein and CO2 is given out from the blood of pulmonary artery.

Question-83

Name and explain some common respiratory diseases caused in man.

Solution:
Respiratory diseases:

(i) Anoxia – Tissue of body gets less oxygen. It may be at high altitude or by shortage of circulating blood, haemoglobin or less number of red blood cells.

(ii) Emphysema – These are destructive changes in alveoli. The lungs lose elasticity. The ventilation of alveoli is reduced.

(iii) Decompression sickness – It is a fatal syndrome characterized by the formation of N2 bubbles in tissues of divers. N2 bubbles may block pulmonary vessels. It may cause paralysis and painful respiration.

(iv) Tuberculosis – Lungs are infected by Mycobacterium tuberculosis causing chest pain, breathlessness, weakness, loss of body weight, persistent coughing and sputum with blood.

In lymph TB glands show tenderizes and shells up in neck or legs.

Question-84

Write the differences between pharynx and larynx.

Solution:
Pharynx Larynx
Vertical tube lying between cranial base and middle of neck. Box like structure which occurs in the upper part of neck called sound box.
It is seldom closed. Closed during swallowing process.
Has a number of openings like internal nares, gullet, glottis, Eustachian tube, buccal cavity. Only two openings, one connected with pharynx while the other leads into trachea.
Little difference in the growth of pharynx between male and female after puberty. After puberty, males show higher growth of larynx than female.
10-14 cm long. 3.4 – 4.4 cm long.
No cartilaginous frame work. It has a cartilaginous frame work.
Lined by stratified epithelium. Lined by pseudo stratified ciliated epithelium.
Passage for both food and air. Passage for air only.
Does not produce sound. Produces sound.

 

Question-85

Differentiate between vital capacity and lung capacity.

Solution:
Vital capacity Total lung capacity
Sum total of tidal volume, expiratory reserve and inspiratory reserve volume. Sum total of vital capacity and residual volume.
Value is 3500 –4500c.c Value is 5000 –6000c.c
It represents maximum amount of air that a person can expel after filling the lungs to the maximum. It represents maximum total amount of air which can be present in lungs after maximum inspiratory effects.

 

Question-86

What is a oxygen dissociation curve? Explain.

Solution:
The relationship between oxygen tension and its absorption by haemoglobin produces a graph called the oxygen dissociation curve. At about 100mm Hg O2 tension Hb is 98% saturated. As it falls, the saturation of Hb decreases slowly. When O2 tension is about 40 mm Hg, Oxyhaemoglobin dissociates and oxygen is available to the tissues.




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