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Karnataka 1st PUC Biology Question Bank Chapter 17 Breathing and Exchange of Gases
1st PUC Biology Breathing and Exchange of Gases NCERT Text Book Questions and Answers
Define vital capacity. What is its significance?
The maximum volume of air a person can breathe in after forced expiration. This includes ERV, TV, and IRV or the maximum volume of air a person can breathe out after a forced inspiration.
It represents the maximum amount of air one can renew in the respiratory system in single respiration. Thus, greater the vital capacity more is the energy available to the body for doing strenuous work. Vital capacity is higher in athletes and mountain dwellers. Young persons would possess more vital capacity as compared to children or older persons.
State the volume of air remaining in the lungs after normal breathing.
Functional Residual capacity.
Diffusion of gases occurs in the alveolar region only and not in the other parts of the respiratory system. Why?
Only alveolar region is made up of squamous epithelium which is favorable for the diffusion of gases.
What are the major transport mechanisms for CO2? Explain.
CO2 is carried by haemoglobin as carbamino haemoglobin. This binding is related to the partial pressure of CO2. When PO2 is low as in the tissues and PCO2 is high, more carbon dioxide binding occurs whereas when PCO2 is low and PO2 is high as in the alveoli, dissociation of CO2from carbamino haemoglobin takes place. RBC contains a high concentration of enzyme carbonic anhydrase that converts carbon dioxide to bicarbonates and vice versa.
CO2 diffuses the blood and forms bicarbonate ions. Thus CO2 is trapped as bicarbonate at the tissue level and transported to the alveoli and released out as CO2. A small amount of CO2 dissolves in the plasma water and forms acid. On reaching the lungs carbonic acid dissociates and releases carbon dioxide. So carbon dioxide is transported as carbamino-hemoglobin, bicarbonates and carbonic acid.
What will be the PO2 and PCO2 In the atmospheric air compared to those in the alveolar air?
1. PO2 lesser, PCO2 higher
2. PO2 higher, PCO2 lesser
3. PO2 higher, PCO2 higher
4. PO2 lesser, PCO2 lesser
(1) Where there is low pO2 high pCO2, high H+ concentration and higher temperature exist, the conditions are favorable for dissociation of oxygen from the oxyhemoglobin.
(2) Where there is high pO2, low pCO2, lesser H+ concentration, and lesser temperature, the factors are all favorable for the formation of oxyhemoglobin whereas in the tissues.
(3) When pCO2, is high and pO2. is low as in the tissues, more binding of carbon dioxide occurs whereas.
(4) When the pCO2, is low and pO2, is high as in the alveoli, dissociation of CO2 from carbamino-hemoglobin takes place, i.e., CO2, which is bound to hemoglobin from the tissues is delivered at the alveoli.
Explain the process of inspiration under normal conditions.
- Inspiration occurs when the pressure within the lungs is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure.
- Inspiration is initiated by the contraction of diaphragm which increases the volume of the thoracic chamber in the anteroposterior axis.
- The contraction of external intercostal muscles lifts up the ribs and the sternum causing an increase in the volume of a thoracic chamber in the dorsoventral axis.
- The overall increase in thoracic volume causes a similar increase in pulmonary volume.
- An increase in pulmonary volume decreases the intrapulmonary pressure, to less than atmospheric pressure which forces the air from outside to move into the lungs i.e., inspiration.
How is respiration regulated?
A specialised centre present in the medulla region of the brain called respiratory rhythm centre is primarily responsible for the regulation of respiration. Another centre present in the pons region of the brain called the pneumatic centre can reduce the duration of inspiration and thereby alter the respiratory rate.
A chemosensitive area situated adjacent to the rhythm centre is highly sensitive to CO2 and hydrogen ions. Increase in these substances can activate this centre, which in turn can signal the rhythm centre to make necessary adjustments in the respiratory process. Receptors associated with aortic arch and carotid artery also can recognise changes in CO2 and H+ concentration and send necessary signals to the rhythm centre for remedial actions.
What is the effect of PCO2 on oxygen transport?
In the alveoli, where there is high PO2 low pCO2 lesser FT concentration, and lesser temperature, the factors are all favorable for the formation of oxyhemoglobin whereas, in the tissues, where low pO2, high pCO2, high H+ concentration, and higher temperature exist, the conditions are favorable for dissociation of oxygen from the oxyhemoglobin. This clearly indicates that O2 gets bound to hemoglobin in the lung surface and gets dissociated from the tissues. Every 100ml of oxygenated blood can deliver around 5 ml of O2, to the tissues under normal physiological conditions.
What happens to the respiratory process in a man going up a hill?
When a man is going uphill or doing some strenuous exercise then there is more consumption of oxygen. This decreases the partial pressure of oxygen in haemoglobin resulting in more demand for haemoglobin. As a result, there is an increased breathing rate to fill the gap.
What is the site of gaseous exchange in an insect?
Insects have a network of tubes (tracheal tubes) to transport atmospheric air within the body so that the cells can directly exchange the gases.
Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?
- Oxygen dissociation curve: It is a graphic representation of the relationship between partial pressure of oxygen or pO2 and percentage saturation of haemoglobin with oxygen.
- The graph is sigmoid as at low p02, there is reduced synthesis of oxyhemoglobin. The percentage of oxyhemoglobin rises with higher pO2 till at about p02 is 100mm Hg, the haemoglobin becomes fully saturated with O2.
- A further rise in pO2 cannot increase the value of oxyhemoglobin as the blood is already saturated with it.
Have you heard about hypoxia? Try to gather information about it, and discuss it with your friends.
Hypoxia refers to the shortage of oxygen supply to the body. It is of different types:
- Anemic hypoxia (deficiency of hemoglobin),
- Cytotoxic hypoxia (impaired utilization as in cyanide poisoning)
- Stagnant hypoxia. Due to heart failure or reduced pumping activity of the heart.
- Hypoxic hypoxia. Insufficient oxygen in the air as at high altitude.
- CO Poisoning. Carbon monoxide binds to hemoglobin irreversibly. Oxygen transport is correspondingly reduced.
(a) IRV and ERV
(b) Inspiratory capacity and Expiratory capacity.
(c) Vital capacity and Total lung capacity.
(a) Inspiratory Reserve volume (IRV) is an additional volume of air a person can inspire by a forcible inspiration. It averages 2500 ml to 3000 ml. Expiratory Reserve volume (ERV) is an additional volume of air that a person can expire by a forcible expiration. This averages 1000 ml to 1100 ml.
(b) Inspiratory capacity (IC) is the total volume of air a person can inspire after a normal expiration. It is the sum of tidal volume and inspiratory reserve volume.
Expiratory capacity (EC) is the total volume of air a person can expire after a normal inspiration. It is the sum of tidal volume and expiratory reserve volume.
(c) Vital capacity is the maximum volume of air a person can breathe in after forced expiration. It is the sum of Tidal volume, expiratory reserve volume and inspiratory reserve volume. It is also the maximum volume of air a person can breathe out after a forced inspiration.
Total lung capacity is the total volume of air accommodated in the lungs at the end of forced inspiration. It is the sum of Residual volume, expiratory reserve volume, tidal volume, and inspiratory reserve volume.
What Is Tidal volume? Find out the Tidal volume (approximate value) for a healthy human in an hour.
The volume of air inspired/breath during normal respiration. It is approximately 500mL.
The number of breaths per minute 12 to 16.
Tidal volume per minute = 500 x 12 to 16 = 6000 – 8000 mL or 6 -8 litres
Tidal volume per hour = 6 to 8 x 60 = 360 – 480 litres.
1st PUC Biology Breathing and Exchange of Gases Additional Questions and Answers
1st PUC Biology Breathing and Exchange of Gases One Mark Questions
What is an expiration?
The movement or exit of air from the alveoli of the lungs to the outer atmosphere is called expiration or exhalation.
What is Ventilation? OR What Is breathing?
It is a process by which air is exchanged between the atmosphere and the alveoli of lungs or Entry of atmospheric air into the alveoli of lungs and exit of air from the alveoli into the atmosphere is called pulmonary ventilation or breathing.
What is inhalation or inspiration?
Entry of air into alveoli of the lungs is called inspiration or inhalation.
Which muscles do you find In diaphragm?
Which process helps in increasing the size of the thorax during respiration? (Oct. 1990, April 1995)
The contraction of the external inter-costal muscles of the ribs and the muscles of the diaphragm.
Name the membrane (covering) of the lungs. (April 91, 93, 94)
Pleural membrane (Pleuron). [The plural membrane (outer Fibrous & inner serous)]
What art; the functional units of lungs called? (Oct. 92, 99, July 2010)
Mention the respiratory pigment.
Haemoglobin. (April 98)
What is Spirometer? (April 2002)
The apparatus used in measuring the amount of air exchanged during breathing & the rate of ventilation is the Spirometer.
Name the last part of the bronchiole tree.
Alveoli. (April 2003)
Which is a common passage for both air and food in man ? (July 2006)
Name the enzyme that acts on carbonic acid in living cells. (Delhi 2006)
Where is carbonic anhydrase found in human body? Give its function.
Carbonic anhydrase is found in RBC. It catalyses the formation of carbonic acid from carbon dioxide and water.
What are the two factors that contribute to the dissociation of oxyhemoglobin in the arterial blood to release molecular oxygen in an active tissue? (Delhi 2000)
Low PO2, high PCO2, high H+ concentration and high temperature.
Name the respiratory organs of
(1) butterfly and
(2) frog larva. (All India 1996)
What is a soundbox?
Larynx is a cartilaginous box which helps in sound production and hence called the sound box.
What are alveoli?
Alveoli are number of very thin, irregular walled and vascularised bag like structures into which terminal bronchioles end.
How does diaphragm help in inspiration? (All India 998 C)
When the diaphragm muscles contract, it moves down towards abdomen, increasing the volume of thoracic cavity, but decrease in air pressure. So air is drawn into the lungs.
What is the maximum number of molecules of oxygen which one molecule of haemoglobin can carry? (All India 1998 C)
What is formed when CO2 combines with globin part of reduced haemoglobin? Where does it occur? (All India 1998 C)
Its formation occurs in metabolicaily active tissues.
Which part (s) of the brain control (breathing movements? (Foreign 1997)
Medulla and pons.
Name two animals where exchange of gases occurs by diffusion across their entire body surface.
Hydra, Sponges, flatworms etc.,
What is the function of pleural fluid?
Pleural fluid reduces the friction on the lung surface.
State the function of exchange part.
Exchange part is the actual site of diffusion of oxygen and carbon dioxide between blood and atmosphere.
What causes the movement of air in and out of lungs?
Pressure gradient between the lungs and the atmosphere.
Name the structures that bring about a pressure gradient between lungs and the atmosphere.
Diaphragm and intercostal muscles.
Why does exchange of respiratory gases continue to occur in the lungs even after a maximum expiration?
Some amount of air, called residual vol-ume, remains in the lungs even after forceful expiration.
Name the primary site of respiratory gas exchange.
Define partial pressure of a gas?
The pressure exerted by an individual gas in a mixture of gases is called partial pressure.
Why can more CO2 diffuse across the respiratory membrane per unit difference in the pressure as compared to oxygen?
Tne solubility of CO2 is 20-25 times higher than that of O2. So more CO2 diffuses across the respiratory membrane.
What is oxyhaemoglobln?
Oxyhaemoglobin is a complex formed when oxygen combines with the Fe2+ part of haemoglobin.
How much of CO2 is transported by 100 ml of blood
About 4 ml.
What is carbamino haemoglobin?
Carbamino haemoglobin is the complex formed when carbon dioxide combines with the amine radical of the globin of haemoglobin.
Where is the respiratory rhythm centre located?
How does pneumotaxic centre alter the respiratory rate.
Pneumotaxic centre can reduce the duration of inspiration and alter the respiratory rate.
Where are the receptors that can sense the changes in CO2 and H+ concentration located?
Receptors are located in the aortic arch and carotid artery.
1st PUC Biology Breathing and Exchange of Gases Two Marks Questions
What is inspiration and expiration.
- Inspiration: Entry of air into alveoli of the lungs is called inspiration or inhalation.
- Expiration: Movement or exit of air from the alveoli of the lungs to outer atmosphere is called expiration or exhalation.
Mention the functions of trachea.
- It is called wind pipe helps for passage of air.
- Cilia move upwards towards the larynx, and this movement keeps out inhaled particles of dust, pollen etc.
- The cartilages which serve to keep the trachea open makes easy passage of air.
Write any two functions of larynx.
- Larynx is called voice box. The vibration of vocal cords produce sound.
- It helps in speech.
- It prevents the entry of food into the lungs.
The epiglottis present in larynx helps to close off the larynx during swallowing.
Mention any four conducting parts of the human respiratory system. (April 83, 92, 99)
- Nasal cavities
- Bronchial tree.
Draw a neat labelled diagram of alveolus.
Write a note on pleura.
The two lungs are covered by a double layered membrane called pleura, with pleural fluid between them. The fluid reduces the friction on the lung surface. The outer pleural membrane is in close contact with the thoracic lining whereas the inner pleural membrane is in contact with the lung surface.
Mention four functions of the conducting part of the human respiratory system.
- It transports the air into alveoli
- It clears the air from foreign particles.
- It moistens and humidifies the air.
- It brings the air to body temperature.
Mention the boundaries of the thoracic cavity. What is the use of them?
The thoracic cavity is formed dorsally by the vertebral column, ventrally by the sternum, laterally by the ribs and on the lower side by the dome:shaped diaphragm. The anatomical setup of lungs in thorax is such that any change in the volume of the thoracic cavity will be reflected in the lung (pulmonary) cavity, which is essential for breathing as we cannot directly alter the pulmonary volume.
How do partial pressures of respiratory gases determine the diffusion of oxygen from the blood capillaries into the tissues?
In the tissues, PCO2 is high, PO2 is low and there is high concentration of H+ ions and high temperature. Since the PO2 is lower than that of the blood, oxyhaemoglobin dissociates and releases the oxygen into the tissues.
How are gases transported in human body?
Blood is the medium of transport for O2 and CO2. About 97% of O2 is transported by RBCs in the blood. The remaining 3% of O2 is carried in a dissolved state through the plasma. Nearly 20-25 percent of CO2 is transported by RBCs whereas 70% of it is carried as bicarbonate. About 7% is carried in a dissolved state through plasma.
Name the factors that affect the binding of oxygen to haemoglobin.
The factors are:-
- Partial pressure of oxygen
- Partial pressure of carbon dioxide
- Hydrogen ion (H+ ) concentration
What is carbonic anhydrase? List the three major forms In which the carbon dioxide is transported in the blood?
Carbonic anhydrase is an enzyme that is present in RBC which catalyses the formation of carbonic acid from carbon dioxide and water. CO2 is transported
- In the dissolved form in the plasma
- As bicarbonates in the plasma and RBC
- As carbamino haemoglobin.
Give the values PO2 and PCO2 respectively of each of the following
(1) Atmospheric air
(2) Tissues of the body
- Atmospheric air PO2= 159 mm Hg; PCO2 = 0.3 mm Hg;
- Tissues of the body PO2= 40 mm Hg; PCO2 = 40 mm Hg;
What is emphysema? What is its major cause?
Emphysema is a chromic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. One of the major causes of this is cigarette smoking.
Where is pneumotaxic centre located in humans? What is its significance inbreathing?
Pneumotaxic centre is located in the pons region of the brain.
Neural signal from this centre can reduce the duration of inspiration and thereby alter the respiratory rate.
Name the three layers of diffusion membrane.
- Squamous epithelium of alveoli
- Endothelium of alveolar capillaries
- Basement substance.
1st PUC Biology Breathing and Exchange of Gases Three Marks Questions
Explain the transport mechanism of oxygen.
Oxygen binds with haemoglobin in reversible manner to form oxyhaemoglobin. About 97% of O2 is transported as oxyhaemoglobin. Each haemoglobin molecule can carry a maximum of four molecules of O2. Binding of O2 with haemoglobin depends on partial pressure of oxygen primarily and also on partial pressure of carbon dioxide, hydrogen ion concentration and temperature.
In the alveoli, where there is high pO2, low pCO2, lesser H+ concentration and lower temperature, the factors are all favourable for the formation of oxyhaemoglobin, whereas in the tissues, where low PO2, high PCO2, high H+ concentration and higher temperature exist the conditions are favourable for dissociation of oxygen from the oxyhemoglobin. This indicates that O2 gets bound to haemoglobin in the lung surface and gets dissociated at the tissues.
Describe the role of haemoglobin in the transport of respiratory gases. (Foreign 2001)
- Oxygen binds to the Fe2+ part of haemoglobin and is transported as oxyhaemoglobin through the RBCs of the blood.
- Each molecule of haemoglobin can transport a maximum of four oxygen molecules.
- CO2 combines with the amine radial of haemoglobin to form carbamino haemoglobin and about 20 – 25% of CO2 is transported in this form.
Draw a neat labelled diagram of human respiratory system showing the mechanism of
Explain the process of expiration under normal conditions.
Expiration takes place when the intra-pulmonary pressure is higher than the atmospheric pressure. The diaphragm and a specialised set of muscles-external and internal intercostals between the ribs, help in generation of such gradients.
Relaxation of the diaphragm and the intercostal muscles returns the diaphragm and sternum to their normal positions after inspiration which reduces the thoracic volume and thereby the pulmonary volume. This leads to an increase in intra-pulmonary pressure to slightly above the atmospheric pressure causing the expulsion of air from the lungs, i.e. expiration.
Give a diagrammatic representation of exchange of gases at the alveolus and the body tissues with blood and transport of oxygen and carbon dioxide.
Draw a labelled diagram of a section of an alveolus with pulmonary capillary.
Name and explain few disorders of respiratory system.
- Asthma: It is a difficulty in breathing causing wheezing due to inflammation of bronchi and bronchioles.
- Emphysema: It is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. This is mainly caused by cigarette smoking.
- Occupational Respiratory disorders: In certain industries, involving grinding and stone breaking the dust produced results in inflammation leading to fibrosis and this causing serious lung damage.
1st PUC Biology Breathing and Exchange of Gases Five Marks Questions
Draw a neat labelled diagram of human respiratory system.
Give the five steps that is involved in respiration.
Respiration involves the following steps:
- Breathing or pulmonary ventilation by which atmospheric air is drawn in and CO2 rich alveolar air is released out.
- Diffusion of gases (O2 and CO2 ) across alveolar membrane.
- Transport of gases by the blood.
- Diffusion of O2 and CO2 between blood and tissues.
- Utilisation of O2 by the cells for catabolic reactions and resultant release of CO2
Define the following:
(a) Inspiratory Reserve volume
(b) Expiratory Reserve volume
(c) Total lung capacity
(d) Residual volume
(e) Functional residual capacity
(a) Inspiratory Reserve volume (IRV): Additional volume of air, a person can inspire by a forcible inspiration.
(b) Expiratory Reserve volume (ERV): Additional volume of air, a person can expire by a forcible expiration.
(c) Total lung capacity: Total volume of air accommodated in the lungs at the end of a forced inspiration. This includes RV, ERV, TV and IRV.
(d) Residual Volume (RV): Volume of air remaining in the lungs even after a forcible expiration.
(e) Functional residual capacity (FRC): Volume of air that will remain in the lungs after a normal expiration.
This includes ERV + RV.