Revision Notes for CBSE Class 11 Biology Chapter 14 (Breathing and Exchange of Gases) - Free PDF Download
Section–A (1 Mark Questions)
1. How many molecules of O2 are carried by one haemoglobin?
Ans. Four molecules of O2 are carried by one haemoglobin.
2. What causes the urge of inhalation in humans?
Ans. Rising pCO2 level causes the urge of inhalation in humans.
3. Which enzyme increases the reaction rate between CO2 and H2O in red blood cells?
Ans. Carbonic anhydrase is the enzyme which increases the reaction rate between CO2 and H2O in red blood cells.
4. Write one respiratory disorder.
Ans. Emphysema
5. Which is the prime site for the exchange of gases inhuman body?
Ans. Alveoli are the prime site for gaseous exchange in the human body.
Section–B (2 Mark Questions)
6. In an old science fiction movie, the hero tried to drown a giant ant by holding its head under water. Would this work? Why?
Ans. Ants breathe in oxygen through spiracles which are a series of holes located on the sides of their bodies. Carbon dioxide exiting through said tubes as well. So no, the giant ant cannot die if its head is under water.
7. A major percentage (97%) of O2 is transported by RBCs in the blood. How does the remaining percentage (3%) of O2 transported?
Ans. Haemoglobin is the Fe-containing respiratory pigment present in blood, and it is a carrier of oxygen. 97% of oxygen is carried with haemoglobin from lungs to tissues and the remaining 3% is dissolved in plasma which carries oxygen to the body cells.
8. Write the organs of respiration in the entities given below:
(i) Flatworm
(ii) Frog
(iii) Birds
(iv) Cockroach
Ans. (i) Flatworm – Body surface.
(ii) Frog – Moist skin and lungs.
(iii) Birds – Lungs.
(iv) Cockroach – Tracheal tubes
9. Write the name of two parts which are involved in the initiating a pressure gradient between the lungs and the atmosphere during normal respiration.
Ans. Diaphragm and a set of external and intercostal muscles between the ribs are involved in the generation of pressure gradient during respiration.
10. Answer the following questions.
(i) What is the amount of O2 supplied to tissues through every 100 mL of oxygenated blood under normal physiological conditions?
(ii) How much CO2 is delivered by 100 mL of deoxygenated blood?
Ans. (i) Every 100 mL of oxygenated blood can deliver around 5 mL of O2 to the tissues under normal physiological conditions.
(ii) Every 100 mL of deoxygenated blood delivers approximately 4 mL of CO2 to the alveoli.
11. Arrange the following terms based on their volumes in an ascending order:
Tidal Volume (TV)
Residual Volume (RV)
Inspiratory Reserve Volume (IRV)
Expiratory Capacity (EC)
Ans. Tidal Volume (500mL) < Residual Volume (1100-1200 mL) < Expiratory capacity (1500-1600 mL) < Inspiratory reserve volume (2500-3000 mL)
PDF Summary - Class 11 Biology Breathing and Exchange of Gases (Chapter 14)
All biological activities require energy to take place and this energy is released by the decomposition of food. So all living things consume food to get high-energy organic molecules that release energy after their decomposition.
The decomposition of food in the presence of oxygen is called oxidation. Cells use oxygen for breaking down complex molecules and produce energy together with oxygen.
Breathing is the process of exchanging atmospheric oxygen with carbon dioxide which is produced by the cells.
The process of oxidation of complex food molecules into simpler molecules within the living cells of an organism is called respiration. The term ‘Respiration’ was coined by Dutrochet. During the oxidation process, the chemical energy stored in the food as complex molecules is released and is temporarily stored in the form of ATP. Breathing is the first step of the respiration process. The molecules of food substances that are decomposed during the respiration process are called respiratory substrates. For example glucose, amino acids, fatty acids, etc.
17.1 Respiratory Organs:
Depending on the body structure and habitat of organisms, the respiratory mechanism is different in different types of organisms and so are the respiratory organs present in them. A table is given below in which organisms and their respiratory organs are given:
17.1.1 Human Respiratory System:
The human respiratory system begins with external nostrils which open into the nasal cavity. The nasal cavity extends into the nasal passage that consists of the larynx, trachea, bronchi, and bronchioles.
The nasal cavity is lined with mucous-secreting cells which secrete a slimy fluid called mucous. It can capture dust and other foreign objects in the inhaled air by keeping the nasal cavity moist. The dust particles present in the air are filtered by the hair present in the nasal cavity. The nasal cavity ends in the beginning part of the pharynx.
Human Respiratory System
The pharynx is the junction between the respiratory and digestive systems. The oropharynx, Nasopharynx, and Laryngopharynx are the three sections of the pharynx. The oropharynx is the section of the pharynx behind the oral cavity that allows food to pass through, while the nasopharynx is the part that allows air to flow through. The region of the pharynx behind the larynx is known as the laryngopharynx. .The glottis, a slit-shaped aperture at the bottom of the nasopharynx, is protected by the epiglottis, a cartilaginous flap. The main purpose of the epiglottis is to keep food from entering the trachea while swallowing. The glottis opens into the windpipe or trachea, a thin-walled tube that lies in front of the oesophagus and travels through the neck.
Labeled Diagram of Nasal and Throat Cavity
Labelled Diagram of Nasal and Throat Cavity
The larynx is the enlarged, upper part of the trachea, meant to produce sound. Cartilage rings like thyroid cartilage and cricoid cartilage support the walls of the larynx. In the case of men, the thyroid cartilage is large in size and protrudes from the neck, and is called Adam’s apple. There are two mucous membranes present in the throat cavity and these membranes are called vocal cords. The vocal cords vibrate which in turn produce sounds.
The trachea is protected by C-shaped rings made up of cartilage. When there is less air in the trachea, the wall of the trachea can be prevented from collapsing by these cartilaginous rings.
Labeled Diagram of Trachea
Labelled Diagram of Trachea
The trachea is further divided into two bronchi which then enter into the lungs. Each lung has one of these two bronchi. Both of the bronchi divides again to form bronchioles, spread in the entire lungs. Each of the bronchioles is divided into several tiny ducts named alveolar ducts. Each alveolar duct is inflated into thin-walled air sacs called alveoli. Infundibulum is the alveolar group or group of alveoli. Therefore, each of the infundibula seems like a bunch of grapes.
Labeled Diagram of Alveoli
Labelled Diagram of Alveoli
The bronchi, bronchioles, and alveoli are the major components of the lungs. Both of the lungs are protected by a double-layered membrane called the pleura. The pleura is filled with pleural fluid, which reduces friction on the surface of the lungs. The external pleural layer is in contact with the thoracic lining and the internal pleural layer is in contact with the surface of the lung.
The Respiratory System is Divided Into Two Parts:
The Conduction Part: The conduction part comprises all the respiratory components from nostrils to alveoli of lungs. The function of this part is to conduct atmospheric air from external nostrils to the alveoli of the lungs. This part also prevents foreign objects from entering the respiratory passage, it moisturizes the transporting air and brings its temperature close to the body temperature.
The Exchange Part: The exchange part consists of the site where Oxygen diffuses between the blood and the atmospheric air present in the lungs.
The lungs are present in the chest cavity. Their dorsal side is bounded by the spine, ventral side is bounded by the sternum, both of the lateral sides are bounded with ribs, and the bottom with a dome-shaped muscular sheet called the diaphragm.
Any changes in the chest cavity volume are expressed in the lung cavity and this change is necessary for breathing.
The Steps Involved in Breathing and Respiration Processes Are Given Below:
The first step is breathing or lung ventilation (inhalation of atmospheric air and exhalation of alveolar air rich in carbon dioxide.
In the second step, gases(oxygen and carbon dioxide) diffuse through the alveolar membrane
In the next step, diffused gases are transported through the blood to their target organs.
Then diffusion of oxygen and carbon dioxide gases occurs between blood and body tissues.
The body cells use oxygen for catabolic reactions and the resulting release of carbon dioxide gas. This process is also known as cellular respiration.
17.2 Mechanism of Respiration:
The influx and efflux of atmospheric air in the lungs, between atmosphere and alveoli, is called breathing. It is a consequence of the expansion and contraction of the lungs.
The lungs contract in two processes:
Inspiration or Inhalation
Expiration or Exhalation.
A pressure gradient is created between the lungs and the atmosphere, to accomplish both of the above processes.
Inspiration or Inhalation: It is an active process that means it uses energy to take place and mainly includes muscle contraction. It occurs when the pressure inside the lungs is less than atmospheric pressure. The lungs are located in the chest or thorax. Contraction of the diaphragm (the muscular sheet that divides the chest and abdomen) and some intercostal muscles (muscles present between the ribs) occur during inhalation, as a result, the ribs are pulled upside and in the outward direction. This process results in increasing the volume of the chest cavity because the sternum increases the volume of the thoracic cavity in the dorsal-ventral axis. An overall increase in the volume of the thoracic cavity also increases the volume of the lungs. Increased lung or pulmonary volume reduces the pressure inside the lungs. As a result, fresh air enters the lungs through the nose.
Expiration or Exhalation: Relaxation of the diaphragm and intercostal muscles causes the diaphragm and sternum to return back to their normal positions. This results in a reduction of the thoracic volume (volume of the chest cavity) and pulmonary volume (volume of lungs) but increases the intrapulmonary pressure (pressure inside lungs). This pressure is slightly higher than the atmospheric pressure, which causes the air to be expelled out from the lungs.
The strength of inhalation and exhalation can be increased with the help of extra-abdominal muscles.
\A healthy person normally breathes 12-16 times per minute, which is about 10 litres of air per minute.
The device used to measure respiratory rate is known as a spirometer or respirometer.
Diagram Showing Mechanism of Respiration
Diagram Showing Mechanism of Respiration
17.2.1 Respiratory Volumes and Capacities:
The air that enters and exits the lungs with each respiration is known as tidal air.
1. Tidal volume (TV): The volume of air inhaled or exhaled during normal breathing is known as the tidal volume. The tidal volume of an adult male is approximately 500 ml. A healthy person can inhale or exhale about 6000-8000 ml of air per minute.
2. Inspiratory reserve volume (IRV): This is the amount of additional air that can be inhaled beyond the normal tidal volume during a forced inhalation. The IRV of a normal person is approximately 2000-3000 ml.
3. Expiratory reserve volume (ERV): This is the additional volume of air that can be exhaled beyond the normal tidal volume during a forced exhalation. The ERV of a normal person is approximately 1100 ml.
4. Residual volume (RV): The residual air volume is the volume of air left in the lungs after forced exhalation. The RV of a normal person is approximately 1100 to 1200 ml. There is always a residual air volume left in the lungs so that even after forced exhalation, gas exchange will continue in the lungs.
5. Pulmonary capacity (PC): The pulmonary capacity is the capacity when two or more lung capacities are considered together.
The important pulmonary capacities of the lungs are given below:
Inspiratory capacity: The total amount of air that a person can inhale after a normal exhalation, is called inspiratory volume. It includes inspiratory reserve and tidal volume.
IC = TV + IRV
3500 mL + 500 mL = 3500 mL
Expiratory Capacity: The amount of air that a person can exhale after a normal inhalation.
EC = TV + ERV
Functional Residual Volume: The amount of air left in the lungs after a normal exhalation. It is the sum total of the expiratory reserve volume and residual volume.
FRC = ERV + RV
2500 ml = 1000 ml + 1500 ml
Vital Capacity: This is the amount of air that is expelled forcefully, after the deepest inhalation. It can be calculated by sum total of inspiratory reserve volume, expiratory reserve volume, and tidal volume.
CV = IRV + ERV + TV
4500 ml = 3000 ml + 500 ml + 1000 ml
Total Lung Volume: The maximum amount of air that the lung can hold is the total lung volume. It is the sum total of inspiratory reserve volume, expiratory reserve volume, tidal volume, and residual volume.
TLC = IRV + ERV + TV + RV or
TLC = VC + RV
17.3 Gas Exchange:
The main part of gas exchange occurs in the alveoli. The exchange of gases takes place between blood and tissues. Gas exchange occurs by simple diffusion based on a pressure gradient or a concentration gradient. The solubility of the gas and the thickness of the film are the important factors affecting diffusion. The partial pressure is the pressure of a single gas in a gas mixture. The partial pressure of oxygen is represented by pO2, and the m=partial pressure of carbon dioxide is represented by pCO2.
Partial pressures of oxygen and carbon dioxide (in mm Hg) at different parts as compared to the other gases present in atmosphere
Diagrammatic Representation of Gas exchange Between Alveoli and Other Body Parts
Diagrammatic Representation of Gas Exchange Between Alveoli and Other Body Parts
The amount of CO2 that can diffuse through the diffusion membrane is greater than the O2 partial pressure. The diffusion membrane is formed by the layer of the squamous epithelium of the alveoli, the endothelium of the capillaries of the alveoli and the basement material between the two layers. The total thickness of the diffusion membrane is less than one millimetre. The diffusion of O2 from the alveoli to the tissues and the diffusion of CO2 from the tissues to the alveoli are aided by all variables in our bodies.
17.4 Gas Transportation:
Both O2 and CO2 gases are transported through the blood. It is reported that 97% of O2 is transported by red blood cells and the remaining 3% is transported through plasma. However, 20-25% of CO2 is transported through RBC, 70% is transported as bicarbonate ions, and the remaining 5-7% of CO2 dissolves in plasma.
17.4.1 Oxygen Transportation:
The red blood cells contain a red-coloured iron-containing pigment that is known as haemoglobin. The iron part of haemoglobin binds with oxygen to form oxyhemoglobin, a combination that is related to the partial pressure of oxygen. One haemoglobin can carry four molecules of oxygen because one molecule of haemoglobin contains four iron-containing parts to which oxygen binds. The binding of oxygen with haemoglobin is affected by CO2 partial pressure, hydrogen ion concentration (pH), and temperature.
The relationship between haemoglobin and oxygen is expressed by plotting per cent saturation of haemoglobin with oxygen against partial pressure of oxygen. This curve is called the oxygen-dissociation curve or oxygen haemoglobin dissociation curve and it is a sigmoid or S-shaped curve.
Oxyhaemoglobin is formed in the alveoli when the pO2 is high, the pCO2 is low, the H+ concentration is low, and the temperature is low. Low pO2, high pCO2, high H+ concentration, and higher temperature occur in the tissues, resulting in oxygen dissociation from oxyhaemoglobin. Hence, oxygen binds to the haemoglobin on the lung surface and is dissociated from the haemoglobin in the tissues. Under normal physiological conditions, 100 mL of oxygenated blood provides about 5mL of oxygen.
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17.4.2 Carbon Dioxide Transportation:
CO2 combines with haemoglobin to form carbamino-haemoglobin, which is proportional to CO2 partial pressure. The binding of carbon dioxide with haemoglobin is affected by the partial pressure of O2. More binding occurs when the partial pressure of CO2 is high and the partial pressure of O2 is low, as more carbon dioxide binding occurs in tissues. When the pCO2 is low and the pO2 is high, as in the alveoli, CO2 dissociates from carbamino-haemoglobin.
The carbonic anhydrase enzyme is abundant in RBCs and is responsible for converting carbon dioxide into bicarbonate ions. This enzyme is only found in trace amounts in plasma.
Because of catabolism, the partial pressure of CO2 in the tissue is high, and it diffuses into the blood to form HCO3- and H+ ions.
CO2 and H2 are formed when the partial pressure of CO2 in the alveolus is low. Bicarbonate ions are formed as a result of carbon dioxide trapping. It moves from the tissue to the alveoli, where carbon dioxide is expelled. 4 mL of carbon dioxide is delivered for every 100 mL of deoxygenated blood.
17.5 Regulation of Respiration Process:
The nervous system regulates the process of respiration or respiratory rhythm. The rate of respiration changes in response to the body's oxygen demand. The respiratory centre is the regulatory centre for respiration. It is made up of a number of neurons located bilaterally in the brain's medulla oblongata. There are three types of respiratory centres: respiratory rhythm centre, pneumatic centre, and chemosensitive area.
17.5.1 Respiratory Rhythm Center:
It is a group of neurons in the medulla oblongata's dorsal region. It is a specialised centre that is in charge of respiration regulation. The basic respiratory rhythm is produced by this group of neurons. Neurons of the respiratory rhythm centre release nervous signals which are transmitted to the diaphragm, the primary inspiratory muscle. These signals cause the inspiratory muscle (diaphragm) to contract, resulting in inspiration.
17.5.2 Pneumotaxic Centre:
It is a group of neurons located dorsally in the brain's upper pons. It has the ability to modulate the functions of the respiratory rhythm centre.
The number and depth of breaths are determined by the signal from the neurons of the pneumatic centre. When the pneumatic centre sends a strong signal, the rate of breathing increases due to the shortening of both inspiration and expiration. The neural signals from the pneumatic centre can also shorten the duration of inspiration and thus change the rate of respiration.
17.5.3 Chemo Sensitive Centre:
This is a region near the respiratory rhythm centre that is extremely sensitive to CO2 and hydrogen ions. The concentration of hydrogen ions and CO2 raises the inspiratory and expiratory signals. There is no direct effect of oxygen on respiratory signals. The chemosensitive centre is activated by the increased concentration of CO2 and Hydrogen ions in the chemosensitive area. Then the signals are transmitted to the respiratory rhythm centre, which adjusts the respiratory process to eliminate these substances.
Changes in the concentration of CO2 and hydrogen ions are recognised by aortic arch and carotid artery receptors. They send the necessary signals to the respiratory rhythm centre in order for immediate control actions to be taken.
17.6 Disorders of the Respiratory System:
Many respiratory diseases and respiratory disorders affect the human respiratory system.
Asthma, emphysema, and occupational respiratory disorders are all common.
Asthma: Asthma is characterised by difficulty breathing and wheezing caused by inflammation of the bronchi and bronchioles.
Emphysema: Emphysema is a chronic obstructive lung disease. It is characterised by abnormal distension or inflation of the alveolar wall, resulting in a loss of elasticity of their walls. Alveolar walls degenerate, and alveoli join together to form large alveoli. Even during expiration, the alveoli remain completely filled with air. This causes an increase in lung size, and cigarette smoking is the leading cause of emphysema.
Occupational Respiratory Disorders: Occupational respiratory disorders are pulmonary diseases caused by exposure to potentially harmful substances such as gas, fumes, or dust in a person's working environment. Silicosis (caused in workers employed in the mining industry, quarry, etc. due to chronic exposure to silica dust from rocks or stones) and asbestosis (caused in workers employed in asbestos factories due to chronic exposure to asbestos dust) are two common examples.
Fast Track Revision:
Cells use oxygen to produce energy by metabolizing nutrients and also produce waste products that are harmful to the cells in nature.
Animals use a variety of methods to exchange gases between the air and body tissues via the blood.
There is a respiratory system that exchanges gases for the body through a series of processes occurring in order.
The process begins with breathing, in which atmospheric air is inhaled and the alveolar air is expelled.
The events that occur are the exchange of oxygen and carbon dioxide between deoxygenated blood and alveoli, as well as the transport of all nutrients and gases.
Inhalation and exhalation are the two mechanisms of respiration. It is accomplished by establishing pressure gradients between the atmosphere and the alveoli. The volumes of air involved during respiration can be estimated using a spirometer and have clinical significance.
Gas diffusion is affected by the partial pressures of oxygen and carbon dioxide, their solubility, and the thickness of the diffusion surface.
All of these factors work together to transport oxygen from the alveoli to the deoxygenated tissues and carbon dioxide from the tissues to the blood.
When oxygen comes into contact with haemoglobin, it produces oxyhaemoglobin.
The respiratory centre in the brain, the medulla oblongata, regulates respiratory rhythm.
Respiration
Respiration is the process of oxygen taken in from the atmosphere with Carbon dioxide produced by the body cells is called Respiration. This include two processes:
Breathing
Gaseous exchange along with its transport.
Breathing is the process of transportation of air in and out of the lungs. It includes inspiration as well as expiration.
Mechanism of breathing varies from one group of animals to another depending upon mainly on their habitats and level of organization. For example: In sponges, coelenterates, flatworms, etc., oxygen is exchanged with carbon dioxide by simple diffusion over the entire body surface.
Some organisms and their respiratory organs are:
Organisms and Their Respiratory Organs
Human respiratory system is well developed and divided into nostrils, nasal passage, pharynx, larynx, trachea, bronchi and lungs.
Nostrils are the openings above the upper lips; it leads to the nasal chamber through the nasal passage.
Nasal chamber extends into the nasopharynx, which is a portion of the pharynx. It is the regular passageway for food and air.
Nasopharynx extends through the glottis of the larynx region into trachea.
Sound box is cartilaginous larynx, which helps in sound production.
Epiglottis is a cartilaginous flap, which is used to prevent the entry of food into the larynx.
The windpipe, which is called Trachea, opens to the mid thoracic cavity and divides at the level of 5th thoracic vertebra into right and left primary bronchi. The primary bronchi divides into many primary bronchioles. These bronchioles are further divided into two and eleven alveolar ducts.
Alveoli are the bag-like structures. They are the basic units of gas exchange in lungs.
The whole network of bronchi, bronchioles and alveoli is composed of lungs. Lungs are covered by double-layered pleura with pleural fluid between them.
Lungs are comprised of the branching network of bronchi, bronchioles and alveoli. There are two lungs in a human body and they are covered by double layered pleura, which have pleural fluid between them. The outer membrane of the pleura is in close contact with the thoracic lining whereas the inner membrane of the pleura is connected with the lung surface.
Lungs are present in a thoracic chamber, which is anatomically an airtight chamber.
Thoracic chamber is formed of:
Vertebral column at dorsal side.
Ventrally by sternum.
Ribs at the lateral side.
At the lower side, a dome-shaped diaphragm.
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Steps of Respirations
Breathing or pulmonary ventilation by which oxygen from the atmospheric air is drawn inside and carbon dioxide rich in alveolar air is released out.
Diffusion on both oxygen and carbon dioxide across the alveolar membrane.
Gases are transported throughout the body cells by blood.
Diffusion of oxygen and carbon dioxide between blood and tissues of the body.
The cells utilize the oxygen for catabolic reactions and results in the release of carbon dioxide.
Mechanism of Breathing
There are two stages in the mechanism of Breathing.
Breathing
↓
_________________________________________
↓ ↓
Inspiration Expiration
(Air is drawn inside) (Alveolar air is released out)
The first stage breathing is Inspiration, which is also known as pulmonary ventilation. This process involves the movement of air into and out of lungs.
Intercostal muscles, which are present between the ribs, plays an important role in the process of breathing.
The movement of diaphragm initiates inspiration. The external intercostal muscle contracts to lift up the ribs and the sternum. The ribs move in upward and downward direction. The diameter of the thoracic cavity increases due to the movement of the ribs. Negative pressure develops into lungs and air rushes inside the lungs.
Expiration or exhalation involves relaxation of external intercostal muscles. Ribcage moves downwards and upwards reducing the volume of thoracic activity. The reduced volume causes positive pressure, which leads to exhalation.
Humans have the ability to increase the strength of inspiration and expiration with the help of additional muscles in the abdomen. On an average, a healthy person breathes 12-16 times per minute. In order to assess the volume of air involved in breathing movements, a spirometer is used.
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Respiratory Volumes and Capacities
Respiratory volumes and capacities are expressed in different ways:
Tidal Volume (TV): It is the amount of air inspired or expired during normal respiration. It is approximately 500ml. A healthy human being inspires or expires 6000 to 8000ml per minute.
Inspiratory Reserve Volume (IRV): It is the extra volume of air, which could be inhaled into the lungs during maximal inspiration.
Expiratory Reserve Volume (ERV): It is the maximum amount of air, which could be expelled out of the lungs during forcible expiration. It is 1000 to 1100ml.
Residual Volume (RV): It is measured as the volume of air remaining in the lungs after forced expiration.
Vital Capacity (VC): It is the maximum volume of air, which can be moved in and out of the lungs.
VC = Tidal volume + IRV + ERV
Inspiratory Capacity (IC): It is the capacity of a person to inspire the amount of air after normal expiration.
It is → (IRV + TV)
Expiratory Capacity (EC): It is the capacity of a person to expire the amount of air after normal expiration.
It is (TV + ERV)
Functional Residual Capacity (FRC): It is the volume of air that will remain in lungs after a normal expiration. It is (ERV + RV).
Total Lung Capacity: The total lung capacity is the accommodation of the volume of air in lungs at the end of forced inspiration. It is VC + residual volume.
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Exchange of Gases
Gas exchange takes place in the primary site i.e., alveoli. The exchange of the gases happens due to a simple diffusion process.
Oxygen travels throughout the body with the help of blood.
The oxygen is released into the body tissues by the blood on the basis of partial pressure. The atmospheric air is a mixture of gases. Each individual gas contributes independently to its total pressure. The pressure of the individual gas contributed in the air is called partial pressure. The difference in the partial pressure determines the movement of gas from one area to another. A gas always travels from higher to lower partial pressure. The partial pressure of oxygen is more in alveoli than in body tissues so the gradient oxygen is transported to the body tissues. In the tissues, the partial oxygen is low. The blood then becomes deoxygenated.
In tissues partial carbon dioxide is high. Blood picks up carbon dioxide from the tissues and releases it in alveoli, where the partial carbon dioxide is low.
Diffusion layer of alveoli is made up of three layers namely,
Thin squamous epithelium.
Endothelium.
Fused basement membrane.
Transport of Gases
Blood is the carrier of oxygen and carbon dioxide throughout the body.
The RBC present in the blood carries 97% of the oxygen. 3% of the oxygen is carried in the dissolved state.
Carbon dioxide is mainly carried in dissolved state through the plasma present in the blood. 70% of the Carbon dioxide is carried as bicarbonate form. 7% of carbon dioxide is carried in a dissolved state and 20-25% is transported by RBC.
Oxygen is transported in the bound form of haemoglobin, which is a red coloured iron containing pigment. Oxygen binds with haemoglobin to form oxyhaemoglobin.
One molecule of haemoglobin binds with oxygen molecules. Binding of haemoglobin with oxygen depends upon:
Partial pressure of oxygen.
Partial pressure of carbon dioxide.
H+ ion concentration.
Temperature.
When the percentage saturation of haemoglobin is plotted against the partial oxygen then the curve is called oxygen dissociation.
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In low temperature, high partial oxygen, low partial carbon dioxide, less H+ ion concentration (acidic pH) shifts the curve towards the right indicating formation of oxyhaemoglobin, whereas in low partial oxygen, high carbon dioxide, basic pH, high temperature curve shifts towards left, which indicates the dissociation of oxygen with haemoglobin.
Transport of Carbon Dioxide
Carbon dioxide is carried out in the form of carbamino-haemoglobin.
More binding of carbon dioxide occurs during high partial carbon dioxide and low partial oxygen as in the alveoli, dissociation of carbon dioxide from carbamino-haemoglobin takes place.
Carbon dioxide diffuses into blood and forms HOCO-3 and H+ ions. Under the action of enzyme carbonic anhydrase,
carbonic carbonic
anhydrase anhydrase
CO2 + H2O ⇄ H2CO3 ⇄ HCO-3 + H+
Reaction proceeds in the opposite direction, where partial carbon dioxide is low.
Regulation of Respiration
Respiration is under the control of our neural system:
Respiratory rhythm centre is present in the medulla region in the brain responsible for regulation of respiration.
Pneumotaxic centres are also present in the pons region of the brain.
- A chemosensitive area present adjacent to this rhythmic centre is highly sensitive to CO2 and H+ ion concentration.
Disorders of Respiration
Asthma: Asthma is the inflammation of bronchi and bronchioles, which causes difficulty in breathing and causes wheezing.
Emphysema: It is a chronic disorder respiratory surface is decreased due to damage in alveolar walls.
Fibrosis: It is an occupational respiratory disorder. Long-term exposure to dust causes inflammation in lungs. It is usually seen in workers involved in grinding or stone breaking.
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FAQs on Breathing and Exchange of Gases Class 11 Notes CBSE Biology Chapter 14 (Free PDF Download)
1. What are the Steps of Respiration?
Breathing or pulmonary ventilation by which oxygen from the atmospheric air is drawn inside and carbon dioxide rich in alveolar air is released out.
Diffusion on both oxygen and carbon dioxide across the alveolar membrane.
Gases are transported throughout the body cells by blood.
Diffusion of oxygen and carbon dioxide between blood and tissues of the body.
The cells utilize the oxygen for catabolic reactions and results in the release of carbon dioxide.
2. Where does the Exchange of Gases Take Place?
The exchange of gases takes place in the alveoli. The exchange of the gases happens due to a simple diffusion process.
3. Define Vital Capacity? What is its Significance?
The maximum amount of air a man breathes in after a forced expiration is called vital capacity. Vital capacity is higher for athletes and singers. Vital capacity shows the strength of our inspiration and expiration.
4. State the Volume of Air Remaining in the Lungs After a Normal Breathing.
The volume of air remaining in the lungs even after a forcible expiration averages 100ml to 1200ml.
5. What is breathing and exchange of gases Class 11 Biology Chapter 7?
For numerous actions, we require energy. Catabolism of numerous dietary components, such as proteins, carbs, lipids, and so on, produces this energy. Catabolic reactions necessitate the use of oxygen, which results in the production of carbon dioxide. As a result, the body requires a constant exchange of gases, with oxygen from the environment being taken in and carbon dioxide is expelled. Breathing or respiration refers to the process of gaseous exchange. A detailed explanation of Chapter 14 Biology Class 11 is available on Vedantu website and the revision notes are also available free of cost.
6. What is breathing?
Breathing is taking in the oxygen in the lungs and exhaling carbon dioxide. Respiration is a procedure in which energy-rich molecules are broken down to create energy for the organism's survival. Depending on the environment and level of organization, various species have different respiratory organs. Humans, like other higher animals, have lungs for breathing. Earthworms have wet skin that helps them breathe. Inspiration or inhalation is the process in which the air is taken in.
7. What is alveolar air Class 11?
Bronchioles end in tiny air sacs called alveoli, which is where oxygen and carbon dioxide is exchanged. The bronchial tree is a network of bronchioles, alveoli, and bronchi. The lungs and atmospheric air exchange oxygen and carbon dioxide continuously. Each person's lungs contain hundreds of millions of alveoli. Oxygen is absorbed into the alveoli from the environment owing to the lower oxygen content in the alveoli, and carbon dioxide is expelled due to increasing carbon dioxide buildup in the lungs. A detailed explanation of Chapter 14 Biology Class 11 is available on Vedantu.
8. What comprises the lungs?
Lungs are made up of a network of bronchi, bronchioles, and alveoli that branch out. A human body has two lungs, each of which is covered by a double-layered pleura with pleural fluid between them. The pleura's outer membrane is in close touch with the thoracic lining, whereas the pleura's inner membrane is linked to the lung surface. A thoracic chamber, which is anatomically an airtight chamber, contains the lungs. For study material related to biology Class 11 Chapter 14 students can visit the vedantu app.
9. How does the blood become deoxygenated?
On the basis of partial pressure, the blood releases oxygen into the bodily tissues. Each gas adds to the total pressure in its own way. The flow of gas from one location to another is determined by the partial pressure difference. Because the partial pressure of oxygen in alveoli is higher than in body tissues, oxygen is delivered in a gradient to the body tissues. The partial oxygen saturation in the tissues is low. The blood becomes deoxygenated as a result.
