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Chapter 14, Breathing and Exchange of Gases, will help students understand how living things breathe and use oxygen to generate energy. Most individuals get confused between breathing and respiration, but they are distinct. Breathing is the physical act of inhaling oxygen and exhaling carbon dioxide. Respiration, on the other hand, is a chemical process by which the body uses oxygen to metabolise food such as glucose to generate energy. The chapter also describes carbon dioxide as a waste product and how the body eliminates it. Students learn how a unique part of the brain regulates breathing called the medulla, which maintains the rhythm of breathing consistent rhythm. The NCERT Solutions have diagrams and clear language in the answers that help these ideas become clearer and more memorable for exams.
NEET Scholarship Test Kit (Class 11): Narayana | Physics Wallah | Aakash | ALLEN
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In the NCERT Solutions for Class 11 Breathing and Exchange of Gases, students will learn how inspiration and expiration occur by generating pressure differences between the air and the alveoli through special muscles such as the intercostal muscles and diaphragm that control breathing.
The solutions are provided below in an easy-to-access format for quick reference and better understanding.
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Given below are the solved exercise questions and answers, providing step-by-step NCERT solutions to help you understand and revise the concepts effectively.
Question 1. Define vital capacity. What is its significance?
Answer:
Vital capacity (VC) refers to the largest volume of air that can be expelled from the lungs following maximum inspiration. It is equal to tidal volume (TV) plus inspiratory reserve volume (IRV) plus expiratory reserve volume (ERV). Vital capacity is a vital measure of lung function and respiratory health.
An increase in VC indicates increased oxygenation and stamina, making it essential for sportspersons and singers. It also helps in the diagnosis of lung diseases such as asthma and COPD. Exercise and breathing exercises can increase VC, whereas ageing and respiratory disease can impair it. VC is quantified through the use of a spirometer during pulmonary function tests.
Question 2. State the volume of air remaining in the lungs after normal breathing.
Answer:
The volume of air remaining in the lungs after normal breathing is called functional residual capacity (FRC). It combines expiratory reserve volume (ERV) and residual volume (RV). ERV is the maximum volume of air that can be exhaled after a normal expiration, and it is about 1000 mL to 1500 mL. RV, on the other hand, refers to the volume of air remaining in the lungs after maximum expiration and is about 1100 mL to 1500 mL.
Thus, FRC = ERV + RV
1500 + 1500 = 3000 mL
Hence, the functional residual capacity of the human lungs is about 2500 - 3000 mL.
Answer:
Diffusion of gases can only take place in the alveolar area since alveoli possess thin walls (one-cell thick), a large surface area, and are well-perfused with blood capillaries, thus facilitating efficient gas exchange. The other structures of the respiratory system, i.e., trachea, bronchi, and bronchioles, are only air passageways and devoid of structural modifications to facilitate diffusion.
The alveolar membrane is permeable and wet, permitting oxygen to diffuse into the blood and carbon dioxide to diffuse out. Moreover, the partial pressure gradient between alveolar air and blood propels the movement of gases. These unique properties render the alveoli the sole location for effective gas exchange.
Question 4. What are the major transport mechanisms for CO2? Explain.
Answer:
The major transport mechanisms for CO2 is transported by sodium bicarbonate as well as red blood cells. See, about 70% of carbon dioxide is transported as sodium bicarbonate. As CO2 diffuses into the blood plasma, a large part of it combines with water to form carbonic acid in the presence of the enzyme carbonic anhydrase.
Carbonic anhydrase is a zinc enzyme that speeds up the formation of carbonic acid. This carbonic acid dissociates into bicarbonate (HCO3–) and hydrogen ions (H+). About 20 – 25% of CO2 is transported by the red blood cells as carbaminohaemoglobin. Carbon dioxide binds to the amino groups on the polypeptide chains of haemoglobin and forms a compound known as carbaminohaemoglobin.
Question 5. What will be the pO2 and pCO2 in the atmospheric air compared to those in the alveolar air?
(i) pO2 lesser, pCO2 higher
(ii) pO2 higher, pCO2 lesser
(iii) pO2 higher, pCO2 higher
(iv) pO2 lesser, pCO2 lesser
Answer:
PO2 is higher, pCO2 lesser
The oxygen partial pressure in atmospheric air is greater than in alveolar air. In atmospheric air, the partial pressure of oxygen is about 159 mm Hg, but in alveolar air, it is around 104 mm Hg. Likewise, the carbon dioxide partial pressure in atmospheric air is less than in alveolar air. In atmospheric air, the partial pressure of carbon dioxide is about 0.3 mm Hg, but in alveolar air, it is around 40 mm Hg.
This partial pressure difference enables oxygen to diffuse into the blood from the alveoli, and carbon dioxide to move into the alveoli from the blood for exhalation. The ongoing exchange of gases provides adequate oxygenation of blood and disposal of waste gases. The effective exchange of gases is vital for cellular respiration and energy yield. Conditions such as altitude, lung disorders, and patterns of breathing can affect these partial pressures.Question 6. Explain the process of inspiration under normal conditions.
Answer:
Inspiration is the process by which atmospheric air is drawn into the body. It can occur if the pressure within the lungs (intrapulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs compared to atmospheric pressure.
It is initiated by the contraction of the diaphragm, which increases the volume of the thoracic chamber in the anteroposterior axis. The contraction ofthe external intercostal muscles lifts the ribs and the sternum, causing an increase in the volume of the thoracic chamber in the dorso-ventral axis. The overall increase in the thoracic volume causes a similar increase in pulmonary volume. An increase in pulmonary volume decreases the intrapulmonary pressure to less than the atmospheric pressure, which forces the air from outside to move into the lungs.
Question 7. How is respiration regulated?
Answer:
A centre present in the medulla region of the brain is called the respiratory rhythm centre, and it is primarily responsible for respiration regulation. Another centre, which is present in the pons region of the brain, is called the pneumatic centre. It can moderate the functions of the respiratory rhythm centre. The neural signal from this centre can reduce the duration of inspiration and thereby alter the respiratory rate.
A chemosensitive area is situated adjacent to the rhythm centre, which is highly sensitive to CO2 and hydrogen ions. An increase in these substances can activate this centre, which in turn can signal the rhythm centre to make necessary adjustments in the respiratory process by which these substances can be eliminated. Receptors associated with the aortic arch and carotid artery also can recognize changes in CO2 and H+ concentration and send necessary signals to the rhythm centre for remedial actions. The role of oxygen in the regulation of respiratory rhythm is quite insignificant.
Question 8. What is the effect of pCO2 on oxygen transport?
Answer:
The pCO2 plays an important role in the transportation of oxygen. The low pCO2 and high pO2 favour the formation of oxyhaemoglobin that takes place at the alveolus. At the tissues, the high pCO2 and low pO2 favour the dissociation of oxygen from oxyhaemoglobin. So, the affinity of haemoglobin for oxygen is enhanced by the decrease of pCO2 in blood. Therefore, oxygen is transported in the blood as oxyhaemoglobin and oxygen dissociates from it at the tissues.
Question 9. What happens to the respiratory process in a man going up a hill?
Answer:
If a man goes uphill, he breathes in less oxygen per inhalation since the oxygen content in the air declines with rising elevation. At the same time, the oxygen level in the blood falls, leading to an acceleration of the rate of breathing to balance the lower level of oxygen. At the same time, the rate of the heart increases to facilitate higher oxygen delivery to tissues and uphold normal body operations.
At greater heights, repeated exposure can result in altitude sickness with symptoms of dizziness, headache, and breathlessness. The body slowly acclimatizes by increasing the number of red blood cells to enhance oxygen-carrying capacity. Individuals dwelling at high altitudes naturally have increased haemoglobin levels for more efficient oxygen use. Gradual ascent and hydration through acclimatisation help the body to adapt to lower oxygen levels.
Question 10. What is the site of gaseous exchange in an insect?
Answer:
In insects, gaseous exchange occurs through a system of tubes referred to as the tracheal system. The minute openings on the sides of an insect's body are referred to as spiracles, where oxygen-rich air enters. The spiracles lead to a system of tubes. Oxygen from the spiracles passes into the tracheae and then diffuses into the cells of the body. The movement of carbon dioxide is the opposite, in which CO₂ from the body cells initially passes through the tracheae and then leaves through the spiracles.
The tracheal system provides direct oxygenation of cells without the use of blood transport. Muscular contraction within the body of the insect controls air movement in and out of the tracheae. The system is very efficient for small creatures, but restricts how large an insect can become. Grasshoppers, for example, actively pump air with movements of the abdomen to maximise gas exchange.Question 11. Define the oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?
Answer:
The oxygen dissociation curve is a plot of the percentage of saturation of oxyhaemoglobin for different partial pressures of oxygen. It portrays the equilibrium of oxyhaemoglobin and haemoglobin at different levels of oxygen. In the lungs, where the partial pressure of oxygen is high, haemoglobin combines with oxygen to produce oxyhaemoglobin.
In tissues, where oxygen partial pressure is low, oxyhaemoglobin breaks to give out oxygen for cellular respiration. The curve is normally sigmoid (S-shaped) as a result of the cooperative binding of oxygen molecules to haemoglobin. pH, temperature, and levels of CO₂ can cause a shift in the curve, promoting oxygen binding and release. A rightward shift suggests increased oxygen release, whereas a leftward shift is associated with tighter oxygen binding. This mechanism is involved in effective oxygen transportation and delivery, depending on the body's requirements.Question 12. Have you heard about hypoxia? Try to gather information about it, and discuss it with your friends.
Answer:
Hypoxia is a type of condition characterised by an inadequate or decreased supply of oxygen to the lungs. It is caused by several extrinsic factors such as a reduction in pO2, inadequate oxygen, etc. It can also be classified as either generalised, affecting the whole body, or local, affecting a region of the body.
Different types of hypoxia are:
Question 13. (a) Distinguish between IRV and ERV
Answer:
The differences between the IRV and ERV are given below:
IRV :
ERV :
Question 13. (b) Distinguish between inspiratory capacity and Expiratory capacity.
Answer:
Difference between Inspiratory capacity and Expiratory capacity:
Inspiratory capacity:
Expiratory capacity:
Question 13. (c). Distinguish between Vital capacity and Total lung capacity.
Answer:
Vital capacity
Total lung capacity
Question 14. What is Tidal volume? Find out the Tidal volume (approximate value) for a healthy human in an hour.
Answer:
Tidal volume is the volume of air that is transported into and out of the lungs ( inspired or expired ) with each normal respiratory cycle. Tidal volume is approximately 6000 to 8000 mL of air per minute for a healthy human.
We can calculate the hourly tidal volume for a healthy human.
If Tidal volume = 6000 to 8000 mL/minute
So, the Tidal volume in an hour will be:
= 6000 to 8000 mL × (60 min)
= 3.6 × 10 5 mL to 4.8 × 10 5 mL
Hence, the hourly tidal volume for a healthy human is approximately 360000 ml- 480000 ml.
NCERT Solutions for Class 11: Subject-wise
NCERT Solutions for Class 11 Maths |
NCERT Solutions for Class 11 Chemistry |
NCERT Solutions for Class 11 Physics |
These questions will help you understand the main ideas better and get ready for your exams with confidence.
Question 1: Which neurotransmitter among the following stimulates the diaphragm during inspiration?
A. Acetylcholine
B. Dopamine
C. Serotonin
D. GABA
Answer:
The nervous system controls the contraction of the respiratory muscles during inspiration. Acetylcholine is the primary neurotransmitter responsible for stimulating and initiating the contraction of the diaphragm.
Hence, the correct answer is option 1) Acetylcholine
Also, check the NCERT Books and NCERT Syllabus here:
NCERT is important for NEET, but studying extra topics and practising more questions can help you score better and understand the concepts more clearly.
Below mentioned are the Chapter-wise solutions:
Breathing is the physical process of taking in oxygen and expelling carbon dioxide from the lungs, while respiration is a biochemical process where oxygen is used to oxidize food molecules to release energy, producing carbon dioxide and water as byproducts.
Breathing involves two stages:
Inspiration: The diaphragm contracts and flattens, and external intercostal muscles lift the ribs, increasing thoracic volume and decreasing pressure inside the lungs, causing air to flow in.
Expiration: The diaphragm and intercostal muscles relax, decreasing thoracic volume and increasing lung pressure, pushing air out
Cockroach: Tracheal system
Earthworm: Moist skin (cutaneous respiration)
Birds: Lungs with air sacs for efficient gas exchange
These are the difference between Inspiratory capacity and Expiratory capacity:
Inspiratory capacity:
Expiratory capacity:
Tidal Volume (TV)
Tidal volume refers to the volume of air that is inhaled or exhaled on a single breath when the individual is breathing comfortably at rest. It is an important measure in respiratory physiology and is usually 500 mL in a resting, healthy adult.
Measurement of Tidal Volume
Tidal volume may be measured by:
It is a crucial measurement in determining lung function and is utilized for diagnosing and treating respiratory disease.
Bohr Effect in Respiration
Bohr effect is a physiological response where an elevation of carbon dioxide (CO₂) level or lowering of blood pH decreases the affinity of haemoglobin for oxygen (O₂), facilitating the release of oxygen to tissues.
Mechanism
Increase in CO₂ or H⁺:
CO₂ in the blood gets dissolved and upon dissociation forms carbonic acid (H₂CO₃) which breaks into H⁺ and HCO₃⁻, decreasing the pH. The binding of more H⁺ with haemoglobin causes its structure change and decreases oxygen-binding capacity.
Oxygen Unloading:
In active tissues (muscles, for example), excess CO₂ production and acidity cause the oxyhemoglobin dissociation curve to shift to the right. This allows for the release of O₂ where it is most needed.
Reversal in Lungs:
In the lungs, CO₂ is removed, pH increases, and haemoglobin's affinity for O₂ returns, promoting oxygen uptake.
Significance
Aids in proper oxygen delivery to metabolically active tissues.
Regulates blood pH and CO₂ transport.
Bohr effect plays an important role in exercise physiology as it permits additional oxygen supply to muscles in circumstances of active load.
Oxygen is crucial for cellular respiration, where it is used to produce ATP (energy) in mitochondria. It serves as the terminal electron acceptor in the electron transport chain, allowing efficient energy generation. In the absence of oxygen, cells resort to anaerobic metabolism, yielding less energy and toxic byproducts such as lactic acid. Oxygen also facilitates organ function and metabolism to maintain survival.
Alveoli are small air sacs in the lungs where gas exchange takes place. Oxygen from the inhaled air diffuses into blood, and carbon dioxide from blood diffuses into alveoli for exhalation. Their thin walls and large surface area facilitate efficient diffusion. Surfactant prevents the collapse of alveoli, and smooth breathing is ensured.
The diaphragm is the main breathing muscle, which contracts to increase the chest cavity and suck air into the lungs during inhalation. On exhalation, it relaxes, decreasing lung volume and forcing air out. This oscillating action keeps airflow and gas exchange going. It also helps with posture and core stability.
Inspiration and expiration are the inspiration and expiration phases of breathing. Inspiration or inhalation is the process of drawing air into the lungs, whereas expiration or exhalation is the act of pushing air out of the lungs. When the lungs are being inspired, the diaphragm pulls inward and descends, and the intercostal muscles spread the ribcage, producing a lower pressure within the lungs, and thus air rushes in. In expiration, the diaphragm relaxes and is pushed upwards, and the ribcage contracts, which raises the pressure within the lungs, expelling air. Inspiration is a muscular process that needs effort, while expiration is largely a passive process that is caused by lung elasticity.
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