NCERT Class 11 Biology Chapter 17 Notes Breathing And Exchange Of Gases - Download PDF Notes

NCERT Chapter 17, Breathing and Exchange of Gases, is a very important chapter of Biology, CBSE Class 11, from an exam point of view. The NCERT Class 11 Biology Chapter 17 notes give you a basic idea of the chapter on breathing and exchange of gases. Chapter 17, Class 11 Zoology from Unit 5—Human Physiology—includes important topics such as respiratory organs, mechanism of breathing, exchange of gases, transport of gases, regulation of respiration, and disorders of respiratory system. Download the CBSE Notes for Class 11 Biology, Chapter 17, PDF to use offline anywhere. Students must go through each topic of Breathing and Exchange of Gases Class 11 notes, Biology, in the easiest and most effective way possible with the help of NCERT Notes for Class 11.

Class 11 Biology chapter 17 notes also cover all the important concepts related to this chapter, which are useful in various competitive exams. Breathing and Exchange of Gases NCERT Notes for Class 11 Biology help you do revision of these major concepts given in the NCERT Book in a short period of time during CBSE Board exam preparation. CBSE Class 11 Biology Chapter 17 notes will help you with quick revision. The Breathing and Exchange of Gases CBSE Class 11 Biology Revision Notes Chapter 17 covers all headings of NCERT. CBSE Class 11 Biology chapter 17 notes also contain important examples that have been frequently asked in the various exams. Having revision notes and NCERT Solutions for Class 11 Biology Chapter 17 handy is beneficial to save you time.The Breathing and Exchange of Gases class 11 Notes Biology pdf can be downloaded through the link given below.

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• NCERT Solutions for Class 11 Biology Chapter 17 Breathing and Exchange of Gases
• NCERT Exemplar Class 11 Biology Chapter 17 Breathing and Exchange of Gases

NCERT Class 11 Biology Chapter 17 Notes

Breathing and Exchange of Gases

Breathing: NCERT notes for Class 11 Biology chapter 17 tells that the process of exchange of O₂ from the atmosphere with CO₂ produced by the cells is called Breathing.

Respiration: Class 11 Biology chapter 17 notes also inform us that the process of oxidation of food releasing energy is called Respiration.

• In different organisms, this process takes place through different methods. For example, in simple organisms through diffusion, in annelids like earthworms through moist cuticles, and in advanced organisms.
• Different respiratory organs are involved in different organisms for carrying out respiration.
• Revision Notes for Class 11 Biology chapter 17 say that there is a special mechanism of breathing in our body.
• The oxygen which is received by our body during the process of respiration is used to break down molecules like glucose to provide energy in the form of ATP.

Respiratory Organs

• Mechanisms of breathing are different among different groups of animals, depending mainly on their habitats and their levels of organisation.
• As in simple organisms, it takes place through a process of diffusion, like in earthworms through their moist cuticle and in advanced organisms like us through Lungs.

Human Respiratory System

• The air which contains different kinds of gases, including carbon dioxide and oxygen, passes initially from the nostrils into the nasal passage.
• Air moves from nasal passage to the nasal chamber and then to the pharynx through the nasopharynx. Then it passes to the glottis by covering its path in between by a flap-like cover called epiglottis.
• Then enters the trachea through larynx which is known as voice box.
• After trachea, it goes into bronchi that are further differentiated into primary secondary and tertiary Bronchioles and then it finally goes into alveoli.

: Human Respiratory System

• While passing through this path of the respiratory system, nasal passage helps in the following three ways :

1. by humidifying the air

2. by maintaining its temperature with body and

3. by cleaning

• Also, the trachea provides a fixed shape to air passage and ensures in absence of air that it doesn’t collide.
• The lungs are located in the thoracic chamber, which is an airtight chamber structurally. The thoracic chamber is formed dorsally by the vertebral column, ventrally by the sternum, and laterally by the ribs, with a dome-shaped diaphragm on the bottom side.
• The lungs are covered by double-layered tissue called pleura, with pleural fluid between layers of pleura that reduces friction on the lung surface.
• Respiration involves:

1. Breathing is the means by which atmospheric air is drawn in and carbon dioxide rich alveolar air is released

2. diffusion of gases across the alveolar membrane

3. transport of gases by blood

4. O₂ and CO₂ diffusion between blood and tissues

5. oxygen use by cells for catabolic processes and carbon dioxide release

Mechanism of Breathing

• It involves two stages - inspiration and expiration.
• Inspiration can occur if the pressure within the lungs that is intrapulmonary pressure is less than atmospheric pressure, that is there is a negative pressure in the lungs with respect to atmospheric pressure.
• The process of inspiration is initiated by the contraction of the diaphragm which in turn increases the volume of the thoracic chamber.
• The process of expiration takes place when the intrapulmonary pressure is higher than atmospheric pressure, the diaphragm and specialised set of muscles-external and internal intercostal between ribs helps in the generation of such gradient.

: Mechanism of Breathing Showing Inspiration and Expiration

• The ribs and sternum are lifted by the contraction, increasing the capacity of the thoracic chamber in the dorsal-ventral axis. When compared to atmospheric pressure, which drives air from outside into the lungs, an increase in thoracic volume induces a corresponding rise in pulmonary volume and hence a drop in pulmonary pressure.
• A healthy person breathes 12 to 16 times each minute on average.

Respiratory Volumes and Capacities

• Tidal volume (TV)- The volume of air inhaled or exhaled during typical respiration is referred to as tidal volume (TV). It is Approx 500 mL and in a minute 6000 to 8000 mL.
• Inspiratory reserve volume (IRV)- Additional volume of air a person can inspire by forcible inspiration, averages from 2500 mL to 3000 mL.
• Expiratory reserve volume (ERV)- Additional volume of air an individual can expire by forcible expiration, averages from 1000 mL to 1100 mL.
• Residual volume (RV)- Volume of air that remains in lungs even after a forcible expiration, averages to 1100 mL to 1200 mL
• Inspiratory capacity (IC)- Total volume of air a person can inspire after a normal expiration that is TV + IRV.
• Expiratory capacity (EC) - is the vice versa of inspiratory capacity. TV + ERV
• Total lung capacity - Total volume of air accommodated in lungs at the end of forced inspiration.

Exchange of Gases

• Pressure contributed by an individual gas in a mixture of gas is called partial pressure and is represented as pO₂ and pCO₂ for oxygen and carbon dioxide respectively.

• O₂ and CO₂ are exchanged in these sites by simple diffusion mainly supported by pressure or concentration gradient

(a)

(b)

: (a) Exchange of Gases at Alveoli and Body Tissues (b) Section Showing Alveolus and Pulmonary Artery.

• The diffusion membrane, including the squamous epithelium, basement, and endothelium together, is less than 1 mm (0.1 cm).

Transport of Gases

Blood is the medium of transport for O₂ and CO₂. Transport of both these gases in the blood can be tabulated as :

Transport of O₂:

: Oxygen Dissociation Curve

• 100 mL of blood has 5 mL of oxygen. Haemoglobin contains 4 molecules of O₂. O₂ can reversibly bind with haemoglobin to form oxyhemoglobin.
• In the alveoli, where there is high pO₂, low pCO₂ and lesser H+ concentration and temperature are low, the factors are all favourable for the formation of oxyhemoglobin known as association whereas, in the tissues low pO₂, high pCO₂, high H⁺ concentration and higher temperature exits, all these conditions are favourable for dissociation.

Transport of CO₂:

• Carbon dioxide gas is carried by the haemoglobin in the form of carbamino haemoglobin.
• RBCs contain a very high concentration of the enzyme carbonic anhydrase and minute quantities of this enzyme are present in plasma also.

Regulation of Respiration

• The respiratory system is regulated by the nervous system and endocrine system.
• In the medulla region, a respiratory rhythm centre is present. In the pons region, the pneumotaxic centre is present, neural signals from this can reduce the duration of inspiration.
• A chemosensitive area is situated adjacent to the rhythm centre which is highly sensitive to carbon dioxide, hydrogen ion concentration, increase in these substances activates the centre and it provides signals to the rhythm centre to make changes.
• Receptors associated with the aortic arch and carotid artery also can recognise changes in carbon dioxide and H⁺ concentration. The role of O₂ in regulation is insignificant.

The following points are important to note:

• The site of respiration in insects is the trachea, also known as tracheal respiration

• when a person goes/climbs a hill his rate of breathing increases as oxygen is deficient there.

• At the tissue side, where the partial pressure of carbon dioxide is high, carbon dioxide diffuses to RBCs and plasma in blood and forms HCO₃- and H⁺. At the alveolar site, the reaction proceeds in the opposite direction leading to the formation of CO₂ and H₂O

• Every 100 mL of deoxygenated blood delivers 4 mL of CO₂ to the alveoli.

Disorders of the Respiratory System

Asthma - This is a disorder in which patients have trouble breathing and wheezing because of inflammation of the bronchi and bronchioles.

Emphysema - It is a chronic condition in which the alveolar walls are damaged, resulting in a reduction in the respiratory surface. Cigarette smoking is a key cause of this condition.

Occupational respiratory disorders - In certain industries like the coal, silica industry that gives rise to inflammation leading to fibrosis which is the proliferation of fibrous tissues causing serious lung damage, they are advised to wear masks.

Chapter-Wise Class 11 Notes Biology

Significance of NCERT Class 11 Biology Chapter 17 Notes

Class 11 Biology chapter 17 notes will assist you in revising the chapter and gaining an understanding of the main subjects addressed. These Class 11 Breathing and exchange of gases notes are also beneficial for covering the main themes of the CBSE Biology Syllabus Class 11 as well as for competitive exams such as AIPMT, AIIMS, NEET, and others. The Class 11 Biology chapter 17 notes pdf download can be utilized for offline preparation.

Subject Wise NCERT Exemplar Solutions

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Subject Wise NCERT Solutions

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• NCERT Solutions for Class 11 Biology