Breathing and Exchange of Gases: Class 11 Biology NCERT Chapter 17

Key Features of NCERT Solutions for Class 11 Biology Chapter 17 – Breathing and Exchange of Gases

In chapter 16 of NCERT class 11 Biology: Digestion and Absorption, You learnt about digestion is one of the most perplexing procedures that happen in our bodies. In this chapter: Breathing and Exchange of gases you will learn the profound jump into the respiratory arrangement of the human framework. It discloses to understudies how it conveys the most extreme significance in the best possible working of the body.

What will occur in the event that you quit breathing? Or on the other hand if your lungs quit working? What is the capacity of the lungs in any case? Our respiratory framework encourages us in breathing and trade of gases. In any case, how accomplishes the framework work to do as such? Does the framework incorporate lungs? We should make a plunge and investigate everything about our respiratory framework. 

The seventeenth section of Class 11 Biology  you will figure out how the trading of gases happens inside the organs of our body. Moreover, it will likewise clarify how the way toward breathing really happens. Breathing and trade of gases class 11 notes will concentrate on the theme in detail, covering every one of its complexities.

Quick Revision Notes

From that point forward, it illuminates how we relax. At the end of the day, it clarifies its instrument. You can likewise find out about the job of different organs in the breathing procedure. While understudies realize that breath happens, you probably won’t know there is additionally the guideline of breath. Thus, it will clarify about the respiratory issues also. 

Sub-topics covered under Breathing and Exchange of Gases –

Respiratory Organs-This segment will show understudies the organs which assume a significant job during the time spent breath. 

Component of Breathing–Over here, one will find out about the organs and muscles which help in making the way toward breathing simple. 

Trade and Transport of Gases–The entire procedure of gas trade happening among oxygen and carbon dioxide is clarified here. 

Guideline of Respiration–It will talk about how the sensory system is answerable for directing the breath of human beings. 

Issues of Respiratory System–You will find out about the normal respiratory issues and how they influence the basic open.

 Quick Revision notes

Gas trade is the procedure that happens among oxygen and carbon dioxide. Oxygen is passed from the lungs to the circulation system and carbon dioxide is killed from the circulatory system to the lungs. Trade of Gas happens in lungs between the alveoli and vessels which are little veins, set at the dividers of alveoli. The pace of dispersion relies upon the thickness of the natural layer which shapes the limit between the outside condition and living beings. We should become familiar with how this gas trade and transport happen. 

Exchange Of Gases

Despite the fact that the essential locales of gas trade are the alveoli, trade of O2 and CO2 likewise occurs among blood and tissues. Gas trade at these destinations occurs by straightforward dispersion dependent on a focus/pressure inclination. The pace of dispersion depends on the dissolvability of gases as well as on the thickness of the films associated with gas trade.

Breathing and Exchange of Gases: Class 11

Fractional weight is the weight that originates from an individual gas in a blend of gases. It is spoken to as pO2 for oxygen and pCO2 for carbon dioxide. The table underneath shows the incomplete weights of these gases in the barometrical air and various destinations of gas trade. 

fixation angle for O2

The information in the above table unmistakably shows that there is a fixation angle for O2 from the alveoli to blood and blood to tissues. Also, CO2 has a fixation slope the other way for example from tissues to blood and blood to the alveoli. The measure of CO2 that can diffuse through a layer is a lot higher than that of O2 since the dissolvability of CO2 is 20-25 times higher than that of O2. 

  • Respiratory Organs 
  • Mechanism of Breathing
  • Regulation of Respiration
  • Disorders of the Respiratory System

Diffusion Membrane

The diffusion membrane has three layers –

  • The thin squamous epithelium of the alveoli.
  • The endothelium containing alveolar capillaries.
  • The basement substance between the epithelium and endothelium.

The all out thickness of the dispersion film is not exactly a millimeter. Every one of these components in our body make it simple for the dissemination of O2 from alveoli to tissues and that of CO2 from the tissues to alveoli.

Cross section of an alveolus

Transport Of Gases

The vehicle of O2 and CO2 occurs through blood. The RBCs in the blood convey 97% of O2 while plasma conveys the remaining 3% of O2 in a broke up state. If there should be an occurrence of CO2, the RBCs convey around 20-25%, plasma conveys 7% of CO2 in a broke down state while the staying 70% is conveyed as bicarbonate. 

Transport Of Oxygen 

O2 ties reversibly to hemoglobin in blood to give oxyhaemoglobin. Hemoglobin is a red shaded color in the RBCs that contains iron. A limit of 4 atoms of O2 can tie to a particle of hemoglobin. The fractional weight of O2 is the essential factor that influences this official. Different elements that can impact this coupling are fractional weight of CO2, temperature and hydrogen particle fixation. 

At the point when we plot the percent of immersion of hemoglobin with O2 against pO2, we get a sigmoid bend. This bend is the ‘Oxygen Dissociation Curve’ and is helpful in examining the impacts of H+ fixation, pCO2 and so on, on the authoritative of O2 with hemoglobin. 

Oxygen Dissociation Curve (Source: Wikimedia Commons)

In the alveoli, there is high pO2, low pCO2, low temperature, and low H+ fixation. These conditions are ideal for the development of oxyhemoglobin. Be that as it may, in the tissues, there is low pO2, high pCO2, high temperature, and high H+ focus which is good for the separation of O2 from oxyhemoglobin. 

Hence, this shows O2 ties to hemoglobin on the lung surface and gets separated in the tissues. Under ordinary physiological conditions, each 100 ml of oxygenated blood conveys around 5 ml of O2 to the tissues. 

Transport Of Carbon Dioxide 

Aside from O2, hemoglobin likewise conveys around 20-25% of CO2, as carbamino-hemoglobin. This coupling is principally identified with the fractional weight of CO2, in any case, pO2 is likewise a central point that influences this authoritative. In the tissues, when the pCO2 is high and pO2 is low, additionally authoritative of CO2 happens. Then again, when pCO2 is low and pO2 is high in the alveoli, CO2 separates from carbamino-hemoglobin framed in the tissues and is delivered in the alveoli

The catalyst – carbonic anhydrase is available in high fixation in the RBCs. Modest quantities of this chemical are additionally present in plasma. This compound catalyzes the accompanying response in the two headings: 

CO2 +H2O ⇔ H2CO3 ⇔ HCO3–+ H+ 

The fractional weight of CO2 is high in the tissues because of catabolism. Here, CO2 diffuses into the blood (plasma and RBCs) and offers ascend to HCO3–and H+. The response happens the other way in the alveoli where the pCO2 is low, prompting the arrangement of CO2 and H2O. Along these lines, at the tissue level, CO2 is caught as bicarbonate, shipped to the alveoli and delivered as CO2. Under typical physiological conditions, each 100 ml of deoxygenated blood conveys around 4 ml of CO2 to the alveoli. 


Q: Which of the accompanying components isn’t positive for oxyhaemoglobin arrangement in the alveoli? 

Low pCO2 

High pO2 

High H+ focus. 

Low temperature 

Arrangement: Therefore, the appropriate response is ‘c’. Development of oxyhemoglobin requires low H+ fixation.

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