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

NCERT Class 11 Biology Chapter 14 Notes: Breathing and the Exchange Of Gases is an important physiological function responsible for the constant supply of oxygen to the cells of the body and for the effective elimination of carbon dioxide, which is a by-product of metabolism. It is important for cellular respiration, in which oxygen is used to generate energy in the form of ATP. NCERT Notes for Class 11 Biology Chapter 14 presents an in-depth insight into the respiratory system, which encompasses respiratory organ structure and function, the mechanism of breathing, and the gas exchange process in various organisms. The chapter also explains why it is necessary to maintain an efficient respiratory system for healthy living.

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This Story also Contains

1. NCERT Class 11 Biology Chapter 14 Notes
2. Human Respiratory System
3. Mechanism of Breathing
4. Exchange of Gases
5. Respiratory Volumes and Capacities
6. Regulation of Respiration
7. Disorders Related to the Respiratory System
8. Chapter-Wise NCERT Class 11 Notes Biology

Knowing respiration is important to understanding how oxygen drives cellular processes and metabolic activities. This chapter explores some of the important topics like respiratory volumes and capacities, mechanics of lung inflation and deflation, and control of breathing by neural and chemical influences. NCERT Notes for Class 11 Biology of this chapter also discusses the role of hemoglobin in the transport of oxygen and the different mechanisms of elimination of carbon dioxide. Further, it delves into NCERT Solutions and how elements such as high elevation, exercise, and respiratory illnesses like asthma, bronchitis, and emphysema affect the efficiency of breathing as well as overall body oxygenation.

Also, students can refer,

• NCERT Solutions for Class 11 Biology Chapter 14 Breathing and Exchange of Gases
• NCERT Exemplar Class 11 Biology Chapter 14 Breathing and Exchange of Gases

NCERT Class 11 Biology Chapter 14 Notes

Here are complete notes on NCERT Biology – Breathing and Exchange of Gases, covering important concepts such as the respiratory system of a human being, the mechanism of respiration, exchange of gases, transport of respiratory gases, capacities of lungs, regulation of breathing, and breathing disorders.

Human Respiratory System

The human respiratory system is tasked with the intake of oxygen and the expulsion of carbon dioxide. It is made up of a number of organs that collaborate to make breathing possible.

Organs Used in the Respiratory System

• Nose: The main air entry point, covered with hair and mucus to trap dust and microbes.
• Pharynx: Shared pathway for food and air that leads air to the larynx.
• Larynx (Voice Box): Holds vocal cords and keeps food out of the trachea.
• Trachea (Windpipe): A Cartilaginous ring-supported tube that provides free passage of air to the lungs.
• Bronchi and Bronchioles: Two bronchi split off from the trachea, each traveling to a different lung, and then branch off into smaller bronchioles.
• Lungs: Primary location of gas exchange, containing alveoli where oxygen is absorbed into the blood and carbon dioxide is expelled.

Function of Alveoli in Gas Exchange

The alveoli are small air sacs within the lungs that maximize the area for gas exchange. Oxygen in the incoming air diffuses into the bloodstream, and carbon dioxide in the blood diffuses into the alveoli to be expelled from the lungs. This is due to the gradient of gases.

Role of the Diaphragm and Intercostal Muscles in Breathing

Diaphragm: A dome-shaped muscle that flattens and contracts when inhaling, expanding lung volume.

Intercostal Muscles: They are between the ribs and expand the chest cavity during inhalation and contract during exhalation. These movements cause pressure differences to let air enter and leave the lungs.

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Mechanism of Breathing

Breathing takes place in two stages: inspiration (inhalation) and expiration (exhalation).

Process of Inhalation and Exhalation

Inhalation: The diaphragm gets contracted, intercostal muscles inflate the ribcage, and lung volume increases. This results in a negative pressure within the lungs, which makes air rush in.

Exhalation: The diaphragm becomes relaxed, intercostal muscles get contracted, and lung volume reduces, which results in a positive pressure forcing air out.

Role of Pressure Gradients in Lung Expansion and Contraction

Air movement is regulated by Boyle's Law, wherein pressure and volume are inversely proportional. When lung volume is greater, pressure within the lungs is lower, and air moves in. When lung volume is lesser, pressure is higher, and air is expelled.

Influencing Factors in the Breathing Rate

Concentration of Oxygen and Carbon Dioxide: Elevated levels of CO₂ stimulate an increased rate of breathing.

Physical Exercise: Elevates the need for oxygen, resulting in more rapid and deeper breathing.

Altitude: Decreased oxygen at high altitudes elevates the breathing rate.

Emotions and Stress: Stress and anxiety will change breathing patterns.

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Exchange of Gases

Gas exchange takes place as a result of partial pressure gradients. Oxygen moves from alveolar air into the bloodstream, and carbon dioxide moves from blood to alveoli. In the tissues, oxygen diffuses into the cells, and carbon dioxide into the bloodstream.

Transport of Oxygen by Hemoglobin

• 98% of oxygen is transported by hemoglobin in red blood cells.
• Hemoglobin combines with oxygen to produce oxyhemoglobin in the lungs and releases it at low-oxygen tissue sites.
• Oxygen dissociation depends on factors such as temperature, CO₂ concentration, and pH.

Transportation of Carbon Dioxide in Blood

Carbon dioxide is transported in three ways:

• Bicarbonate Ions (HCO₃⁻): (~70%) CO₂ combines with water to produce carbonic acid, which disintegrates into bicarbonate.
• Carbaminohemoglobin: (~20%) CO₂ combines with hemoglobin.
• Dissolved in Plasma: (~10%) CO₂ is dissolved directly in the blood plasma.

Respiratory Volumes and Capacities

Key Respiratory Volumes:

• Tidal Volume (TV): Air that passes in a normal breath (~500 mL).
• Inspiratory Reserve Volume (IRV): Additional air inhaled over normal inspiration (~2500–3000 mL).
• Expiratory Reserve Volume (ERV): Additional air exhaled over normal expiration (~1000–1100 mL).
• Residual Volume (RV): Air left in lungs following forced exhalation (~1100–1200 mL).

Lung Capacities:

• Vital Capacity (VC): Total air exhaled following deep inhalation (TV + IRV + ERV).
• Total Lung Capacity (TLC): Total capacity of air the lungs can hold (VC + RV).

Spirometry and Its Significance:

Spirometry is a diagnostic test for measuring lung volumes and capacities. Spirometry is utilized for diagnosing respiratory diseases such as asthma and COPD (Chronic Obstructive Pulmonary Disease).

Regulation of Respiration

Role of Respiratory Centers of the Brain:

Respiration is controlled by the medulla oblongata and pons in the brainstem.

• Medulla Oblongata: Regulates breathing rhythm and depth.
• Pons: Refines the process of breathing.

Chemical Control through CO₂ and O₂ Concentration in Blood:

• Increased CO₂: Activates respiratory centers to raise breathing rate.
• Decreased O₂: Can also cause increased breathing but less than CO₂.
• pH alterations: Acidosis (low pH) quickens the rate of breathing, whereas alkalosis (high pH) reduces it.

Disorders Related to the Respiratory System

Common Respiratory Disorders:

• Asthma: A chronic inflammatory disorder that brings about constriction of airways, making breathing cumbersome. Caused by allergens, cold temperature, or smog.
• Emphysema: Disorder in which alveoli are destroyed, decreasing the surface area for gas exchange. Usually due to smoking.
• Bronchitis: Bronchial inflammation that results in excess mucus production and cough.
• Pneumonia: Bacterial or viral infection that results in inflammation of the lungs and filling of alveoli with fluids.

Effect of Smoking and Pollution on Lung Function:

• Smoking: Raises the risk of lung cancer, emphysema, and chronic bronchitis by causing damage to lung tissues and decreasing oxygen transport efficiency.
• Air Pollution: Exposure to air pollutants such as carbon monoxide, sulfur dioxide, and particulate matter results in respiratory distress, enhanced asthma attacks, and decreased lung function over time.

Chapter-Wise NCERT Class 11 Notes Biology

The chapter Breathing and Exchange of Gases in NCERT Class 11 Biology emphasizes the importance of respiration in the maintenance of life. The proper operation of the respiratory system provides an uninterrupted supply of oxygen and aeration of waste products of metabolism. Knowledge about mechanisms of breathing, exchange of gases, and respiratory diseases may enable people to adopt preventive steps to keep the lungs healthy. A healthy life, non-smoking, and minimizing exposure to pollutants are most important for guaranteeing maximum respiratory efficiency.

Subject Wise NCERT Solutions

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