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

Did you know that breathing is a continuous process that happens automatically, even when you're asleep? The NCERT Notes for Class 11 Biology Chapter 14 are written in simple and easy language. This helps students understand the concepts quickly without any confusion. These notes include important diagrams and cover all key points of the chapter. This chapter includes topics like how we breathe, the role of lungs, respiratory volumes and capacities, and disorders of the respiratory system. These NCERT notes are very useful for quick revision before school exams and for competitive exams like NEET.

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1. Download NCERT Notes for Class 11 Chapter 14 PDF
2. NCERT Notes for Class 11 Chapter 14
3. Chapter 14 Biology: Previous Year Questions and Answers
4. Chapter-Wise NCERT Class 11 Notes Biology

The NCERT Notes for Class 11 Biology help students build a strong foundation for higher classes by covering all concepts. Knowing respiration is important to understand how oxygen supports cellular processes and metabolic activities. This chapter also discusses the role of hemoglobin in the transport of oxygen and the mechanisms of elimination of carbon dioxide. The NCERT Notes for Class 11 are great for doing regular practice, helping students revise important topics. This approach boosts their confidence during exams.

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

Download NCERT Notes for Class 11 Chapter 14 PDF

Breathing and Exchange of Gases is an important chapter that covers topics like respiratory volumes, the mechanism of breathing, and gas exchange in humans. The PDF notes provide a clear understanding of these concepts along with labelled diagrams. Students can download the PDF easily and use it offline for quick revisions, last-minute preparation.

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NCERT Notes for Class 11 Chapter 14

These notes cover key topics like the human respiratory system and the mechanism of respiration. They also explain the exchange of gases simply. Important concepts like transport of respiratory gases and lung capacities are included. These notes are useful for quick revision during exam and help in understanding complex topics easily.

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): The larynx 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.

Mechanism of Breathing

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

Process of Inhalation and Exhalation

Inhalation: The diaphragm gets contracted, the 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, the 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 less, 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.

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, diffusion of oxygen occurs 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.

• The oxygen dissociation curve 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

The regulation of respiration is done 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: It is a respiratory system 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: A Bacterial or viral infection that results in inflammation of the lungs and filling of alveoli with fluid.

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, which leads to lung diseases.

Also, Read

• NCERT Notes for Class 11 Physics
• NCERT Notes for Class 11 Chemistry
• NCERT Notes for Class 11 Mathematics

Chapter 14 Biology: Previous Year Questions and Answers

Going through the previous year's questions provided below allows students to test their knowledge and get familiar with the type of questions asked in exams.

Question 1: The respiratory process is regulated by certain specialised centres in the brain. One of the following listed centres can reduce the inspiratory duration upon stimulation

Option 1. Medullary inspiratory centre

Option 2. Pneumotaxic centre

Option 3. Apneustic centre

Option 4. Chemosensitive centre

Answer:

Inspiration is the process of breathing in oxygen-rich air. The lungs' volume increases during inspiration as a result of the diaphragm being flat and the ribs being drawn higher and outward. To control inspiratory volume and respiratory rate, the pneumatic centre, which is situated in the upper pons, sends inhibitory impulses to the inspiratory centre, stopping inspiration. The fine-tuning of respiration most certainly involves this region.

Hence, the correct answer is Option (2), Pneumotaxic centre.

Question 2: The oxygen-haemoglobin dissociation curve will show a right shift in case of

Option 1. High pCO₂

Option 2. High pO₂

Option 3. Low pCO₂

Option 4. Less H⁺ concentration

Answer:

The curve of oxygen and haemoglobin is shifted to the right when the pO₂ decreases, pCO₂ increases, the concentration of H⁺ increases, pH decreases, and body temperature increases. This rightward shift of the oxygen-hemoglobin dissociation curve is known as the Bohr effect, facilitating oxygen release to tissues during high metabolic activity. Such changes are crucial for meeting the oxygen needs of active tissues like muscles during exercise.

Hence, the answer is option (1), High pCO₂

Question 3: In breathing movements, air volume can be estimated by

Option 1. Stethoscope

Option 2. Hygrometer

Option 3. Sphygmomanometer

Option 4. Spirometer

Answer:

A spirometer is used to estimate the breathing volumes. A spirometer is a medical device that measures the volume of air exchanged during breathing. It helps estimate various lung capacities and is essential for assessing respiratory health and function.

Hence, the answer is option (4) Spirometer

Also Read:

• NCERT Solution

• NCERT Solutions for Class 11

• NCERT Solutions for Class 11 Biology

Chapter-Wise NCERT Class 11 Notes Biology

Here are the links to the notes for each chapter that help students in their Biology revision.