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

NCERT Class 11 Biology Chapter 14 Notes: Download PDF

Breathing and Exchange of Gases is an important chapter that explains topics like respiratory volumes and the mechanism of breathing. The NCERT Class 11 Biology Chapter 14 Notes PDF provides a clear understanding along with labelled diagrams, and students can use it offline for quick revisions and last-minute preparation. The NCERT Notes for Class 11 Biology are perfect for performing well in exams in less time.

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Class 11 Biology Chapter 14 Breathing and Exchange of Gases Notes

The Breathing and Exchange of Gases chapter covers key topics like the human respiratory system, the mechanism of respiration, transport of respiratory gases, and lung capacities. Class 11 Biology chapter 14 notes are prepared by subject experts, following the NCERT guidelines, making it a valuable resource for quick revision during the exam.

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 the 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 contracts, 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 contract, 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. Students can solve these questions after studying the NCERT Class 11 Biology Chapter 14 Notes Breathing and Exchange of Gases.

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 pneumotaxic 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 the 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 correct 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 correct answer is option (4) Spirometer

Also Read:

• NCERT Solutions

• NCERT Solutions for Class 11

• NCERT Solutions for Class 11 Biology

How to Use Breathing and Exchange of Gases Class 11 Notes Effectively?

Breathing is the process through which living organisms take in oxygen and release carbon dioxide. This process is important for cellular respiration and energy production.

1. Study the structure and function of human respiratory organs like lungs, alveoli, and the diaphragm to understand the mechanics of breathing.

2. Use Class 11 Biology Chapter 14 Breathing and Exchange of Gases Notes to revise how oxygen and carbon dioxide are transported in the blood.

3. Draw and label diagrams of alveoli, trachea, and other structures to visualize the process clearly.

4. Refer to Class 11 Biology Chapter 14 Breathing and Exchange of Gases Notes to know about the environmental factors such as altitude, temperature, and humidity.

5. Practice previous year questions on breathing rate, oxygen transport, and carbon dioxide removal to strengthen understanding.

Chapter-Wise NCERT Class 11 Notes Biology

The table below includes notes for all chapters of Class 11 Biology, helping students revise efficiently and prepare well for school as well as competitive exams like NEET.