Class 11 Biology - ISC
Breathing and Exchange of Gases
The chapter 'Breathing and Exchange of Gases' in Class 11 ISC Biology explores how living organisms obtain oxygen from the environment and release carbon dioxide. You will study the human respiratory system, the exact mechanism of breathing involving the diaphragm and intercostal muscles, and how gases are exchanged at the alveolar and tissue levels. It covers the transport of oxygen and carbon dioxide in the blood, emphasizing the role of hemoglobin and the oxygen-hemoglobin dissociation curve. Additionally, the chapter addresses the regulation of respiration by neural centers and common respiratory disorders like asthma, emphysema, and occupational lung diseases, which are high-yield topics for board exams.
Start Learning FreeKey Concepts
Respiratory Organs
Different animals use distinct organs for respiration based on their habitats, such as skin and moist cuticle in earthworms, tracheae in insects, gills in aquatic animals, and lungs in terrestrial vertebrates like humans.
Mechanism of Breathing
Inspiration and expiration occur by creating a pressure gradient between the lungs and the atmosphere, facilitated by the contraction and relaxation of the diaphragm and external/internal intercostal muscles.
Exchange of Gases
Gas exchange takes place across the respiratory membrane of alveoli primarily by simple diffusion, driven by partial pressure gradients of oxygen and carbon dioxide between alveoli, blood, and tissues.
Transport of Gases
Oxygen is primarily transported bound to hemoglobin as oxyhemoglobin (about 97%), while carbon dioxide is transported mainly as bicarbonates (about 70%), dissolved in plasma (7-8%), and as carbaminohemoglobin (20-23%).
Regulation of Respiration
Respiratory rhythm is primarily maintained by the respiratory rhythm center in the medulla oblongata, with the pneumotaxic center in the pons moderating its functions, alongside peripheral chemoreceptors sensitive to CO2 and H+ concentrations.
Important Formulas
Board Exam Info
In the ISC Class 11 Biology examinations, this chapter typically carries around 5 to 7 marks. Questions frequently appear as diagram-based identification of the human respiratory system, explanations of the oxygen-hemoglobin dissociation curve, calculation-based numericals on lung capacities and volumes, and short notes on respiratory disorders like asthma and occupational lung diseases.
Frequently Asked Questions
What is the difference between breathing and respiration?
Breathing is a physical process of inhaling oxygen and exhaling carbon dioxide, whereas respiration is a biochemical process where nutrients are broken down inside cells to release energy in the form of ATP.
Why does the oxygen-hemoglobin dissociation curve shift to the right?
A shift to the right occurs due to factors like increased temperature, increased hydrogen ion concentration (lower pH), and higher partial pressure of carbon dioxide, which decreases hemoglobin's affinity for oxygen and facilitates its release to active tissues (Bohr effect).
What is Residual Volume and why is it important?
Residual Volume is the air that remains trapped in the lungs even after a forceful expiration. It is important because it prevents the lungs from collapsing and ensures a continuous exchange of gases even between breaths.
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