Class 11 Biology - WEST-BENGAL
Breathing and Exchange of Gases
The chapter 'Breathing and Exchange of Gases' in Class 11 Biology under WBBSE explores how living organisms obtain oxygen from the environment and release carbon dioxide. It covers the human respiratory system, the mechanics of pulmonary ventilation, the transport of oxygen and carbon dioxide through blood, and the regulation of respiration. Understanding this chapter is crucial for board exams as it bridges cellular metabolism with organ-level physiology, frequently featuring questions on respiratory volumes, oxygen-hemoglobin dissociation curves, and disorders like asthma and emphysema.
Start Learning FreeKey Concepts
Respiratory Organs
Different animals use different organs for breathing, such as skin and lungs in amphibians, tracheae in insects, and gills in aquatic animals, while humans possess a well-developed pair of lungs.
Mechanism of Breathing
Inspiration and expiration involve pressure gradients generated by the contraction and relaxation of the diaphragm and intercostal muscles, altering thoracic volume.
Exchange of Gases
Gas exchange occurs across the respiratory membrane in alveoli via simple diffusion, driven by partial pressure gradients of oxygen and carbon dioxide.
Transport of Gases
Oxygen is primarily transported bound to hemoglobin as oxyhemoglobin, whereas carbon dioxide is transported mainly as bicarbonate ions, dissolved in plasma, and bound to hemoglobin.
Regulation of Respiration
The respiratory rhythm center in the medulla oblongata primarily regulates breathing, with the pneumotaxic center in the pons moderating its functions based on blood CO2 and H+ concentrations.
Important Formulas
Board Exam Info
In the West Bengal Council of Higher Secondary Education (WBBSE) Class 11 Biology exams, this chapter typically carries around 5 to 7 marks. Questions usually include short answer types (SAQ) on respiratory volumes, descriptive 5-mark questions on the mechanism of breathing or transport of gases, and multiple-choice questions (MCQ) regarding respiratory disorders and partial pressures.
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 glucose is oxidized inside cells to release energy.
What is the partial pressure of O2 in atmospheric air compared to alveoli?
The partial pressure of oxygen in atmospheric air is about 159 mm Hg, while in the alveoli it is around 104 mm Hg, which facilitates the diffusion of oxygen into the blood.
Why does oxygen-hemoglobin dissociation curve shift to the right?
A right shift occurs under conditions of high temperature, high H+ concentration (lower pH), and high PCO2, which promotes the release of oxygen to active tissues (Bohr effect).
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