NCERT Exemplar Solutions for Class 11 Biology Chapter 17 Breathing and Exchange of Gases
The NCERT Exemplar Solutions for Class 11 Biology Chapter 17, Breathing and Exchange of Gases, focus on how humans and other organisms exchange oxygen and carbon dioxide for survival. This chapter covers the structure of the respiratory system, breathing mechanisms, the exchange of gases, the transport of gases in the blood, and the regulation of respiration. It also includes important respiratory disorders. The NCERT Exemplar questions for this chapter are designed to enhance conceptual clarity and provide practice for application-based learning, making them valuable for board preparation and exams like NEET.
The chapter begins with the human respiratory system, which consists of the nostrils, pharynx, larynx, trachea, bronchi, and lungs. The lungs contain alveoli, which serve as the primary sites of gaseous exchange. Exemplar questions often involve labeling diagrams of the respiratory system and explaining how the alveolar structure facilitates efficient gas diffusion. Next, the chapter explains the mechanism of breathing, which includes inspiration and expiration. Inspiration occurs due to the contraction of the diaphragm and external intercostal muscles, leading to the expansion of the thoracic cavity. Expiration is usually passive, caused by relaxation of these muscles. Exemplar questions often ask about the pressure changes in the thoracic cavity during breathing and how these changes drive airflow. The process of exchange of gases is explained in two stages: external respiration (exchange between alveoli and blood) and internal respiration (exchange between blood and tissues). Oxygen diffuses into the blood due to its higher concentration in alveoli, while carbon dioxide diffuses in the opposite direction. Exemplar questions test the concept of partial pressure gradients and diffusion efficiency.
The chapter also emphasizes the transport of gases in the blood. Oxygen is primarily transported by hemoglobin as oxyhemoglobin, while carbon dioxide is transported in three forms: dissolved in plasma, as carbaminohemoglobin, and as bicarbonate ions. Exemplar problems often include graphical interpretation of the oxygen dissociation curve and reasoning questions on the Bohr effect and Haldane effect. Regulation of respiration is controlled by the respiratory centers in the medulla oblongata and pons, which respond to chemical stimuli like CO2 concentration, oxygen levels, and blood pH. Exemplar questions in this section often focus on the role of chemoreceptors and feedback mechanisms that maintain respiratory rhythm. The chapter concludes with respiratory disorders such as asthma, emphysema, occupational lung diseases, and hypoxia. Exemplar questions may involve analyzing causes, symptoms, and preventive measures for these disorders. These problem types help students connect theoretical knowledge with real-life applications. To prepare thoroughly, students should review diagrams of alveoli, oxygen dissociation curves, and breathing mechanisms given in the NCERT textbook. Solving NCERT Exemplar questions allows learners to master theoretical aspects as well as application-based reasoning, ensuring better performance in exams. In summary, NCERT Exemplar Solutions for Class 11 Biology Chapter 17 Breathing and Exchange of Gases provide a detailed understanding of human respiratory physiology. By practicing Exemplar problems, students strengthen their analytical skills, build confidence, and develop a solid foundation for advanced biology and competitive exams.