# Breathing and Exchange of Gases, Class 11 Biology | SwaVid Breathing and Exchange of Gases, NCERT Class 11 Biology: notes with key ideas, key terms, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/biology/chapter/breathing-and-exchange-of-gases Source: https://www.swavid.com/cbse/class-11/biology/chapter/breathing-and-exchange-of-gases # Breathing and Exchange of Gases ## Key terms ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Biology on SwaVid ### Respiratory organs and human tract ### Mechanism of breathing ### Respiratory volumes and capacities ### Exchange of gases ### Transport of gases ### Regulation and respiratory disorders ### Next chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Biology › Breathing and Exchange of Gases Notes written by SwaVid from the NCERT textbook. Class 11 Biology, Chapter 14. Key ideas, formulas and common mistakes. CBSE prints 18 marks for Unit V, not for this chapter alone. Short answer. This chapter covers the human respiratory system, the mechanism of pulmonary ventilation, and the exchange and transport of respiratory gases. It explains how partial pressure gradients drive oxygen and carbon dioxide diffusion and how neural mechanisms regulate respiration. Source: NCERT Biology (Reprint 2026-27) , Chapter 14, Breathing and Exchange of Gases Lower animals use simple diffusion, moist cuticle, or tracheal tubes, whereas aquatic forms use gills and terrestrial vertebrates use lungs. In humans, air enters through external nostrils, moves through the pharynx, larynx, trachea, bronchi, and bronchioles, and terminates in thin-walled, vascular alveoli. Inspiration occurs when diaphragm and external intercostal muscles contract, expanding thoracic volume and lowering intrapulmonary pressure below atmospheric levels. Expiration is passive during quiet breathing as these muscles relax, decreasing thoracic volume and raising intrapulmonary pressure. Spirometry records air volumes moving into and out of lungs. Specific combinations form functional capacities, such as vital capacity and total lung capacity, which are vital for clinical pulmonary assessment. Gases diffuse across the alveolar-capillary membrane based on concentration or partial pressure gradients. Factors affecting diffusion rate include the pressure gradient, gas solubility, and thickness of the diffusion membrane. About 97 percent of oxygen is carried by hemoglobin as oxyhemoglobin, and 3 percent dissolves in plasma. Carbon dioxide is transported as bicarbonate (nearly 70 percent), carbamino-hemoglobin (20 to 25 percent), and dissolved gas in plasma (about 7 percent). Respiration is regulated by the respiratory rhythm center in the medulla, modulated by a pneumotaxic center in the pons and chemosensitive areas responsive to CO2 and H+ ions. Major disorders include asthma, emphysema, and occupational respiratory disorders such as silicosis. Try each question first. Then tap it to see the answer. Vital capacity is the sum of ERV, TV, and IRV: VC = ERV + TV + IRV Substitute given values: VC = 1000 mL + 500 mL + 2500 mL = 4000 mL 4000 mL Functional residual capacity is given by FRC = ERV + RV Substitute the values: FRC = 1100 mL + 1200 mL = 2300 mL 2300 mL Every 100 mL of deoxygenated blood delivers 4 mL of CO2 to the alveoli. For 500 mL of blood: (500 / 100) × 4 mL = 5 × 4 mL = 20 mL 20 mL Body Fluids and Circulation . Neural Control and Coordination . The 19 chapters of Class 11 Biology . CBSE does not give marks to one chapter. It prints 18 marks for Unit V, Human Physiology, which includes Breathing and Exchange of Gases. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Body Fluids and Circulation. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 14 NCERT book - 18 marks, Unit V - 3 quick checks - Believing oxygen plays the primary regulatory role in the neural control of respiration . Oxygen concentration plays an insignificant role in regular respiratory rhythm. Chemosensitive receptors are stimulated predominantly by excess carbon dioxide and hydrogen ion concentrations. - Confusing functional residual capacity with residual volume . Residual volume is the air remaining after maximum forced expiration. Functional residual capacity is the volume remaining after a normal, quiet expiration (FRC = ERV + RV). - Assuming carbon dioxide is primarily transported bound to hemoglobin . Only 20 to 25 percent of carbon dioxide is carried as carbamino-hemoglobin. The majority, about 70 percent, is transported in the form of bicarbonate ions. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 11](https://www.swavid.com/cbse/class-11) - [Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup) - [All 19 chapters](https://www.swavid.com/cbse/class-11/biology/chapters) - [NCERT Biology (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/body-fluids-and-circulation) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/neural-control-and-coordination) - [Class 11 Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup)