Breathing and Exchange of Gases — Class 11 Biology NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 11 Biology chapter "Breathing and Exchange of Gases" — 8 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 11 Biology chapter "Breathing and Exchange of Gases" — 8 important questions with detailed answers for CBS…

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Key Questions Covered:

  1. Define breathing. How is it different from cellular respiration?
  2. Describe the anatomy of the human respiratory system.
  3. Explain the process of inspiration and expiration.
  4. What are tidal volume, vital capacity, and residual volume?
  5. Describe gas exchange in the alveoli. What makes it efficient?
  6. How is oxygen transported in blood? Explain the role of hemoglobin.
  7. + 2 more questions in the full chapter

Solutions Summary:

Question Status
Define breathing. How is it different from cellular respi… ✓ Solved
Describe the anatomy of the human respiratory system. ✓ Solved
Explain the process of inspiration and expiration. ✓ Solved
What are tidal volume, vital capacity, and residual volume? ✓ Solved
Describe gas exchange in the alveoli. What makes it effic… ✓ Solved
How is oxygen transported in blood? Explain the role of h… ✓ Solved

Showing 6 of 8 questions

Q1: Define breathing. How is it different from cellular respiration?

Breathing is the physical process of taking in air (oxygen) into the lungs and removing air (containing CO2) from the lungs through ventilation. Cellular respiration is the biochemical process of oxidation of glucose in cells to release energy as ATP. Difference: Breathing is a mechanical process (lungs, diaphragm); cellular respiration is a chemical process (mitochondria). Breathing facilitates gas exchange; respiration consumes O2 and releases CO2.

Q2: Describe the anatomy of the human respiratory system.

Key components: 1. Nasal cavity: Filters, warms, and humidifies air 2. Pharynx: Common passage for air and food 3. Larynx: Voice box; contains vocal cords 4. Trachea: Windpipe; divides into two bronchi 5. Bronchi and bronchioles: Tubes that branch and narrow 6. Lungs: Two organs containing alveoli for gas exchange; right lung has 3 lobes, left has 2 lobes 7. Diaphragm: Dome-shaped muscle below lungs; primary breathing muscle 8. Intercostal muscles: Between ribs; assist in breathing

Q3: Explain the process of inspiration and expiration.

Inspiration (inhalation): - Diaphragm contracts and flattens (moves downward) - External intercostal muscles contract (rib cage moves up and out) - Thoracic cavity volume increases - Intrapulmonary pressure decreases below atmospheric pressure - Air flows into lungs Expiration (exhalation): - Diaphragm relaxes and returns to dome shape (moves upward) - External intercostal muscles relax - Thoracic cavity volume decreases - Intrapulmonary pressure increases above atmospheric - Air flows out of lu...

Q4: What are tidal volume, vital capacity, and residual volume?

Tidal volume: Volume of air breathed in or out during normal quiet breathing (~500 mL in adults). Vital capacity: Maximum volume of air that can be exhaled after maximum inhalation (~3500-4500 mL). Calculated as inspiratory reserve + tidal volume + expiratory reserve. Residual volume: Volume of air remaining in lungs after maximum expiration (~1100-1200 mL); cannot be expelled. Total lung capacity = Vital capacity + Residual volume (~5500-6000 mL) These measurements are important in assessing re...

Q5: Describe gas exchange in the alveoli. What makes it efficient?

Gas exchange occurs across the alveolar wall between alveolar air and blood in the pulmonary capillaries. Process: O2 diffuses from alveolar air (high pO2) into blood; CO2 diffuses from blood (high pCO2) into alveolar air. Factors making it efficient: 1. Large surface area: ~70 m² provided by millions of alveoli 2. Thin alveolar wall: Allows rapid diffusion 3. Rich blood supply: Extensive capillary network ensures constant removal of CO2 and supply of O2 4. Concentration gradient: Maintained by ...

Q6: How is oxygen transported in blood? Explain the role of hemoglobin.

Oxygen transport: 1. ~97% bound to hemoglobin: O2 + Hb ↔ HbO2 (oxyhemoglobin); transport from lungs to tissues 2. ~3% dissolved in plasma (minor) Hemoglobin (Hb) is a protein in RBCs with 4 subunits, each containing heme with iron (Fe2+) that binds O2. Oxygen affinity of hemoglobin is affected by: - pO2 (higher pO2, higher affinity) - pCO2 (higher pCO2, lower affinity - Bohr effect) - pH (lower pH, lower affinity) - Temperature (higher temperature, lower affinity) At tissues (high pCO2, low pH, ...

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