Cheat sheet · Class 11 · CBSE · Science Biology
Breathing and Exchange of Gases cheat sheet
The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.
CBSE Class 11 · Biology
Cheat sheet
Chapter 14Breathing and Exchange of Gases
Air path: nose → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.
1. Mechanism
- Inspiration: diaphragm contracts, ribs up → volume ↑, pressure ↓.
- Expiration: muscles relax → volume ↓.
2. Respiratory Volumes
| Volume | Value |
|---|---|
| Tidal volume | ≈ 500 mL |
| Inspiratory reserve | 2500–3000 mL |
| Expiratory reserve | 1000–1100 mL |
| Residual volume | 1100–1200 mL |
| Vital capacity | ERV + TV + IRV |
| Total lung capacity | VC + RV |
3. Gas Transport
- O₂: 97% as oxyhaemoglobin, 3% dissolved.
- CO₂: 70% as bicarbonate, 20–25% as carbaminohaemoglobin, 7% dissolved.
- Carbonic anhydrase speeds CO₂ + H₂O ⇌ H₂CO₃.
- O₂ dissociation curve is sigmoid; shifts right with high CO₂, H⁺, temperature.
4. Disorders
- Asthma: bronchi inflamed.
- Emphysema: alveolar walls damaged (smoking).
- Occupational: fibrosis from dust.
5. Key Points
- Respiratory rhythm centre: medulla.
- pO₂ alveoli ≈ 104 mm Hg.
- Each 100 mL blood delivers ~5 mL O₂ to tissues.
- Diffusion membrane is very thin.
Remember: Breathing mechanics | volumes | O₂ & CO₂ transport
Breathing and Exchange of Gases: questions and notes
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