Breathing and Exchange of Gases for NEET UG
Breathing moves air in and out; gas exchange moves oxygen into blood and carbon dioxide out. Learn the mechanics, the lung volumes and how blood carries both gases.
BiologyClass 1175 MCQs2 lessons12 flashcards3 memory tricks
Practise Breathing and Exchange of Gases free
What you'll learn
- Mechanism of breathing and lung volumes
Explain inspiration and expiration and calculate lung capacities. - Gas exchange and transport
Explain how O₂ and CO₂ are exchanged and carried, and read the oxygen dissociation curve.
Key formulas
| Vital capacity | VC = TV + IRV + ERV |
|---|---|
| Total lung capacity | TLC = VC + RV |
| Functional residual capacity | FRC = ERV + RV |
| Minute ventilation | TV × breathing rate (≈ 500 mL × 12–16 per min) |
Memory tricks
RV (1100–1200 mL) stays in the lungs even after a forceful exhalation. Tidal volume about 500 mL. Vital capacity = TV + IRV + ERV.
CO₂ up, Acid (H⁺ up, lower pH), 2,3-DPG up, Exercise, Temperature up: the curve shifts right and haemoglobin releases more O₂ to tissues.
About 70% as bicarbonate, 20–25% bound to haemoglobin as carbamino-haemoglobin, and about 7% dissolved in plasma.
Try 3 NEET-style questions
Q1. The diffusion membrane between the alveoli and blood is made of three major layers:
- pleura, pericardium and diaphragm
- cartilage, muscle and mucus
- thin squamous epithelium of alveoli, endothelium of capillaries, and the basement substance between them
- dura mater, arachnoid and pia mater
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Answer: (3) thin squamous epithelium of alveoli, endothelium of capillaries, and the basement substance between them
The diffusion membrane is made of the thin squamous epithelium of the alveoli, the endothelium of the alveolar capillaries, and the basement substance between them. Its total thickness is much less than a millimetre.
Q2. On average, a healthy human can inspire or expire about how much air per minute during quiet breathing?
- 500 mL
- 6000 to 8000 mL
- 50 to 60 mL
- 50,000 mL
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Answer: (2) 6000 to 8000 mL
With a tidal volume of about 500 mL and 12–16 breaths per minute, a healthy adult moves about 6000 to 8000 mL of air per minute.
Q3. About 70 per cent of the CO₂ carried in blood is transported as
- dissolved CO₂ in plasma
- carbaminohaemoglobin
- bicarbonate
- oxyhaemoglobin
Show answer
Answer: (3) bicarbonate
Nearly 70% of CO₂ is carried as bicarbonate, about 20–25% as carbaminohaemoglobin and about 7% dissolved in plasma.
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