Quick answer: A breathing and exchange of gases NEET PYQ analysis shows that NTA asks about one to two questions a year from this chapter, and the single most repeated topic is respiratory volumes and capacities (asked in 2019, 2020, 2022, 2023, 2024 and 2026). The other repeated areas are the transport of O₂ and CO₂ with the oxygen dissociation curve, partial pressures, the mechanism of breathing, regulation of respiration, respiratory organs in different animals, and disorders such as asthma and emphysema.
This guide breaks down what NTA repeats, the tables to memorise and PYQ-pattern questions with answers. For the full Zoology physiology plan, see our human physiology guide for NEET.
Want to test yourself first? Solve the Breathing and Exchange of Gases PYQs for free, then use this guide to fix the gaps.
Table of Contents
Why This Chapter Is Reliable Marks
Breathing questions are mostly numbers: lung volumes in mL, partial pressures in mm Hg and transport percentages. Learn three tables and you can answer almost every past question. For chapter notes, use our Breathing chapter notes, and to see where it sits among other chapters, check the NEET 2027 chapter weightage.
Gas transport in blood links straight to our Body Fluids PYQ analysis, and respiratory organs in different animals come from our Animal Kingdom PYQ analysis. For a quick warm-up, try these five quick physiology questions.
Breathing and Exchange of Gases NEET PYQ Analysis: What NTA Repeats
When you sort the past NEET biology PYQs from this chapter, five question types cover nearly everything.
| Question type | Frequency | What it tests |
|---|---|---|
| Respiratory volumes and capacities | Most frequent | TV, IRV, ERV, RV and the capacities built from them |
| Transport of gases | Very frequent | O₂ and CO₂ transport percentages, oxygen dissociation curve, factors favouring oxyhaemoglobin |
| Exchange of gases | Regular | Partial pressures, diffusion membrane, solubility of CO₂ |
| Mechanism and regulation of breathing | Regular | Diaphragm and intercostal muscles, respiratory centres |
| Respiratory organs and disorders | Regular | Organs in different animals, asthma, emphysema, occupational disorders |
Respiratory Organs in Animals
| Animals | Respiratory organ or method |
|---|---|
| Sponges, coelenterates, flatworms | Simple diffusion over the whole body surface |
| Earthworms | Moist cuticle |
| Insects | Network of tracheal tubes |
| Most aquatic arthropods and molluscs | Gills (branchial respiration) |
| Fishes | Gills |
| Amphibians (frogs) | Lungs, and also through moist skin (cutaneous respiration) |
| Reptiles, birds, mammals | Lungs (pulmonary respiration) |
This table was asked twice in 2026.
The Human Respiratory System
The air path is: external nostrils → nasal chamber → pharynx (a common passage for food and air) → larynx (the sound box) → trachea → primary, secondary and tertiary bronchi → bronchioles → terminal bronchioles → alveoli.
- The trachea divides into the right and left primary bronchi at the level of the 5th thoracic vertebra.
- The trachea, bronchi and initial bronchioles are supported by incomplete cartilaginous rings.
- The epiglottis, a thin elastic cartilaginous flap, covers the glottis during swallowing so food does not enter the larynx.
- The lungs are covered by a double-layered pleura with pleural fluid between the layers, which reduces friction.
- The conducting part runs from the external nostrils to the terminal bronchioles; it carries, cleans, humidifies and warms the air. The respiratory or exchange part is the alveoli and their ducts.
The steps of respiration, asked in 2023 and 2026, are: breathing (pulmonary ventilation), diffusion of gases across the alveolar membrane, transport of gases by the blood, diffusion between blood and tissues, and use of O₂ by cells (cellular respiration).
Mechanism of Breathing
| Step | Muscles | Effect |
|---|---|---|
| Inspiration | Diaphragm contracts (increases volume front to back); external intercostal muscles contract and lift the ribs and sternum (increases volume top to bottom) | Lung pressure falls below atmospheric pressure, so air flows in |
| Expiration | Diaphragm and intercostal muscles relax; for forceful breathing, abdominal and internal intercostal muscles help | Lung pressure rises above atmospheric pressure, so air flows out |
A healthy adult breathes 12–16 times a minute. Breathing volumes are measured with a spirometer.
Respiratory Volumes and Capacities: The Most Tested Table
| Volume | Meaning | Value |
|---|---|---|
| Tidal volume (TV) | Air inspired or expired in a normal breath | About 500 mL (6000–8000 mL per minute) |
| Inspiratory reserve volume (IRV) | Extra air that can be inspired by a forcible inspiration | 2500–3000 mL |
| Expiratory reserve volume (ERV) | Extra air that can be expired by a forcible expiration | 1000–1100 mL |
| Residual volume (RV) | Air left in the lungs even after a forcible expiration | 1100–1200 mL |
| Capacity | Formula |
|---|---|
| Inspiratory capacity (IC) | TV + IRV |
| Expiratory capacity (EC) | TV + ERV |
| Functional residual capacity (FRC) | ERV + RV |
| Vital capacity (VC) | IRV + TV + ERV |
| Total lung capacity (TLC) | VC + RV |
Most questions give a few values and ask for a capacity, or ask which capacity includes the residual volume. Remember that only FRC and TLC include RV.
Exchange of Gases
| Gas | Atmospheric air | Alveoli | Deoxygenated blood | Oxygenated blood | Tissues |
|---|---|---|---|---|---|
| pO₂ (mm Hg) | 159 | 104 | 40 | 95 | 40 |
| pCO₂ (mm Hg) | 0.3 | 40 | 45 | 40 | 45 |
- Gases move from higher to lower partial pressure: O₂ from alveoli to blood to tissues, and CO₂ the other way.
- CO₂ is 20–25 times more soluble than O₂, so much more CO₂ diffuses per unit difference in partial pressure.
- The diffusion membrane has three layers: 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.
At high altitude, atmospheric pO₂ is lower, so less O₂ binds to haemoglobin in the lungs. This is the basis of altitude sickness, asked in 2023.
Transport of Gases
| Gas | How it is carried |
|---|---|
| O₂ | About 97% by RBCs as oxyhaemoglobin; about 3% dissolved in plasma |
| CO₂ | About 70% as bicarbonate; 20–25% by RBCs as carbamino-haemoglobin; about 7% dissolved in plasma |
- Each haemoglobin molecule can carry up to four O₂ molecules.
- The oxygen dissociation curve (percentage saturation of haemoglobin against pO₂) is sigmoid.
- Oxyhaemoglobin forms in the alveoli, where conditions are: high pO₂, low pCO₂, low H⁺ concentration (higher pH) and lower temperature. In the tissues, the opposite conditions make oxygen dissociate.
- Every 100 mL of oxygenated blood delivers about 5 mL of O₂ to the tissues, and every 100 mL of deoxygenated blood delivers about 4 mL of CO₂ to the alveoli.
- Carbonic anhydrase, found mainly in RBCs, speeds up CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺ in both directions.
The factors favouring oxyhaemoglobin formation were asked in 2024.
Regulation of Respiration
| Centre or receptor | Location | Role |
|---|---|---|
| Respiratory rhythm centre | Medulla | Mainly responsible for the rhythm of breathing |
| Pneumotaxic centre | Pons | Moderates the rhythm centre; can shorten inspiration and change the breathing rate |
| Chemosensitive area | Next to the rhythm centre | Highly sensitive to CO₂ and H⁺ |
| Receptors | Aortic arch and carotid artery | Detect changes in CO₂ and H⁺ |
The role of O₂ in regulating breathing is quite insignificant; CO₂ and H⁺ are the main signals.
Disorders of the Respiratory System
| Disorder | Feature |
|---|---|
| Asthma | Difficulty in breathing and wheezing, due to inflammation of the bronchi and bronchioles |
| Emphysema | Chronic disorder in which the alveolar walls are damaged, reducing the respiratory surface; cigarette smoking is a major cause |
| Occupational respiratory disorders | Long exposure to dust in grinding or stone-breaking causes inflammation and fibrosis of the lungs; workers should wear protective masks |
Worked PYQ-Pattern Questions
Q1. If TV = 500 mL, IRV = 2500 mL and ERV = 1000 mL, the vital capacity is: (a) 3000 mL (b) 3500 mL (c) 4000 mL (d) 5100 mL
Answer: (c) 4000 mL, because VC = IRV + TV + ERV.
Q2. Which of these capacities includes the residual volume? (a) Vital capacity (b) Inspiratory capacity (c) Functional residual capacity (d) Expiratory capacity
Answer: (c) Functional residual capacity (ERV + RV). Total lung capacity also includes RV.
Q3. What is the pO₂ of alveolar air?
Answer: About 104 mm Hg.
Q4. Most CO₂ is carried in the blood as:
Answer: Bicarbonate, about 70%.
Q5. Which conditions favour the formation of oxyhaemoglobin in the alveoli?
Answer: High pO₂, low pCO₂, low H⁺ concentration and lower temperature.
Q6. The pneumotaxic centre is located in the:
Answer: Pons. The rhythm centre is in the medulla.
Common Traps in This Chapter
- Including RV in vital capacity
- Writing 95 mm Hg as the alveolar pO₂ (that is oxygenated blood; alveoli are 104)
- Saying most CO₂ travels as carbamino-haemoglobin (most is bicarbonate)
- Saying high pCO₂ or high temperature favours oxyhaemoglobin formation
- Placing the pneumotaxic centre in the medulla
- Saying O₂ is the main chemical signal regulating breathing
Practise Every Breathing and Exchange of Gases PYQ
This breathing and exchange of gases NEET PYQ analysis shows you where the marks are. Solving real past questions makes the volumes and pressures automatic. Every previous year question from this chapter is available chapter-wise, free:
👉 Solve all Breathing and Exchange of Gases NEET PYQs
Keep the volumes, partial pressure and transport tables beside you for the first round, then solve the second round without them.
Conclusion
Breathing and Exchange of Gases is a chapter of numbers, and NTA keeps asking the same ones. Use this breathing and exchange of gases NEET PYQ analysis to master respiratory volumes and capacities, partial pressures, gas transport, the dissociation curve and regulation. Then practise the past questions until each value comes without thinking.
❓ FAQ
Q: How many questions come from Breathing and Exchange of Gases in NEET? A: Usually one to two questions a year, most often on respiratory volumes and capacities.
Q: What is the most important topic in this chapter for NEET? A: Respiratory volumes and capacities, asked in most recent years, followed by the transport of gases and the oxygen dissociation curve.
Q: What is the formula for vital capacity? A: Vital capacity = IRV + TV + ERV. It is the maximum air a person can breathe out after a forced inspiration.
Q: How is CO₂ transported in blood? A: About 70% as bicarbonate, 20–25% as carbamino-haemoglobin in RBCs and about 7% dissolved in plasma.
Q: Where is the respiratory rhythm centre? A: In the medulla. The pneumotaxic centre in the pons moderates it.
Q: Where can I practise Breathing and Exchange of Gases NEET PYQs for free? A: You can solve every previous year question from this chapter chapter-wise for free using the practice links in this article.
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Body Fluids and Circulation NEET PYQ Analysis: ECG, Cardiac Cycle and Blood
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