NEET PREP | APRIL 2026
NEET UG 2027 — CHAPTER-WISE MCQ PRACTICE | BIOLOGY
• Subject: Biology (Class XI, Chapter 17)
• Expected questions: 3–4 per year from Breathing & Exchange of Gases
• Difficulty: Moderate to High
• NCERT Class: XI — Chapter 17
The human respiratory system is one of the highest-yield topics in NEET Biology. Every year, NTA asks 3–4 questions from NCERT Class 11 Chapter 17: Breathing and Exchange of Gases. This chapter covers the anatomy of respiratory organs, lung volumes and capacities, the mechanism of gas exchange, and the transport of oxygen and carbon dioxide in blood. This post gives you a complete concept review and 10 NEET-pattern MCQs to practice.
For structured coaching, see our NEET coaching program. Want to test yourself on a full paper? Try our free NEET mock test. Check the complete NEET syllabus for chapter-wise weightage.
1. Human Respiratory System — Organs and Structure
• Conducting zone: nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → terminal bronchioles
• Respiratory zone: respiratory bronchioles → alveolar ducts → alveolar sacs → alveoli
• ~300 million alveoli per lung; total surface area ~70 m²
• Alveolar walls: type I cells (squamous, thin) + type II cells (secrete surfactant)
• Diaphragm: primary muscle of inspiration (dome-shaped, contracts and flattens during inhalation)
The respiratory system in humans consists of the conducting zone (passageways that filter and warm air) and the respiratory zone (sites of gas exchange). The trachea divides into right and left primary bronchi, which branch further into secondary and tertiary bronchi, bronchioles, and finally terminal bronchioles. The actual gas exchange occurs only in the alveoli — tiny air sacs with extremely thin walls and rich capillary networks.
Surfactant (dipalmitoyl phosphatidylcholine), secreted by type II alveolar cells, reduces surface tension and prevents alveolar collapse.
2. Lung Volumes and Capacities — Complete Data Table
NEET frequently tests numerical values of lung volumes. Memorize these with a mnemonic:
TV (Tidal) → IRV (Inspiratory Reserve) → ERV (Expiratory Reserve) → RV (Residual) → VC (Vital Capacity) → FRC (Functional Residual Capacity) → IC (Inspiratory Capacity) → TLC (Total Lung Capacity)
| Parameter | Value (Adult) | Definition |
|---|---|---|
| Tidal Volume (TV) | 500 mL | Air breathed in/out in one normal breath |
| Inspiratory Reserve Volume (IRV) | 3000 mL | Extra air inhaled above tidal volume |
| Expiratory Reserve Volume (ERV) | 1100 mL | Extra air exhaled after tidal expiration |
| Residual Volume (RV) | 1200 mL | Air remaining after maximum expiration |
| Vital Capacity (VC) | 4600 mL | TV + IRV + ERV (max air moved) |
| Functional Residual Capacity (FRC) | 2300 mL | ERV + RV (air after quiet expiration) |
| Inspiratory Capacity (IC) | 3500 mL | TV + IRV |
| Total Lung Capacity (TLC) | 5800 mL | TV + IRV + ERV + RV (all air) |
3. Gas Exchange and Transport of O₂ and CO₂
Oxygen: Atmosphere: 159 | Alveolar air: 104 | Oxygenated blood: 95 | Deoxygenated blood: 40 | Tissues: 40
Carbon Dioxide: Atmosphere: 0.3 | Alveolar air: 40 | Oxygenated blood: 40 | Deoxygenated blood: 45 | Tissues: 45
Haemoglobin: 1 Hb molecule binds 4 O₂ molecules (cooperative binding)
Oxygen-Hb Dissociation Curve: Sigmoid (S-shaped) — shifts right with increased CO₂, H⁺, temperature (Bohr Effect)
Transport of CO₂ in blood:
- 70% — as bicarbonate ions (HCO₃⁻) in plasma (via chloride shift)
- 23% — as carbaminohaemoglobin (CO₂ bound to Hb)
- 7% — dissolved in plasma
The enzyme carbonic anhydrase in RBCs catalyzes: CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻. This reaction is reversible and crucial for CO₂ transport and blood pH regulation.
• Vital Capacity is REDUCED in obstructive lung diseases (asthma, COPD)
• RV cannot be measured by spirometry (spirometer measures TV, IRV, ERV only)
• Dead space volume = ~150 mL (air in conducting zone that doesn’t participate in exchange)
• 2,3-BPG (bisphosphoglycerate) decreases Hb-O₂ affinity (shifts curve right)
• Fetal Hb (HbF) has HIGHER O₂ affinity than adult Hb
4. NEET 2027 — 10 MCQ Practice Questions
[cg_quiz data=”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”]
5. Frequently Asked Questions (FAQ)
Q1: What is the difference between breathing and respiration?
Breathing (pulmonary ventilation) is the physical process of inhaling and exhaling air. Respiration includes both breathing and cellular respiration — the biochemical process of energy production using O₂ inside cells.
Q2: Why can residual volume not be measured by a spirometer?
A spirometer only measures air that moves in and out of the lungs. Residual Volume (RV) remains permanently in the lungs and never passes through the spirometer mouthpiece. It requires body plethysmography or gas dilution techniques for measurement.
Q3: What is the Bohr Effect?
The Bohr Effect refers to the decreased affinity of haemoglobin for oxygen when CO₂ levels rise or pH falls (more acidic conditions). This facilitates O₂ release in metabolically active tissues where CO₂ production is high.
Q4: What is the significance of the sigmoid shape of the oxygen-haemoglobin dissociation curve?
The sigmoid (S-shape) reflects cooperative binding — once one O₂ binds to Hb, subsequent O₂ molecules bind more easily. This makes Hb an efficient O₂ loader in the lungs (high pO₂) and an efficient O₂ unloader in tissues (low pO₂).
Q5: What is the neural centre for regulation of breathing?
The respiratory rhythm centre is located in the medulla oblongata. The pneumotaxic centre in the pons moderates breathing rhythm. Chemoreceptors in the medulla are highly sensitive to CO₂/H⁺ levels, which are the primary stimulus for increased breathing rate.
Last Updated: April 2026