Breathing and Exchange of GasesNEET MCQs with solutions
Breathing and Exchange of Gases covers the respiratory organs of animals, the human respiratory system, the mechanics of breathing, lung volumes and how oxygen and carbon dioxide are exchanged and transported. NEET questions are number-heavy here: partial pressures, lung volumes and transport percentages.
- Class
- 11 Biology
- Free on this page
- 24 questions
- In the RankUp app
- 462 questions
- ELITE questions
- 46
- NCERT topics
- 7
Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Respiratory Organs
Respiration in fishes primarily occurs through:
Not quite — the answer is D.
Fishes use gills to extract dissolved O₂ from water. Gills have gill lamellae with rich capillary supply for efficient counter-current exchange. Lungs and trachea are terrestrial adaptations.
Q2Respiratory Organs
External nostrils in humans open into the:
Not quite — the answer is C.
External nostrils lead directly into the nasal chambers, which are lined with mucus and cilia for filtering, warming, and humidifying air. The nasal chamber then opens into the nasopharynx.
Q3Respiratory Organs
The double-layered membrane surrounding each lung is called the pleura. The fluid between its two layers primarily functions to:
Not quite — the answer is C.
Pleural fluid lubricates the two pleural layers (visceral and parietal), reducing friction during respiratory movements. The absence or accumulation of this fluid causes pleuritis or pleural effusion respectively.
Q4Human Respiratory System
The ciliated epithelium lining the nasal chamber primarily helps in:
Not quite — the answer is C.
Cilia beat rhythmically to move the mucus layer (with trapped dust and microbes) toward the pharynx for removal — a mechanism called mucociliary clearance. Warming is done by vascularised mucosa, not cilia directly.
Q5Human Respiratory System
Which structure marks the beginning of the respiratory zone in the human respiratory tract?
Not quite — the answer is B.
The respiratory zone begins at respiratory bronchioles, where alveolar outgrowths first appear enabling gas exchange. Terminal bronchioles are the last purely conducting structures — a distinction frequently tested in NEET.
Q6Human Respiratory System
In the bronchial tree, primary bronchi divide to form secondary bronchi, which further divide to form:
Not quite — the answer is C.
Primary bronchi → secondary (lobar) bronchi → tertiary (segmental) bronchi → bronchioles. Each tertiary bronchus supplies one bronchopulmonary segment. Bronchioles are formed after tertiary bronchi, not directly from secondary bronchi.
Q7Mechanism of Breathing
During inspiration, the ribs move in which direction?
Not quite — the answer is B.
External intercostal contraction pulls ribs upward and outward, increasing both the anteroposterior and lateral diameters of the thorax. Downward and inward rib movement occurs during expiration via internal intercostals.
Q8Mechanism of Breathing
The movement of air into and out of lungs is specifically termed:
Not quite — the answer is B.
Pulmonary ventilation refers specifically to the mechanical breathing movements (inspiration + expiration). External respiration is gas exchange at alveoli; internal respiration is gas exchange at tissues; cellular respiration is ATP production.
Q9Mechanism of Breathing
During forced inspiration, which accessory muscles are recruited in addition to the diaphragm and external intercostals?
Not quite — the answer is D.
During forced inspiration, sternocleidomastoid elevates the sternum and scalene muscles elevate the upper ribs — both further increase thoracic volume. Internal intercostals and abdominals are expiratory muscles, not inspiratory accessory muscles.
Q10Mechanism of Breathing
Forced expiration involves contraction of:
Not quite — the answer is B.
Forced expiration is active: internal intercostals pull ribs downward and inward; abdominal muscles compress abdominal viscera, pushing diaphragm up — both reduce thoracic volume forcefully. External intercostals are inspiratory muscles.
Q11Exchange of Gases
The partial pressure of carbon dioxide in deoxygenated blood reaching the lungs is approximately:
Not quite — the answer is D.
Venous (deoxygenated) blood entering the pulmonary capillaries carries PCO₂ of ~45 mm Hg. Option A (40 mm Hg) is alveolar PCO₂ — the gradient drives CO₂ out of blood into alveoli.
Q12Exchange of Gases
At the pulmonary capillaries, carbon dioxide diffuses from:
Not quite — the answer is D.
Pulmonary capillary blood carries PCO₂ ~45 mm Hg vs alveolar PCO₂ ~40 mm Hg. CO₂ therefore diffuses from blood → alveoli. Option A reverses the correct direction.
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Get RankUp on Google PlayQ13Exchange of Gases
CO₂ diffuses across the respiratory membrane approximately 20–25 times faster than O₂ despite a smaller partial pressure gradient. The primary reason is:
Not quite — the answer is D.
Diffusion rate is proportional to solubility of the gas. CO₂'s ~20–25× higher solubility in biological fluids compensates for its smaller pressure gradient (~5 mm Hg vs ~64 mm Hg for O₂), resulting in faster net diffusion. Options A and C are factually incorrect.
Q14Transport of Gases
Approximately what percentage of carbon dioxide is transported as bicarbonate ions in plasma?
Not quite — the answer is C.
~70% of CO₂ is transported as HCO₃⁻. CO₂ enters RBCs, is hydrated to H₂CO₃ by carbonic anhydrase, then dissociates to H⁺ + HCO₃⁻; HCO₃⁻ moves into plasma. Option D (97%) is O₂-Hb transport percentage — the classic cross-topic trap.
Q15Transport of Gases
During the chloride shift, as bicarbonate ions move out of the RBC into plasma, which ion moves inward to maintain electrochemical neutrality?
Not quite — the answer is B.
As HCO₃⁻ exits the RBC, Cl⁻ enters in exchange (antiport) to maintain electrochemical neutrality — this is the Hamburger shift or chloride shift. Option D (H⁺) is incorrect; H⁺ is buffered inside the RBC by deoxyhaemoglobin.
Q16Transport of Gases
Which of the following best explains why the oxygen-haemoglobin dissociation curve is sigmoid rather than hyperbolic?
Not quite — the answer is B.
Cooperative binding: binding of first O₂ to one subunit induces conformational change increasing affinity of remaining subunits. Option D describes negative cooperativity (which would give a hyperbolic curve, not sigmoid). Option A is false — Hb is not saturated at low PO₂.
Q17Transport of Gases
The Bohr effect refers to:
Not quite — the answer is B.
The Bohr effect: elevated CO₂ and H⁺ (lower pH) reduce Hb–O₂ affinity, promoting O₂ unloading at tissues. Option A reverses the relationship. Option D describes the chloride shift — a separate mechanism.
Q18Regulation of Respiration
The inspiratory centre sends motor impulses primarily to which muscles to initiate inhalation?
Not quite — the answer is D.
The inspiratory centre activates the diaphragm (primary muscle of inspiration) and external intercostal muscles, causing them to contract and expand the thoracic cavity. Internal intercostals are expiratory muscles. Bronchiolar smooth muscle is not directly controlled by the inspiratory centre.
Q19Regulation of Respiration
Which structure integrates signals from both central and peripheral chemoreceptors to adjust breathing rhythm?
Not quite — the answer is C.
The respiratory rhythm centre in the medulla oblongata integrates inputs from central chemoreceptors (local H⁺/CO₂ sensing) and signals relayed from peripheral chemoreceptors (carotid/aortic bodies) to modulate the rate and depth of breathing. The cerebellum coordinates movement but does not regulate respiration.
Q20Regulation of Respiration
Hyperventilation lowers arterial PCO₂. Which of the following correctly predicts the immediate consequence on respiratory drive?
Not quite — the answer is C.
Hyperventilation washes out CO₂, reducing arterial PCO₂ (hypocapnia). This lowers H⁺ in CSF, reducing stimulation of central chemoreceptors and depressing respiratory drive — a classic negative feedback mechanism. This is why forced hyperventilation can cause breath-hold extension (dangerous in swimmers).
Q21Respiratory Disorders
Pneumonia primarily affects alveoli. Which of the following correctly identifies the site of infection?
Not quite — the answer is C.
Pneumonia is an infection of the lung parenchyma, specifically the alveoli, where pathogens (bacterial, viral, or fungal) cause inflammatory exudate to accumulate. This consolidates lung tissue and impairs gas exchange. The trachea and bronchi may be transiently involved but are not the primary site.
Q22Respiratory Disorders
The bacterium responsible for the most common form of bacterial pneumonia is:
Not quite — the answer is A.
Streptococcus pneumoniae (pneumococcus) is the most common cause of community-acquired bacterial pneumonia as per NCERT context. Mycobacterium tuberculosis causes TB, not typical pneumonia. Staphylococcus and Klebsiella are less common and typically hospital-acquired.
Q23Respiratory Disorders
Asthma characteristically makes expiration more difficult than inspiration. Which mechanism explains this?
Not quite — the answer is B.
During asthma, narrowed bronchioles are further compressed by the positive pleural pressure generated during active expiration, worsening obstruction and causing the characteristic wheeze. During inspiration, negative pleural pressure slightly opens airways, making inhalation comparatively easier.
Q24Respiratory Disorders
Which disorder is caused by long-term inhalation of dust particles leading to pulmonary fibrosis and reduced diffusion capacity?
Not quite — the answer is C.
Pneumoconiosis (including silicosis, asbestosis, and coal worker's pneumoconiosis) results from chronic inhalation of mineral or organic dust. The particles trigger fibrotic scarring of lung tissue, thickening the diffusion pathway and reducing gas exchange capacity. Unlike emphysema, alveolar walls are replaced by scar tissue rather than destroyed.
ELITE question · AIR under 50 level
This chapter has 46 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appNumbers and facts to remember
Quick revision: most questions in this chapter test these facts.
| Topic | Key fact |
|---|---|
| Respiratory organs | Body surface (sponges, coelenterates, flatworms); moist cuticle (earthworm); tracheal tubes (insects); gills (most aquatic arthropods, molluscs); lungs (terrestrial animals); amphibians also breathe through skin |
| Airway | Nostrils → nasal chamber → pharynx → larynx → trachea → primary, secondary, tertiary bronchi → bronchioles → alveoli; incomplete cartilaginous rings support trachea and bronchi |
| Breathing rate | 12–16 breaths per minute in a healthy adult |
| Tidal volume | About 500 mL (6000–8000 mL per minute) |
| IRV / ERV / RV | 2500–3000 mL / 1000–1100 mL / 1100–1200 mL |
| Capacities | Vital capacity = ERV + TV + IRV; total lung capacity = VC + RV; FRC = ERV + RV |
| Partial pressures (mm Hg) | Alveoli: O₂ 104, CO₂ 40; deoxygenated blood: O₂ 40, CO₂ 45; oxygenated blood: O₂ 95, CO₂ 40; tissues: O₂ 40, CO₂ 45 |
| Solubility | CO₂ is 20–25 times more soluble than O₂ |
| O₂ transport | About 97% by RBCs as oxyhaemoglobin; about 3% dissolved in plasma |
| CO₂ transport | 20–25% as carbamino-haemoglobin; about 70% as bicarbonate; about 7% dissolved in plasma |
| Delivery | 100 mL oxygenated blood delivers about 5 mL O₂ to tissues; 100 mL deoxygenated blood delivers about 4 mL CO₂ to alveoli |
| Regulation | Respiratory rhythm centre in medulla; pneumotaxic centre in pons; chemosensitive area responds to CO₂ and H⁺ |
| Disorders | Asthma (inflamed bronchi and bronchioles); emphysema (damaged alveolar walls, mainly from smoking); occupational disorders cause lung fibrosis |
What the app covers in this chapter
462 questions in total, each with a detailed explanation.
| Respiratory Organs | 40 |
| Human Respiratory System | 40 |
| Mechanism of Breathing | 40 |
| Exchange of Gases | 20 |
| Transport of Gases | 40 |
| Regulation of Respiration | 40 |
| Respiratory Disorders | 40 |
| Mixed practice and chapter tests | 202 |
Questions students ask
Is Breathing and Exchange of Gases important for NEET?
Yes. It is a scoring Zoology chapter because most questions test fixed numbers — lung volumes, partial pressures and the percentages of O₂ and CO₂ transport — plus the regulation centres and disorders.
Which topics should I revise first?
Learn the lung volumes and capacities first, then the partial pressure table and the transport percentages (use the table on this page), and finish with regulation and disorders.
How many questions from this chapter are on RankUp?
The RankUp app has 462 questions on Breathing and Exchange of Gases, including 46 ELITE questions written for students aiming at AIR under 50. Every question has a detailed explanation.
Can I download these questions as a PDF?
Yes. The free PDF on this page has all 24 questions with the answer key and explanations. No signup is needed.
