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Breathing and Exchange of Gases — NEET Biology MCQs with Solutions
Free NEET Biology Breathing and Exchange of Gases MCQs with step-by-step solutions covering Respiratory Organs & Human System, Mechanism of Breathing, Respiratory Volumes & Capacities, Exchange & Transport of Gases, Regulation of Respiration, Respiratory Disorders. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Respiratory Organs & Human System · easy · theory
The functional units of the lung where gas exchange occurs are the:
A. Alveoli ✓ Correct
B. Bronchi
C. Trachea
D. Larynx
Solution: Alveoli are thin-walled, vascularised sacs where diffusion of O₂ and CO₂ takes place.
Q2 — Respiratory Organs & Human System · easy · theory
The organ commonly called the voice box, located at the beginning of the trachea, is the:
A. Epiglottis
B. Pharynx
C. Bronchus
D. Larynx ✓ Correct
Solution: The larynx (voice box) helps in sound production; the epiglottis covers it during swallowing.
Q3 — Mechanism of Breathing · easy · theory
Inspiration (breathing in) occurs when the pressure inside the lungs (intra-pulmonary pressure) becomes:
A. Equal to atmospheric pressure
B. Less than atmospheric pressure ✓ Correct
C. Greater than atmospheric pressure
D. Zero
Solution: A drop in intrapulmonary pressure below atmospheric draws air into the lungs (inspiration).
Q4 — Mechanism of Breathing · easy · theory
During inspiration, the diaphragm ______ and the external intercostal muscles ______:
A. Relaxes; contract
B. Contracts (flattens); contract ✓ Correct
C. Contracts; relax
D. Relaxes; relax
Solution: Contraction of the diaphragm and external intercostals increases thoracic volume, lowering pressure for inspiration.
Q5 — Respiratory Volumes & Capacities · easy · theory
The volume of air inspired or expired during a normal quiet breath (about 500 mL) is the:
A. Vital capacity
B. Residual volume
C. Tidal volume (TV) ✓ Correct
D. Inspiratory reserve volume
Solution: Tidal volume (~500 mL) is the air moved per normal breath.
Q6 — Respiratory Volumes & Capacities · easy · theory
The volume of air remaining in the lungs even after a forcible expiration is the:
A. Inspiratory reserve volume
B. Residual volume (RV) ✓ Correct
C. Tidal volume
D. Expiratory reserve volume
Solution: Residual volume (~1100–1200 mL) cannot be expelled and keeps the alveoli inflated.
Q7 — Exchange & Transport of Gases · easy · theory
The gas transported mainly as oxyhaemoglobin in the blood is:
A. Carbon monoxide
B. Carbon dioxide
C. Oxygen ✓ Correct
D. Nitrogen
Solution: O₂ binds reversibly to the iron of haemoglobin, forming oxyhaemoglobin (about 97% of O₂ transport).
Q8 — Exchange & Transport of Gases · easy · theory
The major form (about 70%) in which CO₂ is transported in the blood is:
A. As carbaminohaemoglobin
B. Dissolved in plasma
C. As carbonic acid gas
D. As bicarbonate ions (HCO₃⁻) ✓ Correct
Solution: Around 70% of CO₂ travels as bicarbonate; ~20–25% as carbamino-haemoglobin and ~7% dissolved.
Q9 — Respiratory Disorders · easy · theory
The occupational disease caused by inhalation of silica dust (e.g. in stone-grinding) leading to lung fibrosis is:
A. Pneumonia
B. Silicosis ✓ Correct
C. Asthma
D. Emphysema
Solution: Silicosis (and asbestosis) are occupational lung fibroses caused by inhaling fine mineral dust.
Q10 — Respiratory Disorders · easy · theory
Difficulty in breathing due to inflammation of the bronchi and bronchioles, with wheezing, is characteristic of:
A. Emphysema
B. Silicosis
C. Asthma ✓ Correct
D. Pleurisy
Solution: Asthma involves spasm/inflammation of the bronchi and bronchioles, causing difficulty in breathing.
Q11 — Respiratory Organs & Human System · easy · numerical
In which group of animals is a branching network of air-filled tracheal tubes the chief respiratory structure that carries air directly to the body tissues?
A. Amphibians
B. Bony fishes
C. Insects ✓ Correct
D. Mammals
Solution: Insects have a tracheal system that delivers air (and O₂) directly to tissues through tracheoles, so they do not depend on blood for O₂ transport.
Q12 — Respiratory Organs & Human System · easy · numerical
A frog can supplement its pulmonary breathing by exchanging gases across its:
A. gills
B. moist, vascular skin ✓ Correct
C. tracheae
D. air sacs
Solution: In amphibians such as frogs the thin, moist and richly vascularised skin permits cutaneous respiration in addition to lung breathing.
Q13 — Respiratory Organs & Human System · easy · numerical
The human trachea is prevented from collapsing during breathing by:
A. complete rings of bone
B. closely packed alveoli
C. incomplete, C-shaped cartilaginous rings in its wall ✓ Correct
D. a thick layer of smooth muscle only
Solution: The trachea is supported by incomplete (C-shaped) cartilaginous rings that keep the airway open while allowing the oesophagus behind it to expand.
Q14 — Respiratory Organs & Human System · easy · numerical
Fishes carry out exchange of gases with the surrounding water mainly through their:
A. moist skin
B. lungs
C. gills ✓ Correct
D. tracheae
Solution: Aquatic animals like fishes use gills, whose vascularised filaments extract dissolved oxygen from water.
Q15 — Mechanism of Breathing · easy · numerical
On average, a healthy adult human being breathes about how many times per minute?
A. 60 to 72 times
B. 12 to 16 times ✓ Correct
C. 4 to 6 times
D. 30 to 40 times
Solution: A normal healthy adult takes roughly 12-16 breaths per minute at rest.
Q16 — Mechanism of Breathing · easy · numerical
When the diaphragm contracts during inspiration, its dome:
A. becomes more dome-shaped, reducing thoracic volume
B. moves sideways without changing volume
C. flattens, increasing the volume of the thoracic cavity ✓ Correct
D. stays fixed while the ribs alone move
Solution: Contraction flattens the normally dome-shaped diaphragm, enlarging the thoracic chamber in the antero-posterior axis and aiding inspiration.
Q17 — Mechanism of Breathing · easy · numerical
The pneumotaxic centre, which can moderate the activity of the respiratory rhythm centre, is located in the:
A. medulla oblongata
B. cerebellum
C. pons region of the brain ✓ Correct
D. hypothalamus
Solution: The pneumotaxic centre lies in the pons and can reduce the duration of inspiration, thereby altering the breathing rate.
Q18 — Mechanism of Breathing · easy · numerical
A forceful (active) expiration, unlike quiet expiration, additionally involves contraction of the:
A. diaphragm and external intercostal muscles
B. pneumotaxic centre and the pons
C. internal intercostal muscles and abdominal muscles ✓ Correct
D. walls of the alveoli
Solution: Normal expiration is passive, but a forced expiration recruits the internal intercostals and abdominal muscles to push more air out.
Q19 — Respiratory Volumes & Capacities · easy · numerical
The additional volume of air a person can inspire by a forcible inspiration, over and above the normal tidal volume, is called the:
A. Expiratory Reserve Volume
B. Residual Volume
C. Inspiratory Reserve Volume ✓ Correct
D. Tidal Volume
Solution: Inspiratory Reserve Volume (IRV, about 2500-3000 mL) is the extra air breathed in by a forced inspiration beyond a normal tidal inspiration.
Q20 — Respiratory Volumes & Capacities · easy · numerical
The additional volume of air that can be breathed out by a forcible expiration after a normal expiration is the:
A. Residual Volume
B. Inspiratory Reserve Volume
C. Vital Capacity
D. Expiratory Reserve Volume ✓ Correct
Solution: Expiratory Reserve Volume (ERV, about 1000-1100 mL) is the extra air forcibly exhaled beyond a normal (tidal) expiration.
Q21 — Respiratory Volumes & Capacities · easy · numerical
Expiratory Capacity (EC) is the total volume of air a person can expire after a normal inspiration. If tidal volume is 500 mL and expiratory reserve volume is 1000 mL, EC equals:
A. 2500 mL
B. 1000 mL
C. 1500 mL ✓ Correct
D. 500 mL
Solution: EC = TV + ERV = 500 + 1000 = 1500 mL.
Q22 — Respiratory Volumes & Capacities · easy · numerical
The total lung capacity of a normal adult human is approximately:
A. 1200 mL
B. 3000 mL
C. 6000 mL ✓ Correct
D. 500 mL
Solution: Total Lung Capacity (VC + RV) is about 6000 mL, the total air the lungs can hold after a maximum inspiration.
Q23 — Exchange & Transport of Gases · easy · numerical
The partial pressure of oxygen (pO₂) in the alveolar air is approximately:
A. 95 mm Hg
B. 159 mm Hg
C. 104 mm Hg ✓ Correct
D. 40 mm Hg
Solution: Alveolar pO₂ is about 104 mm Hg, higher than the pO₂ of deoxygenated blood (40 mm Hg), so O₂ diffuses from alveoli into blood.
Q24 — Exchange & Transport of Gases · easy · numerical
The approximate percentage of carbon dioxide transported in a dissolved state through the plasma is about:
A. 7% ✓ Correct
B. 97%
C. 70%
D. 23%
Solution: Only about 7% of CO₂ is carried dissolved in plasma; roughly 70% travels as bicarbonate and 20-25% as carbamino-haemoglobin.
Q25 — Exchange & Transport of Gases · easy · numerical
In the blood, oxygen binds to haemoglobin at the:
A. globin protein chains, each binding one O₂ molecule
B. plasma proteins surrounding the red blood cell
C. phospholipid membrane of the erythrocyte
D. iron-containing haem groups, each haemoglobin binding up to four O₂ molecules ✓ Correct
Solution: Each haemoglobin has four haem groups, each with an iron atom that can bind one O₂, so one haemoglobin carries up to four oxygen molecules as oxyhaemoglobin.
Q26 — Exchange & Transport of Gases · easy · numerical
The diffusion membrane across which gases are exchanged in the alveoli consists of three layers: the thin squamous epithelium of the alveoli, the endothelium of the alveolar capillaries, and:
A. the basement substance lying between them ✓ Correct
B. a ring of cartilage
C. a sheet of ciliated columnar cells
D. a thick layer of smooth muscle
Solution: The respiratory (diffusion) membrane is made of the alveolar squamous epithelium, the capillary endothelium and the basement substance in between, keeping the barrier very thin.
Q27 — Respiratory Disorders · easy · numerical
Long-term occupational inhalation of asbestos fibres leads to a fibrotic lung disease known as:
A. emphysema
B. asthma
C. asbestosis ✓ Correct
D. silicosis
Solution: Asbestosis is an occupational respiratory disorder caused by chronic exposure to asbestos dust, leading to fibrosis of the lungs.
Q28 — Respiratory Disorders · easy · numerical
The single most important cause of emphysema is:
A. inhalation of silica dust
B. a pollen allergy
C. a bacterial lung infection
D. cigarette smoking ✓ Correct
Solution: Chronic cigarette smoking is the major cause of emphysema, in which the alveolar walls are damaged and the respiratory surface is greatly reduced.
Q29 — Respiratory Disorders · easy · numerical
Occupational respiratory disorders are most common among workers engaged in industries that:
A. generate large amounts of dust, such as grinding and stone-breaking ✓ Correct
B. work mainly in air-conditioned offices
C. handle only liquids and never dust
D. work exclusively underwater
Solution: Prolonged exposure to airborne dust in industries like grinding and stone-breaking causes occupational lung disorders such as silicosis and asbestosis.
Q30 — Respiratory Disorders · easy · numerical
To minimise occupational respiratory disorders, workers in dusty industries are advised to:
A. use protective masks and follow prescribed safety measures ✓ Correct
B. work only at night
C. avoid drinking water during work
D. breathe more rapidly to expel the dust
Solution: Wearing protective masks and observing safety norms limits the amount of dust reaching the lungs, reducing the risk of fibrosis and other disorders.