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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, 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 · hard · theory
The double-membrane pleura around the lungs, with pleural fluid between its layers, functions to:
A. Exchange gases
B. Reduce friction and allow smooth lung movement during breathing ✓ Correct
C. Store air
D. Produce mucus for digestion
Solution: Pleural fluid lubricates the lung surface, minimising friction against the thoracic wall during breathing.
Q12 — Respiratory Organs & Human System · hard · theory
Which sequence correctly traces air from outside to the site of gas exchange?
A. Trachea → bronchi → pharynx → alveoli
B. Nostrils → pharynx → larynx → trachea → bronchi → bronchioles → alveoli ✓ Correct
C. Nostrils → larynx → pharynx → bronchi → alveoli → trachea
D. Nostrils → trachea → pharynx → alveoli
Solution: Air passes: external nostrils → nasal chamber → pharynx → larynx → trachea → primary bronchi → bronchioles → alveoli.
Q13 — Mechanism of Breathing · hard · theory
The respiratory rhythm centre that controls breathing is located in the:
A. Hypothalamus
B. Medulla oblongata ✓ Correct
C. Cerebellum
D. Cerebrum
Solution: The medulla houses the respiratory rhythm centre; a pneumotaxic centre in the pons can moderate it.
Q14 — Mechanism of Breathing · hard · theory
A rise in CO₂ and H⁺ concentration in the blood is sensed by chemosensitive areas that then:
A. Have no effect
B. Stop breathing
C. Decrease the breathing rate
D. Signal the rhythm centre to increase the rate and depth of breathing ✓ Correct
Solution: CO₂/H⁺ (not O₂ primarily) are the main regulators; their rise stimulates faster, deeper breathing to expel CO₂.
Q15 — Respiratory Volumes & Capacities · hard · theory
Functional Residual Capacity (FRC) — the volume of air remaining in the lungs after a normal expiration — equals:
A. VC + RV
B. ERV + RV ✓ Correct
C. IRV + ERV
D. TV + IRV
Solution: FRC = Expiratory Reserve Volume + Residual Volume.
Q16 — Respiratory Volumes & Capacities · hard · theory
Inspiratory Capacity (IC), the total volume a person can inspire after a normal expiration, is:
A. ERV + RV
B. IRV + RV
C. TV + ERV
D. TV + IRV ✓ Correct
Solution: Inspiratory Capacity = Tidal Volume + Inspiratory Reserve Volume.
Q17 — Exchange & Transport of Gases · hard · theory
The sigmoid oxygen-haemoglobin dissociation curve shifts to the RIGHT (favouring O₂ unloading) when there is:
A. Low pCO₂ and high pH
B. Low temperature only
C. High pCO₂, high H⁺ (low pH) and higher temperature ✓ Correct
D. High pO₂ only
Solution: The Bohr effect: high CO₂, low pH, high temperature (as in active tissues) shift the curve right, releasing more O₂.
Q18 — Exchange & Transport of Gases · hard · theory
In the alveoli, factors favourable for the formation of oxyhaemoglobin are:
A. Low pO₂ and high pCO₂
B. Low pO₂ only
C. High temperature and high H⁺
D. High pO₂, low pCO₂, low H⁺ and lower temperature ✓ Correct
Solution: At the alveoli (high pO₂, low pCO₂/H⁺), haemoglobin binds O₂; in tissues (opposite conditions) it releases O₂.
Q19 — Respiratory Disorders · hard · theory
A major cause of emphysema is cigarette smoking; a common cause of occupational respiratory disorders is:
A. Long-term exposure to industrial dust/grinding without protective equipment ✓ Correct
B. Excess exercise
C. Eating too much sugar
D. High altitude living
Solution: Occupational disorders (silicosis, asbestosis) result from chronic exposure to industrial dusts; protective masks reduce risk.
Q20 — Respiratory Disorders · hard · theory
Which statement about asthma versus emphysema is correct?
A. Neither affects breathing
B. Both are caused only by bacteria
C. Asthma damages alveolar walls; emphysema inflames bronchi
D. Asthma is due to inflammation/spasm of airways; emphysema is due to alveolar wall damage ✓ Correct
Solution: Asthma = reversible airway narrowing/inflammation; emphysema = irreversible alveolar destruction (often from smoking).
Q21 — Respiratory Organs & Human System · medium · theory
Which structure prevents food from entering the trachea (windpipe) during swallowing?
A. Glottis
B. Epiglottis ✓ Correct
C. Diaphragm
D. Pleura
Solution: The epiglottis is a cartilaginous flap that covers the glottis during swallowing, directing food to the oesophagus.
Q22 — Respiratory Organs & Human System · medium · theory
The part of the respiratory pathway that only conducts air (no gas exchange) includes all EXCEPT:
A. Alveoli ✓ Correct
B. Trachea
C. Bronchioles
D. Bronchi
Solution: The conducting zone (nostrils to terminal bronchioles) transports/cleans/moistens air; exchange occurs only in the alveoli.
Q23 — Mechanism of Breathing · medium · theory
Expiration is normally a ______ process because:
A. Active; the diaphragm flattens
B. Passive; the lungs pump air
C. Passive; the diaphragm and intercostals relax, reducing thoracic volume ✓ Correct
D. Active; muscles contract forcefully
Solution: Quiet expiration is passive — muscle relaxation reduces thoracic/pulmonary volume, raising pressure to expel air.
Q24 — Mechanism of Breathing · medium · theory
The contraction of the external intercostal muscles raises the ribs and sternum, increasing the ______ of the thoracic chamber:
A. Vertical axis only
B. Antero-posterior (front-to-back) diameter ✓ Correct
C. Pleural fluid
D. Volume of the abdomen
Solution: External intercostals lift the ribs/sternum, increasing the antero-posterior dimension of the thorax.
Q25 — Respiratory Volumes & Capacities · medium · theory
Vital capacity (VC) is the sum of:
A. ERV + TV + IRV (the maximum air that can be breathed out after maximum inspiration) ✓ Correct
B. IRV + RV
C. TV + RV
D. RV + ERV
Solution: Vital capacity = ERV + TV + IRV — the maximum volume exchangeable with maximal effort.
Q26 — Respiratory Volumes & Capacities · medium · theory
The total lung capacity is the sum of the vital capacity and the:
A. Inspiratory reserve volume
B. Residual volume ✓ Correct
C. Expiratory reserve volume
D. Tidal volume
Solution: Total lung capacity = VC + RV (total air the lungs can hold at maximum inflation).
Q27 — Exchange & Transport of Gases · medium · theory
Gas exchange across the alveoli and tissues occurs by:
A. Facilitated diffusion via carriers
B. Bulk flow only
C. Simple diffusion based on partial pressure gradients ✓ Correct
D. Active transport using ATP
Solution: O₂ and CO₂ diffuse along their partial pressure (pO₂/pCO₂) gradients — no energy is spent.
Q28 — Exchange & Transport of Gases · medium · theory
The enzyme in red blood cells that catalyses the interconversion of CO₂ and water to carbonic acid/bicarbonate is:
A. Carbonic anhydrase ✓ Correct
B. Pepsin
C. Amylase
D. Catalase
Solution: Carbonic anhydrase (in RBCs) speeds CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻, aiding CO₂ transport.
Q29 — Respiratory Disorders · medium · theory
In emphysema, the difficulty in breathing arises because:
A. Blood cannot carry O₂
B. The bronchi are blocked by mucus only
C. The alveolar walls are damaged, decreasing the respiratory surface ✓ Correct
D. The diaphragm is paralysed
Solution: Emphysema (major cause: cigarette smoking) destroys alveolar walls, reducing the gas-exchange surface area.
Q30 — Respiratory Disorders · medium · theory
Inhaled particles are trapped and prevented from reaching the lungs mainly by the ______ of the respiratory tract:
A. Alveolar sacs
B. Mucus and ciliated epithelium ✓ Correct
C. Diaphragm
D. Pleural fluid
Solution: The mucus lining and cilia of the conducting passages trap dust/microbes and move them out.