Breathing and Exchange of Gases: NEET PYQ, 2018–2026

Q1 · Zoology · Breathing and Exchange of Gases

Which gas binds to haemoglobin at the same site as oxygen, with an affinity roughly 200 times greater than that of oxygen, forming a stable compound that blocks O2 transport?

• ACarbon dioxide (CO2)
• BNitrogen (N2)
• CCarbon monoxide (CO)
• DHydrogen sulphide (H2S)

Q2 · Zoology · Breathing and Exchange of Gases

Along the respiratory tract, which region is the first to contain alveoli and therefore marks the start of the respiratory zone where gas exchange occurs?

• ATrachea
• BPrimary bronchi
• CTerminal bronchioles
• DRespiratory bronchioles

Q3 · Zoology · Breathing and Exchange of Gases

Air moving from the trachea towards the alveoli passes through a sequence of conducting and respiratory airways. Which airway segment is the first in which gas exchange can take place?

• ATerminal bronchioles, because they are the last segment of the airway before the alveoli.
• BRespiratory bronchioles, because alveoli first open into their walls.
• CAlveolar ducts, because they are the first structures that are lined by alveolar epithelium.
• DPrimary bronchi, because they are the first airways that carry air into the lungs.

Q4 · Zoology · Breathing and Exchange of Gases

According to Boyle's law, as applied to the lungs during inspiration, when the volume of the thoracic cavity increases at constant temperature:

• AIntra-pulmonary pressure falls below atmospheric pressure, so air flows into the lungs
• BIntra-pulmonary pressure rises above atmospheric pressure, so air flows into the lungs
• CIntra-pulmonary pressure stays the same, and air flows in only because of body temperature
• DIntra-pulmonary pressure becomes zero, creating a vacuum that draws in air

Q5 · Zoology · Breathing and Exchange of Gases

A patient with fibrotic lungs has a vital capacity of 2800 mL and a residual volume of 1200 mL. Taking total lung capacity as the sum of vital capacity and residual volume, the total lung capacity is:

• A1600 mL
• B2800 mL
• C4000 mL
• D2000 mL

Q6 · Zoology · Breathing and Exchange of Gases

The human trachea is kept open by 16 to 20 incomplete rings of hyaline cartilage, and each ring is C-shaped with its open gap facing posteriorly towards the oesophagus rather than forming a complete ring. Which statement best explains this arrangement?

• AThe oesophagus lies directly behind the trachea and must bulge into the posterior space during passage of a food bolus; the gap in each ring is filled by a membranous wall that lets the oesophagus expand without compressing the airway.
• BThe gap allows the trachea to stretch during inspiration, so that the tidal volume can be increased beyond what a complete cartilaginous ring would permit.
• CComplete rings would prevent the ciliated epithelium from beating, so the gap is needed to keep the mucus escalator working.
• DThe open end faces anteriorly so that the larynx can push air backwards into the rings during forced expiration, reducing the work of the diaphragm.

Q7 · Zoology · Breathing and Exchange of Gases

A drug given during an asthma attack works by relaxing the smooth muscle of the bronchioles. What is the direct effect of this action on the airway?

• AThe airway is narrowed, so less air can enter
• BOxygen is blocked from entering the alveoli
• CMucus production in the trachea is increased
• DThe airway is widened, which eases airflow

Q8 · Zoology · Breathing and Exchange of Gases

A fall in arterial pO2 from 100 mm Hg to 50 mm Hg, with arterial pCO2 and pH unchanged, increases breathing mainly through which receptors?

• APeripheral chemoreceptors in the carotid bodies and aortic bodies
• BCentral chemoreceptors on the ventral surface of the medulla, which sense blood pO2 directly
• CStretch receptors in the walls of the bronchi and bronchioles
• DThe pneumotaxic centre in the pons

Q9 · Zoology · Breathing and Exchange of Gases

A man has a lung disorder in which the alveolar walls are damaged. His tidal volume is 500 mL, inspiratory reserve volume is 2500 mL, expiratory reserve volume is 1000 mL, and residual volume is 2400 mL. What is his total lung capacity?

• A6400 mL
• B4000 mL
• C3400 mL
• D5400 mL

Q10 · Zoology · Breathing and Exchange of Gases

Insects take in air through small openings on the body wall called spiracles. Into what structures do the spiracles open, and how does oxygen reach the body tissues?

• AInto a network of tracheae that branch into fine tracheoles, which carry air directly to the cells.
• BInto the haemolymph, where haemoglobin binds oxygen and carries it to the tissues.
• CInto paired book lungs, which exchange gases across thin leaves of tissue.
• DInto alveoli that lie at the end of the bronchi, where gases diffuse into the blood.