Complete Breathing & Exchange of Gases Question Bank & Solutions (24 Questions)
Q1 of 24
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Breathing is best defined as the:
(A)
Oxidation of glucose in cells
(B)
Exchange of O₂ from air with CO₂ from cells
(C)
Transport of nutrients
(D)
Filtration of blood
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Correct Answer: (B) Exchange of O₂ from air with CO₂ from cells
Breathing exchanges atmospheric O₂ for the CO₂ produced by cells, in two phases.
Q2 of 24
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Insects respire through:
(A)
Gills
(B)
Moist skin
(C)
Tracheal tubes
(D)
Lungs
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Correct Answer: (C) Tracheal tubes
Insects use a network of tracheal tubes for gas exchange.
Q3 of 24
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The correct order of the air passage is:
(A)
Larynx → pharynx → trachea → bronchi
(B)
Pharynx → larynx → trachea → bronchi
(C)
Trachea → larynx → bronchi → pharynx
(D)
Bronchi → trachea → larynx → pharynx
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Correct Answer: (B) Pharynx → larynx → trachea → bronchi
Air flows nostrils → nasal chamber → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.
Q4 of 24
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The 'sound box' of the respiratory tract is the:
(A)
Pharynx
(B)
Larynx
(C)
Trachea
(D)
Glottis
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Correct Answer: (B) Larynx
The larynx helps in sound production; the epiglottis guards the glottis during swallowing.
Q5 of 24
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The structural and functional units of the lungs where gas exchange occurs are the:
(A)
Bronchi
(B)
Bronchioles
(C)
Alveoli
(D)
Trachea
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Correct Answer: (C) Alveoli
Thin-walled, highly vascular alveoli provide a vast surface for diffusion.
Q6 of 24
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Trachea and bronchi are supported by cartilage to:
(A)
Aid digestion
(B)
Prevent the airway from collapsing
(C)
Produce sound
(D)
Warm the air
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Correct Answer: (B) Prevent the airway from collapsing
Incomplete cartilaginous rings keep the airways open when air is low.
Q7 of 24
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During inspiration, the diaphragm:
(A)
Relaxes and domes up
(B)
Contracts and flattens
(C)
Does not move
(D)
Closes the glottis
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Correct Answer: (B) Contracts and flattens
Diaphragm contraction (flattening) plus external intercostal contraction enlarges the thorax.
Q8 of 24
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Air moves into the lungs during inspiration because intra-pulmonary pressure becomes:
(A)
Higher than atmospheric
(B)
Lower than atmospheric
(C)
Equal to atmospheric
(D)
Zero
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Correct Answer: (B) Lower than atmospheric
Increased lung volume lowers internal pressure below atmospheric (Boyle's law), drawing air in.
Q9 of 24
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Normal expiration is:
(A)
An active, energy-using process
(B)
A passive process from muscle relaxation
(C)
Caused by diaphragm contraction
(D)
Impossible without the pneumotaxic centre
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Correct Answer: (B) A passive process from muscle relaxation
Relaxation of the diaphragm and intercostals reduces lung volume; expiration is passive.
Q10 of 24
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Tidal volume in a healthy human is about:
(A)
150 mL
(B)
500 mL
(C)
1200 mL
(D)
2500 mL
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Correct Answer: (B) 500 mL
Tidal volume — air moved in a normal breath — is about 500 mL.
Q11 of 24
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Air remaining in the lungs after a forced expiration is the:
(A)
Tidal volume
(B)
Vital capacity
(C)
Residual volume
(D)
Inspiratory reserve volume
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Correct Answer: (C) Residual volume
Residual volume (~1100–1200 mL) cannot be expelled even by forced expiration.
Q12 of 24
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Vital capacity is equal to:
(A)
TV + RV
(B)
ERV + TV + IRV
(C)
RV + ERV
(D)
TLC + RV
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Correct Answer: (B) ERV + TV + IRV
VC = ERV + TV + IRV, the maximum air moved between a forced inspiration and expiration.
Q13 of 24
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Total Lung Capacity equals:
(A)
VC − RV
(B)
VC + RV
(C)
TV + IRV
(D)
ERV + RV
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Correct Answer: (B) VC + RV
TLC = VC + RV = RV + ERV + TV + IRV (~6000 mL).
Q14 of 24
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Lung volumes and capacities are measured with a:
(A)
Sphygmomanometer
(B)
Spirometer
(C)
Stethoscope
(D)
Hygrometer
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Correct Answer: (B) Spirometer
A spirometer measures respiratory volumes for clinical pulmonary assessment.
Q15 of 24
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Gas exchange at the alveoli occurs mainly by:
(A)
Active transport
(B)
Simple diffusion along pressure gradients
(C)
Endocytosis
(D)
Bulk flow through pumps
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Correct Answer: (B) Simple diffusion along pressure gradients
O₂ and CO₂ diffuse across the membrane following their partial-pressure gradients.
Q16 of 24
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The diffusion membrane is made of how many main layers?
(A)
One
(B)
Two
(C)
Three
(D)
Five
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Correct Answer: (C) Three
Alveolar epithelium, capillary endothelium and the basement substance — about 0.2 mm thick.
Q17 of 24
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The partial pressure of oxygen (pO₂) in the alveoli is about:
(A)
159 mm Hg
(B)
104 mm Hg
(C)
40 mm Hg
(D)
0.3 mm Hg
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Correct Answer: (B) 104 mm Hg
Alveolar pO₂ ≈ 104 mm Hg, higher than in deoxygenated blood (40), so O₂ diffuses into blood.
Q18 of 24
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Most oxygen is transported in the blood as:
(A)
Dissolved in plasma
(B)
Oxyhaemoglobin
(C)
Bicarbonate
(D)
Carbamino compounds
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Correct Answer: (B) Oxyhaemoglobin
About 97% of O₂ travels bound to haemoglobin as oxyhaemoglobin; ~3% is dissolved.
Q19 of 24
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One haemoglobin molecule can bind a maximum of how many O₂ molecules?
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Correct Answer: (C) 4
Each haemoglobin can reversibly carry up to four O₂ molecules.
Q20 of 24
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A right shift of the oxygen-dissociation curve (Bohr effect) is favoured by:
(A)
High pO₂, low pCO₂
(B)
Low pO₂, high pCO₂, high H⁺
(C)
Low temperature
(D)
Low H⁺ concentration
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Correct Answer: (B) Low pO₂, high pCO₂, high H⁺
In tissues, high CO₂/H⁺ and higher temperature shift the curve right, releasing O₂.
Q21 of 24
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The largest fraction of CO₂ is transported as:
(A)
Dissolved CO₂
(B)
Carbamino-haemoglobin
(C)
Bicarbonate ions
(D)
Carbonic acid
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Correct Answer: (C) Bicarbonate ions
About 70% of CO₂ travels as bicarbonate (HCO₃⁻), formed with the help of carbonic anhydrase.
Q22 of 24
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The enzyme carbonic anhydrase is found in high concentration in:
(A)
Plasma
(B)
Red blood cells
(C)
Alveolar cells
(D)
The liver
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Correct Answer: (B) Red blood cells
RBC carbonic anhydrase speeds CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺ in both directions.
Q23 of 24
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The basic respiratory rhythm is controlled by a centre in the:
(A)
Pons
(B)
Medulla oblongata
(C)
Cerebellum
(D)
Spinal cord
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Correct Answer: (B) Medulla oblongata
The respiratory rhythm centre lies in the medulla oblongata; the pons has the pneumotaxic centre.
Q24 of 24
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Emphysema, in which alveolar walls are damaged, is most often caused by:
(A)
Bacteria
(B)
Cigarette smoking
(C)
Low calcium
(D)
Pollen allergy
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Correct Answer: (B) Cigarette smoking
Chronic cigarette smoking damages alveolar walls and reduces the respiratory surface area.