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A Level Biology: Gas exchange MCQs — Biology

13 multiple-choice questions on A Level Biology: Gas exchange from Biology, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. The function of cartilage in the trachea is to

  1. exchange gases
  2. produce mucus
  3. keep the airway open
  4. contract to narrow the airway

Answer: C) keep the airway open

Explanation: Cartilage prevents collapse. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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2. Which feature maintains a steep oxygen concentration gradient at the alveoli?

  1. Mucus in the alveoli
  2. Continuous blood flow through capillaries
  3. Few alveoli
  4. Thick alveolar walls

Answer: B) Continuous blood flow through capillaries

Explanation: Blood carries O₂ away. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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3. Which tissue lines the alveoli?

  1. Squamous epithelium
  2. Cartilage
  3. Smooth muscle
  4. Ciliated epithelium

Answer: A) Squamous epithelium

Explanation: Thin flat cells give a short diffusion distance. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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4. The diffusion pathway for oxygen from alveolar air to blood passes through

  1. cartilage and smooth muscle
  2. goblet cells
  3. alveolar epithelium and capillary endothelium
  4. the pleural membranes only

Answer: C) alveolar epithelium and capillary endothelium

Explanation: Two thin cell layers. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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5. Cilia in the airways

  1. kill bacteria directly
  2. sweep mucus up towards the throat
  3. pump air into the alveoli
  4. absorb oxygen

Answer: B) sweep mucus up towards the throat

Explanation: Mucociliary escalator. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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6. Bronchioles differ from bronchi because bronchioles have

  1. squamous epithelium only
  2. C-shaped cartilage
  3. no smooth muscle
  4. no cartilage

Answer: D) no cartilage

Explanation: Bronchioles lack cartilage. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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7. Goblet cells

  1. support the airway
  2. secrete mucus
  3. exchange gases
  4. beat to move mucus

Answer: B) secrete mucus

Explanation: Goblet cells make mucus. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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8. Which structure has both elastic fibres and squamous epithelium but no cartilage or cilia?

  1. Larynx
  2. Trachea
  3. Bronchus
  4. Alveolus

Answer: D) Alveolus

Explanation: Alveoli are thin and elastic. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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9. Smooth muscle in the bronchioles

  1. prevents collapse
  2. changes the diameter of the airways
  3. is absent
  4. makes mucus

Answer: B) changes the diameter of the airways

Explanation: Contraction narrows airways. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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10. Gases must dissolve before diffusing, so the alveolar surface is

  1. ciliated
  2. lined with cartilage
  3. waxy
  4. moist

Answer: D) moist

Explanation: A thin water layer lines alveoli. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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11. Where are C-shaped rings of cartilage found?

  1. Trachea
  2. Capillaries
  3. Bronchioles
  4. Alveoli

Answer: A) Trachea

Explanation: The trachea has C-shaped rings. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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12. Mucous glands are found in the

  1. capillaries
  2. trachea and bronchi
  3. red blood cells
  4. alveoli

Answer: B) trachea and bronchi

Explanation: Glands in the submucosa of larger airways. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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13. Elastic fibres in the alveoli

  1. keep bronchi open
  2. trap bacteria
  3. recoil during expiration to help push air out
  4. produce mucus

Answer: C) recoil during expiration to help push air out

Explanation: Stretch and recoil aids expiration. AS & A Level Biology · Topic 9 Gas Exchange · 9.1 The gas exchange system

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