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CAIE A-Level Biology AS 9.1 The Gas Exchange System Questions

Practise CAIE AS Biology 9.1 by tracing airway structure, comparing tissue locations, identifying features in micrographs and explaining diffusion between alveoli and blood.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • Trace inhaled air from trachea through bronchi and bronchioles to alveoli on a labelled diagram.
  • Identify alveoli, airways, capillaries and their wall tissues in micrographs.
  • Compare cartilage, cilia, goblet cells and smooth muscle across airways and alveoli in a feature table.
  • Explain how goblet cells and mucous glands trap particles while cilia move mucus from airways.
  • Relate cartilage, smooth muscle and elastic fibres to airway support, lumen control and recoil.
  • Trace O2 into blood and CO2 into alveoli across thin walls as ventilation and blood flow maintain gradients.

Covered syllabus points

9.1.1—Structure of human gas exchange system9.1.2—Tissue distribution in gas exchange system9.1.3—Gas exchange image recognition9.1.4—Plan diagrams of trachea and bronchus walls9.1.5—Airway secretory and ciliated cells9.1.6—Airway and alveolar tissue functions9.1.7—Gas exchange between alveolar air and blood

Question 1

[Maximum number: 3]

The Weibel Lung model was developed after an extensive study of the gas exchange system. The model includes detailed measurements of airway diameters (lumen diameters of the airways). In the model, different parts of the gas exchange system are identified with a generation number, as outlined in Fig. 6.1.

Fig. 6.1

Fig. 6.1

Question (a)

(a)

The Weibel Lung model describes how each airway divides into two.

Name the airways in generation 1, labelled X in Fig. 6.1, that branch from generation 0.

[ 1 ]

Question (b)

(b)

The airways are well supplied with blood. However, the airways from generation 0 to generation 16, shown in Fig. 6.1, are not able to carry out gas exchange.

Suggest why the airways from generation 0 to generation 16 are not able to carry out gas exchange.

[ 2 ]

Question 2

[Maximum number: 1]

Which structure of the gas exchange system always contains cartilage?

A

alveoli

B

bronchiole

C

capillary

D

bronchus

Question 3

[Maximum number: 1]

The photomicrograph shows a section through part of the human gas exchange system.

Figure for Question 3 — CAIE A-Level Biology AS

Which structure is shown?

A

alveolus

B

bronchiole

C

bronchus

D

trachea

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