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Question 18M.2.SL.TZ1.a

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Date May 2018 Marks available [Maximum mark: 4] Reference code 18M.2.SL.TZ1.a
Level SL Paper 2 Time zone TZ1
Command term Outline Question number a Adapted from N/A
a.
[Maximum mark: 4]
18M.2.SL.TZ1.a

Outline the role of the parts of an alveolus in a human lung.

[4]

Markscheme

a. the (spherical) wall of an alveolus maximizes/allows gas exchange 

b. pneumocytes I (optimize) gas exchange 

c. pneumocytes II produce surfactant 

d. adjacent capillaries enclose alveolus for efficient gas exchange with blood 

e. surfactant reduces surface tension/prevents collapse of alveolus

f. (alveolar) macrophages/phagocytes help with defense/homeostasis/response to foreign substances

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