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Question 18M.2.HL.TZ2.b

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Date May 2018 Marks available [Maximum mark: 4] Reference code 18M.2.HL.TZ2.b
Level HL Paper 2 Time zone TZ2
Command term Outline Question number b Adapted from N/A
b.
[Maximum mark: 4]
18M.2.HL.TZ2.b

All living organisms depend on a continuous supply of energy.

Outline how ventilation in humans ensures a supply of oxygen. 

[4]

Markscheme

a. ventilation is exchange of gases between lungs and air. 

b. during inhalation diaphragm contracts AND lowers. 

Both needed.

c. external intercostal muscles contract, raising ribs upwards and outwards 

d. increase in volume AND decrease in pressure within thoracic cavity 

e. air drawn into alveoli bringing fresh supply of oxygen 

f. oxygen concentration in alveolar sacs is higher than in blood capillaries 

g. «oxygen concentration gradient» causes oxygen to diffuse out of alveoli into red blood cells in capillaries 

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