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Date May 2017 Marks available 2 Reference code 17M.3.HL.TZ1.21
Level Higher level Paper Paper 3 Time zone Time zone 1
Command term Explain Question number 21 Adapted from N/A

Question

The graph below shows the oxygen dissociation curve at a low CO2 concentration.

Outline the main changes in the lungs that occur in patients with emphysema.

[2]
a.i.

State a treatment for emphysema.

[1]
a.ii.

An increase in metabolic activity results in greater release of CO2 into the blood. On the graph, draw the oxygen dissociation curve during intense exercise when the CO2 concentration of the blood is high.

[1]
b.i.

Explain how the increase in CO2 concentration affects the release of oxygen to respiring cells.

[2]
b.ii.

Markscheme

a. air sacs/alveoli break down/rupture 

b. creating one larger air space instead of many small ones / reduces the surface area of the lungs 

c. loss of elasticity of lung tissue

a.i.

supplemental oxygen / breathing techniques / bronchodilators / inhaled steroids / lung surgery to remove damaged tissue / lung transplant

a.ii.

curve has to be towards the right and starting together

Must start together but can finish slightly below the original curve.

b.i.

a. increased levels of CO2 lower the pH of the blood 

b. «which results in» decreased affinity of the hemoglobin for oxygen / greater release of oxygen 

c. this shifts the oxygen dissociation curve to the right/Bohr shift

b.ii.

Examiners report

[N/A]
a.i.
[N/A]
a.ii.
[N/A]
b.i.
[N/A]
b.ii.

Syllabus sections

Option D: Human physiology » Option D: Human physiology (Additional higher level topics) » D.5 Hormones and metabolism
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Option D: Human physiology » Option D: Human physiology (Core topics) » D.1 Human nutrition
Option D: Human physiology » Option D: Human physiology (Additional higher level topics) » D.6 Transport of respiratory gases
Option D: Human physiology » Option D: Human physiology (Core topics) » D.2 Digestion
Option D: Human physiology » Option D: Human physiology (Core topics) » D.3 Functions of the liver
Option D: Human physiology » Option D: Human physiology (Core topics) » D.4 The heart
Option D: Human physiology » Option D: Human physiology (Core topics)
Option D: Human physiology » Option D: Human physiology (Additional higher level topics)
Option D: Human physiology

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