DP Biology (last assessment 2024)

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Question 23M.3.HL.TZ1.23

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Date May 2023 Marks available [Maximum mark: 6] Reference code 23M.3.HL.TZ1.23
Level HL Paper 3 Time zone TZ1
Command term Explain, Outline, State Question number 23 Adapted from N/A
23.
[Maximum mark: 6]
23M.3.HL.TZ1.23

The graph shows the oxygen dissociation curves for hemoglobin in a fetus, a healthy adult and an adult with emphysema.

[Source: Reproduced with permission of the © ERS 2023: European Respiratory Journal 26 (2) 204–213;
DOI: 10.1183/09031936.05.00095204 Published 1 August 2005.]

(a)

State where in the body the blood would be flowing at point X on the graph.

[1]

Markscheme

lungs/alveoli;

Examiners report

The majority of candidates correctly identified the lungs as the area in the body that corresponded to point X, the highest oxygen saturation point on the oxygen dissociation curve.

(b)

Outline the reason that the curve for fetal hemoglobin is to the left of normal adult hemoglobin.

[1]

Markscheme
  1. fetal hemoglobin has a higher affinity for oxygen then normal hemoglobin;
  2. oxygen will pass from normal/maternal/mother’s hemoglobin to fetal hemoglobin (in the placenta);
Examiners report

Most could also get the mark for fetal hemoglobin having a higher affinity for oxygen than adult hemoglobin.

(c)

State where the curve for myoglobin would be drawn on the diagram.

[1]

Markscheme

to left of the curve for fetal hemoglobin;

Do not accept above the curve.

Examiners report

The majority of candidates could also correctly indicate that the oxygen dissociation curve of myoglobin is to the left of the curve for fetal hemoglobin. Some inaccurately stated that it was 'above' the curve.

(d)

The micrographs show mammalian lung tissue in its healthy condition and with emphysema.

Explain how emphysema is treated.

[3]

Markscheme
  1. help smokers to quit smoking as smoking worsens emphysema;
  2. pulmonary rehabilitation/learning special breathing techniques to reduce breathlessness;
  3. use inhaler/bronchodilator/medications to open the air passages in the lungs
    OR
    steroids can help relieve symptoms of emphysema associated with asthma/bronchitis;
  4. patients may require a device that gives them supplemental oxygen;
  5. lung transplantation may be an option for some patients with emphysema;
  6. lung volume reduction surgery to remove damaged lung tissue may be recommended;
  7. AAT/alpha-1 antitrypsin to slow progression of lung damage (in patients with AAT deficiency);
Examiners report

Few candidates scored the full three marks but many were able to get one or two marks for the treatment of emphysema.

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