DP Biology (first assessment 2025)

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Question 22M.2.SL.TZ2.6c

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Date May 2022 Marks available [Maximum mark: 7] Reference code 22M.2.SL.TZ2.6c
Level SL Paper 2 Time zone TZ2
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 7]
22M.2.SL.TZ2.6c
(c)

Explain how blood clotting occurs and the consequence for a person who has hemophilia.

[7]

Markscheme

       Clotting process:

  1. blood clotting seals cuts in the skin;
  2. clotting factors are released (from platelets);
  3. thrombin is activated;
  4. a cascade reaction occurs (with thrombin);
  5. (thrombin causes) fibrinogen is converted to fibrin;
  6. fibrin forms a clot/blocks the cut/prevents blood from being lost;
    Consequences of hemophilia:
  7. if a person does not have enough clotting factors/hemophilia, the clot will not form;
  8. pathogens can enter the body more easily;
  9. (in hemophiliacs) blood will be lost from a cut which affects blood pressure/bleeding to death;
  10. loss of blood affects amount of hemoglobin/O2 carried around the body;
  11. reference to lifestyle / menstrual/birth problems

e.g. surgery, contact sports

Examiners report

The formation of a clot by the final formation of fibrin was reasonably well known, although many implied that the thrombin directly converted the fibrinogen and did not mention the cascade of reactions. In the consequences for haemophiliacs the fact that the clot would not form and they risked bleeding to death and were more susceptible to infections were well known. There were some G2 comments that 7 marks seemed difficult to attain, this did not seem to be the case with an average of 4.1 marks for the question.

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