DP Biology (first assessment 2025)

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Question 22N.2.HL.TZ0.6c

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Date November 2022 Marks available [Maximum mark: 7] Reference code 22N.2.HL.TZ0.6c
Level HL Paper 2 Time zone TZ0
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 7]
22N.2.HL.TZ0.6c
(c)

Explain how cells in the bloodstream cause a specific immune response.

[7]

Markscheme
  1. (specific immune response is) production of antibodies in response to a particular pathogen;
  2. antibody is specific to/binds to a specific antigen;
  3. macrophages/phagocytes engulf/present antigens from pathogens/viruses/bacteria;
  4. T lymphocytes activated by antigens/antigen presentation/antigens presented by macrophage;
  5. (activated) T lymphocytes activate B lymphocytes;
  6. only B lymphocytes that produce antibodies against the antigen/pathogen are activated;
  7. (activated) B lymphocytes clone/divide by mitosis to form plasma cells;
  8. plasma cells then secrete (large quantity) of an antibody/secrete antibodies of same type;
  9. some B lymphocytes/plasma cells form memory cells;
  10. memory cells give long-lasting immunity/faster response to a disease/pathogen;

Accept B and T cells instead of B and T lymphocytes.

Examiners report

Here again there was a wide range of answers. The best focussed throughout on how specificity in immune responses is achieved. The weakest were very muddled, with confusion between antigens and pathogens and between antigens and antibodies. Nearly all candidates mentioned memory cells and their role in long term immunity.

Syllabus sections