Explain how the body produces antibodies in response to a pathogen, and describe the role of memory cells if the same pathogen enters the body a second time.

Eduqas A-Level Biology — 3.1 Photosynthesis · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

When a pathogen enters the body for the first time, the immune system mounts a specific defence response involving white blood cells.

Model answer (5 marks)

White blood cells recognise antigens on the pathogen’s surface. Lymphocytes then produce antibodies that are complementary to that antigen. The antibodies bind to the antigens, neutralising the pathogen or causing agglutination. After the infection, memory cells remain in the body. If the same pathogen re‑enters, memory cells divide rapidly and produce antibodies more quickly, destroying the pathogen before symptoms appear.

Examiner tips

  • Use the word ‘recognise’ for detection, ‘produce’ for antibody synthesis, and ‘bind’ for neutralisation/agglutination.
  • Mention memory cells and rapid secondary response to show understanding of immunity.”]
  • common_mistakes
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Mark scheme (5 marks)

  1. White blood cells detect antigens on the surface of the pathogen
  2. Lymphocytes release/produce antibodies that are complementary/specific to that antigen
  3. Antibodies bind to the antigens on the pathogen to neutralise it / clump pathogens together (agglutination)
  4. After the infection, memory cells remain in the body
  5. If the same pathogen enters again, memory cells divide rapidly to produce antibodies more quickly, destroying the pathogen before symptoms appear

Key terms in this question

memory cell

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