Explain how phagocytes and lymphocytes work together to destroy a pathogen that has entered the body for the first time.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
White blood cells recognise the pathogen by detecting antigens on its surface. Lymphocytes then stimulate the production of antibodies that are complementary to those antigens. The antibodies bind to the pathogen, neutralising it and/or causing agglutination. Lymphocytes also activate phagocytes, which engulf the antibody‑coated pathogen and digest it with enzymes (phagocytosis). After the infection, memory cells persist, so a subsequent encounter with the same pathogen is destroyed more rapidly.
Examiner tips
- Use the term ‘antigens’ and ‘antibodies’ early to show understanding of the immune response.
- Show the sequence: detection → antibody production → antibody action → phagocyte activation → memory cell formation.
- Include the word ‘phagocytosis’ to gain the full 5 marks.
Common mistakes
- Confusing phagocytes with lymphocytes; they are different cell types.
- Omitting the role of antibodies or memory cells.
- Using vague terms like ‘immune cells’ instead of specific names such as ‘white blood cells’ or ‘lymphocytes’.
Mark scheme (5 marks)
- White blood cells detect the pathogen by identifying antigens on its surface
- Lymphocytes trigger the release of antibodies that are specific/complementary to the antigen
- Antibodies bind to antigens on the pathogen, neutralising it and/or clumping pathogens together (agglutination)
- Lymphocytes activate phagocytes, which engulf and digest the pathogen using enzymes (phagocytosis)
- After the infection, memory cells remain so that if the same pathogen enters again, it is destroyed more quickly
Key terms in this question
Related
- All Eduqas A-Level Biology revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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