Explain how the immune system responds when a pathogen enters the bloodstream for the first time.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. White blood cells recognise the pathogen as foreign.
2. Specific antibodies are produced against the pathogen’s antigens.
3. The antibodies bind to the pathogen, neutralising or clumping it for removal.
4. Memory cells are formed, enabling a quicker response on re‑infection.
2. Specific antibodies are produced against the pathogen’s antigens.
3. The antibodies bind to the pathogen, neutralising or clumping it for removal.
4. Memory cells are formed, enabling a quicker response on re‑infection.
Examiner tips
- Use the exact terms ‘white blood cells’, ‘antibodies’, ‘antigens’, and ‘memory cells’.
- Show the sequence: detection → antibody production → action → memory.
- Keep each point brief and separate with numbers.
Mark scheme (4 marks)
- White blood cells detect the pathogen / recognise it as foreign
- Antibodies are produced that are specific to the antigens on the pathogen
- The antibodies destroy / neutralise / clump together the pathogens
- Memory cells are produced so the response is faster if the same pathogen is encountered again
Key terms in this question
Related
- All WJEC GCSE Biology (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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