Explain how the human body uses non-specific defences and the immune system to protect itself after a pathogen enters through a cut in the skin.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Blood clotting rapidly seals the cut, forming a mechanical barrier that stops further pathogen entry.
White blood cells (phagocytes) are recruited to the wound and engulf the invading pathogen.
The phagocytes digest the pathogen by phagocytosis, using enzymes to break it down.
Lymphocytes recognise the pathogen’s antigens and produce specific antibodies that bind to the pathogen.
Memory cells persist after the infection, so if the same pathogen enters again, antibodies are produced more quickly.
White blood cells (phagocytes) are recruited to the wound and engulf the invading pathogen.
The phagocytes digest the pathogen by phagocytosis, using enzymes to break it down.
Lymphocytes recognise the pathogen’s antigens and produce specific antibodies that bind to the pathogen.
Memory cells persist after the infection, so if the same pathogen enters again, antibodies are produced more quickly.
Examiner tips
- Use the word "seals" for clotting and "engulf" for phagocytes; mention "antigens" and "antibodies" for lymphocytes.
- Show the sequence: clotting → phagocytosis → antibody production → memory cells.
- Include the word "specific" when describing antibodies and memory cells.
Common mistakes
- Confusing clotting with inflammation; forgetting to mention antibodies; using vague terms like "immune response" without detail.
Mark scheme (5 marks)
- Blood clotting seals the wound / acts as a mechanical barrier to prevent further pathogens entering
- White blood cells (phagocytes) engulf / ingest the pathogen
- Phagocytes digest the pathogen using enzymes (phagocytosis)
- Lymphocytes produce antibodies that are specific / complementary to the antigens on the pathogen
- Memory cells remain after the infection so that if the same pathogen enters again, antibodies are produced 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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