Explain how antibodies contribute to the destruction of pathogens in the body.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Antibodies are proteins produced by plasma cells that are specific to a particular antigen.
They bind to antigens on the surface of pathogens, forming antigen–antibody complexes.
This binding can agglutinate pathogens, clumping them together so phagocytes can engulf them more easily.
Antibodies can also neutralise pathogens or their toxins by blocking active or binding sites, preventing entry into host cells or damage.
They bind to antigens on the surface of pathogens, forming antigen–antibody complexes.
This binding can agglutinate pathogens, clumping them together so phagocytes can engulf them more easily.
Antibodies can also neutralise pathogens or their toxins by blocking active or binding sites, preventing entry into host cells or damage.
Examiner tips
- Use the term "plasma cells" for antibody production. Show the four mechanisms in separate sentences. Mention "agglutination" and "neutralisation" explicitly.
Common mistakes
- Confusing plasma cells with B‑cell precursors. Failing to mention that antibodies are specific to antigens. Omitting the neutralisation mechanism.
Mark scheme (4 marks)
- Antibodies are proteins produced by plasma cells (effector B cells) that are specific to a particular antigen.
- Antibodies bind to antigens on the surface of pathogens, forming antigen–antibody complexes.
- Antibodies can agglutinate (clump) pathogens together, making them easier for phagocytes to engulf.
- Antibodies can neutralise pathogens or their toxins by blocking active/binding sites, preventing them from entering host cells or causing damage.
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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