Explain why a person who has recovered from a bacterial infection is unlikely to become seriously ill if they are infected by the same type of bacterium again.

Eduqas GCSE Biology — 2.6.2 The immune system · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Memory cells (lymphocytes) are produced during the first infection.
These memory cells recognise the same antigen on the bacterium when it enters the body again.
Antibodies are produced more rapidly and in greater quantities during the second infection.
The pathogen is destroyed before it can cause serious illness or symptoms.

Examiner tips

  • Use the term "memory cells" and link them to a faster, stronger antibody response. Show the sequence: first infection → memory cells → rapid second response → pathogen destroyed. Keep the answer concise and directly address each point.
  • Avoid vague phrases like "immune system" without specifying memory cells or antibodies.

Common mistakes

  • Forgetting to mention memory cells. Confusing the first and second responses. Using the wrong terminology (e.g., "immune memory" instead of "memory cells").

Mark scheme (4 marks)

  1. Memory cells (lymphocytes) are produced during the first infection
  2. Memory cells recognise the same antigen on the bacterium when it enters the body again
  3. Antibodies are produced more rapidly / in greater quantities during the second infection
  4. The pathogen is destroyed before it can cause serious illness / symptoms

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