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CAIE A Level Biology 9700 · Immunity

Immunity: describe question

Describe7 marksChallenge

A toxin-producing bacterium, Clostridium tetani, causes tetanus. Three individuals are exposed to the tetanus toxin:

  • Individual A receives an injection of antitoxin (antibodies against the toxin).
  • Individual B is vaccinated with a toxoid (inactivated toxin) before exposure.
  • Individual C is infected by the bacterium and recovers naturally.

Describe the type of immunity (active/passive and natural/artificial) that each individual develops. In your answer, explain how the molecular structure of antibodies enables the antitoxin to neutralise the toxin. Also, explain why the immunity in Individual B lasts longer than that in Individual A.

0 words · 7 marks

No account needed for your first marks. Your answer is used only to mark it.

How this question is marked

7 marks, so the mark scheme is looking for about 7 separate creditworthy points. Making the same point twice in different words earns it once.

Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.

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