A-Level Biology May/June 2025 Q5(b): Diabetes mellitus is a disease in which the blood glucose concentration cannot be contr…

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  There are several advantages of using recombinant human insulin compared to insulin extracted from animals:

  • Reduced immune response: As recombinant insulin is identical in its amino acid sequence to the insulin produced in the human body, it is less likely to be recognised as foreign and cause an allergic or immune response.

  • Large scale supply: The genetically modified bacteria used to produce the insulin can be grown in large industrial fermenters. This means that a large, reliable, and continuous supply can be produced to meet the demand from people with diabetes worldwide, which is not limited by the availability of animal pancreases.

  • Fewer ethical objections: The use of microorganisms for production avoids the ethical and religious objections associated with slaughtering animals, such as pigs or cattle, to extract insulin. This makes it acceptable to a wider range of people, including vegetarians and vegans.

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  How the marks are awarded

  • MP 2 — The first point correctly states that there is less likelihood of an immune or allergic response because the recombinant insulin is identical to human insulin.
  • MP 1 — The second point explains that a large-scale supply can be produced to match demand, a key advantage of using microbial fermentation over animal extraction.
  • MP 6 — The third point identifies that using microorganisms avoids the ethical or religious objections that are associated with using animal products.

  Common mistakes

  • Simply stating 'it is more effective' or 'it works better' without explaining why (e.g., due to identical structure or faster action).
  • Confusing the source, for example, stating that recombinant insulin is still taken from animals but is just 'purified better'.
  • Repeating the same marking point in different words, such as 'it doesn't cause an immune response' and 'it doesn't cause an allergic reaction', which would only score one mark.
  • Stating that animal insulin does not work at all, which is incorrect; it is effective but has disadvantages.

  Examiner tip: For questions asking for advantages or disadvantages, structure your answer with clear, separate points to ensure you provide enough distinct reasons to earn all the available marks.

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