Explain how insulin and glucagon work together to maintain a stable blood glucose concentration when blood glucose concentration first rises above the normal level and then falls below it.

Cambridge International IGCSE Biology (0610) — 14.3 Hormones · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

When blood glucose rises, the pancreas releases insulin. Insulin stimulates liver and muscle cells to take up glucose and store it as glycogen, reducing the glucose level in the blood.
When glucose falls, the pancreas releases glucagon. Glucagon signals the liver to break down glycogen into glucose, which is released into the blood, raising the glucose level back to normal.
This reciprocal action of insulin and glucagon constitutes a negative‑feedback system that keeps blood glucose concentration stable.

Examiner tips

  • Use the exact terms ‘insulin’, ‘glucagon’, ‘liver’, ‘muscle’, ‘glycogen’, ‘negative feedback’. Show the sequence of events for high and low glucose. Keep the answer concise – 4 marks, so one sentence each for high and low.
  • Remember to mention that insulin lowers glucose and glucagon raises it, and that this is a negative‑feedback loop.

Common mistakes

  • Confusing the organs involved (e.g. saying pancreas stores glycogen). Using vague language such as ‘helps’ instead of ‘stimulates’. Omitting the negative‑feedback description.

Mark scheme (4 marks)

  1. When blood glucose concentration is too high, the pancreas secretes insulin.
  2. Insulin causes liver (and muscle) cells to take up glucose and convert it to glycogen, lowering blood glucose concentration.
  3. When blood glucose concentration falls too low, the pancreas secretes glucagon.
  4. Glucagon causes the breakdown of glycogen to glucose in the liver, raising blood glucose concentration back to normal — this is an example of negative feedback.

Key terms in this question

insulin · glucagon · blood glucose concentration

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