A student eats a large meal containing a lot of sugar. Explain how the body detects the change in blood glucose concentration and responds to return it to the normal set point.

Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.6 Homeostasis · Explain · 5 marks · View as Markdown

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

After eating, the concentration of glucose in the blood rises above the normal set point. The body must detect this change and respond to restore the normal blood glucose concentration.

Model answer (5 marks)

The pancreas contains glucose‑sensing β‑cells that detect the rise in blood glucose.
The β‑cells release insulin into the bloodstream.
Insulin binds to receptors on liver (and muscle) cells, stimulating the enzyme glycogen synthase to convert glucose into glycogen.
The uptake and storage of glucose lowers the blood glucose concentration back towards the normal set point.
This is a negative‑feedback system: the response (insulin release) opposes the initial increase in glucose.

Examiner tips

  • Use the word ‘pancreas’ and ‘β‑cells’ to show detection. Mention insulin release and its target cells. Explain the conversion to glycogen. State the fall in glucose. Identify the system as negative feedback.
  • common_mistakes
  • :
  • Confusing insulin with glucagon. Failing to mention the pancreas as the sensor. Omitting the negative‑feedback description.

Mark scheme (5 marks)

  1. The pancreas detects the rise in blood glucose concentration
  2. The pancreas releases / secretes insulin
  3. Insulin causes the liver (or muscle cells) to convert glucose to glycogen
  4. Blood glucose concentration falls back to / towards the normal set point
  5. This is an example of negative feedback — the response opposes / reverses the original change

Key terms in this question

blood glucose concentration · set point

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