A person has not eaten for several hours and their blood glucose concentration falls below the normal set point. Explain how the body detects and responds to this change to restore blood glucose concentration to the normal level.

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).

Model answer (5 marks)

The pancreas contains glucose‑sensing cells that detect the fall in blood glucose concentration.
The pancreas then releases glucagon into the bloodstream.
Glucagon binds to receptors on liver cells.
In the liver, glucagon stimulates glycogenolysis, converting glycogen to glucose.
The glucose is released into the blood, raising the blood glucose concentration back to the normal set point.

Examiner tips

  • Mention the pancreas as the glucose sensor and glucagon release; link glucagon to liver action; state glycogenolysis and glucose release; keep answer concise and use correct terminology.

Common mistakes

  • Confusing insulin with glucagon; omitting the liver as the site of action; failing to mention glycogenolysis explicitly.

Mark scheme (5 marks)

  1. The pancreas detects the fall in blood glucose concentration
  2. The pancreas releases / secretes glucagon
  3. Glucagon acts on the liver
  4. Glycogen is converted to glucose (glycogen is broken down to glucose) in the liver
  5. Glucose is released into the blood, raising blood glucose concentration back to the normal set point / normal level

Key terms in this question

blood glucose concentration · set point

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