A person has not eaten for several hours. Their blood glucose concentration begins to fall below the normal level. Explain how hormonal coordination returns the blood glucose concentration to normal.

Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.5 Hormonal coordination · 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 senses the drop in blood glucose.
The pancreas releases glucagon.
Glucagon enters the bloodstream and reaches the liver.
In the liver, glucagon stimulates glycogenolysis, converting glycogen to glucose.
The glucose is released into the blood, restoring normal glucose concentration.

Examiner tips

  • Use the word ‘senses’ or ‘detects’ for the pancreas; examiners look for the correct organ. Mention ‘glucagon’ explicitly. Show the pathway: pancreas → bloodstream → liver. Explain the liver reaction as glycogenolysis. Finish with ‘glucose released into blood, normalising concentration’.

Common mistakes

  • Forgetting to name glucagon. Using ‘insulin’ instead of glucagon. Omitting the liver as the site of glycogenolysis.

Mark scheme (5 marks)

  1. The pancreas detects the fall in blood glucose concentration
  2. The pancreas releases/secretes glucagon
  3. Glucagon travels in the blood(stream) to the liver
  4. The liver converts glycogen into glucose (glycogen is broken down to glucose)
  5. Glucose is released into the blood(stream), returning blood glucose concentration to normal

Key terms in this question

hormonal coordination · blood glucose concentration

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