Explain how the body maintains blood glucose concentration within its normal range following ingestion of a carbohydrate-rich meal.

IB DP Biology Higher Level (2023 syllabus) — D3.3 Homeostasis · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

1. After a carbohydrate‑rich meal, blood glucose rises.
2. The rise is sensed by beta cells of the islets of Langerhans.
3. Beta cells secrete insulin into the bloodstream.
4. Insulin stimulates uptake of glucose by liver and muscle and promotes glycogenesis, lowering blood glucose; when glucose falls to the set point, insulin secretion stops, completing the negative feedback loop.

Examiner tips

  • Use the exact sequence of events: rise → detection → insulin release → action → return to set point.
  • Show the negative feedback loop explicitly.
  • Include the key organs (pancreas, liver, muscle).

Common mistakes

  • Confusing glucagon with insulin as the hormone released.
  • Omitting the role of glycogenesis or the organs involved.

Mark scheme (4 marks)

  1. Rising blood glucose is detected by beta cells of the islets of Langerhans in the pancreas
  2. Beta cells secrete insulin into the blood in response to high blood glucose
  3. Insulin causes body cells (especially liver and muscle) to take up glucose / promotes conversion of glucose to glycogen (glycogenesis)
  4. As blood glucose falls back to the set point, the stimulus for insulin secretion is removed, illustrating negative feedback

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