Explain how insulin and glucagon work together to maintain a stable blood glucose concentration after a person eats a meal rich in carbohydrates.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
After eating a meal rich in carbohydrates, the blood glucose concentration rises. The pancreas detects this change and responds by secreting hormones to restore normal blood glucose levels.
Model answer (4 marks)
After a carbohydrate meal the pancreas releases insulin.
1. Insulin binds to receptors on liver and muscle cells.
2. It stimulates glucose uptake into these cells.
3. In the liver it also activates glycogen synthase, converting glucose to glycogen, reducing blood glucose.
If glucose falls, the pancreas secretes glucagon.
4. Glucagon binds to liver receptors, activating glycogen phosphorylase, breaking glycogen into glucose, which is released into the blood to restore normal levels.
1. Insulin binds to receptors on liver and muscle cells.
2. It stimulates glucose uptake into these cells.
3. In the liver it also activates glycogen synthase, converting glucose to glycogen, reducing blood glucose.
If glucose falls, the pancreas secretes glucagon.
4. Glucagon binds to liver receptors, activating glycogen phosphorylase, breaking glycogen into glucose, which is released into the blood to restore normal levels.
Examiner tips
- Use the word ‘stimulates’ or ‘activates’ for insulin actions; use ‘breaks down’ for glucagon.
- Show the sequence: insulin → uptake & glycogen synthesis; glucagon → glycogenolysis.
- Mention the pancreas as the source of both hormones.
Common mistakes
- Confusing the actions of insulin and glucagon (e.g., saying insulin causes glycogen breakdown).
- Omitting the role of the pancreas as the source of the hormones.
Mark scheme (4 marks)
- The pancreas secretes insulin when blood glucose concentration is too high
- Insulin causes liver and muscle cells to increase their uptake of glucose AND causes conversion of glucose to glycogen in the liver, lowering blood glucose concentration
- If blood glucose concentration falls too low, the pancreas secretes glucagon
- Glucagon causes the breakdown of glycogen to glucose in the liver, raising blood glucose concentration back to normal
Key terms in this question
insulin · glucagon · blood glucose concentration
Related
- Revision notes: Hormonal coordination →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →