Insulin and glucagon work together to maintain a stable blood glucose concentration. Explain how these two hormones bring blood glucose concentration back to the optimum level after a person eats a large meal containing carbohydrates, and after a period of intense exercise.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
The pancreas produces hormones that control blood glucose concentration. This is an example of a negative feedback system.
Model answer (5 marks)
After a large carbohydrate meal the blood glucose level rises above the optimum.
1. The pancreas senses the high glucose and secretes insulin.
2. Insulin stimulates liver (and muscle) cells to take up glucose and convert it to glycogen for storage.
3. Glycogen synthesis removes glucose from the blood, lowering the concentration back to the optimum.
During intense exercise the blood glucose level falls below the optimum as cells use glucose.
4. The pancreas releases glucagon in response to the low glucose.
5. Glucagon signals the liver to break down glycogen into glucose, which is released into the blood, raising the concentration back to the optimum.
1. The pancreas senses the high glucose and secretes insulin.
2. Insulin stimulates liver (and muscle) cells to take up glucose and convert it to glycogen for storage.
3. Glycogen synthesis removes glucose from the blood, lowering the concentration back to the optimum.
During intense exercise the blood glucose level falls below the optimum as cells use glucose.
4. The pancreas releases glucagon in response to the low glucose.
5. Glucagon signals the liver to break down glycogen into glucose, which is released into the blood, raising the concentration back to the optimum.
Examiner tips
- Use the sequence of events: rise/fall → hormone release → action → effect on glucose level.
- Show the two different situations (post‑meal and exercise) clearly.
- Use the exact terms: insulin, glucagon, glycogen, liver, blood glucose.
Mark scheme (5 marks)
- After a meal, blood glucose concentration rises above the optimum / increases
- The pancreas releases insulin in response to high blood glucose
- Insulin causes the liver (and cells) to convert glucose into glycogen for storage, lowering blood glucose concentration back to the optimum
- During intense exercise, blood glucose concentration falls below the optimum / decreases as glucose is used in respiration
- The pancreas releases glucagon, which converts glycogen back into glucose, raising blood glucose concentration back to the optimum
Key terms in this question
insulin · glucagon · blood glucose concentration
Related
- All Eduqas A-Level Biology revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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