A student has been sitting quietly studying. They suddenly remember they have a test tomorrow and begin to feel anxious. Explain how the hormone glucagon maintains a suitable blood glucose concentration when the student skips dinner to keep revising, and describe the role of the pancreas in this process.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
When blood glucose concentration falls below the normal level, the body responds by releasing a hormone to restore balance. This is an example of hormonal coordination.
Model answer (5 marks)
The pancreas senses the fall in blood glucose.
1. Pancreatic α‑cells detect the low glucose level.
2. They secrete the hormone glucagon into the bloodstream.
3. Glucagon travels to the liver, its target organ.
4. In the liver, glucagon stimulates glycogenolysis, breaking down glycogen to glucose.
5. The released glucose enters the blood, raising glucose concentration back to the normal set point and restoring balance.
1. Pancreatic α‑cells detect the low glucose level.
2. They secrete the hormone glucagon into the bloodstream.
3. Glucagon travels to the liver, its target organ.
4. In the liver, glucagon stimulates glycogenolysis, breaking down glycogen to glucose.
5. The released glucose enters the blood, raising glucose concentration back to the normal set point and restoring balance.
Examiner tips
- Use the exact sequence of events: detection → secretion → transport → action → result.
- Show the role of the pancreas as the sensor and hormone source.
- Mention the target organ (liver) and the specific metabolic process (glycogenolysis).
Common mistakes
- Confusing glucagon with insulin or describing insulin action.
- Omitting the pancreas as the detecting organ or the liver as the target organ.
- Failing to state the metabolic process (glycogenolysis) or the restoration of balance.
Mark scheme (5 marks)
- The pancreas detects that blood glucose concentration has fallen (below normal level)
- The pancreas releases / secretes glucagon
- Glucagon travels in the blood to the liver (as its target organ)
- Glucagon causes the liver to convert glycogen into glucose (glycogenolysis)
- This raises blood glucose concentration back to the normal / set level, restoring balance
Key terms in this question
glucagon · pancreas · blood glucose concentration
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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