Blood Glucose Regulation
Laura Armstrong
Teacher
Contents
Recall Questions
This topic requires prior knowledge of blood glucose regulation from GCSE Biology. You can test your knowledge on this below.
Which hormone lowers blood glucose levels?
Insulin.
Which organ monitors and regulates blood glucose?
The pancreas.
What happens to excess glucose in the body?
It is converted to glycogen and stored in the liver and muscle cells.
Topic Explainer Video
Why Blood Glucose Must Be Regulated
- Glucose is vital for respiration, especially in brain cells.
- Too much glucose → lowers water potential of blood → osmotic dehydration of cells.
- Too little glucose → cells can't produce enough ATP → fatigue, seizures.
Key Hormones & Organs
| Component | Role |
| Pancreas | Detects blood glucose changes, secretes hormones from endocrine regions known as the Islets of Langerhans. |
| Insulin | Lowers blood glucose (secreted by β cells in the Islets of Langerhans). |
| Glucagon | Raises blood glucose (secreted by α cells in the Islets of Langerhans). |
| Adrenaline | Raises glucose in emergencies (from adrenal glands). |
| Liver | Main target organ for hormonal action as it stores glucose as glycogen. |
When Blood Glucose Is Too High vs Too Low
When Blood Glucose Is Too High – Insulin
- Detected by β (beta) cells in the islets of Langerhans in the pancreas.
- Insulin is secreted into the blood. Glucagon secretion stops.
- Insulin binds to receptors on liver and muscle cells → triggers:
- Increased glucose uptake (increased permeability via more carrier proteins).
- Activation of enzymes that convert glucose to glycogen (glycogenesis).
- Increased respiration of glucose in cells.
- Result: Blood glucose falls back to normal (negative feedback).
When Blood Glucose Is Too Low – Glucagon & Adrenaline
Glucagon (α cells)
- Detected by α (alpha) cells in the islets of Langerhans in the pancreas.
- Glucagon is secreted into the blood. Insulin secretion stops.
- Glucagon binds to receptors on liver → triggers:
- Activation of enzymes that convert Glycogen → glucose (glycogenolysis).
- Gluconeogenesis (new glucose made from amino acids/glycerol/fatty acids).
- Reduced glucose uptake by liver cells.
- Result: Blood glucose rises back to normal.
Adrenaline (from adrenal glands)
- Released in fight-or-flight or stress response.
- Binds to receptors on liver → activates enzymes via second messenger system (cAMP).
- Stimulates glycogenolysis in the same way as glucagon does.
A-level content includes second messenger model (adrenaline/glucagon → activates adenylate cyclase → converts ATP to cAMP → activates enzyme cascade). This will be covered in more detail in a further study note.
Summary Table
| Condition | Hormone | Released From | Target Organ | Effects |
| High blood glucose | Insulin. | Pancreas (β cells). | Liver/muscles. | ↑ glucose uptake, glycogenesis, ↓ BGC. |
| Low blood glucose | Glucagon. | Pancreas (α cells). | Liver. | Glycogenolysis, gluconeogenesis ↑ BGC. |
| Low glucose (stress) | Adrenaline. | Adrenal glands. | Liver. | Glycogenolysis via cAMP ↑ BGC. |
Key Terms
- Glycogenesis: Formation of glycogen from glucose (stimulated by insulin).
- Glycogenolysis: Breakdown of glycogen to glucose (stimulated by glucagon/adrenaline).
- Gluconeogenesis: Formation of new glucose from non-carbohydrates (e.g. amino acids/ fatty acids).
- Glycogen: A polysaccharide made of many alpha glucose monomers. Stored in the liver and in skeletal muscle cells.
- Second messenger model: Process where hormone binding triggers intracellular signalling via cAMP.
No answer provided.
Exam Tip
If you think you will mix up all of the ‘G’ words, don’t use them! Just describe the processes instead so you don’t lose marks for using incorrect terms.
Remember, insulin, glucagon and adrenaline are hormones made of protein. They do not enter target cells themselves as they are too large. Don’t imply these hormones directly break down glycogen or make glycogen. Instead say ‘they bind to receptors which then activates enzymes which…’
No answer provided.
Explain how glucagon increases blood glucose concentration. Do not include detail of the second messenger model. (5 marks)
- Glucagon binds to specific receptors on liver cell membranes.
- This activates enzymes
- These enzymes trigger glycogenolysis (or the hydrolysis of glycogen → glucose).
- Glucagon also stimulates gluconeogenesis (or making glucose from amino acids/glycerol/fatty acids).
- Glucose then diffuses into the blood.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!