Cells and organisation · GCSE Biology
Blood glucose control
Explain how the pancreas, insulin and glucagon control blood glucose for GCSE Biology, with emphasis on liver, muscle and organisational links to homeostasis.
High glucose → pancreas releases insulin → liver and muscles take up glucose, store as glycogen → level falls. Low glucose → glucagon → glycogen to glucose. Liver is key organ; negative feedback.
The important bits
What you need to know
- 1
Blood glucose concentration must stay within a narrow range so cells receive enough fuel and the blood is not too concentrated osmotically.
- 2
After a meal, blood glucose rises. The pancreas detects this and secretes insulin into the blood.
- 3
Insulin causes liver and muscle cells to take up excess glucose from the blood and convert it to glycogen for storage. Blood glucose falls.
- 4
When blood glucose is too low (e.g. during exercise or fasting), the pancreas releases glucagon (Higher tier).
- 5
Glucagon causes glycogen in the liver to be broken down into glucose, which is released into the blood, raising blood glucose.
- 6
The liver is the main organ for glycogen storage and glucose release; muscle glycogen is mainly for local use during exercise.
- 7
This is negative feedback: a change is detected, a hormone corrects it, and the response is switched off when the level returns to normal.
- 8
Type 1 diabetes: pancreas produces little or no insulin — treated with insulin injections. Type 2: body cells respond poorly to insulin — often managed with diet, exercise and later medication.
Quotations worth analysing
Short evidence. Real method.
“Insulin causes blood glucose to decrease by increasing uptake and storage as glycogen.”
Insulin does not “destroy sugar”. Uptake and glycogen storage are the mark-scheme verbs.
“Glucagon causes glycogen to be converted back to glucose when blood glucose is low.”
Foundation may focus on insulin only; Higher adds glucagon and the two-way control.
“The pancreas acts as both a detector and an effector gland in blood glucose control.”
Link organ (pancreas) to hormone (insulin/glucagon) to target tissues (liver, muscle).
Go deeper
Organisation: which cells and organs are involved?
Pancreas (endocrine islets) = gland producing hormones. Blood = transport. Liver hepatocytes = store glycogen, release glucose. Muscle fibres = store glycogen for contraction. All are specialised cells in organs working as part of the endocrine control of metabolism — an organisation answer, not just “homeostasis”. After eating, digested glucose is absorbed in the ileum, enters blood, reaches pancreas and liver. Without insulin, glucose stays high; kidneys may excrete excess in severe diabetes, and cells may lack fuel despite high blood sugar.
Go deeper
Insulin and glucagon as a pair (Higher tier)
High glucose → insulin ↑ → glucose → glycogen in liver/muscle → glucose ↓. Low glucose → glucagon ↑ → glycogen → glucose in liver → glucose ↑. The two hormones oppose each other. Negative feedback means neither hormone keeps rising forever — as glucose normalises, secretion drops. Graph questions may show a meal spike and return to baseline. Do not write insulin for low glucose or glucagon for high glucose.
Go deeper
Diabetes from an organisation angle
Type 1: autoimmune destruction of insulin-producing cells — the effector gland fails. Treatment replaces the missing hormone. Type 2: receptors on target cells respond poorly, often linked to excess adipose tissue — the communication step fails even if insulin is present. Both show why coordinated organ function matters: digestion supplies glucose, pancreas signals storage/release, liver executes much of the storage. Lifestyle changes in Type 2 improve target cell response and reduce glucose load.
See the idea in action
After eating a carbohydrate-rich meal, explain how blood glucose is returned to normal (4 marks). Glucose from digested food is absorbed into the blood, raising blood glucose. The pancreas releases insulin. Insulin causes liver and muscle cells to take up glucose and convert it to glycogen. Blood glucose concentration falls back towards the normal range. This is negative feedback.
Exam technique
Turn knowledge into marks
Always pair hormone with correct direction of change. Name liver and glycogen. For Type 1 vs 2, match cause to treatment. Organisation questions want organ names, not just “the body controls sugar”.
Common mistakes
Do not give these marks away
- 01
Saying insulin raises blood glucose, or that insulin breaks down glucose.
- 02
Using glucagon when describing a post-meal rise in glucose (wrong hormone).
- 03
Confusing Type 1 (no insulin, injections) with Type 2 (poor response, lifestyle first).
What does insulin cause when blood glucose is too high?
AGlycogen is broken down to glucose in the liver
BGlucose is taken up and stored as glycogen in liver and muscle
CGlucagon is released from the pancreas
DThe kidneys absorb more glucose from urine
Show the answer
Glucose is taken up and stored as glycogen in liver and muscle. Insulin lowers blood glucose by promoting uptake and glycogen storage. Glucagon does the opposite when glucose is low.
Quick questions
If this is the bit you searched
What is the role of insulin?
It is released when blood glucose is high and causes liver and muscle cells to take up glucose and store it as glycogen, lowering blood glucose.
What does glucagon do?
When blood glucose is low, it triggers breakdown of glycogen to glucose in the liver, raising blood glucose.
Why is the liver important in blood glucose control?
It stores glucose as glycogen when insulin is high and releases glucose when glucagon is high.
What is negative feedback in blood glucose control?
A rise or fall in glucose triggers a hormone response that reverses the change, returning levels toward normal.