How is blood glucose concentration controlled, and what goes wrong in diabetes?
The control of blood glucose by insulin and glucagon, the role of the pancreas and liver, the difference between Type 1 and Type 2 diabetes, and how each is treated.
A focused answer to AQA GCSE Biology 4.5.3.2, covering the control of blood glucose by insulin and glucagon, the role of the pancreas and liver, and the causes and treatment of Type 1 and Type 2 diabetes.
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What this dot point is asking
AQA wants you to explain how blood glucose concentration is controlled by insulin and glucagon (higher tier), the role of the pancreas and liver, and the differences between Type 1 and Type 2 diabetes and how each is treated.
Controlling blood glucose
- If blood glucose is too high: the pancreas releases insulin. Insulin causes glucose to move from the blood into the liver and muscle cells, where it is stored as glycogen. Blood glucose then falls back towards normal.
- If blood glucose is too low (higher tier): the pancreas releases glucagon. Glucagon makes the liver convert stored glycogen back into glucose, which is released into the blood, raising the level.
Keeping blood glucose steady matters because cells need a constant supply of glucose for respiration, while a level that is too high damages blood vessels and a level that is too low starves the brain of energy.
Type 1 and Type 2 diabetes
In Type 1 diabetes, injecting insulin lowers the blood glucose after a meal, but the dose must be judged carefully: too much insulin can make blood glucose fall too low. Type 2 diabetes is increasingly common because rates of obesity have risen.
Try this
Q1. Explain what the pancreas does when blood glucose rises too high. [2 marks]
- Cue. It releases insulin, which makes the liver and muscles take up glucose and store it as glycogen.
Q2. State the main difference between Type 1 and Type 2 diabetes. [2 marks]
- Cue. Type 1: the pancreas does not make enough insulin. Type 2: the body cells stop responding to insulin.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20194 marksExplain how blood glucose concentration is controlled when a person eats a meal containing carbohydrate and later goes without food for several hours. Refer to the hormones and organs involved.Show worked answer →
A 4-mark higher-tier explain question rewards both halves of the negative-feedback loop.
After a meal, blood glucose rises as carbohydrate is digested to glucose and absorbed. The pancreas detects this and releases insulin. Insulin makes the liver and muscle cells take up glucose from the blood and store it as glycogen, so blood glucose falls back to normal.
During fasting, blood glucose falls, so the pancreas releases glucagon. Glucagon makes the liver convert stored glycogen back into glucose, which is released into the blood, raising it to normal.
Markers reward insulin causing storage as glycogen when glucose is high, and glucagon causing release of glucose when it is low, with the pancreas and liver correctly involved.
AQA 20214 marksCompare the causes and treatments of Type 1 and Type 2 diabetes. Suggest why Type 2 diabetes is increasingly common.Show worked answer →
A 4-mark question rewards comparison plus a reasoned suggestion.
In Type 1 diabetes the pancreas does not produce enough insulin, usually from a young age, so blood glucose can rise dangerously high; it is treated with insulin injections along with controlling diet and exercise. In Type 2 diabetes the body cells stop responding properly to insulin, so glucose stays high; it is usually treated first with a carbohydrate-controlled diet and exercise, and sometimes medication.
Type 2 is becoming more common because obesity is a major risk factor, and rates of obesity have risen with diets high in sugar and fat and with less physical activity.
Markers reward the correct cause and treatment of each type, and obesity (or lifestyle) as the reason for the rise in Type 2.
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Sources & how we know this
- AQA GCSE Biology (8461) specification — AQA (2016)