Blood glucose and diabetes — Edexcel GCSE Biology
How insulin and glucagon control blood glucose, the two types of diabetes, and how BMI and waist:hip ratio are used.
Revision notes
5 short notes, in the order of the specification. Each one in short:
Insulin is a hormone secreted by the pancreas when blood glucose concentration rises, for example after a meal. Insulin makes cells take up glucose from the blood, and in the liver and muscles glucose is converted into glycogen for storage. Blood glucose concentration then falls back to normal. The pancreas makes insulin, and the liver stores glycogen.
Glucagon
Higher tierGlucagon is a hormone secreted by the pancreas when blood glucose concentration falls too low, for example between meals or during exercise. It acts on the liver, which changes glycogen into glucose and releases it into the blood, so blood glucose concentration rises back to normal. Insulin and glucagon work against each other by negative feedback.
Type 1 diabetes is a condition in which the pancreas does not produce enough insulin, so body cells do not take up enough glucose and blood glucose concentration stays too high after a meal. It is controlled by injections of insulin, monitoring blood glucose concentration and controlling the amount of carbohydrate in the diet. Diet alone cannot control it.
Type 2 diabetes is a condition in which body cells no longer respond properly to insulin, so blood glucose concentration stays too high. It is linked to being overweight or obese. It is controlled by a carefully controlled diet, regular exercise and losing weight if overweight, and some people also need medication or insulin.
BMI (body mass index) is calculated as mass in kilograms divided by height in metres squared. There is a correlation between body mass and type 2 diabetes: the higher the body mass, the greater the chance of developing it. The waist:hip ratio shows where fat is stored, and a correlation does not prove that one thing causes the other.
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Quick check questions
Which organ makes insulin and which organ stores glycogen?
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The pancreas makes insulin. The liver stores glycogen.
What does glucagon do? (Higher)
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It makes the liver change glycogen into glucose, so blood glucose concentration rises.
State the cause of type 1 diabetes.
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The pancreas does not produce enough insulin.
State the cause of type 2 diabetes.
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Body cells no longer respond to insulin.
Write the BMI equation.
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BMI = mass (kg) ÷ height (m)².
Frequently asked questions
What does insulin do to blood sugar?
Insulin lowers blood sugar. The pancreas secretes insulin into the blood when blood glucose concentration rises, for example after a meal. Insulin makes cells take up glucose from the blood, and in the liver and muscles the glucose is converted into glycogen for storage. Blood glucose concentration then falls back to normal.
How does the body control blood glucose levels?
Higher tier The pancreas controls blood glucose using two hormones. When blood glucose is too high, it secretes insulin, so cells take up glucose and the liver stores it as glycogen. When blood glucose is too low, it secretes glucagon, so the liver changes glycogen into glucose. This negative feedback keeps blood glucose close to normal.
What is the difference between type 1 and type 2 diabetes?
In type 1 diabetes the pancreas does not produce enough insulin, so it is controlled by insulin injections, blood glucose monitoring and diet. In type 2 diabetes the body cells no longer respond properly to insulin. Type 2 is linked to obesity and is controlled by diet, exercise and weight loss, sometimes with medication.
How do you calculate BMI?
BMI is calculated by dividing mass in kilograms by height in metres squared. Square the height first, then divide. For example, a person with a mass of 85 kg and a height of 1.70 m has a BMI of 85 ÷ 2.89 = 29.4. A higher body mass is linked to a greater chance of type 2 diabetes.
How do you test urine for glucose?
Add Benedict's solution to a sample of urine in a test tube and heat it in a hot water bath for a few minutes. Blue means no sugar, while green, yellow, orange and brick red show more and more sugar. Glucose in urine suggests that blood glucose concentration is too high, as in untreated diabetes.
Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026