How is blood glucose controlled, and how do diabetes and obesity affect health?
The control of blood glucose concentration by insulin and glucagon (and the role of adrenaline), the negative feedback maintaining glucose levels, the causes and effects of type 1 and type 2 diabetes, and the measurement and health consequences of obesity.
An SQA Higher Human Biology answer on blood glucose and obesity, covering the control of blood glucose by insulin and glucagon, the role of glycogen and adrenaline, negative feedback, the causes and effects of type 1 and type 2 diabetes, the glucose tolerance test, and the measurement and health risks of obesity.
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What this dot point is asking
The SQA wants you to explain how blood glucose is controlled by insulin and glucagon through negative feedback, describe the role of glycogen and adrenaline, compare the causes and effects of type 1 and type 2 diabetes, and explain how obesity is measured and why it harms health.
Controlling blood glucose
The pancreas detects the glucose level and responds with two opposing hormones:
- When blood glucose rises (for example after a meal), the pancreas releases insulin. Insulin causes the liver and other cells to take up glucose and convert it to glycogen for storage, lowering the blood glucose back to normal.
- When blood glucose falls (for example during fasting or exercise), the pancreas releases glucagon. Glucagon causes the liver to break glycogen back down into glucose and release it into the blood, raising the level back to normal.
Diabetes
There are two main types, with different causes:
- Type 1 diabetes. The body cannot produce insulin, because the insulin-secreting cells of the pancreas have been destroyed, usually appearing early in life. Because no insulin is made, it is treated with insulin injections.
- Type 2 diabetes. The body still produces insulin, but the cells become less sensitive to it (insulin resistance), so glucose is not taken up properly. It usually develops later in life, is strongly linked to obesity, and is managed by diet, weight loss and exercise.
Diabetes can be investigated with a glucose tolerance test, in which a person drinks a glucose solution and their blood glucose is measured over the next couple of hours. In a diabetic person the glucose rises higher and takes much longer to return to normal, because the control mechanism is not working.
Obesity
BMI is used to classify whether someone is underweight, a healthy weight, overweight or obese. Obesity matters because it raises the risk of serious conditions, especially type 2 diabetes (through insulin resistance) and cardiovascular disease (through raised cholesterol and blood pressure). Because obesity usually results from taking in more energy than is used, it can largely be controlled by a balanced diet and regular exercise.
Examples in context
Example 1. Blood glucose after a meal. After eating, blood glucose rises and the pancreas releases insulin, so the liver stores the excess as glycogen and the level returns to normal within a couple of hours. In a diabetic person this return is delayed, which a glucose tolerance test reveals.
Example 2. Obesity and type 2 diabetes. A person who is obese over many years can develop insulin resistance, so their cells respond poorly to insulin and blood glucose stays high. Losing weight through diet and exercise often restores their sensitivity to insulin, showing how obesity and type 2 diabetes are linked.
Try this
Q1. Name the hormone that lowers blood glucose by promoting its storage as glycogen. [1 mark]
- Cue. Insulin.
Q2. Explain why type 2 diabetes is described as insulin resistance rather than insulin deficiency. [1 mark]
- Cue. The pancreas still produces insulin, but the body cells respond poorly to it, so glucose is not taken up properly.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA Higher 20184 marksExplain how the body lowers a raised blood glucose concentration and how it raises a low blood glucose concentration.Show worked answer →
A 4-mark answer needs both opposing hormonal responses controlled by the pancreas.
When blood glucose rises (for example after a meal), the pancreas releases the hormone insulin. Insulin causes the liver and other cells to take up glucose and convert it to glycogen for storage, which lowers the blood glucose back to normal.
When blood glucose falls (for example during fasting or exercise), the pancreas releases the hormone glucagon. Glucagon causes the liver to break glycogen back down into glucose and release it into the blood, raising the blood glucose back to normal. Adrenaline can also raise blood glucose in the same way during stress.
Award (1) high glucose triggers insulin from the pancreas, (2) insulin causes conversion of glucose to glycogen, (3) low glucose triggers glucagon, and (4) glucagon causes breakdown of glycogen to glucose.
SQA Higher 20213 marksCompare the causes of type 1 and type 2 diabetes, and state one way the body mass index (BMI) is used in assessing obesity.Show worked answer →
This is a 3-mark compare-and-state question.
In type 1 diabetes, the body cannot produce insulin because the insulin-secreting cells of the pancreas have been destroyed, usually early in life. It is treated with insulin injections.
In type 2 diabetes, the body still produces insulin but the cells become less sensitive to it (insulin resistance), so glucose is not taken up properly. It develops later in life and is linked to obesity, and is managed by diet, weight loss and exercise.
BMI is calculated from a person's mass and height and is used to classify whether someone is underweight, a healthy weight, overweight or obese. Markers reward (1) type 1 cannot make insulin, (2) type 2 produces insulin but cells are resistant, and (3) BMI uses mass and height to classify weight category.
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