2.5.8 Diabetes · 2. Variation, Homeostasis and Micro-organisms | Wjec GCSE Science (Double Award): Biology

Section 1 of 9What is diabetes?

Diabetes mellitus is a condition in which the blood glucose concentration cannot be controlled properly and remains too high. Because the glucose level is not lowered normally after meals, glucose can appear in the urine, and the person may feel very thirsty, pass large volumes of urine, feel tired and lose weight. There are two main types.

Section 2 of 9Type 1 diabetes

In type 1 diabetes the immune system destroys the insulin-producing cells of the pancreas, so little or no insulin is made. It often starts in childhood and is not caused by lifestyle. After a meal, glucose is not taken up by cells or stored as glycogen, and the blood glucose rises dangerously high. Treatment includes:

Type 1 diabetes

injections of insulin

, usually several times a day,

or via an insulin pump, at times related to meals and exercise,
since insulin is a protein and would be digested if taken as a tablet;

controlling the diet to limit the amount of carbohydrate eaten at once;

regular monitoring of blood glucose.

If too much insulin is injected, blood glucose drops too low (hypoglycaemia) and the person may become shaky, sweaty and confused; the treatment is a sugary snack or drink.

Section 3 of 9Type 2 diabetes

In type 2 diabetes the pancreas may still make insulin, but the body cells no longer respond to it properly (insulin resistance) or not enough is made.

Type 2 diabetes

The main risk factors are obesity, a diet high in refined sugar and fat, lack of exercise, age and family history.

It is more common in older adults, although it is increasingly seen in younger people.

Treatment usually begins with a carbohydrate-controlled diet, weight loss and increased exercise,

and may add drugs that improve insulin response or release; some patients eventually need insulin injections.

Feature	Type 1	Type 2
Cause	No insulin produced because pancreatic cells are destroyed	Body cells do not respond to insulin properly
Usual age of onset	Childhood or young adult	Usually later in life
Link to lifestyle	None	Strong (obesity, inactivity)
Treatment	Insulin injections, diet	Diet, exercise, weight loss, drugs

Section 4 of 9Monitoring and data

Patients monitor blood glucose by pricking a finger and applying a drop of blood to a test strip read by a meter, and some use continuous sensors.

1

Data questions give graphs of blood glucose concentration against time for a healthy person and a person with diabetes after a meal.

2

The person with diabetes shows a higher peak and a slower return to the normal level, because insulin is missing or ineffective.

3

A graph for a person who has injected insulin shows the peak is reduced.

4

Describe the comparison using values.

5

Type 2 diabetes is linked to obesity, and body mass index (BMI = mass in kg divided by height in m squared) is often used to identify the risk.

Section 5 of 9Hyperglycaemia and ketones and case example

When cells in an untreated type 1 patient cannot use glucose, they break down fat instead, producing acidic substances called ketones that lower blood pH; this can cause diabetic coma. Early signs include fruity-smelling breath, thirst and frequent urination, which is why regular blood tests are used to protect health.

A student on a school trip with type 1 diabetes checks her blood glucose before lunch and finds it is 4 mmol per dm³, lower than ideal because of an active morning.

Hyperglycaemia and ketones and case example

She eats extra carbohydrate and reduces the insulin dose.

This example illustrates that insulin dose depends on food eaten and exercise, since exercise lowers blood glucose as muscles use more.

Section 6 of 9Long-term outcomes and public health and consequences and links

Public health measures for type 2 diabetes include taxes on sugary drinks, food labelling and encouraging exercise. Rates have risen as obesity has become more common. Screening of adults at risk can detect diabetes early, so treatment starts before complications arise, and this is often presented in exam data as bar charts of diabetes prevalence against BMI category.

Long-term poorly controlled diabetes can damage blood vessels, nerves, eyes and kidneys, and may cause kidney failure and the need for dialysis.

1

Prevention of type 2 diabetes involves a healthy diet, regular exercise and maintaining a healthy body mass.

2

This links to non-communicable disease and lifestyle choices in the health topics.

3

Research into replacing damaged pancreatic cells with stem cells is a possible future treatment for type 1 diabetes.

Section 7 of 9Exam-style questions

Compare the causes of type 1 and type 2 diabetes. [3]3 marks
Explain why people with type 1 diabetes inject insulin rather than taking it as a tablet. [2]2 marks
A man has a mass of 95 kg and a height of 1.70 m. Calculate his BMI and suggest why this is relevant to diabetes. [3]3 marks

Section 8 of 9Key terms

Term	Meaning
Diabetes	Condition in which blood glucose concentration cannot be controlled properly.
Type 1 diabetes	Disorder in which the pancreas does not produce enough insulin.
Type 2 diabetes	Disorder in which body cells no longer respond properly to insulin.
Insulin resistance	Reduced response of cells to insulin.
Hypoglycaemia	Blood glucose concentration that is too low.
BMI	Body mass index; mass in kilograms divided by height in metres squared.

Section 9 of 9Exam technique

1

Saying that diabetes is an infection or can be "caught".

2

Writing that type 2 diabetics make no insulin. Their cells respond poorly, or too little is made.

3

Stating that insulin can be taken as a tablet.

4

Forgetting that diet and exercise are the first treatment for type 2.

5

Confusing diabetes with high blood pressure or other conditions.