Diabetes (AQA GCSE Biology Combined Science): Revision Notes
Diabetes
What is diabetes?
Diabetes happens when your body can't control the amount of glucose (sugar) in your blood properly. This means blood sugar levels can become dangerously high or low.
Glucose is the main source of energy for your body's cells. When diabetes develops, this essential energy source can't be properly regulated, leading to serious health complications if left untreated.
Two main types of diabetes
There are two different types of diabetes. They have different causes and need different treatments.
Type 1 diabetes
Type 1 diabetes is an autoimmune condition where the body's own immune system mistakenly attacks healthy cells.
What causes it:
- The body's immune system attacks and destroys special cells in the pancreas
- These cells normally make insulin
- Without enough insulin, blood sugar can't be controlled
Type 1 diabetes is NOT caused by lifestyle factors or diet. It's an autoimmune condition that cannot be prevented or cured, only managed with insulin therapy.
How it's treated:
- Insulin injections are needed regularly
- People must inject insulin to replace what their pancreas can't make
When it happens:
- Usually develops in childhood
- Not linked to being overweight
Type 2 diabetes
Type 2 diabetes develops when the body becomes resistant to insulin or doesn't produce enough of it.
What causes it:
- Liver cells and muscle cells stop responding properly to insulin
- The pancreas might not make enough insulin
- Often linked to being overweight
How it's treated:
- Controlling what you eat (especially carbohydrates)
- Regular exercise
- Sometimes medication is needed too
When it happens:
- Usually develops when people are over 30 years old
- More common in people who are overweight
Unlike Type 1, Type 2 diabetes can often be prevented or delayed through healthy lifestyle choices. Early intervention with diet and exercise can sometimes reverse the condition.
Body mass index (BMI)
BMI helps doctors work out if someone is a healthy weight. Being overweight increases the risk of getting Type 2 diabetes.
BMI categories
| BMI (kg/m²) | Category |
|---|---|
| Less than 18.5 | Underweight |
| 18.5-25 | Normal weight |
| 25-30 | Overweight |
| Over 30 | Obese |
How to calculate BMI
Formula: BMI = mass in kg ÷ (height in m)²
Using LaTeX notation:
Worked Example: Calculating BMI
A person weighs 66 kg and is 1.73 m tall
Step 1: Write down the formula
Step 2: Substitute the values
Step 3: Calculate the height squared (rounded to 3.0)
Step 4: Complete the division
Result: This person has a normal weight (BMI between 18.5-25)
The link between BMI and diabetes
Research shows that people with higher BMIs are more likely to develop Type 2 diabetes:
- The risk increases gradually from normal weight to overweight
- The risk increases much more dramatically when people become obese
- Women are affected more than men at the highest BMI levels
Studies have found that people with a BMI over 30 have a significantly higher risk of developing Type 2 diabetes compared to those with normal weight. The risk can be up to 7 times higher for obese individuals.
Important facts about insulin
People with Type 1 diabetes need different amounts of insulin depending on several factors throughout the day.
Insulin Requirements Vary Based On:
- What food they've eaten (especially carbohydrates)
- How much exercise they've done
- Their blood sugar levels at the time
This is why people with Type 1 diabetes must regularly monitor their blood glucose and adjust their insulin doses accordingly.
Key Points to Remember:
- Diabetes means the body can't control blood sugar properly
- Type 1 usually starts in childhood and needs insulin injections
- Type 2 usually starts after age 30 and is linked to being overweight
- BMI over 30 (obese) greatly increases Type 2 diabetes risk
- Type 2 can often be managed with diet and exercise