How is blood glucose controlled, and what goes wrong in diabetes?
Explain the importance of homeostasis, how insulin and glucagon control blood glucose concentration, the causes and control of type 1 and type 2 diabetes, and the correlation between body mass and type 2 diabetes.
A focused answer to Edexcel GCSE Biology 7.9 and 7.13 to 7.17, covering homeostasis, the control of blood glucose by insulin and glucagon, type 1 and type 2 diabetes, and BMI and waist-to-hip calculations.
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What this dot point is asking
Edexcel statements 7.9 and 7.13 to 7.17 want you to explain why homeostasis matters, how insulin and glucagon control blood glucose, the causes and control of type 1 and type 2 diabetes, and the correlation between body mass and type 2 diabetes including BMI and waist-to-hip calculations.
Homeostasis
It matters because enzymes and cells only work well within a narrow range of conditions. If blood glucose, temperature or water content moves too far from the set point, reactions slow down or cells are damaged, so the body uses control systems (often negative feedback) to correct any change.
Controlling blood glucose
The pancreas monitors and controls blood glucose using two hormones with opposite effects:
This is a negative-feedback system: a rise triggers insulin (which lowers it), and a fall triggers glucagon (which raises it), keeping blood glucose near a set point.
Type 1 and type 2 diabetes
Body mass and type 2 diabetes
There is a strong correlation between a high body mass (obesity) and the risk of type 2 diabetes. Doctors assess this using:
A BMI above about is classed as obese and is linked to higher type 2 diabetes risk. The waist-to-hip ratio (waist circumference divided by hip circumference) is also used, because fat stored around the abdomen is especially linked to the disease. Remember that a correlation does not by itself prove that obesity causes diabetes, but the evidence for a causal link here is strong.
Try this
Q1. State which hormone lowers blood glucose and where it is made. [2 marks]
- Cue. Insulin, made by the pancreas.
Q2. Give one difference between the causes of type 1 and type 2 diabetes. [1 mark]
- Cue. Type 1: the pancreas does not make enough insulin. Type 2: the body's cells stop responding to insulin.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20194 marksExplain how the body reduces the blood glucose concentration after a meal high in carbohydrate.Show worked answer →
A 4-mark explain question rewards the insulin pathway.
- After the meal, the blood glucose concentration rises as carbohydrate is digested and absorbed.
- This rise is detected by the pancreas, which releases the hormone insulin into the blood.
- Insulin causes body cells, especially in the liver and muscles, to take up glucose from the blood.
- The liver converts the excess glucose into glycogen for storage, so the blood glucose concentration falls back to normal.
Markers reward the pancreas detecting the rise, releasing insulin, cells taking up glucose, and the liver storing it as glycogen. Confusing insulin with glucagon (which raises glucose) loses marks.
Edexcel 20213 marksA person has a mass of 90 kg and a height of 1.5 m. Calculate their BMI using BMI = mass / height squared, and state what this suggests about their risk of type 2 diabetes.Show worked answer →
A 3-mark calculation rewards correct substitution and a sensible interpretation.
BMI .
A BMI of is in the obese range (well above the healthy to ). A high BMI is correlated with a higher risk of type 2 diabetes, so this person has an increased risk.
Markers reward squaring the height (not doubling it), the correct BMI of , and linking a high BMI to greater type 2 diabetes risk. Forgetting to square the height is the usual error.
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Biology (1BI0) specification — Pearson (2016)