Understanding Diabetes


If you are doing A Level Biology, you should have encountered the concept of feedback loops in the human body. As part of a negative feedback loop, the body recognizes that a certain variable has deviated from its original ‘setpoint’, and so activates mechanisms to correct that change. Hormones can act as blood-borne, biochemical messengers in negative feedback loops of the body. For instance, you would already have learned about insulin, which helps maintain blood glucose at 4-7mM in the human body.


A rise in blood glucose is sensed by beta cells in the islets of Langerhans in the pancreas. As glucose is metabolised by the islet cells, this produces energy (ATP) that then activates multiple signalling events, finally leading to insulin release from islet cells. The greater the rise in glucose above the setpoint, the more the insulin secreted. Insulin is carried by the bloodstream to its target organs. In organs such as skeletal muscle, adipose (fat) and liver, insulin initiates responses that convert glucose into long-term energy stores (anabolism) or use it immediately as fuel for cellular functions.

Patients with diabetes mellitus have abnormally high blood glucose levels. This arises when the pancreas’s ability to produce insulin is impaired (Type 1), or target organs are less responsive to insulin, even if insulin is being produced by the pancreas (Type 2).

IMPORTANT: This resource assumes basic knowledge of insulin and diabetes mellitus as taught in A Level Biology. It aims to build on that understanding in exploring:

1. The typical profile of a patient with Type 2 diabetes mellitus,

2. The biology behind the symptoms and complications of Type 2 diabetes mellitus,

3. Proposed mechanisms of insulin resistance in Type 2 diabetes mellitus, as compared to insulin resistance in other diseases,

4. Treatments for insulin resistance.

Work through the activities below to find out more about diabetes.

Video Resource

Resource activities

Epidemiology and classification of diabetes mellitus

Who gets Type 2 diabetes mellitus? Explore the statistics around the prevalence of Type 2 diabetes in this activity.


Understanding the symptoms and complications of Type 2 diabetes mellitus

What symptoms do patients report and how do they arise?


Understanding insulin resistance

How do we define insulin sensitivity and resistance?


Insulin Resistance in Patients

How can we better manage insulin resistance in patients?


Activity questions

  • What is insulin sensitivity?
  • What are the factors that influence insulin sensitivity even in a healthy individual?
  • Many people with Type 2 diabetes mellitus are at risk of foot ulcers. From your understanding of how other complications of the condition arise, can you think of possible reasons why foot ulcers may develop?
  • A health promotion campaign encourages people to ‘stave off diabetes mellitus’ by having a healthy diet and exercising regularly. How accurate is this statement?

Reflective questions

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Task 1

What are the key arguments, concepts, points contained within it?

Task 2

What are you struggling to understand?

What could you do to improve your understanding of these concepts/terminology etc.?

Task 3

What further questions has this resource raised for you?

What else are you keen to discover about this topic and how could you go about learning more?

Can you make any links between this topic and your prior knowledge or school studies?

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Further reading

  • Diabetes UK

    Keep up to date with the most recent developments in diabetes research through the Diabetes UK website.


    Spit of lizard proves diabetes viability