Insulin & Diabetes (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note

Insulin & Blood Glucose Control

• Regulation of blood glucose is an example of homeostasis

• The concentration of glucose in the blood must be kept within a narrow range 

  • Excessively high levels of glucose in the blood can lead to cells of the body losing water by osmosis, which can be dangerous

  • Excessively low levels of glucose in the blood can lead to the brain receiving insufficient glucose for respiration, potentially leading to a coma or even death

• Blood glucose levels are regulated by the pancreas and the liver using hormones insulin and glucagon

  • Insulin stimulates cells to take in glucose from the bloodstream (particularly liver and muscle cells)

  • In liver and muscle cells excess glucose is converted into glycogen (a polymer of glucose) for storage

Glucagon & Blood Glucose Control (HT Only)

Higher Tier Only

• The pancreas acts as an endocrine gland, secreting the two hormones required in glucoregulation

  • Insulin - which converts glucose to glycogen (which is insoluble so can be stored for later use)

  • Glucagon - which converts glycogen to glucose (for respiration)

• Both hormones act to maintain the blood glucose levels within the optimum limits as part of a negative feedback cycle

A negative feedback cycle

If the blood glucose concentration gets too low

• Cells in the pancreas detect the decreased blood glucose levels

• The pancreas produces the hormone glucagon and secretes it into the blood

• Glucagon causes the glycogen stored in the liver to be converted into glucose and released into the blood

• This increases the concentration of glucose in the blood back to normal levels, at which point the pancreas stops secreting glucagon

If the blood glucose concentration gets too high

• Cells in the pancreas detect the increased blood glucose levels

• The pancreas produces the hormone insulin, secreting it into the blood

• Insulin stimulates muscles and the liver to take up glucose from the bloodstream and store it as glycogen (a polymer of glucose)

• This reduces the concentration of glucose in the blood back to normal levels, at which point the pancreas stops secreting insulin

Glucose is regulated by the action of hormones insulin and glucagon

Type 1 & Type 2 Diabetes

Type 1 diabetes

• Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin to control blood glucose levels

• Scientists think this is a result of a person’s own immune system destroying the cells of the pancreas that make insulin during development

• Type 1 diabetes is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections

Type 2 diabetes

• In Type 2 diabetes the body cells no longer respond to insulin produced by the pancreas - the person still makes insulin but their cells are resistant to it and don’t respond as well as they should

• This can also lead to uncontrolled high blood glucose levels

• Obesity is a big risk factor for Type 2 diabetes; probably because a person who is obese may consume a diet high in carbohydrates, and over-production of insulin results in resistance to it developing

• A carbohydrate-controlled diet and an exercise regime are common treatments for Type 2 diabetes