Control of Blood Glucose Concentration (AQA GCSE Biology: Combined Science)

• Blood glucose concentration is monitored and controlled by the pancreas
• The pancreas is an endocrine gland (making and secreting hormones into the bloodstream) and it also plays a vital (but separate) role in digestion (making and secreting enzymes into the digestive system)
• Blood glucose concentration must be kept within a narrow range, so it’s another example of homeostasis (like temperature control)
• Eating foods containing carbohydrate results in an increase of glucose into the bloodstream
• If the blood glucose concentration is too high, the pancreas produces the hormone insulin to bring it back down
  • Too high a level of glucose in the blood can lead to cells of the body losing water by osmosis, which can be dangerous

• 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

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

Comparing Type 1 & Type 2 diabetes

Higher tier only

• If the blood glucose concentration is too low, the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.
• Glucagon and insulin interact as part of a negative feedback cycle to control blood glucose (sugar) levels in the body:
  • Insulin is produced when blood glucose rises and stimulates liver and muscle cells to convert excess glucose into glycogen to be stored – this reduces the blood glucose level
  • Glucagon is produced when blood glucose falls too low and stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the bloodstream – this increases the blood glucose level

Negative feedback regulation of blood glucose levels