Control of Blood Glucose Concentration (AQA GCSE Biology): Revision Note

Control of blood glucose

• 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

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

• 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

Summary of type 1 and type 2 diabetes

• Type 1

  • Cause: inability of pancreas to produce insulin

  • Treatment: monitoring blood glucose levels and injecting human insulin throughout the day (particularly after meals consumed)

• Type 2

  • Cause: cells of the body become resistant to insulin or insufficient insulin produced by the pancreas

  • Treatment: maintain a low-carbohydrate diet and regular exercise to reduce need for insulin

Interpreting information about blood glucose levels

Negative feedback control of blood glucose

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

Diagram of Negative feedback regulation of blood glucose levels

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