AQA GCSE FOUNDATION Biology: Control of Blood Glucose

AQA GCSE Foundation Biology: Control of Blood Glucose

Introduction

Your body needs a constant supply of glucose for energy. However, the amount of glucose in your blood (blood glucose concentration) needs to be tightly controlled. If it's too high, you can develop serious health problems like diabetes. If it's too low, you can feel dizzy and weak.

The Role of Insulin and Glucagon

The control of blood glucose is mainly achieved by two hormones: insulin and glucagon. These hormones are produced by the pancreas, a gland located near the stomach.

Insulin is released when blood glucose levels are high. It helps to lower blood glucose by:

• Stimulating cells to take up glucose from the blood.
• Promoting the conversion of glucose to glycogen for storage in the liver and muscles.
• Inhibiting the breakdown of glycogen to glucose.

Glucagon is released when blood glucose levels are low. It helps to raise blood glucose by:

• Stimulating the breakdown of glycogen to glucose in the liver.
• Promoting the conversion of other molecules (e.g. fatty acids) to glucose (gluconeogenesis).

The Control Mechanism

This is a simplified diagram of how insulin and glucagon work together to maintain a stable blood glucose concentration:

High blood glucose  ->  Pancreas releases insulin  ->  Blood glucose lowers
Low blood glucose  ->  Pancreas releases glucagon  ->  Blood glucose rises

Understanding the Process

• After a meal: Blood glucose levels increase as glucose from the food is absorbed into the bloodstream. This triggers the release of insulin. Insulin helps cells take up glucose, reducing blood glucose levels back to normal.
• Between meals: Blood glucose levels start to drop. This triggers the release of glucagon. Glucagon stimulates the liver to release glucose, increasing blood glucose levels back to normal.

Importance of Control

• Maintaining a stable blood glucose concentration is essential for the proper functioning of all body systems.
• High blood glucose levels can lead to long-term damage to blood vessels, nerves, and organs, increasing the risk of diabetes complications like heart disease, stroke, and kidney failure.
• Low blood glucose levels can cause feelings of dizziness, weakness, and confusion, and in severe cases, can lead to loss of consciousness.

Key Points to Remember

• The control of blood glucose is a homeostatic mechanism, maintaining a stable internal environment.
• Insulin and glucagon work together to regulate blood glucose levels.
• Insulin lowers blood glucose, while glucagon raises it.
• Maintaining a stable blood glucose concentration is essential for overall health.