Glucagon

Definition

Glucagon is a peptide hormone produced by the alpha cells of the pancreas that plays a vital role in regulating blood glucose levels. It acts primarily to raise blood glucose levels by promoting glycogenolysis and gluconeogenesis in the liver, counterbalancing the effects of insulin and ensuring the body has sufficient energy, especially during fasting or low-carbohydrate intake.

5 Must Know Facts For Your Next Test

1. Glucagon is released in response to low blood glucose levels, typically when fasting or after intense exercise.
2. It primarily targets the liver, where it promotes glycogen breakdown and glucose release into the bloodstream.
3. Glucagon has a counter-regulatory function to insulin; when insulin decreases, glucagon levels rise to prevent hypoglycemia.
4. The hormone also enhances fatty acid oxidation in adipose tissue, providing an alternative energy source when glucose is low.
5. Glucagon secretion can be influenced by factors such as stress, exercise, and high protein intake, which may raise blood sugar needs.

Review Questions

• How does glucagon interact with insulin to maintain blood glucose homeostasis?
  • Glucagon and insulin work together to regulate blood glucose levels. When blood sugar drops, glucagon is secreted to stimulate glycogenolysis and gluconeogenesis, increasing glucose availability. Conversely, when blood sugar rises after eating, insulin is released to promote glucose uptake by cells and storage as glycogen. This balance between glucagon and insulin ensures that blood glucose levels remain stable within a healthy range.
• What are the metabolic processes stimulated by glucagon, and how do they contribute to energy balance during fasting?
  • Glucagon stimulates two key metabolic processes: glycogenolysis and gluconeogenesis. Glycogenolysis breaks down stored glycogen in the liver to release glucose into the bloodstream, while gluconeogenesis produces glucose from non-carbohydrate sources. Together, these actions help maintain energy balance during fasting periods by ensuring a continuous supply of glucose for vital bodily functions, preventing hypoglycemia.
• Evaluate the physiological significance of glucagon secretion in response to dietary protein intake versus carbohydrate intake.
  • Glucagon plays a significant role in responding to different dietary compositions. In high-protein meals, glucagon is secreted alongside insulin to enhance gluconeogenesis from amino acids, helping maintain appropriate blood sugar levels despite lower carbohydrate availability. In contrast, with high carbohydrate intake, insulin predominates to lower blood sugar levels while glucagon decreases. This balanced response illustrates glucagon's importance in adapting energy metabolism based on dietary intake and maintaining homeostasis.

Related terms

Insulin:

A hormone produced by the beta cells of the pancreas that lowers blood glucose levels by facilitating cellular uptake of glucose and promoting glycogen storage.

Glycogenolysis: The metabolic process of breaking down glycogen into glucose molecules, primarily occurring in the liver and muscle tissue, which glucagon stimulates during fasting.

Gluconeogenesis: The synthesis of glucose from non-carbohydrate sources, such as amino acids and glycerol, which is stimulated by glucagon to maintain adequate blood sugar levels.