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Glucagon

Insulin and glucagon are antagonistic hormones. Glucagon is produced by the alpha cells of the islets of Langerhans in response to a low blood sugar concentration. The only cells that have glucagon receptors are liver cells and fat cells. Glucagon raises the blood glucose concentration by breaking down glycogen in the liver (glycogenolysis), reducing the amount of glucose absorbed by liver cells and increasing gluconeogenesis.Gluconeogenesis is the formation of glucose from non-carbohydrate sources e.g. fatty acids and amino-acids.

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Specification: OCR Biology A (H420), A-level, 5.1.4 Hormonal communication. Topic: Hormonal Communication.

Key terms in this lesson

Hormone
A chemical messenger, secreted directly into the blood by an endocrine gland, that travels to target cells and alters their activity.
Glycogenolysis
The breakdown of glycogen to glucose, occurring mainly in the liver in response to glucagon or adrenaline.
Gluconeogenesis
The production of glucose from non-carbohydrate sources such as amino acids and fatty acids.
Islets of Langerhans
Groups of endocrine cells in the pancreas containing alpha cells, which secrete glucagon, and beta cells, which secrete insulin.
Insulin
A hormone secreted by beta cells of the islets of Langerhans in response to high blood glucose concentration that increases the uptake of glucose by cells.

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All 19 lessons in Hormonal Communication · All OCR A-level Biology topics