What is glucagon?

Glucagon is a molecule secreted by the alpha cells within groups of cells in the pancreas called islets of Langerhans. The pancreas contains over 1 million of these glucagon- secreting islets! 

The way I remember the function of Glucagon is that it is secreted when all the GLUCose is GONe. It is released in response to low glucose levels in the blood, such as during vigorous exercise, and acts to restore homeostasis by releasing glucose. Note that generally, glucagon has  the opposite effects to insulin. 

Glucagon has several biochemical effects, including: 

1. Conversion of glucose storage molecule, glycogen, to glucose. 
2. Conversion of fat molecules, triglycerides, to fatty acids i.e. lipolysis. This provides the cell with energy (ATP). 
3. Activating the conversion of amino acids to glucose (gluconeogenesis).  

Glucagon affects the majority of organs. I have annotated the diagram below to outline how different organs respond to glucagon. 

Diving a bit deeper into the signalling mechanism, glucagon binds to G protein coupled receptors (GPCRs) on the cell, which activates an enzyme called adenylate cyclase.

This enzyme converts ATP to  cAMP molecules. This activates protein kinase A.

This protein phosphorylates and activates enzymes that act to inhibit anabolic (synthesis) processes and activate catabolic (breakdown) processes.

It can also activate calcium channels in cardiac muscle cells, chloride ion channels in the small intestine, and modify expression of certain genes. This is what causes the bodily responses discussed.  

Glucagon is a peptide hormone secreted from the pancreas.

A peptide hormone is a molecule made up of amino acids which the body uses to transfer signals. They are essentially large proteins that are normally transported in the bloodstream to their target location. A huge variety of peptide hormones exist in the body to control lots of different functions - everything from growth to blood pressure.

Glucagon, specifically, is secreted from alpha cells in the islets of Langerhans - small structures within the pancreas. Its main role is to stimulate glucose production. It is secreted into the blood in response to hypoglycemia (low blood glucose levels). It then binds to glucagon receptors, which are mainly found on the surface of cells in the liver (though they are also found in other places such as the kidneys). It triggers the liver cells to convert glycogen into glucose.

Glycogen is the molecule the body uses to store sugars as it is more compact than glucose and is insoluble, so it doesn't enter the bloodstream. However, glycogen cannot be used for respiration, so the action of glucagon is important to increase glucose production and ensure sufficient sugars are circulating in the bloodstream to allow respiration to occur.

Glucagon is a hormone that attaches itself to the surface of target cells and then activates enzymes which are involved in the conversion of glycogen to glucose or glycerol and amino acids into glucose.

Glucagon is a hormone which is secreted by Alpha cells in the Islets of langerhans (pancreas cells), the function of glucagon is to regulate blood glucose concentration by converting glycogen into glucose.

glucagon is a pancreatic hormone assisting in glycogen breakdown

to remember think: when glycogen needs to be GONe - use GlucoGON

Glucagon is a hormone involved in blood glucose regulation. When your blood glucose levels increase, for example after a meal, the rise is detected by the pancreas and a hormone called insulin is released from cells in teh islets of Langerhans. This travels all round the body and attaches to receptors on most of your body cells, increasing their uptake of glucose, which they use in respiration. Liver and muscle cells take up this glucose and store it as a large storage carbohydrate, called glycogen. When your blood glucose drops, for example after exercise, this is also detected by teh pancreas. This time GLUCAGON is released into the blood. This is carried around the body in the bloodstream and when it reaches liver cells, it attaches to receptors on teh cell surface membrane. This causes the stores of glycogen to be broken down, in a process called glycogenolysis (lysis means "to split"). It also promotes the formaiton of glucose (gluconeogenesis) and inhibits glycogen formation. All these actions increase the glucose levels in the blood.

Hi Orie,

Glucagon is a hormone that helps to control blood sugar levels. Specifically, it prevents blood glucose levels from dropping too low. Glucagon is produced by alpha cells, in the islet of langerhans, and released into the boodstream from the pancreas.

Glucagon stops blood glucose levels from dropping too low by acting on the liver in the following ways:

-stimulates glycogenolysis - the conversion of stored glycogen to glucose. Glucose is then released into the blood stream.

-stimulates gluconeogenesis - where amino acids are used to make glucose.

Glucagon also stimulates the breakdown of fat stores in adipose tissue.

Glucagon is a hormone that stimulates the breakdown of glycogen into glucose, increasing the blood-glucose concentration. It is produced in the Isle of Langerhans of the pancreas.

Glucagon plays an active role in allowing the body to regulate the utilisation of glucose and fats.

Glucagon is released in response to low blood glucose levels and to events whereby the body needs additional glucose, such as in response to vigorous exercise.

Glucagon is a hormone produced in the pancreas as a response to low levels of glucose in the blood. It promotes the breakdown of glycogen into glucose in the liver.

Glucagon is a hormone produced by the alpha cells in the islets of Langerhan cells in the pancreas and it signals to the liver to convert glycogen to glucose (glycogenolysis) which is then released into the bloodstream to increase the blood sugar level. It is released when the blood glucose level drops below normal levels, usually during strenuous exercise or when fasting.

A hormone that converts stored glycogen to glucose

Glucagon is a hormone in the body which causes stored glycogen to be converted into glucose. When blood sugar levels are low the pancreas releases glucagon into the bloodstream. This causes glycogen stores in the liver and muscles to break down into glucose (glycogen is simply a long chain of glucose molecules joined together). This release of glucose into the blood restores the blood sugar level back to normal.