What are the functions of glycogen?

The excess carbohydrates will be converted to fat and stored in body as fat.  The main stores of glycogen in the body are found in skeletal muscle and liver, although most other cells store small amounts of glycogen for their own use.

Stored glycogen is synthesized during a high carbohydrate meal due to hyperglycemia and an increase in the insulin: glucagon ratio.

Muscle glycogen 
The function of muscle glycogen is to serve as a fuel reserve for the synthesis of adenosine triphosphate (ATP) during muscle contraction.

The production of energy from glucose involves oxidation of sugar with the release of water and carbon dioxide, which are easily removed from the body.

Liver glycogen
Liver glycogen function is to maintain the blood glucose levels, particularly during the early stages of a fast.

The liver releases glucose from the breakdown of glycogen and from gluconeogenesis for utilization by peripheral tissues mainly the brain cells and red blood cells.
What are the functions of glycogen?