As Glycogen .
The carbohydrate in the food that animals eat is broken down into the simplest carbohydrate glucose.
The glucose is used as fuel to carry out the processes through which an animal stays alive. When all the requirement of glucose are fulfilled the excess glucose is stored as glycogen(a large complex molecule) in the liver so that it can be used again when required.
Glycogen is also stored in muscle cells.
But why as glycogen? Basically it is a polysacchride of glucose. It’s structure allows it to be packed compactly so more of it can be stored in cells and that means less wastage.
Glycogen is just a chain of glucose molecules with many branched chains:
There are two types of glycosidic bonds (bonds b/w two glucose molecules) in glycogen:
Interesting fact : Fungi also store excess glucose as glycogen!
Plants also store glucose but as a different polysacchride called starch .