Here's how it works:

* Glycogenesis: When blood glucose levels are high, the excess glucose is converted into glycogen. This process occurs in the liver and muscles, and it's catalyzed by the enzyme glycogen synthase.

* Glycogen Structure: Glycogen is a highly branched polymer of glucose molecules. This branching structure allows for rapid glucose release when needed.

* Glycogenolysis: When blood glucose levels are low, glycogen is broken down back into glucose by the enzyme glycogen phosphorylase. This process releases glucose into the bloodstream to fuel the body's energy needs.

In addition to glycogen, animal cells can also store glucose in small amounts as:

* Free glucose: This is glucose that is dissolved in the cytoplasm.

* Other polysaccharides: While less significant than glycogen, some glucose can be stored in other polysaccharides like starch.

It's important to note that:

* Animal cells cannot store as much glucose as plant cells, which store glucose as starch.

* The amount of glycogen stored varies depending on the animal's species, age, and nutritional status.

Overall, glycogen is the primary way that animal cells store glucose, providing a readily available source of energy for the body.