The molecule that is a source of energy store in the body and can mix with water is glycogen.

Here's why:

* Energy store: Glycogen is the primary form of carbohydrate storage in animals. It is made up of many glucose molecules linked together. When the body needs energy, glycogen is broken down into glucose, which is then used by cells for fuel.

* Mixes with water: Glycogen is a highly branched molecule and is hydrophilic (water-loving). This means it readily dissolves in water, allowing it to be stored and transported within the body.

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