What is glycogen? How is it different from starch?

Explanation

### Step-by-Step Solution:

**Step 1: Define Glycogen**
Glycogen is a polysaccharide that serves as a form of energy storage in animals. It is a polymer made up of repeating units of alpha-D-glucose. Glycogen is primarily stored in the liver and muscle tissues.

**Step 2: Define Starch**
Starch is also a polysaccharide and serves as an energy storage form in plants. Like glycogen, starch is composed of alpha-D-glucose units, but it has a different structure.

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