Glycogen vs. Amylose — What's the Difference?

Glycogen is the primary form of energy storage in animals, fungi, and bacteria, functioning similarly to starch in plants. It is a highly branched molecule, allowing for rapid release of glucose when energy is needed. Amylose, on the other hand, is a component of starch and serves as an energy reserve in plants. It is mostly linear with a few branches, which makes it less readily accessible for quick energy release compared to glycogen.

The structure of glycogen with its extensive branching allows for quick access and breakdown by enzymes, leading to fast energy release during metabolic processes. Amylose’s structure, being more linear, is digested more slowly, providing a gradual release of energy. This structural difference affects how energy is stored and released in organisms that rely on glycogen versus those that store amylose.

In terms of solubility, glycogen is generally less soluble in water than amylose due to its larger size and extensive branching. However, both are insoluble in alcohol. Amylose tends to form a colloidal suspension in hot water, which can be identified with an iodine test that turns it blue, indicating the presence of starch.

Glycogen’s synthesis and degradation are regulated by hormones such as insulin and glucagon, which respond to the energy needs of an animal’s body. Amylose synthesis, part of starch synthesis in plants, occurs in plastids (like chloroplasts) and is not regulated by hormones but rather by the plant's metabolic needs and available resources.

Lastly, glycogen has a compact structure due to its branches, which allows it to be densely packed in cells. Amylose contributes to the semi-crystalline structure of starch granules in plants. The packing of glucose units in amylose is not as dense due to its more linear chains, affecting how it is stored in plant cells.