Inclusions

Inclusions are non-living components found within cells. They are diverse in nature and can include pigments, crystals, and stored nutrients among others. Inclusions are not considered organelles as they are not bounded by membranes. They are often considered to be by-products of cellular metabolism.

Types of Inclusions

There are several types of inclusions found in cells. These include:

• Lipofuscin - This is a brown-yellow material that accumulates in the cells of aging organisms. It is composed of lipid-containing residues of lysosomal digestion.

• Glycogen - This is a multi-branched polysaccharide of glucose that serves as a form of energy storage in animals and fungi.

• Starch - This is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. It is the most common carbohydrate in the human diet and is contained in large amounts in staple foods.

• Melanin - This is a broad term for a group of natural pigments found in most organisms. Melanin is produced through a multistage chemical process known as melanogenesis.

Functions of Inclusions

Inclusions serve various functions in cells. They can provide energy, serve as a reservoir of metabolic products, or contain pigments that color the cell. Inclusions are also involved in aging, with lipofuscin being a key player in cellular aging.

See Also

• Cell (biology)
• Organelle
• Cellular metabolism