Vesicle

Vesicle is a small structure within a cell, consisting of fluid enclosed by a lipid bilayer. Vesicles form naturally during the processes of secretion (exocytosis), uptake (endocytosis) and transport of materials within the plasma membrane. Alternatively, they may be prepared artificially, in which case they are called liposomes. Vesicles can be used as tools for the study of membrane structure, as well as for the targeted delivery of drugs and other substances to specific tissues.

Structure and Composition

Vesicles are composed of a lipid bilayer membrane, surrounding an aqueous core. The lipid bilayer is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around cells. The lipid bilayer membrane is semi-permeable, allowing only certain molecules to diffuse across the membrane.

Function

Vesicles perform a variety of functions. They help to transport materials within the cell. Vesicles can also fuse with other membranes within the cell system. They also play a role in metabolism and enzyme storage. They are integral parts of the endomembrane system of eukaryotic cells.

Types of Vesicles

There are many types of vesicles, including:

• Vacuoles
• Lysosomes
• Transport vesicles
• Secretory vesicles

See Also

• Cell (biology)
• Endomembrane system
• Lipid bilayer
• Exocytosis
• Endocytosis