A vesicle is a small membrane-bound sack that stores and transports substances throughout the cell. They can form naturally within the cell to aid in cellular secretion such as exocytosis, endocytosis or phagocytosis or they can be artificially prepared by chemists and biologists.
Vesicles perform a variety of functions. They mostly store, transport or digest cellular products and cellular waste. Since they are separate from the cytosol of the cell they have a completely different internal environment than the cell. For this reason, vesicles can digest cellular machinery and recycle cellular materials. To transport materials into or out of the cell, vesicles fuse with the cell’s plasma membrane and release or uptake contents from outside of the cell. In total, there are four main types of vesicles. Vacuoles are vesicles that contain mostly water and are found in plant cells. They transport water in and out of the cell. Lysosomes are vesicles that are found in eukaryotic cells. They are involved in cellular digestion and can also be utilized to recycle damaged cellular organelles. Transport vesicles work primarily with the endoplasmic reticulum and the Golgi apparatus. They transport molecules such as proteins and fats in between these two organelles. Secretory vesicles are the fourth main type of vesicle. They contain materials that need to be excreted from the cell. Most commonly they contain waste products.