Secretory Vesicles- Definition, Structure, Functions and Diagram


Secretory vesicles are membrane-bound sacs that store and transport substances from one cell to another or from one part of a cell to another. They are involved in the process of secretion, which is the release of molecules from a cell to the outside environment or to another cell. Secretion can be either constitutive or regulated. Constitutive secretion occurs continuously and does not require a specific stimulus. Regulated secretion occurs only in response to a specific signal, such as a hormone or a nerve impulse.

Secretory vesicles can contain different types of molecules, depending on the function and location of the cell. Some examples of secreted molecules are hormones, neurotransmitters, enzymes, antibodies, and growth factors. Secretory vesicles can also contain waste products or toxins that need to be eliminated from the cell.

Secretory vesicles are formed by budding off from the trans-Golgi network (TGN), which is the final compartment of the Golgi apparatus. The TGN sorts and modifies the proteins and lipids that are synthesized in the endoplasmic reticulum (ER) and transported through the Golgi apparatus. The TGN also adds specific markers to the vesicles that determine their destination and mode of fusion with the target membrane.

Secretory vesicles can fuse with the plasma membrane of the cell, which is the outermost layer that separates the cell from its surroundings. This fusion allows the release of the vesicle contents to the extracellular space or to another cell. This process is called exocytosis. Alternatively, secretory vesicles can fuse with other organelles within the cell, such as lysosomes or endosomes. This fusion allows the delivery of the vesicle contents to these organelles for further processing or degradation. This process is called endocytosis.

Secretory vesicles play an important role in many biological processes, such as cell communication, immune response, digestion, metabolism, and development. They also contribute to various diseases and disorders, such as diabetes, Alzheimer`s disease, Parkinson`s disease, and cystic fibrosis. Therefore, understanding the formation, transport, and fusion of secretory vesicles is essential for advancing biomedical research and developing new therapies.