The Golgi complex, or Golgi apparatus, is a cell structure that is found in cells of all animals. The main purpose of the Golgi complex is to package molecules such as proteins and fats that are synthesized by the endoplasmic reticulum. The proteins and fats that pass through the Golgi are either stored for later use, taken to the cell membrane where they are released outside of the cell, or become part of the cell membrane.
The Golgi complex is made up of five to eight flattened membrane sacs, which are referred to as cisternae. The flattened membranes, which are about one micrometer in diameter, sit on top of each other and are connected. There are five functional regions on the cisternae stack that package or release proteins to other regions of a cell. In order for the Golgi complex to store or send off proteins and fats, the smooth endoplasmic reticulum pinches off vesicles, which are small bubbles of liquid, that are taken up by the Golgi. A functional region called the cis-Gogli network fuses with the trans-Golgi to take up the vesicle.
As proteins pass through the Golgi complex, enzymes make changes to the size and shape of the proteins in the vesicle by either adding or removing parts of a protein. These enzymes are able to convert proteins into other molecules that are important for health, such as insulin. After the enzymes are done making changes to some proteins and fats within the vesicle, a new vesicle called a secretory vesicle is formed and is released out into the cell. Once the secretory vesicle is released out into the cell, the newly formed molecules, such as insulin, can remain in the vesicle until needed, or be excreted out of the cell and taken to other regions of the body, or become part of the cell membrane.
When molecules, such as hormones, are released from a secretory vesicle, the molecules are taken out of the cell by a process known as exocytosis. Exocytosis is an active transport process that helps remove particles from the secretory vesicle to be released outside of the cell wall. Some of the particles that are not released out of the cell can become part of the cell membrane. In this case, the particles will be able to help with the functions of transport or self-recognition of other molecules.