The Golgi apparatus collects simple chemicals in the cell and assembles them into large, complex structures such as proteins. It also plays a role in the process of simple chemical secretion by forming closed vesicles around the substance to be transported. These vesicles then pinch off from the Golgi apparatus and drift to the cell's plasma membrane where the transported substance is released from the cell.
The Golgi apparatus, also known as the Golgi complex or body, performs the essential role of sifting through the fragments of various macromolecules in the process of synthesis by the rough endoplasmic reticulum. It gathers these components together, stores some components and transfers others farther along its length for further synthesis before their eventual release. Once the macromolecules are assembled, the Golgi apparatus can either store them until needed or release them immediately for secretion through the cell membrane.
The transport vesicles released by the Golgi apparatus do not pass through the plasma membrane of the cell. Instead, they merge with the membrane, opening as they do so, and simply expose their contents to the bloodstream. This method of cellular transport is highly efficient and, after the initial separation from the complex, does not require the consumption of adenosine triphosphate, or ATP.