The Golgi apparatus manufactures, stores, sorts, and ships. Many transport vesicles fresh from the ER move next to the Golgi to be modified or stored, then sent on to new destinations. Cells that specialize in secretion have extensive Golgi. The organelle consists of flattened membrane sacs--cisternae. Vesicles in the area are involves in the transfer of material between the Golgi and other structures.

There is distinct polarity between the membranes at either end of the stack. The ends differ in thickness and molecular composition. They are called the cis face and the trans face. The cis face receives material and the trans face ships it. The cis face usually is near ER. Transport vesicles that bud from ER move material from their maker to the Golgi's cis face. The trans face creates more vesicles, filled with material that has been processed and is ready to move to another location.

The Golgi manufactures, by itself, certain macromolecules, such as many polysaccharides. One such Golgi product is hyaluronic acid, a sticky substance that works as glue between animal cells. Golgi products destined for secretion exit from the trans face in vesicles that will fuse with the plasma membrane to allow their contents to pass through.

Substances are manufactured and/or refined in stages within different cisternae containing various groups of enzymes and seem to be transported from cisternae to cisternae by vesicles. Before sending products out, the Golgi sorts them, aiming them for certain areas of the cell. Adding a molecular ID tag, such as a phosphate group, aid in the sorting process. Also, transport vesicles may have external membrane molecules to recognize a "docking site" on an organelle surface.