Properly folded and assembled proteins are selectively packaged into vesicles that exit the ER. Motor proteins transport these vesicles to the Golgi apparatus for adding modifications that make these proteins functional at their destination.

The Golgi apparatus is a eukaryotic organelle that has a distinctive ribbon-like appearance. It is a primary sorting and dispatch station for cargo arriving from the ER. Newly arriving vesicles enter the cis face of the Golgi, closest to the ER, and are transported through a stack of membrane-enclosed cisternae. Each cisterna contains unique compositions of enzymes and performs specific protein modifications, such as phosphorylation and glycosylation. After modifications in the trans cisterna, proteins are given tags that define their cellular destination.

Depending on the molecular tags, proteins are packaged into vesicles and trafficked to particular cellular locations, such as the plasma membrane. Specific markers on the membranes of these vesicles allow them to dock at the appropriate cellular location.