After translation, the protein passes into the channels of the rough endoplasmic reticulum (ER) for transportation. The protein is then passed from the rough ER to the Golgi apparatus inside tiny fluid-filled sacs, called vesicles . The Golgi apparatus is a system of membranes [ membrane : a very thin layer of tissue ] , which are responsible for the modification, processing, and packaging of the proteins. The protein may have a carbohydrate added, to form a glycoprotein. The Golgi apparatus packages the protein in a secretory vesicle, which fuses with the cell membrane and releases the protein from the cell.