Final answer:
Proteins synthesized in the ER are packaged into transport vesicles that fuse with the Golgi apparatus's cis face. After modifications such as glycosylation, proteins are sorted and repackaged into new vesicles leaving from the trans face, destined for the plasma membrane or other cellular organelles.
Step-by-step explanation:
The general pathway a protein takes from the ER to the Golgi involves a vesicle which is a small, membrane-enclosed sac that carries proteins. Initially, proteins synthesized in the rough endoplasmic reticulum (ER) are packaged into transport vesicles. These vesicles bud off from the ER and then fuse with the Golgi apparatus on its receiving, or cis, face. Inside the Golgi apparatus, the proteins undergo various modifications. Commonly, this includes glycosylation, the addition of sugar molecules to the protein, which is essential for proper protein function.
After modification in the Golgi apparatus, the proteins are sorted and packaged into new vesicles that bud off from the outgoing, or trans, face of the Golgi. These vesicles then carry the modified proteins to various destinations, including the plasma membrane, where some proteins are embedded, or to other organelles within the cell. This critical process ensures that proteins are properly processed and directed to where they are needed to maintain cellular functions.