Final answer:
Proteins transported in vesicles are synthesized by ribosomes on the rough endoplasmic reticulum, processed in the Golgi apparatus, and then sorted into vesicles that either become part of the plasma membrane or fuse with organelles inside the cell.
Step-by-step explanation:
Proteins that require transportation in vesicles are primarily synthesized by the ribosomes that are found on the rough endoplasmic reticulum (RER). After being synthesized, these proteins enter the lumen of the RER and may also become incorporated into the RER membrane. Following these events, the proteins are packaged into transport vesicles which then move to and fuse with the Golgi apparatus. Within the Golgi apparatus, they undergo further modifications. Finally, the modified proteins are sorted and packed into secretory vesicles at the trans face of the Golgi, which then transport the proteins to their final destinations. Some of these vesicles are involved in exocytosis, where they merge with the plasma membrane to release contents outside of the cell, and others may fuse with different organelles within the cell, such as lysosomes, for various functions.