Final answer:
The cis Golgi network receives molecules from the ER, which are then modified within the Golgi apparatus. The trans Golgi network sends off modified proteins and lipids to their final destinations in the cell. These modifications and sorting are crucial for proper cellular functioning.
Step-by-step explanation:
The Golgi apparatus functions as a critical packaging and distribution center for proteins and lipids within the cell. This organelle has two key faces: the cis Golgi network (CGN) and the trans Golgi network (TGN). The CGN is the entry face for material coming from the endoplasmic reticulum (ER), where transport vesicles fuse with the Golgi apparatus and release their contents.
As substances progress through the Golgi apparatus, they undergo various modifications, such as glycosylation, where short chains of sugar molecules are added. Additionally, these modified proteins and lipids may be tagged with phosphate groups or other small molecules, which helps direct them to their final destinations within or outside the cell. The TGN is the exit face of the Golgi apparatus, from where transport vesicles containing the processed proteins and lipids bud off and travel to other parts of the cell, such as the plasma membrane or various organelles.