Final answer:
The Golgi apparatus is the major site of carbohydrate synthesis in the biosynthetic secretory pathway, where it synthesizes oligosaccharides and polysaccharides, sorting and tagging proteins and lipids for their destinations.
Step-by-step explanation:
The major site of carbohydrate synthesis in the sorting and shipping department of the biosynthetic secretory pathway is the Golgi apparatus. In the Golgi apparatus, oligosaccharides start their synthesis in the rough endoplasmic reticulum (RER) where a core glycoside is formed. As proteins with partial glycans attached to them travel through the Golgi vesicles, they undergo terminal glycosylation; additional sugars are attached to form complete glycoproteins. In plant cells, the Golgi apparatus also plays a crucial role in synthesizing polysaccharides which are incorporated into the cell wall or used in other parts of the cell. These proteins and lipids are then tagged and routed to their proper destinations.