The Golgi apparatus (Golgi body) is a stack of flattened, curved, membrane-bound sacs called cisternae, with many small vesicles around its edges. Unlike the ER, the sacs are not connected to one another.
• Modifying proteins: proteins from the RER are modified as they pass through the cisternae, for example by adding carbohydrates to make glycoproteins, or by trimming or folding them further.
• Modifying lipids, for example making glycolipids.
• Sorting and packaging: the finished molecules are sorted and packaged into vesicles addressed to different destinations.
• Making lysosomes: vesicles containing hydrolytic enzymes bud off and become lysosomes.The secretory pathway
For a protein made for export, such as a digestive enzyme:
ribosomes on RER → lumen of RER → vesicle → Golgi apparatus (modified) → secretory vesicle → cell surface membrane
The secretory vesicle moves along the cytoskeleton, fuses with the cell surface membrane and releases its contents by exocytosis. The vesicle membrane becomes part of the cell surface membrane.Cells that secrete a lot, such as goblet cells (mucus) and pancreatic cells (enzymes), have a large, well-developed Golgi apparatus.
• Modifying proteins: proteins from the RER are modified as they pass through the cisternae, for example by adding carbohydrates to make glycoproteins, or by trimming or folding them further.
• Modifying lipids, for example making glycolipids.
• Sorting and packaging: the finished molecules are sorted and packaged into vesicles addressed to different destinations.
• Making lysosomes: vesicles containing hydrolytic enzymes bud off and become lysosomes.The secretory pathway
For a protein made for export, such as a digestive enzyme:
The secretory vesicle moves along the cytoskeleton, fuses with the cell surface membrane and releases its contents by exocytosis. The vesicle membrane becomes part of the cell surface membrane.Cells that secrete a lot, such as goblet cells (mucus) and pancreatic cells (enzymes), have a large, well-developed Golgi apparatus.