The Golgi apparatus, a series of flattened membranes, sorts and packages materials before they leave the cell to ensure they arrive at the proper destination. It is also part of the endomembrane system.
The receiving side of the Golgi apparatus is called the cis face. The opposite side is called the trans face. The transport vesicles that formed from the ER travel to the cis face, fuse with it, and empty their contents into the lumen of the Golgi apparatus. As the proteins and lipids travel through the Golgi, they undergo further modifications that allow them to be sorted. The most frequent modification is the addition of short chains of sugar molecules. These newly-modified proteins and lipids are then tagged with phosphate groups or other small molecules so that they can be routed to their proper destinations.
The modified and tagged proteins are packaged into secretory vesicles that bud from the trans face of the Golgi. While some of these vesicles deposit their contents into other parts of the cell where they will be used, other secretory vesicles fuse with the plasma membrane and release their contents outside the cell.
Practice Questions
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Key Points
• The Golgi apparatus is a series of flattened sacs that sort and package cellular materials.
• The Golgi apparatus has a cis face on the ER side and a trans face opposite of the ER.
• The trans face secretes the materials into vesicles, which can be transported to where they are needed.
Key Terms
Golgi apparatus: a series of flattened membranes that sorts and packages materials before they leave the cell
Vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer and transport of materials within the plasma membrane
Lumen: the cavity or channel within a tube or tubular organ
Plasma membrane: separates the interior of the cell from the outside environment