GolgiApparaten

Golgiapparaten, or the Golgi apparatus, is a membrane-bound organelle in most eukaryotic cells that serves as the central hub for post-translational modification, sorting, and trafficking of proteins and lipids produced in the endoplasmic reticulum. It is essential for the maturation of many secreted proteins and for directing cargo to lysosomes, the plasma membrane, or endosomes.

The Golgi consists of flattened membrane-bound sacs called cisternae that are stacked into a compact structure near the cell nucleus. Each stack has a cis face that receives cargo from ER-derived vesicles and a trans face that ships vesicles to final destinations. Within the stack, the cis, medial, and trans compartments contain distinct enzymes that execute successive modification steps, and the apparatus can reorganize during the cell cycle.

Key functions include glycosylation, both N-linked and O-linked, as well as sulfation and phosphorylation of proteins and lipids. Proteolytic processing and the assembly of complex molecules such as proteoglycans also occur here. The Golgi sorts cargo according to molecular signals and packages it into transport vesicles, which may be directed to the plasma membrane, lysosomes, or secretory granules. It also participates in quality control of secreted proteins.

Golgi organisation varies among organisms. In most animal cells it forms a perinuclear ribbon, while in plants and some fungi multiple Golgi stacks operate throughout the cytoplasm. The Golgi is dynamic, relying on microtubules and tethering factors for trafficking and on coat proteins such as COPI and clathrin at different steps. It is part of the broader endomembrane system and supports the cell’s secretory pathway.