L'appareil de Golgi

The Golgi apparatus is a stack of disc-shaped, membrane-bound compartments called cisternae, organized with two distinct faces: the cis face facing the endoplasmic reticulum and the trans face facing away. Each cisterna contains unique enzymes and trafficking proteins that process proteins and lipids as they move through the organelle.

Proteins undergo specific modifications at each cisterna. In the cis-Golgi, some carbohydrate modifications from the ER are removed. In the medial cisterna, enzymes add sugars, phosphates, or sulfates to proteins, forming glycoproteins. These chemical changes affect protein stability, activity, and help direct proteins to their correct cellular destinations.

The trans-Golgi network, farthest from the endoplasmic reticulum, sorts molecules based on their final destinations. Each molecule receives a sorting signal tag that directs it to the correct organelle. Cargo is then packaged into transport vesicles and sent to destinations including the cell membrane, lysosomes, or extracellular space.

Properly folded proteins from the ER are packaged into vesicles and transported by microtubules and cell motility machinery. These vesicles fuse together to form vesicular tubular clusters that arrive at the cis face of the Golgi. This transport system ensures selective delivery of cargo to the Golgi for processing and sorting.

The Golgi apparatus functions as a major sorting and dispatch station within eukaryotic compartmentalization and microenvironments, receiving products from the ER and directing them to specific cellular locations. This sorting capability ensures proteins and lipids reach their intended destinations, maintaining proper cellular organization and function across different membrane-bound compartments.

The Golgi apparatus fully disassembles and reassembles during cell division. Previously viewed as a static structure through which proteins moved, scientists now understand the collection of Golgi cisternae as dynamic structures that advance as a unit from the cis to the trans face during the cell cycle.

Beyond protein modification and sorting, the Golgi apparatus modifies membrane phospholipids and manufactures and secretes polysaccharides. These additional functions support cellular communication, structural integrity, and the production of extracellular molecules essential for cell-to-cell interactions and tissue organization in multicellular organisms.