Golgi apparatus

The Golgi apparatus, named after its discoverer [Camillo Golgi]? (1843-1926), is the central delivery system of all but the simplest eukaryotic cell (which can have one to several hundreds of them). Most of the transport vesicles that leave the endoplasmic reticulum (ER) are transported to the Golgi apparatus, where they are modified, sorted and shipped towards their final destination. The structure and internal function of the Golgi apparatus is quite complex and subject of scientific dispute. The Golgi apparatus consists, like the ER, of membranous structures. Its cis face is the side facing the ER, while the trans face is directed towards the plasma membrane (Fig. 1). Cis and trans face have a different membranous composition. The transport vesicles from the ER fuse with the cis face of the Golgi apparatus and empty their protein content into the Golgi lumen (the internal space of the Golgi apparatus). The proteins are then transported through the Golgi apparatus towards the trans face and are modified on their way. The transport mechanism itself is not yet clear; it could happen by [cisternae progression]? (the movement of the apparatus itself, building new cisternae at the cis face and destroying them at the trans face) or by budding (small vesicles transport the proteins from one cisterna? to the next, while the cisternae remain unchanged). Once the proteins reach the trans face, they are embedded into transport vesicles and brought to their final destinations. The Golgi apparatus can also transport other molecules (e.g., lipids) the same way as it does proteins.

Figure 1 : Image of nucleus, endoplasmic reticulum and Golgi apparatus.
(1) Nucleus. (2) Nuclear pore. (3) Rough endoplasmic reticulum (RER). (4) Smooth endoplasmic reticulum (SER). (5) Ribosome on the rough ER. (6) Proteins that are transported. (7) Transport vesicle. (8) Golgi apparatus. (9) Cis face of the Golgi apparatus. (10) Trans face of the Golgi apparatus. (11) Cisternae of the Golgi apparatus.(12) Secretory vesicle. (13) Plasma membrane. (14) Expelled proteins. (15) Cytoplasm. (16) Extracellular space.

See also : organelle

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