Golgi Apparatus

Most of the transport vesicles that leave the Endoplasmic Reticulum (ER), specifically ''rough'' ER, Are Transported To The Golgi Apparatus , where they are modified, sorted, and shipped towards their final destination. The Golgi apparatus is present in most Eukaryotic Cell s, but tends to be more prominent where there are many substances, such as Protein s, being secreted. For example, Plasma B Cell s, the Antibody -secreting cells of the immune system, have prominent Golgi complexes.

FUNCTION

The Golgi apparatus is considered more or less the " Post Office " of the cell. It handles all incoming lipids, proteins, etc., and controls their export, as well.

The transport vesicles from the Endoplasmic Reticulum (ER) fuse with the ''cis'' face of the Golgi apparatus (to the Cisternae ) and empty their Protein content into the Golgi Lumen . The proteins are then transported through the medial region toward the ''trans'' face and are modified on their way. Possible modifications include Glycosylation and Phosphorylation . The proteins are also labeled with a sequence of molecules according to their final destination. For example, the Golgi apparatus adds a Mannose-6-phosphate label to proteins destined for lysosomes.

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 ''vesicular transport'' (small vesicles transport the proteins from one Cisterna to the next, while the cisternae remain unchanged).
It is also proposed that the cisternae are interconnected, and the transport of cargo molecules within the Golgi is due to Diffusion , while the localisation of Golgi-resident proteins is achieved by an unknown mechanism.

Once the proteins reach the ''trans'' face, they are embedded into coated transport vesicles and brought to their final destinations. The form of the vesicle is determined by the type of protein and the label it acquired.

An example of the Golgi complex's functioning is the modification of glycoproteins (used in Cell Membrane s). Vesicles from the ER contain simplified glycosylated proteins. In the Golgi complex, carbohydrates are attached and removed from these glycoproteins, creating a diversity of carbohydrate structures on the proteins. After they have been secreted in to the cell the vesicles fuse to the cell membrane and release their contents.

Along with protein modification, Golgi apparatus is involved in the transport of Lipid s around the cell, as well, creating Lysosome s, Organelle s involved in Digestion .

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Golgi Apparatus