Golgi apparatus


Also known as the Golgi complex, Golgi body, or simply the Golgi.

It is an organelle found in most eukaryotic cells.

It is part of the endomembrane system in the cytoplasm.

Golgi are adjacent to endoplasmic reticulum (ER) exit sites

The Golgi apparatus is made up of a series of compartments and is a collection of fused, flattened membrane-enclosed disks known as cisternae.

Between four and eight cisternae are usually present in a stack.

Ciisternae is broken down into cis, medial, and trans compartments, making up two main networks: the cis Golgi network (CGN) and the trans Golgi network (TGN).

The CGN is the first cisternal structure.

The trans Golgi network (TGN) is the final, from which proteins are packaged into vesicles destined to lysosomes, secretory vesicles, or the cell surface.

The trans-Golgi network (TGN) of the Golgi is the point at which proteins are sorted and shipped to their intended destinations by their placement into one of at least three different types of vesicles, depending upon the signal sequence they carry.

Regulated secretory vesicles contain proteins destined for extracellular release.

After the vesicles are packaged, they bud off and are stored in the cell until a signal is given for their release.

Vesicles contain proteins and ribosomes destined for the lysosome.

The lysosome is a degradative organelle containing many acid hydrolases, or lysosome-like storage organelles.

These proteins include both digestive enzymes and membrane proteins.

Exocytotic vesicles contain proteins destined for extracellular release.

When the vesicles bud off and move towards the plasma membrane, then fuse and release the contents into the extracellular space in a process known as constitutive secretion.

It originates from vesicular clusters that bud off the endoplasmic reticulum.

A cell typically contains 40 to 100 stacks of cisternae.

It resides at the intersection of the secretory, lysosomal, and endocytic pathways.

It processes proteins for secretion, contains a set of glycosylation enzymes that attach various sugar monomers to proteins as the proteins move through the apparatus.

Golgi apparatus have individual stacks of different assortments of enzymes, allowing for progressive processing of cargo proteins as they travel from the cisternae to the trans Golgi face.

Enzymatic reactions within the Golgi near its membrane surfaces, where enzymes are anchored, in contrast to the endoplasmic reticulum which has soluble proteins and enzymes in its lumen.

Much of the enzymatic processing is post-translational modification of proteins such as: phosphorylation of oligosaccharides on lysosomal proteins, removal of mannose residues, and addition of N-acetylglucosamine, addition of galactose and sialic acid,sulfation of tyrosines and carbohydrates.

Other modifications of proteins include the addition of carbohydrates via glycosylation and phosphorylation, and the formation of proteoglycans.

Proteins destined for areas of the cell other than either the endoplasmic reticulum or the Golgi apparatus are moved through the Golgi cisternae towards the trans face, to a complex network of membranes and associated vesicles known as the trans-Golgi network (TGN).

A single Golgi apparatus is usually located near the cell nucleus, close to the centrosome.

It packages proteins into membrane-bound vesicles inside the cell before the vesicles are sent to their destination.

Following protein synthesis in the rough endoplasmic reticulum they are packaged into transport vesicles and secreted and travel to and fuse with Golgi vesicles.

A hooked shaped organelle with a stack of sacs next to the nucleus, which concentrates secretions of granules, and segregating carbohydrates.

Within the lumen secretory and membrane bound proteins are modified in one of three major regions or the Cis, medial or trans Golgi networks.

Proteins synthesized in the ER are packaged into vesicles, which then fuse with the Golgi apparatus.

These cargo proteins are modified and secreted via exocytosis or for use in the cell.

The Golgi apparatus is also involved in lipid transport and lysosome formation.

Proteins are repackaged into second transport vesicles and delivered to organelle membranes, plasma membranes and lysosomes.

The Golgi apparatus is larger and more numerous in cells that synthesize and secrete large amounts of substances; the antibody-secreting plasma B cells of the immune system have prominent Golgi complexes.

The Golgi apparatus is a major collection and dispatch station of protein products received from the endoplasmic reticulum.

Part of the Golgi apparatus and part of the endoplasmic reticulum form lysozymes.

Functions by distributing proteins and lipids from the endoplasmic reticulum to the plasma membrane, lysosomes, and secretory vesicles.

Modifies N-oligosaccharides on asparagines,

Adds O-oilgosaccharides to serine and threonine residues.

Assembles proteoglycan form core proteins.

Adds mannose-6-phosphate to proteins.

Products of the Golgi apparatus are exported from the cell, when a vesicle fuses with the plasma membrane.

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