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The Golgi apparatus (/ ˈ ɡ ɒ l dʒ i /), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. [1] Part of the endomembrane system in the cytoplasm , it packages proteins into membrane-bound vesicles inside the cell before the vesicles are sent to their destination.
Then the protein passes through the golgi apparatus, where it is packaged into a vesicle. In the vesicle, more parts are cut off, and it turns into mature insulin. In molecular biology, post-translational modification (PTM) is the covalent process of changing proteins following protein biosynthesis.
Since the ER is the site of protein synthesis, it would serve as the parent organelle, and the cis face of the golgi, where proteins and signals are received, would be the acceptor. In order for the transport vesicle to accurately undergo a fusion event, it must first recognize the correct target membrane then fuse with that membrane.
The Golgi apparatus (also known as the Golgi body and the Golgi complex) is composed of separate sacs called cisternae. Its shape is similar to a stack of pancakes. The number of these stacks varies with the specific function of the cell. The Golgi apparatus is used by the cell for further protein modification.
For example, in epithelial cells, a special process called transcytosis allows some materials to enter one side of a cell and exit from the opposite side. Also, in some circumstances, late endosomes/MVBs fuse with the plasma membrane instead of with lysosomes, releasing the lumenal vesicles, now called exosomes , into the extracellular medium.
The signal peptide sequence is removed in the endoplasmic reticulum, yielding a propeptide. The propeptide travels to the Golgi apparatus where it is proteolytically cleaved and processed into multiple peptides. Peptides are packaged into dense core vesicles, where further cleaving and processing, such as C-terminal amidation, can occur.
Hemicelluloses are synthesised from sugar nucleotides in the cell's Golgi apparatus. [9] Two models explain their synthesis: 1) a '2 component model' where modification occurs at two transmembrane proteins, and 2) a '1 component model' where modification occurs only at one transmembrane protein.
Glucose is added onto ceramide from its precursor in the endoplasmic reticulum, before further modifications occur in the Golgi apparatus. [8] Galactose, on the other hand, is added to ceramide already in the Golgi apparatus, where the galactosphingolipid formed is often sulfated by addition of sulfate groups.