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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.
The Coat Protein Complex II, or COPII, is a group of proteins that facilitate the formation of vesicles to transport proteins from the endoplasmic reticulum to the Golgi apparatus or endoplasmic-reticulum–Golgi intermediate compartment.
In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form naturally during the processes of secretion ( exocytosis ), uptake ( endocytosis ), and the transport of materials within the plasma membrane .
The Golgi apparatus is used by the cell for further protein modification. The section of the Golgi apparatus that receives the vesicles from the ER is known as the cis face, and is usually near the ER. The opposite end of the Golgi apparatus is called the trans face, this is where the modified compounds leave.
Electron micrograph of in vitro–formed COPI-coated vesicles. Average vesicle diameter at the membrane level is 60 nm. COPI is a coatomer, a protein complex [1] that coats vesicles transporting proteins from the cis end of the Golgi complex back to the rough endoplasmic reticulum (ER), where they were originally synthesized, and between Golgi compartments.
Vesicles pass between the Golgi and endosomes in both directions. The GGAs and AP-1 clathrin-coated vesicle adaptors make vesicles at the Golgi that carry molecules to endosomes. [ 18 ] In the opposite direction, retromer generates vesicles at early endosomes that carry molecules back to the Golgi.
The vesicle then buds outwards and breaks free into the cytoplasm. The vesicle is moved towards its target location then docks and fuses. Once vesicles are produced in the endoplasmic reticulum and modified in the Golgi body they make their way to a variety of destinations within the cell. Vesicles first leave the Golgi body and are released ...
In most eukaryotes, these protein-carrying vesicles are released and further modified in stacks of flattened vesicles , the Golgi apparatus. [28] Vesicles may be specialized; for instance, lysosomes contain digestive enzymes that break down biomolecules in the cytoplasm. [29]