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It is important that translated proteins are delivered to their specific cellular location.

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To accomplish this, the protein is transferred through a series of membrane structures.

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A principal membrane component is the Golgi apparatus.

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The Golgi apparatus is the sorting organelle of the cell.

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Proteins from the rough endoplasmic reticulum are sent to the Golgi.

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As the proteins move through the Golgi apparatus, they are modified and packaged into vesicles.

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Because the Golgi apparatus receives proteins from one location and targets them for delivery

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to a second location, it is sometimes considered the post office of the cell.

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The Golgi apparatus consists of general components.

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The cis-cisterna nearest the endoplasmic reticulum, or ER, the medial and trans-cisternae,

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and the trans-Golgi network.

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Other key players in this process are the proteins being transported and the enzymes

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that modify them.

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Translated proteins are encapsulated in vesicles in the ER.

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A group of these vesicles fuse, and these fused vesicles form the cis cisterna.

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As the protein moves through the stack, it is modified by resident Golgi enzymes at specific

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locations in the apparatus.

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These modifications are important because they provide the signal that determines the

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final destination of the protein.

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So how does the protein move through the Golgi?

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Movement occurs in waves.

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First, the cis cisterna becomes part of the medial Golgi cisternae.

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Behind it, a new cis cisterna is formed by the fusion of vesicles from the ER.

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Meanwhile, one of the medial cisternae migrates and becomes the new trans cisterna.

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Collectively this process is known as the cismaturation model.

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Proteins are sorted within the transgolgi network.

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Proteins with the same target sequence are destined for delivery to the same location.

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The transgolgi network then buds off into vesicles.

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These vesicles then migrate to their target location.

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These locations include internal organelles such as the lysosome, the digestive organelle

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of the cell.

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The vesicles can also be targeted to the cell membrane, where the targeted protein can be

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released from the cell for delivery elsewhere in the organism.