Golgi Apparatus

(Click image to enlarge in new window)

Objective: To find and learn about the Golgi Apparatus!

It’s been a long walk, searching for all these organelles! Wouldn’t it be great if there was something that could transport us to all parts of the cell so that we don’t have to walk so much? Well, good for us, there is something called the Golgi apparatus that acts as the transport system of the entire cell! Let’s hitch a free ride in one of those vesicles and search for the Golgi apparatus!

<Scroll to bottom for correct location…>
 
The Golgi Apparatus:

Introduction:

Once the proteins leave the rough ER via transport proteins, they go to the Golgi apparatus, where products of the ER are modified, stored, and transported to the needed parts of the cell. Like the ER, the Golgi apparatus has very extensive membranes so that it can secrete packages that can reach vast parts of the cell. Also, the Golgi apparatus has membranous sacs called cisternae, which are separate from each other.

This picture shows the transportation of vesicles from the ER to the Golgi apparatus.

Product transfer through the Golgi apparatus:

When products go through the Golgi apparatus, the are usually modified by enzymes inside the Golgi apparatus – especially the carbohydrate parts of the glycoproteins, in addition to altering sugar monomers to produce a huge variety of carbohydrates on proteins. However, when these products pass through the Golgi apparatus, it must go from the cis face (receiving station on the Golgi apparatus) to the trans face (where proteins depart from the Golgi apparatus). These parts differ from one another, and the cis face is near the ER. When the transport vesicle fuses with the Golgi apparatus to release the protein, the vesicle’s membrane adds onto the Golgi apparatus’ membrane (the cis face). When the products leave the Golgi apparatus, a vesicle pinches off from the trans face to transport the product and again fuse with the plasma membrane of the organelle that needs the product.

This is a diagram of the Golgi apparatus. Note how the products go in one direction from the cis to trans face.

Macromolecules:

The Golgi apparatus also makes its own macromolecules, such as non-cellulose polysaccharides made by plant cells to include in their cell walls along with cellulose.

Product Modification and Tags:

A model called the cisternal maturation model discribes how the product passes through the Golgi apparatus. This model proposes that the cisternae move from the cis face to the trans face, during which the product is modified as it is carried throughout the Golgi apparatus. When the product is about to depart, the Golgi apparatus organizes these products by using molecular identification tags such as phosphate groups. These molecular tags also help the vesicle to recognize the “docking sites” on the surface of the specific organelle that needs the product.

Extras:

Another NDSU Virtual Cell video:

…and an animation by John Kyrk:

http://www.johnkyrk.com/golgiAlone.html

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