Collins, Jocelyn and Roy Volkwyn. "Endoplasmic Reticulum." (Last updated July 16, 1999). Online. 9 Feb. 2000. Picture: MIT Biology Hypertextbook (1996).

http://www.botany.com/uwc.ac.za/sci_ed/std8/cells/er.htm

First off, what is the Endoplasmic Reticulum and why are there smooth ones and rough ones?

The Endoplasmic Reticulum is a network of flattened, interweaving tubules which are formed by membranes within the cell. (4) They create mazes of narrow channels. (Refer to the picture below.) Eukaryotic cells (remember, these are the cells that have genetic material inside of the membrane-enclosed nucleus) have two types of Endoplasmic Reticulum: rough ER and smooth ER. The Rough ER varies from the smooth ER in that it has many small studs on its outside known as ribosomes, hence the name 'rough'. The smooth ER and the rough ER also vary in their functions. (To find out more about smooth ER click here.)

Why is it important to have ribosomes on the rough enoplasmic reticulum?

The ribosomes enable the rough ER to synthesize proteins and amoung these are membrane proteins. Almost all of the membrane that is created in the rough ER actually ends up providing new membrane for the ER when it is needed. However, some of the membrane that does not get used either moves inward to replace nuclear membrane or outward to form the Golgi complex, lysosomes or the plasma membrane. (1)

The ribosomes on the rough ER have another important function. They produce proteins that certain secretory cells need to export into their environment, such as digestive enzymes and protein hormones. (1) Once these proteins have been made, they are moved through the channels of the ER. The proteins eventually gather up in little pockets towards the end of the ER. The pockets called vesicles expand like water balloons and are carried off to the Golgi in the cell.

Electron micrograph of the Rough Enoplasmic Reticulum

Audesirk, Gerald and Teresa. Biology: Life on Earth. Fifth Edition. New Jersey: Prentice-Hall, Inc., 1999.

Diagram of the Rough Endoplasmic Reticulum

Collins, Jocelyn and Roy Volkwyn. "Endoplasmic Reticulum." (Last updated July 16, 1999). Online. 9 Feb. 2000. Picture: MIT Biology Hypertextbook (1996).

http://www.botany.com/uwc.ac.za/sci_ed/std8/cells/er.htm

Works cited

(1)Audesirk, Gerald and Teresa. Biology: Life on Earth. Fifth Edition. New Jersey: Prentice-Hall, Inc., 1999.

(2)Dalton, Mark. "The Endoplasmic Reticulum." Online. 9 Feb. 2000.

http:/www.cbu.umn.edu/~mwd/cell_www/chapter2/ER.html

(3)Cells Alive! "Endoplasmic Reticulum." Quill Graphics, Virginia.

http://www.cellsalive.com/cells/er.htm

(4) Collins, Jocelyn and Roy Volkwyn. "Endoplasmic Reticulum." (Last updated July 16, 1999). Online. 9 Feb. 2000. Picture: MIT Biology Hypertextbook (1996).

http://www.botany/uwc.ac.za/sci_ed/std8/cells/er.htm

To Find Out More on The Rough Endoplasmic Reticulum,

Check out These Two Web Sites:

http://www.botany/uwc.ac.za/sci_ed/std8/cells/er.htm

http://www.cellsalive.com/cells/er.htm

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