of an animal cell

The Nucleolus of a cell is the sites of Ribosome Assembly. It consists of RNA, proteins, ribosomes in different synthesis, and DNA. Each cell nucleus typically contains on or more nucleoli, which appear as irregulary shaped, dense areas of fibers and granules. Ribosomes are small particales composed of Rna and several proteins that are the foundation for synthesis of proteins. The same set of proteins can be used to do different things. For example, one ribosome can systhensize many proteins. Ribosomes can be found in clusters along the membranes of nuclear envelope and endoplasmic reticulum (smooth and rough). They can also be found in thecytoplasm as dark granules.

Genetic information for ribosmal proteins, found in the nucleus, is copied into special messenger RNA (mRNA). It then travels out of the nucleus into the cell's cytoplasm where info is translated into ribosomal proteins. The new proteins enter the nucleolus and combines with subunits like RNA to create two ribosomal stuctures, the large and small subunits. They both enter the cytoplasm and exit the nucleus where they can make a complete ribosome. It takes about an hour for the nucleous to make a single ribosome, but thousands are made by each nuclelous at the same time.

Complete Cell Sturcture and Functions

http://www.sturgeon.ab.ca/rw/Alan_K/Cell_Components.html

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Marc A. Jordan-Menlo School-2000