View source

[[es:N�cleo celular]] [[ja:&#32048;&#32990;&#26680;]] [[ms:Nukleus]] [[nl:celkern]] [[sv:cellk�rna]]

The cell nucleus is an [[organelle]] within an [[eukaryote|eukaryotic]] [[biological cell|cell]]. Its has two main functions :
* to control chemical reactions in the cell [[cytoplasm]]
* to store information needed for when the cell [[cell division|divides]]

== Structure ==

The nucleus, being the largest [[organelle|sub-cellular compartment]], varies in diameter from 10 to 20 [[micrometre]]s. It is surrounded by a double [[membrane]] forming the ''[[nuclear envelope]]'', about 30 nm wide. This selectively allows molecules to enter and leave the nucleus, and separates chemical reactions taking place in cytoplasm from reactions happening within the nucleus. The outer membrane has [[ribosome]]s. The inner and outer membrane fuse at regular spaces, forming ''[[nuclear pore]]s''. 

Similar to the cytoplasm of a cell, the nucleus contains [[nucleoplasm]] - a highly viscous solid containing the chromosomes and [[nucleolus|nucleoli]]. Chromosones contain information encoded in [[DNA]] attached to proteins called ''[[histone]]s'' and are usually arranged in to a dense network called ''[[chromatin]]''. Nucleoli are granular structures which make ribonucleic DNA ([[rDNA]]) and assemble it with [[protein]]s.

====References====
* Adapted from the [[Wikipedia]] article, "Cell nucleus" http://en.wikipedia.org/wiki/Cell_nucleus December 5, 2003