Nucleus+&+Nucleolus

=// The Nucleus &  the Nucleolus   //=

The Nucleus, or the "brain," of any eukaryotic plant or animal cell plays an essential role in keeping the cell alive and functional. It serves two distinct and important purposes. The first one is that it monitors and controls all cellular processes, such as growth, protein synthesis, and metabolism. The second role the nucleus plays is housing all genetic material - necessary for reproduction - in its densely compacted nucleolus. =// Structure Dictates Function //= The most prominent organelle in the eukaryotic cell (//prokaryotes// feature a smaller, less complex nucleoid), the nucleus accounts for 10 percent of a cell's total volume, and is typically 11 to 22 micrometers in diameter. As indicated by the picture, a nucleus' outer shell, or "nuclear envelope," is composed of a double cellular membrane similar to that of other organelles. In order to breach this wall, matter must pass through a //nuclear pore// in the outer membrane (//see video for more details//). Once inside, a densely tangled mass of chromation is kept, which is utilized for all the important functions of the nucleus. this mass, (or masses, if there are more than one) is called the "nucleolus." As indicated by the picture below, there is nothing separating the nucleolus from the rest of the nucleus but nucleoplasm (similar to cytoplasm).  media type="google" key="6374761646657730470&hl=en&fs=true" width="400" height="326" =//** The Nucleus puts the "fun" in Cellular Function! ** // = The nucleus has two complex roles: it contains all of the genetic material that is necessary for the cell to reproduce and it controls all activities within the cell.



The DNA in the nucleolus is gathered with proteins into material called chromatin. The nucleus (see image: http://www.wlu.ca/galleries_photo.php?g_id=138&gp_id=1954 ), along with chromatin (see photogragh: http://www.wlu.ca/galleries_photo.php?g_id=138&gp_id=1952 ), can be seen through light microscopes and electron microscopes. When the cell is ready to divide, the chromatin, which appears as long, string-like strands, becomes tangled and condenses, turning into chromosomes. Chromosomes are made of the thick chromatin and appear as separate structures. The species of a eukaryotic cell is determined by the number of chromosomes in the nucleus. In humans, there are nearly six feet of DNA, and 46 chromosomes.

When a cell divides, the nucleolus disappears, and is formed again when the chromosomes gather together. a cell may have up to four nucleoli (plural of nucleolus) but each species has a certain number of nucleoli. The nucleolus may possibly be linked to cell aging.

Ribosomes are manufactured in the nucleolus, which control protein synthesis. It sends messages into the cytoplasm in messenger RNA, or mRNA, which is created in the nucleus using instructions from DNA. The mRNA brings the genetic material into the cytoplasm through the nuclear pores. The mRNA then attaches to ribosomes and the genetic message is used to create the first part of a specific protein.

Quiz Yourself! Take a quiz on the nucleus: Easier: http://www.biology4kids.com/extras/quiz_cellnuc/index.html More Difficult: http://library.thinkquest.org/27819/cgi-bin/quiz.cgi?quiz=3_4

=**//Sources / Works Cited://**=

__Laurier Canadian Excellence__. Laurier. 27 Oct. 2008 .

[|__Rader's Biology4Kids.com__. Andrew Rader Studios. 27 Oct. 2008 .]

Campbell, Neil. "The Nucleus and Ribosomes." __Biology__. 5th ed. Boston: Benjamin-Cummings Company, 1999. 107-11.

"Animal Cell Nucleus." Cartage. 27 Oct. 2008 <http://www.cartage.org.lb/en/themes/sciences/zoology/animalphysiology/anatomy/animalcellstructure/Nucleus/Nucleus.htm

Patel, Samir S. "Nuclear Transport Animations." __Sspatel.googlepages.com__. 2001. 28 Oct. 2008 http://sspatel.googlepages.com/nuclearporecomplex.

Ferguson, John B. "Nucleus (biology)." Microsoft® Student 2007 [DVD]. Redmond, WA: Microsoft Corporation, 2006.
 * Microsoft ® Encarta ® 2007. © 1993-2006 Microsoft Corporation. All rights reserved.**