Nucleus+-+Animal

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The **nucleus** controls the cell's activities and contains all the genetic material

[|**Nucleus**] - The nucleus is a highly specialized organelle that serves as the information processing and administrative center of the cell. This organelle has two major functions: it stores the cell's hereditary material, or DNA, and it coordinates the cell's activities, which include growth, intermediary metabolism, protein synthesis, and reproduction (cell division).

__.:NUCLEUS  :. __
 * The animal cell is a typical eukaryotic cell. It is surrounded by a plasma membrane, which forms a selective barrier allowing nutrients to enter and waste products to leave. The cytoplasm contains specialized organelles, each of which is surrounded by a membrane. There is only one nucleus and it contains all the genetic information necessary for cell growth and reproduction. The other organelles occur in multiple copies and carry out the various functions of the cell, allowing it to survive and participate in the functioning of the larger organism. ||

= **__CELL THEORY RAP__ __The Difference Between Plants and Animal Cells__** = media type="youtube" key="CVb_sKn24as" height="344" width="425"media type="youtube" key="t8yzHVAxKhQ" height="344" width="425"

= __Cell Nucleus__ __Cell City__ =

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=__Nucleus__=


 * One or more per cell
 * Spherical shape
 * Denser than surrounding cytoplasm
 * Contains many organelles such as the nucleolus

The nucleus controls many of the functions of the cell (by controlling protein synthesis) and contains DNA (in chromosomes). The nucleus surrounded by a double membrane and contains chromatim, a combination of DNA and protein. DNA stores hereditary information and directs the synthesis of RNA, which then directs the synthesis of proteins into the cytosol. The nulcear matrix helps the nucleus keep its round spherical shape. The nuclear envelope is the double membrane that surrounds the nucleus, protecting it. In the nuclear envelope is chromatin, which is a mix of DNA and proteins. Chromatin when coiled up become chromosomes. The nucleus stores all hereditary info in DNA and where RNA is copied from the DNA. The RNA directs the protein synthesizing, which occurs in the cytosol. RNA must travel from the nucleus to the cytosol for this to work, therefore it has to leave the nucleus thru the nucleus pores.

 __The Nuclear Envelope__
 The nucleus is enveloped by a pair of membranes enclosing a lumen that is continuous with that of the endoplasmic reticulum. The inner membrane is stabilized by a meshwork of intermediate filament proteins called **lamins**. The nuclear envelope is perforated by thousands of **nuclear pore complexes** (**NPC**s) that control the passage of molecules in and out of the nucleus.


 The nucleus contains the chromosomes of the cell. Each chromosome consists of a single molecule of DNA complexed with an equal mass of proteins. Collectively, the DNA of the nucleus with its associated proteins is called **chromatin**. Most of the protein consists of multiple copies of 5 kinds of **histones**. These are basic proteins, bristling with positively charged arginine and lysine residues. (Both Arg and Lys have a free amino group on their R group, which attracts protons (H+) giving them a positive charge.) Just the choice of amino acids you would make to bind tightly to the negatively-charged phosphate groups of DNA. Chromatin also contains small amounts of a wide variety of **nonhistone proteins**. Most of  the protein consists of multiple copies of 5 kinds of **histones**. These are basic proteins, bristling with positively charged <span style="font-family: 'Comic Sans MS', cursive;">arginine  <span style="font-size: 120%; font-family: 'Comic Sans MS', cursive;"><span style="font-family: 'Comic Sans MS', cursive;"> and  <span style="font-size: 120%; font-family: 'Comic Sans MS', cursive;"><span style="font-family: 'Comic Sans MS', cursive;">lysine  <span style="font-size: 120%; font-family: 'Comic Sans MS', cursive;"><span style="font-family: 'Comic Sans MS', cursive;"> residues. (Both Arg and Lys have a free amino group on their <span style="font-size: 120%; font-family: 'Comic Sans MS', cursive;"><span style="font-family: 'Comic Sans MS', cursive;">R group  <span style="font-size: 120%; font-family: 'Comic Sans MS', cursive;"><span style="font-family: 'Comic Sans MS', cursive;">, which attracts protons (H+) giving them a positive charge.) Just the choice of amino acids you would make to bind tightly to the negatively-charged  <span style="font-size: 120%; font-family: 'Comic Sans MS', cursive;"><span style="font-family: 'Comic Sans MS', cursive;">phosphate groups  <span style="font-family: 'Comic Sans MS', cursive;"><span style="font-size: 120%; font-family: 'Comic Sans MS', cursive;">of DNA. Chromatin also contains small amounts of a wide variety of **nonhistone proteins**. Most of these <span style="font-family: 'Comic Sans MS', cursive;">

=<span style="font-size: 110%; font-family: 'Comic Sans MS', cursive;">__The Nucleus__ = =<span style="font-size: 110%; font-family: 'Comic Sans MS', cursive;"> =

<span style="font-size: 110%; font-family: 'Comic Sans MS', cursive;">The nucleus is the most obvious organelle in any eukaryotic cell. It is a membrane-bound organelle and is surrounded by a double membrane. It communicates with the surrounding cytosol via numerous nuclear pores

= <span style="font-size: 110%; font-family: 'Comic Sans MS', cursive;"> = = <span style="font-size: 110%; font-family: 'Comic Sans MS', cursive;">   =

<span style="font-size: 110%; font-family: 'Comic Sans MS', cursive;"> This picture represents everything that makes up the Nucleus.

**Structure/function correlations**
The cell nucleus is a remarkable organelle because it forms the package for our genes and their controlling factors. It functions to: Store genes on chromosomes Organize genes into [|chromosomes] to allow cell division. Transport regulatory factors & gene products via [|nuclear pores] Produce messages ([| messenger Ribonucleic acid or mRNA]) that code for proteins Produce [|ribosomes]in the [|nucleolus] Organize the [nm DNA|uncoiling of DNA]to replicate key genes

The nucleus is a highly specialized organelle that serves as the information and administrative center of the cell. This organelle has two major functions. It stores the cell's hereditary material, or DNA, and it coordinates the cell's activities, which include intermediary metabolism, growth, protein synthesis, and reproduction (cell division).
 * In** [|**cell biology**]**, the nucleus (pl. //nuclei//; from** [|**Latin**] **//nucleus// or //nuculeus//, kernel) is a membrane-enclosed** [|**organelle**] **found in most** [|**eukaryotic**] [|**cells**]**. It contains most of the cell's** [|**genetic material**]**, organized as multiple long linear** [|**DNA**] **molecules in complex with a large variety of** [|**proteins**]**, such as** [|**histones**]**, to form** [|**chromosomes**]**. The** [|**genes**] **within these chromosomes make up the cell's** [|**nuclear genome**]**. The function of the nucleus is to maintain the integrity of these genes and to control the activities of the cell by regulati**

Only the cells of advanced organisms, known as **eukaryotes**, have a nucleus. Generally there is only one nucleus per cell, but there are exceptions such as slime molds and the Siphonales group of algae. Simpler one-celled organisms (**prokaryotes**), like the bacteria and cyanobacteria, don't have a nucleus. In these organisms, all the cell's information and administrative functions are dispersed throughout the cytoplasm. The spherical nucleus occupies about 10 percent of a cell's volume, making it the cell's most prominent feature. Most of the nuclear material consists of chromatin, the unstructured form of the cell's DNA that will organize to form chromosomes during mitosis or cell division. Also inside the nucleus is the nucleolus, an organelle that synthesizes protein-producing macromolecular assemblies called ribosomes. A double-layered membrane, the nuclear envelope, separates contents of the nucleus from the cellular cytoplasm. The envelope is riddled with holes called nuclear pores that allow specific types and sizes of molecules to pass back and forth between the nucleus and the cytoplasm. It is also attached to a network of tubules, called the endoplasmic reticulum, where protein synthesis occurs. These tubules extend throughout the cell and manufacture the biochemical products that a particular cell type is genetically coded to produce. Each DNA strand wraps around groups of small protein molecules called histones, forming a series of bead-like structures, called nucleosomes, connected by the DNA strand. Under the microscope, uncondensed chromatin has a "beads on a string" appearance. The string of nucleosomes, already compacted by a factor of six, is then coiled into an even denser structure, compacting the DNA by a factor of 40. This compression and structuring of DNA serves several functions. The overall negative charge of the DNA is neutralized by the positive charge of the histone molecules, the DNA takes up much less space, and inactive DNA can be folded into inaccessible locations until it is needed. There are two types of chromatin. Euchromatin is the genetically active portion and is involved in transcribing RNA to produce proteins used in cell function and growth. Heterochromatin contains inactive DNA and is the portion of chromatin that is most condensed, since it not being used. Throughout the life of a cell, chromatin fibers take on different forms inside the nucleus. During interphase, when the cell is carrying out its normal functions, the chromatin is dispersed throughout the nucleus in what appears to be a tangle of fibers. This exposes the euchromatin and makes it available for the transcription process. When the cell enters metaphase and prepares to divide, the chromatin changes dramatically. First, all the chromatin strands make copies of themselves through the process of DNA replication. Then they are compressed to an even greater degree than at interphase, a 10,000-fold compaction, into specialized structures for reproduction, termed chromosomes. As the cell divides to become two cells, the chromosomes separate, giving each cell a complete copy of the genetic information contained in the chromatin. *** Nuclear Envelope ||  || The Cell Nucleus**
 * **Chromatin/Chromosomes** - Packed inside the nucleus of every human cell is nearly 6 feet of DNA, which is divided into 46 individual molecules, one for each chromosome and each about 1.5 inches long. Packing all this material into a microscopic cell nucleus is an extraordinary feat of packaging. For DNA to function, it can't be crammed into the nucleus like a ball of string. Instead, it is combined with proteins and organized into a precise, compact structure, a dense string-like fiber called chromatin.
 * - The nuclear envelope is a double-layered membrane that encloses the contents of the nucleus during most of the cell’s lifecycle. The space between the layers is called the perinuclear space and appears to connect with the rough endoplasmic reticulum. The envelope is perforated with tiny holes called nuclear pores. These pores regulate the passage of molecules between the nucleus and cytoplasm, permitting some to pass through the membrane, but not others. The inner surface has a protein lining called the nuclear lamina, which binds to chromatin and other nuclear components. During mitosis, or cell division, the nuclear envelope disintegrates, but reforms as the two cells complete their formation and the chromatin begins to unravel and disperse.
 * * Nuclear Pores **- The nuclear envelope is perforated with holes called nuclear pores. These pores regulate the passage of molecules between the nucleus and cytoplasm, permitting some to pass through the membrane, but not others. Building blocks for building DNA and RNA are allowed into the nucleus as well as molecules that provide the energy for constructing genetic material.** The pores are fully permeable to small molecules up to the size of the smallest proteins, but form a barrier keeping most large molecules out of the nucleus. Some larger proteins, such as histones, are given admittance into the nucleus. Each pore is surrounded by an elaborate protein structure called the nuclear pore complex, which probably selects large molecules for entrance into the nucleus. ||
 * [[image:http://cellbio.utmb.edu/cellbio/nucleus2.jpg width="437" height="604" align="left"]] ||

Within the nucleus is the DNA responsible for providing the cell with its unique characteristics. The DNA is similar in every cell of the body, but depending on the specific cell type, some genes may be turned on or off - that's why a liver cell is different from a muscle cell, and a muscle cell is different from a fat cell. When a cell is dividing, the DNA and surrounding protein condense into chromosomes (see photo) that are visible by microscopy.

The nucleus is the most obvious organelle in any eukaryotic cell. It is enclosed in a double membrane and communicates with the surrounding cytosol via numerous neclear pores. Within the nucleus is the DNA responsible for providing the cell with its unique characterisitics. The DNA is similar in every cell of the body, but depending on the specific cell type, some genes may be turned on or off- that's why a liver cell is defferent from a muscle cell, and a muscle cell is defferent from a fat cell.