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"Nucleus." Web. 12 Nov. 2020.

Rachel Baxter BSc, MSc. "Cell Nucleus." Kenhub. Kenhub, 29 Oct. 2020. Web. 12 Nov. 2020.

"Nucleus." Encyclopædia Britannica. Encyclopædia Britannica, Inc. Web. 12 Nov. 2020.

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The nucleus is one of the most obvious parts of the cell when you look at a picture of the cell. It's in the middle of the cell, and the nucleus contains all of the cell's chromosomes, which encode the genetic material. So this is really an important part of the cell to protect. The nucleus has a membrane around it that keeps all the chromosomes inside and makes the distinction between the chromosomes being inside the nucleus and the other organelles and components of the cell staying outside. Sometimes things like RNA need to traffic between the nucleus and the cytoplasm, and so there are pores in this nuclear membrane that allow molecules to go in and out of the nucleus. It used to be thought that the nuclear membrane only allowed molecules to go out, but now it's realized that there is an active process also for bringing molecules into the nucleus.

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The nucleus is one of the most obvious parts of the cell when you look at a picture of the cell. It's in the middle of the cell, and the nucleus contains all of the cell's chromosomes, which encode the genetic material. So this is really an important part of the cell to protect.

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The Cell 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).

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 the cells of 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 of the cell's information and administrative functions are dispersed throughout the cytoplasm.

The spherical nucleus typically occupies about 10 percent of a eukaryotic cell's volume, making it one of the cell's most prominent features. A double-layered membrane, the nuclear envelope, separates the 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 and sacs, called the endoplasmic reticulum, where protein synthesis occurs, and is usually studded with ribosomes (see Figure 1).

The semifluid matrix found inside the nucleus is called nucleoplasm. Within the nucleoplasm, most of the nuclear material consists of chromatin, the less condensed form of the cell's DNA that organizes to form chromosomes during mitosis or cell division. The nucleus also contains one or more nucleoli, organelles that synthesize protein-producing macromolecular assemblies called ribosomes, and a variety of other smaller components, such as Cajal bodies, GEMS (Gemini of coiled bodies), and interchromatin granule clusters.

Chromatin and 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 Nucleolus - The nucleolus is a membrane-less organelle within the nucleus that manufactures ribosomes, the cell's protein-producing structures. Through the microscope, the nucleolus looks like a large dark spot within the nucleus. A nucleus may contain up to four nucleoli, but within each species the number of nucleoli is fixed. After a cell divides, a nucleolus is formed when chromosomes are brought together into nucleolar organizing regions. During cell division, the nucleolus disappears. Some studies suggest that the nucleolus may be involved with cellular aging and, therefore, may affect the senescence of an organism.

The Nuclear Envelope - 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.

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Molecular Expressions Cell Biology: The Cell Nucleus

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The nucleus is a highly specialized organelle that serves as the information and administrative center of the cell.

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-The nucleus varies in size from cell to cell. Depending on the species and the cell, they can look differently.
-In the 1800's, Robert Brown found the nucleus.
-The nucleus is a double membrane -bound organelle.
-You can see the nucleus with a simple compound microscope.

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- NUCLEAR ENVELOPE: The nuclear envelope is the barrier between the nucleus and the cytoplasm. It contains a lot of proteins.
- CHROMATIN: This is the material that makes up chromosomes. It contains DNA and protein.
-NUCLEOLUS: This is the part of the cell that produces and assembles ribosomes.
-ENDOPLASMIC RETICULUM: This is the area where proteins are created.
-NUCLEAR PORE: This is a large complex of proteins that allows for molecules and ions to go in and out of the nucleus.
-NUCLEOPLASM: This is where DNA is stored. It also regulates an environment where actions can take place.

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As amazing as the nucleus is, there are some problems. Genes are found in the nucleus. When genes move from their correct location, this will cause malfunctions. These malfunctions can lead to the breaking down of muscles, the heart, and blood vessels. Muscles will not be able to develop correctly. This can also lead to heart failure.

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The nucleus is responsible for the creation of every molecule in the cell. This is the control center for all other organelles. Without the nucleus, the cell would eventually die. The cell would not know what do do without it and could not conduct necessary actions.

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The nucleus is located at the center of the cell. It is considered to be the brain of the cell. The nucleus contains all genetic material and information. It coordinates all of the cells activities, such as reproduction, growth, intermediary metabolism, and protein synthesis. The nucleus also stores chromatin fibers which come together to form complex structures called chromosomes. In the chromosomes we can find genes. Genes contain information that is necessary for building certain proteins that have particular functions. Some of these functions consist of building structures, communicating, and passing along information.