In cell biology, the nucleus (pl. nuclei; from Latin nucleus or nuculeus, meaning kernel) is a membrane-enclosed organelle found in 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 are 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 regulating gene expression — the nucleus is, therefore, the control center of the cell. The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and unifies its contents from the cellular cytoplasm, and the nucleoskeleton (which includes nuclear lamina), a mesh work within the nucleus that adds mechanical support, much like the cytoskeleton, which supports the cell as a whole. Because the nuclear membrane is impermeable to large molecules, nuclear pores are required to allow movement of molecules across the envelope. These pores cross both of the membranes, providing a channel that allows free movement of small molecules and ions. The movement of larger molecules such as proteins is carefully controlled, and requires active transport regulated by carrier proteins. Nuclear transport is crucial to cell function, as movement through the pores is required for both gene expression and chromosomal maintenance. The interior of the nucleus does not contain any membrane-bound sub compartments, its contents are not uniform, and a number of sub-nuclear bodies exist, made up of unique proteins, RNA molecules, and particular parts of the chromosomes. The best-known of these is the nucleolus, which is mainly involved in the assembly of ribosomes. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA.
Other articles related to "cells, cell, cell nucleus, nucleus":
... Cells also have a set of "little organs," called organelles, that are adapted and/or specialized for carrying out one or more vital functions ... Both eukaryotic and prokaryotic cells have organelles but organelles in eukaryotes are generally more complex and may be membrane bound ... There are several types of organelles in a cell ...
... growth factor (TGF)-beta, and thus regulates multiple cellular processes, such as cell proliferation, apoptosis, and differentiation ... translocation of this protein into the cell nucleus, where it binds to target promoters and forms a transcription repressor complex with other cofactors ... beta (TGFβ) superfamily of growth factors into the cell nucleus ...
... As the major defining characteristic of the eukaryotic cell, the nucleus' evolutionary origin has been the subject of much speculation ... to explain the existence of the nucleus, although none have yet earned widespread support ... between the archaea and bacteria created the nucleus-containing eukaryotic cell ...
... Protoplasm is the living contents of a cell that is surrounded by a plasma membrane ... In eukaryotes the protoplasm surrounding the cell nucleus is known as the cytoplasm and that inside the nucleus as the nucleoplasm ... granular, semi-fluid" substance within plant cells, to distinguish this from the cell wall, cell nucleus and the cell sap within the vacuole ...
... perikarya), or cyton, is the bulbous end of a neuron, containing the cell nucleus ... σῶμα, meaning "body" the soma of a neuron is often called the "cell body" ... The cell nucleus is a key feature of the soma ...
Famous quotes containing the words nucleus and/or cell:
“You know that the nucleus of a time is not
The poet but the poem, the growth of the mind
Of the world, the heroic effort to live expressed
As victory. The poet does not speak in ruins
Nor stand there making orotund consolations.
He shares the confusions of intelligence.”
—Wallace Stevens (18791955)
“A cell for prayer, a hall for joy,
They treated nature as they would.”
—Ralph Waldo Emerson (18031882)