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The cell nucleus (from Latin nucleus or nuculeus 'kernel, seed'; pl.: nuclei) is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells , have no nuclei , and a few others including osteoclasts have many .
The cytoplasm contains the cytoskeleton, a network of protein filaments found in all cells, while the nucleoplasm is believed to contain the nuclear matrix, a hypothetically analogous network of filaments that organizes the organelles and genetic information within the nucleus. While the structure and function of the cytoskeleton have been well ...
The nuclear envelope, also known as the nuclear membrane, [1] [a] is made up of two lipid bilayer membranes that in eukaryotic cells surround the nucleus, which encloses the genetic material. The nuclear envelope consists of two lipid bilayer membranes: an inner nuclear membrane and an outer nuclear membrane. [ 4 ]
The nucleolus (/ nj uː ˈ k l iː ə l ə s, ˌ nj uː k l i ˈ oʊ l ə s /; pl.: nucleoli /-l aɪ /) is the largest structure in the nucleus of eukaryotic cells. [1] It is best known as the site of ribosome biogenesis. The nucleolus also participates in the formation of signal recognition particles and plays a role in the cell's response to ...
Most important among these is a cell nucleus, [2] an organelle that houses the cell's DNA. This nucleus gives the eukaryote its name, which means "true kernel (nucleus)". Some of the other differences are: The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may or may not be present.
Nuclear pores are found in the nuclear envelope that surrounds the cell nucleus in eukaryotic cells. The nuclear envelope is studded by a great number of nuclear pores that give access to various molecules, to and from the nucleoplasm and the cytoplasm. Small molecules can diffuse easily but other larger molecules need to be transported across. [1]
An example of such function is cell signalling, a process which is dependent on the manner in which signaling molecules are allowed to diffuse across the cell. [9] While small signaling molecules like calcium ions are able to diffuse with ease, larger molecules and subcellular structures often require aid in moving through the cytoplasm. [ 10 ]
Eukaryotic cells have a variety of internal membrane-bound structures, called organelles, and a cytoskeleton which defines the cell's organization and shape. The nucleus stores the cell's DNA, which is divided into linear bundles called chromosomes; [19] these are separated into two matching sets by a microtubular spindle during nuclear ...