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Most animal cells have one MTOC during interphase, usually located near the nucleus, and generally associated closely with the Golgi apparatus.The MTOC is made up of a pair of centrioles at its center, and is surrounded by pericentriolar material (PCM) that is important for microtubule nucleation.
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.
Nucleoplasm is quite similar to the cytoplasm, with the main difference being that nucleoplasm is found inside the nucleus while the cytoplasm is located inside the cell, outside of the nucleus. Their ionic compositions are nearly identical due to the ion pumps and permeability of the nuclear envelope, however, the proteins in these two fluids ...
The centrosome is thought to have evolved only in the metazoan lineage of eukaryotic cells. [2] Fungi and plants lack centrosomes and therefore use other structures to organize their microtubules. [3] [4] Although the centrosome has a key role in efficient mitosis in animal cells, it is not essential in certain fly and flatworm species. [5] [6] [7]
Specialized cells can have a lot of smooth endoplasmic reticulum and in these cells the smooth ER has many functions. [5] It synthesizes lipids, phospholipids, [18] [19] [20] and steroids. Cells which secrete these products, such as those in the testes, ovaries, and sebaceous glands have an abundance of smooth endoplasmic reticulum. [21]
The cytoplasm, the cytoplasmic membrane and the cell wall are subcellular localizations, whereas the extracellular environment is clearly not. Most Gram-negative bacteria also contain an outer membrane and periplasmic space. Unlike eukaryotes, most bacteria contain no membrane-bound organelles, however there are some exceptions (i.e. magnetosomes).
A study of the comparative genomics, evolution and origins of the nuclear membrane led to the proposal that the nucleus emerged in the primitive eukaryotic ancestor (the “prekaryote”), and was triggered by the archaeo-bacterial symbiosis. [24] Several ideas have been proposed for the evolutionary origin of the nuclear membrane. [25]
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles [1] and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell and contained within the nuclear membrane is termed the nucleoplasm .