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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 main components of the nuclear envelope are a double membrane, nuclear pore complexes, and a nuclear lamina internal to the inner nuclear membrane. These components are dismantled during prophase and prometaphase and reconstructed during telophase, when the nuclear envelope reforms on the surface of separated sister chromatids.
Karyorrhexis involves the breakdown of the nuclear envelope and the fragmentation of condensed chromatin due to endonucleases. In cases of apoptosis, karyorrhexis ensures that nuclear fragments are quickly removed by phagocytes.
During this phase, the nuclear envelope breaks down, causing the condensed chromatin to break apart and then distribute nuclear fragments throughout the cytoplasm. Karyorrhexis occurs in apoptosis– with a different cause and purpose than necrosis–and, on rare occasions, occurs in normal cell differentiation processes.
The nuclear lamina consists of two components, lamins and nuclear lamin-associated membrane proteins. The lamins are type V intermediate filaments which can be categorized as either A-type (lamin A, C) or B-type (lamin B 1, B 2) according to homology of their DNA sequences, biochemical properties and cellular localization during the cell cycle.
The nuclear envelope consists of two membranes, an inner and an outer nuclear membrane, perforated by nuclear pores. [ 10 ] : 649 Together, these membranes serve to separate the cell's genetic material from the rest of the cell contents, and allow the nucleus to maintain an environment distinct from the rest of the cell.
A nuclear pore is a channel as part of the nuclear pore complex (NPC), a large protein complex found in the nuclear envelope of eukaryotic cells.The nuclear envelope (NE) surrounds the cell nucleus containing DNA and facilitates the selective membrane transport of various molecules.
The nuclear envelope surrounds the nucleus, separating its contents from the cytoplasm.It has two membranes, each a lipid bilayer with associated proteins. [21] The outer nuclear membrane is continuous with the rough endoplasmic reticulum membrane, and like that structure, features ribosomes attached to the surface.