anatomy 25 Organelles cytoskeleton
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The centrome is a spherical organelle in the cytoplasm of the cell and near the nucleus. It does not have a membrane, instead it is made up of a cloud of proteins called the "centrosome matrix" at the center of which are two centrioles, perpendicular to each other.
Each centriole is made of 9 sets of 3 short microtubules. These microtubules do not break down and rebuild themselves, they stay permanent. The matrix of proteins around them feed the centrioles proteins to allow them to build the microtubules as well as the components of cilia and flagella.
Microtubules are the thickest of the three structures that make up the cytoskeleton. They are made of sphere shaped proteins called tubulins. Microtubules determine the overall shape of the cell.
Microtubules have a + and - end ( not positive and negative charge, just different ends ). Small motor proteins called kinesins attached to the outside of the microtubule pull organelles along the microbubule from the - to + end. Dynesins do the same thing but from the + to - end. This is how organelles move around within the cell.
Microtubules make up cilia ( in nose, airways, ear ) and flagella ( the tail on sperm ).
Microtubules originate from the centrosome matrix at the center of the cell, and are always breaking and rebuilding.
Microfilaments are the thinnest of the structures that make up the cytoskeleton. Microfilaments are made of the protein, actin and are sometimes called "actin filaments". They exist just inside the cell membrane, or just deep to the cell membrane.
Microfilaments work with another protein called myacin to allow the cell to contract and change shape and plays a role in contracting the cell into cell division.
The ability to move the cell shape also allows it to facilitate endocytosis and exocytosis - the movement of the cell membrane reaching out to pull stuff in and reaching in to push stuff out. It also allows for amoeboid movement of cells.
G-actin, F-actin: G-actin connect to form F-actin which is a chain ( of G-actin proteins ) that forms pairs of chains which make up the microfilament.
Microfilaments also facilitate the production and removal of microvilli.
Microfillaments also give organelles something to anchor themselves to.
Intermediate filaments ( as the name sugguests ) are the middle-sized structures of the cytoskeleton.
They are tougher, stronger, and more permanent than the microtubules or microfilaments. Their man purpose is to hold the cell together to resist the stress of the pulling forces placed on the cell by microfilaments.
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