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( 9ano of 11)
The cytoskeleton is a complex three dimensional network of protein fibers of different thickness in the cytoplasm of cells.
The cytoskeleton forms a framework for cell stability, organization and movement of organelles and raw materials across the cytoskeleton's crissrcross highway extraordinaire. Most organelles are attached to the cytoskeleton by cytoskeleton fibers. The cytoskeleton also plays a role in cell division.
The cytoskeleton was thought to be unique to eukaryotic cells, but
researchers think prokaryotic cells may also have structures that resemble a cytoskeleton. I say, since prokaryotic cells carry out many of the same functions as eurkaryotes, then we must lean towards there being a cytoskeleton unless it is already known that cellular functions of prokaryotes are carried out by other means. Is it reasonable to think that supposedly less evolved cells can do the same or more functions with less structure?
Cytoskeleton Fibers Come In Three Flavors
1. Microfilaments are fine, thread-like protein fibers mainly composed of a contractile protein called actin, which is the most abundant cellular protein. Microfilament association with the protein myosin is responsible for muscle contraction. I suspect there are other proteins that counteract actin and myosin, thus are responsible for expansion/extension.
2. Microtubules act as a scaffold to determine cell shape, and provide a set of "tracks" for cell organelles and vesicles to travel on. Microtubules also form the spindle fibers for separating chromosomes during cell division.
Microtubules are hollow pipes and are assembled in such a way that they have a polarity (one end is positive and the other is negative). This gives the overall microtubule, a flow of current thus the ability to guide movement in a certain direction.
Microtubules are a mobile pipeline that is rapidly assembled and broken down many times within a short span of time, while intermediate filaments are more stable.
3. Intermediate filaments provide tensile strength for the cell.
Intermediate filaments are rope-like fibers made of a variety of proteins. The rope-like structure [woven, braided, twisted] of intermediate filaments gives them great strength and their main function is to provide mechanical strength to cells to help cells resist being damaged or pulled apart during stretching and changing shape.
Intermediate filaments form a network in the cytoplasm, surrounding the nucleus and radiating out to the plasma membrane of the cell. Intermediate filaments are also found in the nucleus, where they form the meshwork called the nuclear lamina underlying the inner membrane of the nuclear envelope.
Intermediate filaments also connect cells, thus these filaments run through the interstitial fluid.
The cytoskeleton is much less rigid and permanent than its name implies. It is a dynamic structure that is continually reorganized as cells move and change shape.
To make the inner cytoskeletons even stronger,
cells and their cytoskeletons are connected to the extracellular region which weaves and sews them together to form tissues and organs.
The cytoskeleton pulls things together, pulls things apart and holds things together, thus must also help push things apart. It's structural behavior mimics the interstitium's constant shapeshifting. I wonder if the cytoskeleton also contains fluid -filled compartments?
