CYTOSKELETAL STRUCTURES
1. Cytosteletan is an intracellular framework composed of microtubules, microfilaments and intermediate filaments.
2. Cytoskeleton helps to define and control the shape of the cell, is involved in cell movements, and is important in cell division.
3. All three components are composed of protein subunits that can assemble or disassemble rapidly.
Microtubules
4. Microtubules were discovered by De Roberts and Franchi.
5. The term 'microtubule' was coined by Slautterback in 1963.
6. Microtubules are long, hollow, cylindrical structures, 25 nm diameter, formed by the polymerization of two - part subunits of globular protein tubulin into helical stacks.
7. Microtubules play a role in general cell structure and in cell division.
8. Microtubules radiate from each end of the cell to form a basket - like arrangement (the spindle) which helps in the movement of chromosomes to poles.
9. Chemicals like colchicine disrupt microtubules and arrest the cell division.
10. Microtubules also play a key role in the structure and movement of cilia and flagella.
Microfilaments
11. Microfilaments are long, thin, helically intertwined polymers of the protein actin.
12. Microfilaments play a structural role and interact with microtubules and intermediate filaments in form cytoskeleton.
Intermediate Filaments
13. Many eukaryotic cells have tough, rope-like bundles of proteins known as intermediate filaments with diameter between 8-10 nm.
14. Intermediate filaments consist of a variety of proteins like keratin, vimentin, desmin, peripherin, lamin, etc.
15. Intermediate filaments provide mechanical stability to animal cells, they form basket around nucleus and present in cell - cell junctions.
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