Cytoskeleton


It's a complex network of microtubules, actin filaments (microfilaments), and intermediate filaments.It provides the shape to the cells and also play a role in movement of organelles and movement of entire cell.

Microtubules:

• 25nm in diameter
• Found in all eukaryotic cells
• tubulin polymers-rapid assembly and disassembly of  α- and β-tubulin
• defective in Chediak-Hegashi syndrome
• important in spindle formation during meiosis and mitosis
• involved in intracellular vesicle and organelle transport
• kinesin and dynein-ATPase responsible for generating force that drives
• CLINICAL:The antimitoticalkaloids are useful tools in cell biology (eg, colchicineis used to arrest chromosomes in metaphase and to prepare karyotypes) and in cancer chemotherapy(eg, vinblastine, vincristine, and taxolare used to arrest cell proliferation in tumors).

Intermediate filaments:

• 10nm-12nm in diameter
• they play role in cytoplasmic link between extracellular matrix,cytoplasm and nucleus
• contain several tissue specific proteins like cytokeratins,desmin,vimentin,neurofilaments and glial fibrillary acidic protein

Microfilaments:

• 6nm in diameter
• composed of F-actin and G-actin
• Twotypes of movement:

1. local movement(e.g endocytosis,phagocytosis,cytokinesis and amoeboid movement)-inhibitid by cytochalasin B
2. sliding filament movement actin in almost every cell.