Cytoskeleton | Description, Structure, & its Function
It is made up of extremely minute, fibers, filamentous, & tubular proteinaceous structures which form the structural framework inside the cell. The cytoskeleton occurs only in eukaryotic cells & is involved in many functions such as mechanical support, motility, maintenance, of the shape of the cell.
Structure of Cytoskeleton
The microtubules are found in the cytoplasmic matrix of all eukaryotic cells. They also occur in cilia, flagella, centrioles & basal bodies, mitosis apparatus etc. Prokaryotic cells lack microtubules.
The microtubules are hollow, unbranched cylinders, generally about 25 nm in diameter with a hollow core of about 15 nm. The boundary of a microtubules is composed of 13 parallel protofilaments. Each protofilament is made up of α & β subunits of tubulin protein (non contractile protein). The assembly & disassembly of microtubules require GTP & Ca2+.
- These help in the spindles & astral rays formation during cell division.
- These form the cytoskeleton of cilia & flagella.
- These help in generating the shape, rigidity & form of the cell & cell motility.
- Microtubules help in the anaphasic movement of chromosomes.
- Microtubules help in the intracellular transport of nutrients & inorganic ions.
- Position of future cell plate is determined by microtubules.
The microfilaments are found in eukaryotic cells. The microfilaments are Solid, unbranched, rod – like fibrils of indefinite length. They are mainly composed of a globular protein actin, but have filamentous protein myosin also. They form an extensive network in the cytoplasm of cells & may be associated with plasma membrane.
- The microfilaments provide support to plasma membrane.
- These represent the contractile system of the cell & are involved in cytoplasmic steaming & amoeboid movements.
- Help in pseudopodia formation.
- These help in the formation of cleavage furrow during cell division.
(C) Intermediate Filaments
Non – contractile hollow filaments of acidic proteins. They are involved in formation of scaffolds for chromatin & in forming a basket around nucleus.