Wednesday, January 16, 2013

Cytoskeleton

The cytoskeleton is another most important structure present in all eukaryotic cells. What do you mean by cytoskeleton? 'Cyto' means 'cell' and 'skeleton' means 'supporting structure/frame'. Thus, as the name suggests, cytoskeleton helps in maintaining the shape of the cell. However, its primary importance/function is cell motility.

Structure:
Cytoskeleton is the dynamic structure that fills the spaces in the cytoplasm of the cell. Cytoskeleton is a complex and organized network of three filaments as - microtubules, microfilaments (actin filaments) and intermediate filaments. What are the differences between them? Lets try to understand.
Three Different Components of Cytoskeleton
a. Microtubules: Microtubules are hollow cylindrical structures which are around 20-25 nm in diameter. They are composed of further subunits of protein called tubulin and further differentiated into alpha and beta tubulin.
b. Microfilaments/ Actin filaments: Microfilaments as the name suggests are thread like filaments or fibers of around 3-6nm in diameter. They are composed of subunits of protein called actin. Do you know that actin is the most abundant protein present in the cell? Microfilaments are also known to associate with another protein called myosin and this is responsible for muscle contractions.
c. Intermediate filaments: These filaments are around 10nm in diameter. They are heterogeneous constituents of the cell. The intermediate filaments include proteins like vimentin, lamin (these give structural support to the cell), keratin (protein which is found in skin, nail, hair etc.)

Functions:
Microtubules act as scaffold and determines the shape of the cell. They also from spindle fibers for separating chromosomes during the process of mitosis (cell division). They are also involved in the synthesis of cell walls in plants.
Microfilaments are for muscle contraction. They are responsible for movement of cells, for eg.; gliding.
Intermediate filaments provide tensile strength for the cell. They act as structural components and also help in anchoring organelles. They also are involved in cell-cell junctions.