Outlines•What is cytoskeleton•Functions of Cytoskeleton•Types of cytoskeleton•Microtubules•Intermediate Filaments•Thin/ Microfilaments
Cytoplasm contains a complex network of filamentsand microtubules which form a structural frameworkknown as CYTOSKELETON.
Filaments. Microtubules The primary components of the cytoskeleton- microtubules, actin filaments (aka microfilaments) and intermediate filaments- have been known for some time and their properties have been extensively studied
It provides structural support to the cell. It also functions in cell motility and regulation. Often protects the cell. Is very important in cell division. Plays an important role in intracellular transport.
There are three types of cytoskeleton Microfilaments, Microtubules and Intermediate filaments.
Microfilaments, the thinnest class of the cytoskeletal fibers, are solid rods of the globular protein actin. An actin microfilament consists of a twisted double chain of actin subunits. Microfilaments are designed to resist tension. With other proteins, they form a three- dimensional network just inside the plasma membrane
Microtubules, the thickest fibers, are hollow rods about 25 microns in diameter. Microtubule fibers are made up of the globular protein, tubulin, and they grow or shrink as more tubulin molecules are added or removed.
Intermediate in size at 9 - 11 nanometers, are specialized for bearing tension. Intermediate filaments are built from a diverse class of subunits from a family of proteins called keratins. Intermediate filaments are more permanent fixtures of the cytoskeleton than are the other two classes.
The basic unit of microtubules is dimer consisting of α- and β-tubulins. Microtubules have a long tubular structure, with each turn of the helix containing 13 dimers. They have plus and minus ends, and polymerization occurs at the plus end. An organelle that serves as the polymerization origin of microtubules exists in cells. This structure is called the centrosome, localized near the nucleus. Special protein complexes that serve as the starting point in the polymerization of microtubules are found in the centrosome. In most cells, microtubules radiate from the centrosome . Therefore, their growth ends (i.e., those opposite from the centrosome) are the plus ends.