2. Outlines
•What is cytoskeleton
•Functions of Cytoskeleton
•Types of cytoskeleton
•Microtubules
•Intermediate Filaments
•Thin/ Microfilaments

3. Cytoplasm contains a complex network of filaments
and microtubules which form a structural framework
known as CYTOSKELETON.

4.  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

5.  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.

8.  There are three types of cytoskeleton
 Microfilaments,
 Microtubules and
 Intermediate filaments.

9.  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

11.  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.

13.  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.

15.  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.