Cytoskeleton

CYTOSKELETON

By: MUHAMMAD FAISAL YAQOOB

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

Outlines

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

COMPOSITION OF 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

FUNCTIONS OF CYTOSKELETON 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.

TYPES OF CYTOSKELETON

MICRO 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. 

MICROTUBULES

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.

INTERMEDIATE FILAMENTS

TUBULINS AND THE FORMATION OF MICROTUBULES 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.