CytoskeletonCytoskeleton

The The cytoskeletoncytoskeleton (also CSK) is a cellular " (also CSK) is a cellular "scaffolding" or "" or "skeleton" contained within the " contained within the cytoplasm that is made out of that is made out of protein. The . The cytoskeleton is present in all cells; it was once cytoskeleton is present in all cells; it was once thought this structure was unique to thought this structure was unique to eukaryotes, but recent research has identified , but recent research has identified the the prokaryotic cytoskeleton. .

It is a dynamic structure that maintains cell It is a dynamic structure that maintains cell shape, protects the cell, enables cellular shape, protects the cell, enables cellular motion (using structures such as motion (using structures such as flagella, , cilia and and lamellipodia), and plays important roles in ), and plays important roles in both intracellular transport (the movement of both intracellular transport (the movement of vesicles and organelles, for example) and and organelles, for example) and cellular division..

The concept and the term (The concept and the term (cytosquelettecytosquelette, in , in French) was first introduced by French French) was first introduced by French embryologist embryologist Paul Wintrebert in 1931. in 1931.

Cells contain elaborate arrays of protein fibers Cells contain elaborate arrays of protein fibers that serve such functions as: that serve such functions as:

establishing cell shape establishing cell shape providing mechanical strength providing mechanical strength locomotion locomotion Cell division Cell division intracellular transport of organellesintracellular transport of organelles

The cytoskeleton is made up of three kinds of The cytoskeleton is made up of three kinds of protein filaments: protein filaments:

Actin filamentsActin filaments (also called (also called microfilamentsmicrofilaments) ) Intermediate filamentsIntermediate filaments and and MicrotubulesMicrotubules

Actin FilamentsActin Filaments

is composed of two intertwined actin chains is composed of two intertwined actin chains most concentrated just beneath the cell membrane, most concentrated just beneath the cell membrane,

and are responsible for resisting tension and and are responsible for resisting tension and maintaining cellular shape.maintaining cellular shape.

MicrotubulesMicrotubules Microtubules are cylindrical tubes, 20-25 nm in Microtubules are cylindrical tubes, 20-25 nm in

diameter. diameter. They are composed of subunits of the protein tubulin--They are composed of subunits of the protein tubulin--

these subunits are termed alpha and beta. these subunits are termed alpha and beta. Microtubules act as a scaffold to determine cell shape, Microtubules act as a scaffold to determine cell shape,

and provide a set of "tracks" for cell organelles and and provide a set of "tracks" for cell organelles and vesicles to move on. vesicles to move on.

Microtubules also form the spindle fibers for separating Microtubules also form the spindle fibers for separating chromosomes during mitosis.chromosomes during mitosis.

When arranged in geometric patterns inside flagella and When arranged in geometric patterns inside flagella and cilia, they are used for locomotion. cilia, they are used for locomotion.

Intermediate Filaments Intermediate Filaments Intermediate Intermediate filaments are about 10 nm diameter and filaments are about 10 nm diameter and provide tensile strength for the cell. provide tensile strength for the cell.

Different intermediate filaments are:Different intermediate filaments are: made of made of vimentins, being the common , being the common

structural support of many cells. structural support of many cells. made of made of keratin, found in skin cells, hair and , found in skin cells, hair and

nails. nails. neurofilaments of neural cells. neurofilaments of neural cells. made of lamin, giving structural support to the made of lamin, giving structural support to the

nuclear envelope.nuclear envelope.