The eukaryotic cytoplasm has a set of long, thin fibers called the cytoskeleton, which plays three important roles in cellular structure and function:

1. Maintains cell shape and support.2. Provides for various types of cell movement.3. Helps move things within the cell.

Figure 4.21 The Cytoskeleton

Three important components of the cytoskeleton are:

Microfilaments

Intermediate filaments

Microtubules

Figure 4.21 The Cytoskeleton

Microfilaments are made up of strands of the protein actin.

Actin monomer

They have two major roles:

1. They help the cell or parts of the cell to move.

2. They stabilize cell shape.

Figure 4.21 The Cytoskeleton

Intermediate filaments are made up of fibrous proteins that are organized into tough, ropelike assemblages.

They have two major structural functions:

1. They stabilize cell structure.

2. They resist tension.

Fibrous subunit

Figure 4.21 The Cytoskeleton

Microtubules are long, hollow cylinders made up of many molecules of the protein tubulin.

Tubulin consists of two subunits: -tubulin and -tubulin.

Tubulin dimer

-Tubulin monomer -Tubulin monomer

Microtubules have two roles:

1. They form a rigid internal skeleton.

2. They act as a framework along which motor proteins can move structures in the cell.

- End

+ End

Figure 4.21 The Cytoskeleton