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Figure 4.21 The Cytoskeleton
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.
They have two major roles:
1. They help the cell or parts of the cell to move.
2. They stabilize cell shape.
Actin monomer
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.
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
Tubulin dimer
 
-Tubulin monomer -Tubulin monomer