cytoskeleton | Cell and subcellular organelle | Chapter 3: F.Sc. 1st Year Biology | Lec#31

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12- Cytoskeleton
It is a network of protein fibres present in cytoplasm. It includes the following
types of fibres:
1. Microfilaments:
These are present in all eukaryotic cells.
Composition. Microfilaments are solid rods made of a globular protein, called
actin.
Functions.
 Cell Movements. Microfilaments disassemble and reassemble and help the
cells to change shape and move.
 Cell division. Microfilaments also enable a dividing cell to pinch off into
two cells.
 Cellular contraction. In association with myosin, microfilaments help in
cellular contraction.
2. Microtubules:
These straight, hollow cylinders are composed of subunits.
Composition. Each subunit is made of two different tubulin proteins known
as alpha-tubulin and beta-tubulin.
Functions.
 Microtubules give structure and shape to a
cell.
 They also serve as highways for the transport
of organelles.
 Microtubules are the major components of
cilia and flagella,
 Participate in the formation of spindle fibres
during cell division.
3. Intermediate filaments:
These are found only in some higher animal groups.
Composition. They are made of different proteins but the most common type
of protein subunit is vimentin. Some cells may have intermediate filaments
made of other proteins. For example, skin cells contain a protein keratin.
Functions. Intermediate filaments maintain cell shape and rigidity, and serve
to anchor several organelles, including the nucleus.