Serves as a structural framework for eukaryotic cells and acts as a transport system (can also change the shape of the cell).

Has three main components:

Microtubules (thickest)

Microfilaments (thinnest)

Intermediate Filaments

Composed of dimers of alpha and beta tubulin. The dimers are linked together to form a protofilament.

13 protofilaments form a microtubule (one end is alpha the other end is beta).

Microtubules function in moving organells and chromosomes and in cell motility. Microtubules originate in "centrioles". In generall, the β end grows and the α end shrinks (if both are growing, the β end grows faster). Major component of eucaryotic flagella and cilia.

Dynein: pushes microtubule from the + to the - end.

Kinesin: walks along microtubule from the - to the + end.

Maintain cell shape

Change cell Shape (eg. pseudopodia)

Are composed of two chains of actin: G-actin is the individual molecules and F-actin is the microfilament as a whole.

Whereas microtubules resist compression, microfilaments resist stretching. Microfilaments interact with the protein myosin to generate skeletal muscle contractions.

Are fibrous proteins that are coiled to form cables.

Maintain cell shape by association with membranes and anchor organelles. Are found in nuclear lamina and provide support for microvilli in the intestines.