| Property |
Microtubules (Tubulin Polymers) |
Microfilaments (Actin filaments) |
Intermediate Filaments
|
| Structure
|
Hollow tubes; wall consists of 13 columns of tubulin molecules
|
Two intertwined strands of actin, each a polymer of actin subunits
|
Fibrous proteins supercoiled into thicker cables
|
| Diameter
|
25nm with 15nm lumen
|
7nm
|
8–12nm
|
| Protein Subunits
|
Tubulin, a dimer consisting of α-tubulin and β-tubulin
|
Actin
|
One of several different proteins of the keratin family, depending on cell type
|
| Main functions
|
- maintenance of cell shape (compression-resisting "girders")
- Cell motility (cilia or flagella)
- Chromosome movements in cell division
- Organelle movements
|
- Maintenance of cell shape (tension-bearing elements)
- Changes in cell shape
- Muscle contraction
- Cytoplasmic streaming
- Cell motility (pseudopodia)
- Cell division (cleavage furrow formation)
|
- Maintenance of cell shape (tension-bearing elements)
- Anchorage of Nucleus and certain other organelles
- Formation of nuclear lamina
|