Microfilaments are cytoplasmic cytoskeletal fibers built from the protein actin, whose monomers polymerize into actin polymers that twist together into a filament; they are dynamic structures that lengthen by polymerization and shorten by depolymerization, and this reversible assembly generates gross cell movement and shape change. Intermediate filaments, by contrast, are assembled from many different protein types strung into polymers that twist together, and are essentially permanent rather than dynamic, functioning to provide structural support and to resist mechanical stress by restoring the cell's shape after deformation. The concept belongs to cell biology, specifically cytoskeletal structure and function, and it establishes the organizing distinction — dynamic force-generating filaments versus stable load-bearing filaments — that separates the three cytoskeletal classes (microfilaments, intermediate filaments, microtubules).
Microfilaments are cytoplasmic cytoskeletal fibers built from the protein actin, whose monomers polymerize into actin polymers that twist together into a filament; they are dynamic structures that le…