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This illustration shows two actin filaments wound together. Each actin filament is composed of many actin subunits connected together to form a chain.
Two intertwined actin strands comprise microfilaments. Source: OpenStax Biology 2e

OpenStax Biology 2e

Of the three types of protein fibers in the cytoskeleton, microfilaments are the narrowest. They function in cellular movement, have a diameter of about 7 nm, and are comprised of two globular protein intertwined strands, which we call actin. For this reason, we also call microfilaments actin filaments.

– What is a family of globular multi-functional proteins that form microfilaments and participates in many important cellular processes, including muscle contraction, cell motility, cell division and cytokinesis, vesicle and organelle movement, cell signaling, and the establishment and maintenance of cell junctions and cell shape?

ATP powers actin to assemble its filamentous form, which serves as a track for the movement of a motor protein we call myosin. This enables actin to engage in cellular events requiring motion, such as cell division in eukaryotic cells and cytoplasmic streaming, which is the cell cytoplasm’s circular movement in plant cells. Actin and myosin are plentiful in muscle cells. When your actin and myosin filaments slide past each other, your muscles contract.

Microfilaments also provide some rigidity and shape to the cell. They can depolymerize (disassemble) and reform quickly, thus enabling a cell to change its shape and move. White blood cells (your body’s infection-fighting cells) make good use of this ability. They can move to an infection site and phagocytize the pathogen.

– What is one function of microfilament that is a part of the cell division process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells?

The importance of the proper regulation of the microfilament system in the nervous system becomes particularly evident when examining the pathology of a number of neurological diseases. Considering that microfilaments constitute the primary structural components of neuronal synapses in the central nervous system, disturbance of this system has severe effects on brain function. Evidence for the deregulation of components of the microfilaments includes diseases in cognition such as Alzheimer’s and psychotic disorders.


Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/details/books/biology-2e