Lazarides, Elias Department of Biology, California Institute of Technology, Pasadena, California.
Last reviewed:April 2021
- Actin filaments
- Intermediate filaments
- Related Primary Literature
- Additional Reading
A system of protein filaments found in the cytoplasm of cells that is responsible for cell shape, support, movement, and organization. The protein fibers that compose the structural framework of a cell are collectively known as the cytoskeleton. The filamentous cytoskeletal fibers are responsible for cell shape, cell locomotion and elasticity, interconnection of the major cytoplasmic organelles, cell division, chromosome organization and movement, and the adhesion of a cell to a surface or to other cells. Because this filamentous system is too small to be resolved by light microscopy, its several subcomponents, structural features, and cytoplasmic associations were not discovered until the electron microscope was developed. With this instrument, which can magnify a section of a cell by many thousands of times, three major classes of filaments could be resolved on the basis of their diameter and cytoplasmic distribution: actin filaments (or microfilaments) [Fig. 1], each with an average diameter of 6 nanometers (nm); microtubules (Fig. 1), with an average diameter of 25 nm; and intermediate filaments, whose diameter of 10 nm is intermediate to that of the other two classes. In muscle cells, an additional class of thick filaments, known as myosin filaments, is found whose function is to interact with actin filaments and generate the force necessary for muscle contraction. The presence of this system of filaments in all cells, as well as their diversity in structure and cytoplasmic distribution, has been recognized only in the modern period of biology. See also: Cell (biology); Cell biology; Cell organization; Cytoplasm; Electron microscope; Protein
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 46 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information