The cytoskeleton is a network of protein fibers that acts as a kind of scaffolding, giving shape and protection to both prokaryotic and eukaryotic biological cells. However this minute network does much more than keep the cell in its proper shape.
Cytoskeleton in Motion
The cytoskeleton enables some cell motion, through the use of cellular appendages such as flagella and cilia. The fibers also play an important role in intra-cellular transport; the movement of vesicles and organelles around within the cell. And when it is time to make the big move, cell division, components of the cytoskeleton help sort out the genetic material and elongate the cell before it splits in two.
Microtubules, Intermediate Filaments & Microfilaments
The cytoskeleton consists of three types of protein fibers: microtubules, intermediate filaments and microfilaments.
Microfilaments: These subunits of the cytoskeleton are twisted double strands of the protein actin. Actin microtubule filaments are responsible for cell movement and shape, as well as simply holding the cell together.
Intermediate Filaments: This component is made of eight subunits in rope-like strands. Although the structure varies depending on the type of tissue that the cell is part of, intermediate filaments help maintain cell shape, support nerve cell extensions, and attach cells together.
Microtubules: Tiny tubes, made up of spiraling tubulin in two-part subunits, aid in chromosome movement, transport of organelles, and the movement of cellular appendages. These are the “highways” along which the organelles travel and are conveyed. The microtubule roads are dynamic. Assembled at one end while being disassembled at the other. Microtubules may work alone, or join with other proteins to form more complex structures called cilia, flagella or centrioles.
Centioles and Centrosomes
A centriole is a barrel-shaped organelle found in many eukaryotic cells, though absent in higher plants and fungi. Each centriole is composed of nine triplets of microtubules.
A centrosome is an associated pair of centrioles, arranged perpendicularly, and functioning like little microtubule factories within animal cells. During animal cell division, the centrosome divides and the centrioles replicate (make new copies). The result is two centrosomes, each with its own pair of centrioles. The two centrosomes move to opposite ends of the cell’s nucleus, and produce microtubules that grow into a “spindle” responsible for moving the replicated chromosomes to opposite ends of the cell and ultimately, once the cell splits, into the two daughter cells.
Campbell, N. A. & Reece J. B. (2005) Biology, seventh edition. Pearson Education Inc.
Campbell, N. A., Reece J. B. & Simon, E. (2004) Essential Biology with Physiology. Pearson Education Inc.