The Cytoskeleton

Source:  The Cytoskeleton    Tag:  an example of a prokaryotic cell
It's very interesting how the cytoskeleton in a cell was first observed in 1931 while the theory of a cell came out literally hundreds of years ago (1665). Does this mean that people thought organelles just floated around in space until Paul Wintrebert came along? Feel free to answer that question!

The cytoskeleton is more abundant in eukaryotic cells.  Although some prokaryotic cells have elements of cytoskeleton in their bodies, most do not. For example, microtubules can be present in in prokaryotic cells but it's very rare. While all eukaryotic cells have intermediate filaments, prokaryotic cells have cresetin. This relates to one of the four big ideas of bioligy: the process of evolution drives the diversity and unity of life. Because eukaryotic cells have more complex structures, their cytoskeleton is far more important than a prokaryotic cell's cytoplasm.

Cytoskeleton consists of microfilaments (small and thin), microtubules (large with a tube-like structure), intermediate filaments (medium sized), and intermediate junctions (stick the cells together). Microfilaments are small strands of actin molecules that are intertwined together. Their function is to maintain the structure of the cell, contract muscles, and divide the cells by making the cleft borrow.  More functions include cytoplasmic streaming, the movement of cytoplasm, well as cell motility, the ability to actively transport itself while simultaneously obtaining energy. An example of microtubules in cell motility are  pseudopods. They extend their "false feet" out with the help of the microfilaments to reach food.

The microtubules are a bundle of Tubulin proteins that also help also help in cell motility. When a bundle of microtubules are connected together at the edge of a cell, they will for a tail-like structure called flagella. This can be done because Tubulin is a scaffolding protein that can extend.  The flagella and cilia help the cell move to reach its food. Microtubules are great communicators between organelles too. To send a message from one organelle to another, a motor molecule travels above the microtubules carrying the message along with it. In the movie trailer posted below, George (the Golgi apparatus)  is trying to send a message to Pam (the plasma membrane) through the microtubule with the help of his friend Masa (the motor molecule).

Intermediate filaments are fibrous proteins (Keratin) that primarily function in cell structure. When the plasma membrane comes in contact with extra cellular fluid or other cells, the intermediate filaments are there to rescue it. They are not to be confused with intercellular junctions which actually bind cells together.

There are three types of intercellular junctions: Anchoring junctions, tight junctions and gap junctions. Anchoring junctions are cells that are attached to other cells and/or extracellular fluid. They help create tissues within organelles. Tight junctions are strong bonds between two cells to act as a barrier. Gap junctions have gaps between their connections to each other so that they can communicate.

The interesting fact about cytoskeleton is that it works with all organelles inside the cell. Not just the vesicles, the Golgi apparatus, or the mitochondria, but everything.


video
"Cell." UXL Encyclopedia of Science . U*X*L, 2007. Student Resources in Context . Web. 16 Oct. 2014.
http://biology.kenyon.edu/HHMI/Biol113/cytoskeleton.htm