What is Cytoskeleton?
The cytoskeleton is a network of filaments that shapes the cell, supports its plasma membrane, organizes its internal structures, and is involved in transport, mobility, and cell division.
The cytoskeleton is the internal structure that supports tension and compression forces maintaining the shape of the cell. In this sense, the cytoskeleton is literally the skeleton of the cell and is located throughout the cell in the cytoplasm.
Among its functions is to fix the plasma membrane, the cell nucleus and all other cell structures in place. In addition, it provides the tracks for the transport of protein vesicles or organelles within the cell and is an essential component for the formation of specialized structures in eukaryotic cells such as flagella, cilia, and centrosomes.
In prokaryotic cells , which do not have a defined cell nucleus, they also have a cytoskeleton that maintains the shape of the cell and helps its cell division, but its composition is different and was only discovered in 1990. 3 elements named: FtsZ, MreB and crescentina.
3 elements are identified in the cytoskeleton structure of eukaryotic cells: microfilaments, intermediate filaments and microtubules.
Microfilaments are the thinnest fibers of the 3 types that make up the cytoskeleton. They are also known as actin filaments, since they are made up of monomers linked to actin proteins in a way that looks like a double helix.
They are characterized by having directionality. This means that each end of the microfilament is different.
The function of the microfilament is the proportion of rails for the movement of motor proteins called myosin, which, in turn, also form filaments.
Microfilaments can be found in the division of animal cells, such as in muscle cells, which, coordinated with other filament structures, helps muscle contraction.
The intermediate filaments
The intermediate filaments are made up of many interwoven fibrous protein chains . They are more permanent than microfilaments or microtubules and depending on the cell in which it is found, with keratin being the most common.
The function of the intermediate filaments is to support cell tension while maintaining the shape of the cell. Furthermore, they organize internal structures by anchoring the nucleus and organelles in place.
Microtubules are made of tubulin proteins that form a hollow tube. Each tubulin is made up of 2 subunits: alpha-tubulin and beta-tubulin.
Their structure, like that of microfilaments, is dynamic, that is, they can grow and disassemble quickly and they also have directionality, each end being different.
Microtubules have several functions:
- First, it provides structural support to the cell by helping it resist compressive forces.
- Second, they create rails so that motor proteins (kinesins and dyneins) can transport vesicles and other elements.
- Third, they are the key components for the formation of flagella, cilia, and centrosomes, specialized structures in eukaryotic cells.
The flagella are structures that help the movement as we see, for example, in sperm. On the other hand, the cilia , being shorter and more numerous than the flagella, also help mobility, such as in respiratory cells, displacing dust from the nasal passages.
The structure of both flagella and cilia form a cylinder of 9 pairs of microtubules with another pair in its center plus a basal body that would join these 2 structures. The basal body is considered a modified centriole, being the centriole composed of 9 triplets of microtubules.
And finally, the centrosomes that organize the microtubules that separate the chromosomes during animal cell division. Each centrosome contains 2 centrioles, the spindle-shaped mcrotubules of which are an important part of mitosis and chromosome separation.
Cytoskeleton Element Summary
|7 nm||Actin protein||Directionality
Double helix-like shape
|Create tracks to facilitate the transport of vesicles or organelles||Helps the displacement of white blood cells|
|Intermediate filaments||8 to 10 nm||Fibrous proteins||They are the most permanent elements of the cytoskeleton
Composed of coiled fibrous subunits
|Withstand tension while maintaining cellular shape
Keeps the cell nucleus and other cell organelles in place
|Laminins, a type of intermediate filaments, are vital for the reform of the nuclear envelope after cell division ( mitosis or meiosis ).|
|Key component for the formation of flagella, cilia and centrosomes||Provides structural support
Form clues for motor proteins