Cytoskeleton - Definition, Structure, Function, Filament Type

What is Cytoskeleton?

The cytoskeleton is a complex, dynamic network of interlinking protein filaments and tubules that extends through the cytoplasm of all cells, including bacteria and archaea.

 

The cytoskeleton is the internal supporting network of cells. It laced all of the material within a cell. It provide shape of the cells and gives ability to carry out coordinated cellular movements and cell division.

 

The cytoskeleton network supports the cell, gives it shape, organization and tethers (order to connect like with a rope or chain) the organelles. It has key role in molecule transport, cell division and cell signalling.

For example; adhesion, migration, and movement through cilia and flagella. 

 

 

Cytoskeleton Structure

 

The eukaryotic cytoskeleton consists of three main types of protein filaments. Cytoskeleton filaments are- 

 

1. Microfilaments/actin filaments

2. Intermediate filaments

3. Microtubules

 

 

 

1. Microfilaments/Actin Filaments

 

Microfilaments are also called actin filaments because they are mostly made of the protein actin. Actin filaments are the smallest type, with a diameter of only about 3- 6 nm.

 

1. It aid in cytokinesis (division of a cytoplasm of a cell when dividing into two daughter cells).

2. They aid in cell motility (to move), responsible for cellular movements, contraction, and gliding.

3. They are involve in flowing of cytosol (liquid part of the cytoplasm) throughout the cell and also help to transports nutrients and cell organelles.

4. Microfilaments are particularly found in muscle cells. skeletal muscle consist of the protein actin, responsible for muscle contraction, where actin filaments slide along filaments of another protein called myosin to make the cells contract.

 

 

2. Intermediate Filaments

It is called intermediate because they are placed in-between the size of microfilaments and microtubules. The diameter of intermediate filaments are about 8-12 nm wide.

 

The intermediate filaments network in the cytoplasm involve in maintain the shape of cell, provide structural support to the cell and bear tension. It provides tensile (stretched) strength to the cell.

Intermediate filaments are facilitate formation of different proteins such as keratin (found in hair and nails) and neurofilaments (NF) proteins.

 

 

3. Microtubules

 

Microtubules are the largest of the cytoskeleton’s fibers network with a diameter of about 25 nanometers (nm). They  are composed of a tubulin protein. It appears like small, hollow, round tubes.

Microtubules help in transporting cellular materials within the cell and dividing chromosomes during cell division.

Microtubules are also involved in transporting molecules. Most of the microtubules in an animal cell come from the centrosome cell organelle. Centrosome is a microtubule organizing center (MTOC).

Microtubules involve in forming the spindle apparatus (or mitotic spindle). They separates the sister chromatids to form daughter cell during cell division.

 

Microtubules are also involved in the formation of the cell wall in plant cells.

 

 

The cytoskeleton network is also composed of certain motor proteins. These includes-

 

1. Kinesin

These proteins move along the microtubule filaments carrying the cellular components. There function is to pull the organelles along the cell membrane and to transport organelles within cells.

 

2. Dyneins

These proteins also move along microtubules in cells. There function is to pull the cell organelles towards the nucleus.

 

3. Myosin

Myosin motors act upon actin filaments mean s myosin motors move on actin filaments to generate cell surface contractions.

 

 

Function of Cytoskeleton

 

The important functions of cytoskeleton are -

 

1. It gives the cell’s shape, especially important for cells that are without cell walls, such as animal cells. It keeps the structures in place, providing support to the cell, and giving the cell a definite shape.

 

2. Cytoskeleton is responsible for movement of whole cell, for example, for phagocytosis, movement of organelles and flow of chemicals with in the cell.

 

3. The cytoskeleton structure helps the cells to maintain their internal organization and established the intracellular organization of the cytoplasm. It provides the mechanical support to cell that enables cells to carry out essential functions like division and movement.

 

4. The cytoskeleton organizes the cell and keeps in place the cell’s organelles. It assists to holds different cell organelles in place but they also help in the movement of organelles within the cell and endocytosis.

 

5. Cytoskeleton is responsible for contraction and aids in cell motility, movement of organelles, migration of cell, crawling movement and through the cytoplasm. It supports intracellular movements such as the migration of cell organelles, transportation of vesicles in and out of the cell.

 

For example, during endocytosis when a cell engulf substances, microfilaments pull the engulfed particles vesicle into the cell.

 

6. Cytoskeleton helps move chromosomes during cell division and cytokinesis.

 

7. It aids in cell signaling, regulation of filament.

 

Also, check out here function of centrosome and centriole.