Cytoskeleton

The cytoskeleton is made up of a matrix of fibres that serves as the “structure” of prokaryotic and eukaryotic cells as well as archaeans. These fibres in eukaryotic cells are composed of a complex web of protein chains with motor proteins which help in cell mobility and cell stabilisation.

The cytoskeleton consists of a framework of tubules and filaments that runs across a whole cell, via the cytoplasm, which includes the majority of the substance inside a cell excluding the nucleus. This can be present in every cell, although the proteins which make it up differ among species. The cytoskeleton provides support for the cell, shapes it, organises and anchors the organelles, as well as participates in molecular transport, cell proliferation, and cell signalling.

Cytoskeleton Structure

All cells contain a cytoskeleton, however, when we talk about the cytoskeleton, we tend to indicate the cytoskeleton within the eukaryotic cells. Eukaryotes are multicellular organisms with their cells having a nucleus as well as organelles. Eukaryotic cells are found in plants, mammals, protists and fungi. Prokaryotic cells are much less complicated, with no proper nucleus and organelles other than ribosomes, and thus are present in archaea and bacteria, which are single-celled creatures. The cytoskeleton of prokaryotes was assumed to be non-existent at first, and that wasn’t identified until the 1990s.

The cytoskeleton is made up of three kinds of filaments. These filaments are basically elongated protein chains: microtubules, intermediate filaments, and microfilaments.

1. Microtubules – 

Microtubules are empty rods that serve as “pathways” for organelles to traverse along as well as to assist in supporting and structuring the cell. Every eukaryotic cell has microtubules. These differ in size and have a diameter of around 25 nm.

1. Intermediate filaments – 

Intermediate filaments are prevalent in several cells and help to keep microtubules and microfilaments in alignment by keeping them in position. These filaments combine to create keratins, which are present in epithelial cells, as well as neurofilaments, which are prevalent in neurons. These have a diameter of 10 nm.

1. Microfilaments – 

Microfilaments, also known as actin filaments, are tiny, solid threads that help muscles to contract. Within muscle tissue, microfilaments are especially abundant. They are present in every eukaryotic cell and, like microtubules, are ubiquitous. Microfilaments, which can be around 8 nm in size, are primarily made up of a contractile protein called actin. They are also involved in the motion of organelles.

Cytoskeleton Functions

The cytoskeleton spreads across the cytoplasm of a cell and controls a variety of vital processes. The functions of the cytoskeleton are listed below.

• It aids in the stability of the cell’s structure and provides support to it.
• The cytoskeleton holds several cellular organelles in position.
• It helps develop vacuoles.
• The cytoskeleton is basically a dynamic framework that may deconstruct and rearrange its components to allow for internal as well as systemic cell movement. 
• Movement of vesicles to and from the cell, chromosomal rearrangement throughout meiosis and mitosis, as well as organelle movement are all examples of intracellular motion assisted mostly by the cytoskeleton.
• Cell mobility is required for tissue building and restoration, cytokinesis (the process of cytoplasmic division) in the generation of daughter cells, as well as immune cell responsiveness to pathogens, all of which are made possible by the cytoskeleton.
• The cytoskeleton facilitates the movement of information signals among cells.
• In certain cells, it generates protrusions resembling cellular appendages like flagella and cilia.

Cytoplasmic Streaming

• Cytoplasmic streaming is made possible by the cytoskeleton. 
• This method, also referred to as cyclosis, facilitates the transportation of cytoplasm inside a cell in order to distribute organelles, nutrients, as well as other materials.
• Exocytosis and endocytosis, or even the movement of substances in and out of the cells, are also aided by cyclosis.
• The contraction of cytoskeletal microfilaments aids in the direction of cytoplasmic material circulation. 
• When microfilaments linked to organelles compress, the organelles are dragged along with them, and thus the cytoplasm travels in a similar path.
• Both eukaryotic, as well as prokaryotic cells, exhibit cytoplasmic streaming.
• This very process results in pseudopodia, which are cytoplasmic projections in protists such as amoebae. Such structures are utilised to capture food as well as to move about.

Conclusion

The cytoskeleton is a framework of filaments and fibres found in the cytoplasm of a cell. The cytoskeleton arranges the cell’s various elements, controls the cell’s structure, and is also in charge of the cell’s mobility as well as the motion of the many organelles inside it. The cytoskeleton’s strands are so minute that their presence was only found owing to the electron microscope’s higher resolving capability.

Actin filaments, intermediate filaments and microtubules comprise the three primary kinds of filaments that constitute the cytoskeleton. The actin filaments are found in cells in the shape of meshworks and coils of parallel strands; they assist control the cellular structure as well as its ability to attach to the surface. Actin filaments are continually altering arrays that assist in the cell movement and mediate certain actions inside it, including cell splitting during the process of mitosis.