What is Responsible for Support Structure and Movement in Cells

The cytoskeleton is responsible for support, structure, and movement in cells. It also helps the cells to maintain their shape.

The cytoskeleton is found throughout the cytoplasm of both animal and plant cells. It is a web made up of long tubes and fibers of proteins. The three main components of the cytoskeleton are microtubules, microfilaments, and intermediate filaments.

Key Areas Covered

1. What is Responsible for Support Structure and Movement in Cells
      – Functions of Cytoskeleton
2. What is the Structure of the Cytoskeleton
     – Microtubules, Microfilaments, Intermediate Filaments

Key Terms: Cytoskeleton, Intermediate Filaments, Microfilaments, Microtubules

What is Responsible for Support Structure and Movement in Cells

The cytoskeleton is the cellular structure responsible for the mechanical support of the cell while performing important functions such as movement and cell division. It composes a network of protein filaments that extend throughout the cytoplasm. In addition to the support, the cytoskeleton is also responsible for the organization of the cellular structures such as organelles and large molecules within the cytoplasm. It also serves as a scaffold that maintains the shape of the cell. The dynamic structure of the cytoskeleton is responsible for both internal and external movement of the cell. The internal movement of the cytoplasm is called cytoplasmic streaming, and the cytoskeleton governs this movement. Further, the cytoskeleton makes up the cellular protrusions, which aid in the external movement of the cell, such as flagella and cilia. The figure 1 shows the structure of the cytoskeleton.

Figure 1: Microtubules (green) and Microfilaments (red) of Cytoskeleton

What is the Structure of Cytoskeleton

As mentioned earlier, cytoskeleton contains microtubules, microfilaments, and intermediate filaments that form a network within the cytoplasm. Microtubules are the thickest while the microfilaments are the thinnest protein filaments in the cytoskeleton.

Microtubules 

Microtubules are the polymers of tubulin protein formed by the polymerization of the dimer alpha and beta tubulin. The outer and the inner diameter of a microtubule is around 24 nm and 12 nm respectively. The contractile forces generated by microtubules are responsible for the changing the shape of the cell while moving.

Microfilaments 

Microfilaments made up by the polymerization of actin filaments compose two strands in a helical nature. The diameter of an actin filament is around 7 nm. Microfilaments play a role in cell shape, cell contractility, mechanical stability, cytokinesis, exocytosis, and endocytosis. The figure 2 shows the cytoskeletal structures.

Figure 2: Cytoskeletal Filaments
(a)Microtubules, (b) Microfilaments, (c) Intermediate Filaments

Intermediate Filaments 

Intermediate filaments made up of variable protein subunits are less dynamic than the microtubules and microfilaments. It provides support and strength to the fragile cytoskeletal structures. 

Conclusion

The cytoskeleton is responsible for support and movement of the cell. The three types of protein components of the cytoskeleton are microtubules, microfilaments, and intermediate filaments. The contractile nature of both microtubules and microfilaments aid in the movement of the cell while intermediate filaments are responsible for the support and the strength of the cell.

Reference:

1. Cooper, Geoffrey M. “The Cytoskeleton and Cell Movement.” The Cell: A Molecular Approach. 2nd Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.

Image Courtesy:

1. “FluorescentCells” By  (Public Domain) via Commons Wikimedia
2. “0317 Cytoskeletal Components” By OpenStax – (CC BY 4.0) via Commons Wikimedia