- The cellular organelle present throughout the cytoplasm is called cytoskeleton.
- The shape of the cell is determined by it and also gives support to the cell.
- It is of varying sizes and is a complex network of structures.
- It also helps in the cellular movements and also gives response to the cell to external stimuli.
- It consists of three major protein components that are as follows:
Image source: Pediaa.com
B) Intermediate filaments
- These are the narrow, straight, hollow and tubular structure present in the cytoskeleton.
- These structures are arranged in different bundles and are without the limiting membrane.
- It has a diameter of 20-30nm and the length varies which is more than 1000 times than the thickness.
- Bundles of globular protein called tubulin forms the microtubules structurally where tubulin contains two subunits called α-subunit and β-subunit.
Functions of microtubules
- Microtubules may function singly or join with other proteins to form more complex structures like cilia, flagella or centrioles and perform various functions.
- They help to determine the shape of the cell.
- Structural length to the cell is provided by microtubules.
- They act as conveyer belts allowing the movement of granules, vesicles, protein molecules and some organelles like mitochondria to different parts of the cell.
- They also form the spindle fibres that help to separate chromosome during mitosis.
- They also allow the movement of centrioles and the complex cellular structures like cilia.
B) Intermediate Filaments
- They are the structures forming a network around the nucleus extending to the periphery of the cell.
- They are about 10 nm in diameter and are formed by rope-like polymers which are made up of fibrous proteins.
Subclasses of intermediate filaments
- There are five subclasses of intermediate filaments. They are:
- Keratins (in epithelial cells)
- Glial filaments (in astrocytes)
- Neurofilaments (in nerve cells)
- Vimentin (in many types of cells)
- Desmin (in muscle fibres)
Function of Intermediate Filaments
- Intermediate filaments help in maintaining the shape of the cell and also connecting the adjacent cells through desmosomes.
Image Source: Javatpoint
- They are long, fine thread like structures having a diameter of about 3 to 6 nm.
- Non-tubular contractile proteins called actin and myosin make these filaments where actin is more abundant than myosin.
- They are present throughout the cytoplasm and contain only actin molecules in ectoplasm.
- The microfilaments present in the endoplasm contains both actin and myosin molecules.
Functions of the microfilaments
- Cell gets structural length due to microfilaments.
- They provide resistance to the cell against the pulling forces.
- Cellular movements like contraction, gliding and cytokinesis (partition of cytoplasm during cell division) are also possible due to presence of microfilaments.
Cytoskeleton and Its Components