CYTOSKELETON

The cytoskeleton is a complex network of filamentous pro­tein structures that can be found within the cytoplasm. It gives support to the cell and determines its shape. It is an extensive network of structures of varying sizes.

The cytoskeleton consists of three types of protein component:

1. Microtubule

2. Intermediate filaments

3. Microfilaments

2.12.1 Functions of Cytoskeleton

Structural support, movement, and maintain the cell morphology.

Microtubules are the tubular structures of the cytoskel­eton. These organelles without a limiting membrane are organized in different bundles. The diameter of each tubule is between 20 to 30 nm. The microtubule length varies and it may be 1000 times higher than the thickness. The micro­tubules are structurally formed by bundles of globular pro­tein called tubulin. Tubulin has two subunits, namely α and β subunit.

2.12.1.1 Function of Microtubule

They form the cytoskeleton and are responsible for main­taining the shape of the cell and providing structural strength to the cell. The centrosphere surrounding the centriole emits these structures, which then assemble into spindle fibers. They constitute the cytoskeleton of cilia and flagella. Additionally, they play a crucial role in facilitating the movement of chromosomes during cell division.

Intermediate filaments are structures that form a net­work around the nucleus and extend to the cell’s periphery. Intermediate Filaments are near about 10 nm diameter. The intermediate filaments are made up of fibrous proteins.

2.12.1.2 Functions of Intermediate Filaments

They help to maintain the structure and shape of the cell. These filaments also link to the nearby cells through desmosomes.

Microfilaments are long and fine structures that resem­ble threads. The diameter of microtubules is near about 3 to 6 nm. Actin and myosin are non-tubular contractile proteins that make up these filaments. Microfilaments are present throughout the cytoplasm (ectoplasm and endoplasm both). The endoplasmic microfilament contains both actin and myosin protein whereas ectoplasmic microfilament con­tains only actin protein.

2.12.1.3 Functions of Microfilaments

Provides structural strength of the cells and resistance to the cell against the pulling force. They are responsible for movements of cells such as contraction, gliding and cytokinesis.

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