Cytoskeleton Overview and Functions

Study Notes

The cytoskeleton is a network of protein fibers that provides structure, support, motility, and regulation to cells.
Key functions include: maintaining cell shape, providing mechanical strength, enabling cell movement, organizing cell components, and facilitating intracellular transport.
The cytoskeleton is involved in various cellular processes such as endocytosis, cell division, and the formation of specialized structures like flagella and cilia.

The cytoskeleton is composed of three major types of filaments: actin filaments, microtubules, and intermediate filaments.
Each filament type has unique mechanical properties, dynamics, and biological roles.
All three types of filaments work together to provide cells with strength, shape, and mobility.

Actin filaments are helical polymers of the protein actin.
They are thin and long fibers with a diameter of 7-8 nm.
They contribute to cell surface shape and are essential for cell locomotion.
They are also involved in cell division, specifically in the pinching process that separates one cell into two.

Microtubules are hollow tubes composed of α- and β-tubulin protein dimers.
They play a crucial role in organizing organelles within the cell.
They also serve as tracks for motor proteins like kinesin and dynein, which transport cargo and vesicles throughout the cell.
Microtubules form the mitotic spindle responsible for segregating chromosomes during cell division.

Intermediate filaments are composed of various proteins and provide mechanical strength to cells.
They are more stable than actin filaments and microtubules.
They help maintain cell shape and resist tension.
They also provide structural support to tissues and organs.

Accessory proteins play a crucial role in regulating the assembly and function of cytoskeletal filaments.
They link filaments to other cell components, forming a complex and dynamic network.
Motor proteins are among these accessory proteins, and they convert energy from ATP hydrolysis into mechanical force.
This force is used to move organelles along filaments or to rearrange the filaments themselves.