The cytoskeleton comprises a group of proteins that gives a cell shape, supports intercellular structures, moves around organelles and helps move a cell. Three types of proteins comprise the cytoskeleton: intermediate filaments, microfilaments and microtubules.
Microfilaments are the smallest cytoskeletal structures. They have a helix shape and consist of G-actin protein. Intermediate filaments look like cords and are made of keratin. Microtubules take the shape of hollow tubes made of alpha and beta tubulin subcomponents.
Without cell walls, cells do not have much structure. Cells need the action of the cytoskeleton to give the cell shape. The intermediate filaments are responsible for providing the cell with a more rigid structure.
The cytoskeleton has important roles during cell division. Microtubules move chromosomes to opposite sides of the cell to get it ready to divide into two daughter cells. Microfilaments squeeze the area between the two daughter cells to help them separate.
With endocytosis, the process by which a cell engulfs a substance, the cell forms a vesicle around what it is "eating." Microfilaments pull these vesicles toward the center of the cell. The endoplasmic reticulum and Golgi complex also move vesicles around using the cytoskeleton.
Finally, the cytoskeleton enables some cells to move around. Whip-like flagella and beating cilia are made up of cytoskeletal components. The amoeba-like movement of white blood cells is also governed by the actions of the cytoskeleton.