Cytoskeleton is a ‘framework’ or ‘skeleton’ found within the cytoplasm of all cells and is made out of protein. 

There are 3 main types of cytoskeletal filaments in eukaryotes:

Microfilaments (actin filaments): They are fibres that are found in muscle cells that can move against each other, causing movement. They move some organelles around inside cells and they cause the movement seen in some white blood cells.

Microtubules: They are fibres in a cylinder shape, made up of a protein called tubulin (alpha and beta tubulin). They are about 23-25nm in diameter and can help move a microoganism through a liquid, or to waft a liquid past the cell (e.g flagella on a sperm cell can help it move). Other proteins found on microtubules, called microtubule motors, move organelles and other cell contents along the fibres. For example, chromosomes are moved this way during mitosis and this is how vesicles move from the endoplasmic reticulum to the Golgi apparatus.

Microtubules use energy from ATP* to drive these movements.

Key definition:

  • The cytoskeleton refers to the network of protein fibres found within cells that gives structure and shape to the cell, and also moves organelles around inside the cells.

Exam tip:

* Remember to state that the movements of the cilia and organelles inside cells are from the energy provided from ATP