The cytoskeleton consists of protein fibers that extend throughout the cytoplasm of a eukaryotic cell. They act as a framework to give shape to the cell and enable structures within it, or the entire cell, to move. Microfilaments and intermediate filaments are thin strands of two or more proteins wrapped around one another. Microtubules are hollow tubes made of globular proteins arranged in spirals. Microtubules can contract or expand and help to move material around in the cell, for example, the spindle fibers that move chromosomes during mitosis and meiosis.
