Microfilaments are fine, thread-like protein fibers, 3-6 nm in diameter. They are composed predominantly of a contractile protein called actin, which is the most abundant cellular protein. Microfilaments' association with the protein myosin is responsible for muscle contraction. Microfilaments can also carry out cellular movements including gliding, contraction, and cytokinesis.
Microtubules are cylindrical tubes, 20-25 nm in diameter. They are composed of subunits of the protein tubulin--these subunits are termed alpha and beta. Microtubules act as a scaffold to determine cell shape, and provide a set of "tracks" for cell organelles and vesicles to move on. Microtubules also form the spindle fibers for separating chromosomes during mitosis. When arranged in geometric patterns inside flagella and cilia, they are used for locomotion.
Intermediate filaments are about 10 nm diameter and provide tensile strength for the cell.
Examples of the cytoskeleton in epithelial cells
In the epithelial (skin) cells of the intestine, all three types of fibers are present. Microfilaments project into the villi, giving shape to the cell surface. Microtubules grow out of the centrosome to the cell periphery. Intermediate filaments connect adjacent cells through desmosomes.
1.) Genetic Control- Nucleus and Ribosomes.
2.) Manufacturing, Distribution, and Breakdown- Rough ER, Smooth ER, Golgi Apparatus, Lysosomes, Vacuoles, Peroxisome
3.) Energy Processing- Mitochondria, Chloroplasts
4.) Structural Support, Movement, and Communication Between Cells- Cytoskeleton, Extracellular matrix, Cell junctions, Cell walls