protein filament, about 7-nm wide, formed from a chain of globular actin molecules. a major constituent of the cytoskeleton of all eukaryotic cells and especially abundant in muscle cells.
specialized layer of cytoplasm on the inner face of the plasma membrane. in animal cells it is an actin-rich layer responsible for cell-surface movements.
short cylindrical array of microtubules, usually found in pairs at the center of a centrosome in animal cells. also found at the base of cilia and flagella (and called basal bodies).
centrosome (cell center)
centrally located organelle of animal cells that is the primary microtubule-organizing center and separates to form the two spindle poles during mitosis. in most animal cells it contains a pair of centrioles.
cilium (plural cilia)
hairlike extension of the surface of a cell with a core bundle of microtubules and capable of performing repeated beating movements. cilia in large numbers drive the movement of fluid over epithelial sheets as in the lungs.
system of protein filaments in the cytoplasm of a eukaryotic cell that gives the cell shape and the capacity for directed movement. it's most abundant components are actin filaments, microtubules, and intermediate filaments.
the property shown microtubules of growing and shrinking repeatedly through the addition and loss of tubulin subunits from their exposed ends.
member of a family of large motor proteins that undergo ATP-dependent movement along microtubules. dynein is responsible for the bending of cilia.
filopodium (plural filopodia)
long thin actin-containing extension on the surface of an animal cell. sometimes has an exploaratory function, as in a growth cone.
flagellum (plural flagella)
long, whiplike protrusion that drives a cell through a fluid medium by its beating. eukaryotic flagella are longer versions of cilia; bacterial flagella are completely different, being smaller and simpler in construction.
fibrous protein filament (about 10 nm in diameter) that forms ropelike networks in animal cells. often used as a structural element that resists tension applied to the cell from outside.
a large family of motor proteins that use the energy of ATP hydrolysis to move along a microtubule.
dynamic sheetlike extension on the surface of an animal cell, especially one migrating over a surface.
long, stiff, cylindrical structure composed of the protein tubulin. used by eukaryotic cells to regulate their shape and control their movements.
protein such as myosin or kinesin that uses energy derived from ATP hydrolysis to propel itself along a protein filament or polymetric molecule.
long, highly organized bundle of actin, myosin, and other proteins in the cytoplasm of muscle cells that contracts by a sliding filament mechanism.
type of motor protein that uses ATP to drive movements along actin filaments. Myosin II is a large protein that forms thick filaments of skeletal muscle. Smaller myosins, such as myosin I, are widely distributed and are responsible for many actin-based movements.
fibrous layer on the inner surface of the inner nuclear membrane formed as a network of intermediate filaments made from nuclear lamins.
refers to a stucture such as an actin filament or a fertilized egg that has an inherent asymmetry-so that on end can be distinguished from the other.
rho protein family
family of small GTPases involved in signaling that causes a rearrangement of the actin cytoskeleton.
repeating unit of a myofibril in a muscle cell, about 2.5 micrometers long, composed of an array of overlapping thick (myosin) and thin (actin) filaments.