CELL BIOLOGY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z           HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site microfilament Microfilament structure A linear assemblage of the protein actin; microfilaments, also called actin filaments, are one of three main components of the cytoskeleton. Microfilaments serve a number of functions. They: form a band just beneath the cell membrane that provides mechanical strength to the cell links transmembrane proteins (e.g., cell surface receptors) to cytoplasmic proteins anchors the centrosomes at opposite poles of the cell during mitosis pinches dividing animal cells apart during cytokinesis; generate cytoplasmic streaming in some cells; generate locomotion in cells such as some leukocytes (white blood cells) and the amoeba; interact with myosin ("thick") filaments in skeletal muscle fibers to provide the force of muscular contraction. The microfilament is a single-stranded helix with each monomer rotated 166° with respect to neighboring subunits; this means that every 36 nanometers, or every 13 subunits, subunits eclipse each other at what appears to be a crossover. Because actin subunits have polarity, so also do the microfilaments from which they are built. Traditionally, the ends of a microfilament have been referred to as "pointed" and "barbed," a nomenclature that arises from the resemblance of microfilaments decorated with fragments of myosin II to arrowheads in the electron microscope. Related category    • CELL BIOLOGY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History BACK TO TOP