cell cycle details

consists of a network of protein filaments that extends throughout the cytoplasm

intermediate filaments microtubules actin filaments

• when the cell divides actin filaments are recognised and the cell becomes spherical • polarised microtubule array arranges to form mitotic spindle responsible for aligning and then segregating the duplicated chromosomes • actin filaments then form a contractile ring at the centre of the cell that pinches the cell in two • two daughter cells reorganise their microtubule and actin cytoskeletons enabling them to crawl their separate ways

filaments have linear strings of subunits joined end to end but also laterally associated with other filaments (non covalent interactions)

found in the cytoplasm of eukaryotic cells provides large strength - eg. epithelial skin cells maintains shape connects desmosomes to hemidesmosomes

monomers coil up to form a coil of 8 hiararical subunits

thin, flexible protein threads a two-stranded helix

provides a binding site for ATP/ADP

used to catalyse the formation of an actin filament

enable cell migration ATP-actin adds to the plus end of an actin filament as ADP-actin is lost from the minus end

the behaviour of actin filaments in vertebrate cells assembled actin filaments

tension

lamellipodia (flat feet)

outward extension of plasma membrane

projections of the membrane that allow cells to explore signals

found on the top of some cell types very large surface area allows increased absorption

• polymerisation of cytoplasmic actin monomers at the leading edge of the cell pushes the plasma membrane forward (protrusion) • new points of anchorage are made • contraction at the rear of the cell meditated by myosin draws the body of the cell forward • repeat

allow cells to explore a new territory (organelles also move along)

hollow tubes made of globular tubulin protein subunits has structural polarity with a plus end and a minus end relatively rigid

guide transport of organelles, vesicles and macromolecules in both directions along a nerve cell axon form spindles that divide and split cells in mitosis allow cilia to move fluid to desired locations

GTP hydrolysis

drive cell movement use energy derived from repeated cycles of ATP hydrolysis to travel steadily along the microtubule or actin filament in a single direction

myosin and kinesin

a head and tail domain