functions of intermediate filaments

provide tensile and mechanical strength

functions of microtubules

cell organization and division

functions of actin filaments



molecular motors required for muscle contractions and other functions


molecular motors associated with microtubules - move cargo toward the plus end


molecular motors associated with microtubules - usually move cargo toward the minus end


cytoplasmic intermediate filaments - epithelial


cytoplasmic intermediate filaments - in connective tissue and muscle and neuroglia


cytoplasmic intermediate filaments - in nerve cells

nuclear lamins

nuclear intermediate filaments - in all nucleated cells

structure of intermediate filaments

two conserved alpha-helical monomers form a coiled-coil dimer; two dimers form a staggered tetramer; eight tetramers twist into a ropelike filament; globular heads vary in shape and size

structure of microtubules

hollow cylinders made of the protein tubulin - a dimer formed from alpha and beta tubulin associated with 2 GTP; grow from centrally located centrosome in cytoplasm of cell

structure of actin filaments

two-stranded helical polymers of the protein actin; have structurally unique plus and minus ends

classes of actin binding proteins

monomer sequestering proteins; nucleating proteins; bundling proteins; motor proteins; side-binding proteins; capping proteins; severing proteins; cross-linking proteins

monomer sequestering proteins

interact with actin monomers to prevent them from assembling

nucleating proteins

interact with actin to facilitate the addition of subunits at the plus end

bundling proteins

bundle actin filaments to make larger and stiffer structures

motor proteins

myosins - interact with actin to produce movement

side-binding proteins

selectively stabilize actin filaments

capping proteins

prevent further addition of subunits at the plus or minus end of actin filaments

severing proteins

fragment actin filaments to increase fluidity

cross-linking proteins

hold actin filaments together in a gel-like meshwork within the cell cortex

power stroke

occurs as myosin head pivots; causes motion of actin filament

action of myosin motors

ATP binding causes myosin head dissociation; ATP is hydrolyzed to ADP and phosphate; power stroke due to conformational change of the myosin head is triggered by the release of phosphate

mechanism of directed cell migration

involves polarized assembly of actin based machinery; localized cell adhesion; actin-based membrane protrusion at the leading edge to produce lamellipodium; actin-myosin interaction at the tail

colchicine-derived drugs

bind to free tubulin and prevent their polymerization into microtubules; stalls cell in mitosis


bind to microtubules to prevent them from losing subunits; stalls cell in mitosis

axonal microtubule polarity

plus ends of microtubules are distal to the cell body

dendritic microtubule polarity

polarity of microtubules is mixed


a protein dimer composed of alpha and beta tubulin


strands of tubulin dimers

energy source in microtubules

GTP bound to subunits of tubulin


the microtubule organizing center; typically located close to the cell nucleus


structures found in the centrosome; made up of a cylindrical array of short microtubules

dynamic instability

the process of alternating microtubule growth and shrinkage


microtubule-associated proteins; regulate microtubule assembly and stability

gamma-tubulin ring complexes

nucleation sites for microtubule growth; ring-shaped

primary cilium

a signaling structure found in every differentiated cell

roles of cilia

motility; sensory


a microtubule-based cytoskeletal structure found inside cilia

basal body

a specialized centriole; anchors cilia

ciliary membrane

extends from the plasma membrane

anaphase A

the stage in mitosis during which chromatids separate; kinetochore mucrotubules shorten by depolymerization

anaphase B

the stage in mitosis during which the spindle poles move apart; kinesins and dyneins act on overlapping microtubules and astral microtubules


the paired protein structure to which centrosomes attach; responsible for spindle assembly and regulation of microtubule dynamics and separation of chromosomes

overlapping microtubules

overlap in the center of the cell; involved in anaphase B; push spindle poles apart

astral microtubules

radiate outward from centrosomes; involved in anaphase B

tubulin flux

a constant slow flux of microtubules in the spindle; ""treadmilling

proposed mechanisms for kinetochore microtubule shortening

ATP motor protein driven? Microtubule disassembly driven?


cell-cell spot adhesions formed by interactions between cadherins and intermediate filaments


cell-extracellular matrix spot adhesions formed by interactions between integrins and intermediate filaments

actin-myosin interactions

myosin moves toward the plus end of actin filaments

structure of myosin

head and neck and tail regions; head region = motor domain

mechanism of cilia and flagella movement

dynein-driven microtubule sliding