• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

Card Range To Study



Play button


Play button




Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

44 Cards in this Set

  • Front
  • Back
3 main types of major filaments
actin, micrtubules, intermediate filaments
function of actin filaments
cytoplasmic streaming,
provide mechanical strength to a cell by forming a band under the plasma membrane
generte locomotion in cells
functions of microtubules
They determine the positions of
membrane-enclosed organelles and direct intracellular transport
intermediate filaments provide
mechanical strength
depend on lateral budnling and coiled coils
tubulin actin molecules assemble
head to tail to create polar filamentst
tubulin is a
what is the rate limiting step in formation of a cytoskeleton polymer
filament treadmilling and dynamic instabilty are
consequences of nucleotide hydrolysis by tubulin and actin
as filament grows, elongation is faster than hydrolysis at the plus end and the terminal subunits are always in T form. at minus end its vice versa in d form
treadmilling occurs
at intermediate concentrations of free subunits
actin molecules nucleate at the
plasma membrane
actin elongation is regulated by
how are actin filaments organzed
by crosslinking proteins
A protein complex containing γ-tubulin nucleate
Microtubules emanate from the
centrosome in animal cells
Stathmin binds to two tubulin heterodimers and
prevents their addition to
the ends of microtubules.
t/f the role of ATP hydolysis in actin polymerization is simlar to the role of GTP hydrlys
t/f in most animal cells, minus end directed microtuble motors deliver their cargo the peryphery of the cel
t/f motor neyrons triffer action potentials in cell membanes that open voltage sensitve in t
how does lateral association promote the subsequent rapid formation of a microtubule
once first association has occured, th enext alpha beta dimer can bind much more readily because its stabilized by lateral and longitudnal contact
how many alpha beta tubulin dimers are added to the ends of a microtubule each second
54 per second
how does a centrosome know when its found the center of the cell
it nucleates a 3d array of microtubes that grow until they encounter an obstacle, the plasma membrane. dynamic nstability of microtubules plus equal pushing in each direction eventually lead it to the center. when alll oppositely directed microtubles are the same length, its in the center
the concentration of actin in cells is 50-100 times grater han the critical condition ovserved for pure actine in a test tube. how is this possible
in cells, most of the actin subunits are bound to thymosin, which locks actin in a form that cant hydrolyze its boudn atp and cant be added to filament ends. thymosin reduces concentration o ffree actin to around the critical cocenctraion. Advantage is that the cell can maintain a large pool of subunits for explosive growth at the sites and times of its choosng.
what is a tubulin homolog in bacteria
intermediate filaments
example: nucelar lamins
subunits are fibrous elongated, not globular
ARP complex of actin grows from the
negative end, allowing elongation at the positve end
proteins that play a role:Arp 2 and Arp3
works best when attached at a 70 degree angle
dimer. Associates with the plus end. Binds to actin subunit and elongates filament only through the + end
locks actin so that it cannot bind to the positve or negative end
associates with plasma membrane and recruits actin monomers
it binds to the site opposite of actin binding site
has 7 actin filaments
filaments by binding simultaneously
to seven adjacent actin subunits in one protofilament This prevents
other proteins from binding to actin
destabilizes by forcing a really tight twist
Stathmin of microtubules
binds the two heterodimers so they are not available for growth. When microtubules need to grow, phosphorylate stathmin and release microtubules
family of minus end directed microtubules
2 tyoes:
cytoplasmic dyneins and axonemal dyneins
cytoplasmic found in eucaryotes for vesicle transportation
t/f the structural polarity of all microtubules is taht alpha is exposed at one end and beta exposed at the other
t/f like actin filaments and microtubules, cytoplasmic intermediate filaments are found in all eurcaryotic cells
only in metozoans
what are the general functions of intermdiate filaments, acin, and microtubules
intermediate filaments: mechanical stability
actin: determine cell shape and are required for locomotion
microtubules: direct intracellular transport and determine position of organelles
why are humans strong if connections weak?
large number of filaments so stress is spread out so their interaction strength will not be exceeded
lag phase
actin monomers assmeble into a nucleus for polumerization
B- is formation of a nucleas/rapid growth
C-equilibrium between rates of addition and release of actin
why does a microtubule shrink
it lost its GTP cap
if you add enough GTP subunits, you can stop shrinking
what is GAP for beta tubulin
tubulin itself, it accelerates GTP hydrolysis by the formation of intersubunit contacts during polymer- ization.
few examples of the differences between bacteria and animal cells
Animal cells are much larger, diversely shaped, and do not have a cell
wall. Cytoskeletal elements are required to provide mechanical strength
and shape in the absence of a cell wall.
Animal cells have internal organelles.
Animal cells, and all other eucaryotic cells, have a nucleus that is shaped
and held in place by intermediate filaments
disulfide bonds do not form in cytosol of eucaryotic cells yet keratin intermediate filaments in skin are corsslinked by disulfide bonds. How can this be?
these bonds form after the cell has died
why are these drugs toxic to dividing cells?
Cell division depends on ability of microtubules to polymerize and depolymerize. Taxol- treated cells are prevented from depolymerizing their existing microtubules, and thus cannot form a mitotic spindle. Colchicine-treated cells cannot polymerize new microtubules, and thus are also prevented from forming a mitotic spindle.
is acrylamide toxicity mediated through its effects on neurofilaments?
probably notIf the original hypothesis were correct, then acrylamide toxicity would have been expected to be absent in mice that are missing neurofila- ments.
how does cofolin distinguish old from new
older has more ADP actin