EXAM 4 LEC 16

Question 1

listeria monocytogenes

Answer 1

casual agent of listeriosis

Question 2

microtubules (green)

Answer 2

originate at centrosomes near the nucleus
terminate at the plasma membrane
exhibit dynamic instability

Question 3

actin filaments (red)

Answer 3

mostly aligned parallel and just underneath the plasma membrane (the cell cortex)
exhibit treadmilling

Question 4

intermediate filaments (not highlighted)

Answer 4

found inside the nuclear envelope and plasma membrane
stable complexes
found mostly in vertebrates

Question 5

what color is nuclear DNA stained

Answer 5

blue

Question 6

what color are membranes stained

Answer 6

unstained

Question 7

how are cytoskeletal components built

Answer 7

from subunits that interact noncovalently at several levels of organization

Question 8

what are intermediate filaments unique to

Answer 8

animal cells

they contribute strength to the tissues

Question 9

connection of filaments

Answer 9

indirectly connected to adjacent cells through desmosomes, providing continuity of mechanical strength

Question 10

how are filaments built

Answer 10

from fibrous polypeptide subunits that organize into arrays held together by noncovalent interactions.

Question 11

unique class of filaments found in epithelial cells

Answer 11

keratin

Question 12

unique class of filaments found in muscle cells

Answer 12

vimentin

Question 13

unique class of filaments in nerve cells

Answer 13

neurofilament

Question 14

nuclear lamin

Answer 14

strengthens the nuclear envelope in all animal cells
dissemble and reassemble with cell division
controlled by phosphorylation/dephosphorylation

Question 15

intermediate filament organization

Answer 15

subunits are fibrous polypeptides with an alpha-helical central rod domain, globular N-terminal head and C-terminal tail
2 subunits interact in parallel through the central rod domain as a coiled-coil homodimer
2 dimers staggered and antiparallel interact as a tetramer

Question 16

tetramers of intermediate filament organization

Answer 16

8 tetramers twist into the intermediate filament, which has a 10 nm diameter
an additional 8 fuse end to end to make the filament

Question 17

relationship of microtubules and ER

Answer 17

microtubules grow into leading edge

ER extends along microtubule tracks, providing membrane and proteins

Question 18

interphase cells

Answer 18

a track system in cells
anchor membrane-bound organelles in cell
guide intracellular transport
grow from centrosome (animal cells) and gamma-tubulin ring or centrioles in plants

Question 19

roles of microtubules

Answer 19

form mitotic spindle extending form spindle poles in dividing cells to segregate chromosomes
form permanent structures from basal bodies
orient cellulose microfibril synthesis outside the plant cell by microtubules in the cell under the plasma membrane

Question 20

basal bodies

Answer 20

cilia to move fluids past the cell

flagella to move cell

Question 21

heterodimeric protein

Answer 21

formed by the alpha and beta tubulin subunits

Question 22

heterodimers

Answer 22

stack as alternating subunits to form a protofilament that has an orientation of a minus and plus end

Question 23

minus end

Answer 23

where microtubules are anchored

Question 24

plus end

Answer 24

where microtubules grow and shrink

Question 25

microtubules of nondividing cells

Answer 25

grow from gamma tubulin ring complexes in organized nucleation centers

Question 26

nondividing microtubules of animals

Answer 26

one centrosome (with two centrioles) per cell found close to the nucleus, forms microtubule network from nucleus to plasma membrane

Question 27

nondividing microtubules of plants

Answer 27

organizing center is less clearly defined in the nuclear envelope

Question 28

microtubules of dividing cells

Answer 28

the mitotic/meiotic spindle apparatus

Question 29

microtubules of cells with cilia and flagella

Answer 29

permanent structures grow from basal bodies