Cytoskeleton I

Question 1

cytoskeleton is responsible for what type of mvt important to 2 cell types discussed in lecture

Answer 1

crawling

fibroblasts and white blood cells

Question 2

describe the significance of RBC shape

Answer 2

cytoskeleton is responsible for maintaining their biconcave structure, imperative for protecting them against mechanical stress

mutations = anemia

Question 3

cytoskeleton filaments are made up of?

Answer 3

several protofilaments made up of protein subunits

Question 4

thermally unstable

Answer 4

a single protofilament

only requires 1 bond breakage

Question 5

thermally stable

Answer 5

several protofilaments with lateral noncovalent links

requires the breakage of 3 bonds to remove 1 subunit

Question 6

list the families of cytoskeleton filaments

Answer 6

1. actin filaments – beads
2. microtubules – slinky
3. intermediate filaments – girders

Question 7

general structure of actin filaments

Answer 7

2 stranded right handed helical polymer of actin monomers

Question 8

functions of actin filaments

Answer 8

1. cell surface shape
2. whole cell locomotion, secretion, endocytosis
3. contractile ring in mitosis

Question 9

list the diameters of cytoskeleton filaments

Answer 9

actin - 5-9nm

microtubules - 25/14

intermediate - 10

Question 10

arrangement of actin monomers

Answer 10

head to tail

structural polarity

Question 11

differentiate between the ends of actin filaments

Answer 11

plus end = fast growing/shrinking

minus end = slow end

Question 12

gross structure of microtubules

Answer 12

long hollow spiral cylinder of alpha and beta subunits

Question 13

centrosome

Answer 13

all microtubules emanate from a central microtubule organization center

Question 14

actin is flexible where microtubules are ____ and intermediate filaments are ____.

Answer 14

more rigid

strength

Question 15

functions of microtubules

Answer 15

1. position organelles
2. intracellular transport
3. separate chromosomes
4. divide the cell
5. centrioles and mitotic spindles
6. flagella and cilia for sperm and eggs

Question 16

microtubule protofilaments

Answer 16

hetero-dimer and alpha and beta subunits
via non-covalent bonds

a single strand

Question 17

microtubule is = ?

Answer 17

13 protofilaments arranged in a hollow cylinder

making structure stiff and hard to bend

Question 18

Tubulin-GTP conformation

Answer 18

straight stiff protofilaments

Question 19

Tubulin-GDP conformation

Answer 19

GTP cap lost
protofilaments curve
prone to depolymerization

Question 20

what is nucleoside hydrolysis?

Answer 20

the hydrolysis of bonded ATP/GTP to ADP/GDP on actin and microtubules

Question 21

subunits of intermediate filaments

Answer 21

elongated fibrous protein

central helical region

Question 22

list the progression of intermediate subunits to filaments

Answer 22

1. subunit
2. coiled dimer
3. staggered tetramer = protofilament
4. IF = 8 protofilaments

Question 23

staggered side to side arrangement of coiled dimers allows?

Answer 23

allows for bending and stretching of intermediate filaments

Question 24

what is the strongest cytoskeleton filament?

Answer 24

intermediate filaments

Question 25

functions of intermediate filaments

Answer 25

1. mechanical strength 2. resist mechanical stress 3. formation of hair and nails 4. strengthen CAMs

Question 26

2 monomers of intermediate filaments

Answer 26

coil/spiral about each other to form a coiled dimer

Question 27

2 dimers of an intermediate filament

Answer 27

arrange in staggered antiparallel arrangement = a staggered tetramer

Question 28

arrangement of terminals in a staggered tetramer

Answer 28

N to C and C to N

Question 29

___ number of protofilaments to create an intermediate filament

Answer 29

8 protofilaments = 8 tetramers

Question 30

which cytoskeleton filaments does not bind to triphosphates?

Answer 30

intermediate filaments

Question 31

example of intermediate filaments

Answer 31

keratins

Question 32

example of apical projections made of actin

Answer 32

microvilli important for intestinal cells to 4x increase absorption

Question 33

basolateral domains of intestinal cells

Answer 33

transfer nutrients to blood stream

Question 34

desmosomes and hemidesmosomes

Answer 34

basolateral CAM junctions supported by intermediate filaments

Question 35

what is nucleation?

Answer 35

in order for filaments to form, subunits must first assemble into an aggregate/nucleus

Question 36

actin nucleation

Answer 36

the random collision of 3 monomers

Question 37

phases of growth

Answer 37

1. nucleation 2. elongation 3. steady state

Question 38

T form

Answer 38

actin or microtubules bound to ATP/GTP

Question 39

D form

Answer 39

actin or microtubules bound to ADP/GDP

Question 40

describe treadmilling of _____

Answer 40

actin constant addition at plus end = rate of depolymerization equilibrium polymer length constant

Question 41

define catastrophe and actin

Answer 41

rapid conversions C - from normal growth to rapid loss R - from rapid loss to normal addition

Question 42

describe the dynamic instability, predominating in ____

Answer 42

microtubules loss of GTP cap, causing a conformational change into curved protofilaments resulting in prone/easily removed subunits progressive disruption/dissociation

Question 43

dynamic instability is imperative to?

Answer 43

how microtubules separate chromosomes in division

Question 44

motor proteins are responsible for?

Answer 44

1. move organelles 2. move the filament itself 3. transport vesicles