Cytoskeleton

Question 1

what colors do microtubules, microfilaments and intermediate filaments show on fluorescent staining

Answer 1

microtubules- green
microfilament/actin - red
intermediate filaments - blue

Question 2

which is the largest

a) actin filaments
b) microtubules
c) intermediate filaments

Answer 2

microtubules

Question 3

is the cytoskeleton larger in prokaryotes or eukaryotes

Answer 3

eukaryotes

Question 4

is the cytoskeleton static or dynamic

Answer 4

dynamic

Question 5

what are intermediate filaments composed of

Answer 5

fibrous protein

Question 6

which cytoskeleton structure is a rope-like fiber

Answer 6

intermediate filament

Question 7

which cytoskeleton structure forms a meshwork structure

Answer 7

intermediate filaments

Question 8

what is a desmosome

Answer 8

cell structure specialized for cell-to-cell adhesion

Question 9

what are the intermediate filaments in the nucleus

Answer 9

nuclear lamins

Question 10

what are the intermediate filaments in epithelial cells

Answer 10

keratin filaments

Question 11

what are the intermediate filaments in the connective tissue, muscle cells, and glial cells

Answer 11

vimentin and vimentin related filaments

Question 12

nuclear lamins are only located in a few animal cells. true or false

Answer 12

false. they are located in all animal cells

Question 13

what intermediate filaments are in nerve cells

Answer 13

neurofilaments

Question 14

what is Epidermolysis bullosa simple

Answer 14

A genetic disease, keratin gene mutation. A mutant form of keratin makes skin more prone to blistering

Question 15

what aids in the bundling of intermediate filaments and links these filaments to other cytoskeletal protein networks

Answer 15

plectin

Question 16

what does plectin mutation cause

Answer 16

a combination of; Epidermolysis bullosa simple muscular dsytrophy and neurodegenaration

Question 17

what happened to mice lacking plectin gene

Answer 17

died within a few days due to abnormal heart muscles

Question 18

what do defects in nuclear lamins cause

Answer 18

cause a rare class of premature aging disorders called progeria i.e. the nucleus loses its shape

Question 19

what is the major microtubule organizing centre in animal cells

Answer 19

the centrosome

Question 20

what drives the dynamic instability of microtubules

Answer 20

GTP hydrolysis

Question 21

drugs cannot modify dynamic instability of microtubules true or false.

Answer 21

false. they can

Question 22

what do microtubules help motor proteins do

Answer 22

drive intracellular transport

Question 23

what does dynein do

Answer 23

They convert the chemical energy stored in ATP to mechanical work. Dynein transports various cellular cargos, provides forces and displacements important in mitosis, and drives the beat of eukaryotic cilia and flagella

Question 24

where do microtubules grow from at their plus ends

Answer 24

gamma tubulin

Question 25

microtubules grow independently of their neighbors. true or false

Answer 25

true

Question 26

what is selective stabilization of microtubules

Answer 26

where the length of some microtubules are maintained and others arent

Question 27

what do capping proteins do

Answer 27

control access to the free barbed ends of actin filaments and is therefore a major factor affecting actin filament elongation

Question 28

what does selective stabilization do to a cell

Answer 28

polarize it

Question 29

how does GTP hydrolysis control stabilization

Answer 29

by GTP binding to tubulin dimer causing more addition of GTP-tubulin

Question 30

what causes shrinking of the microtubule

Answer 30

GDP binding to the tubulin dimer

Question 31

what drug binds and stabilizes microtubules

Answer 31

taxol (treat breast and ovarian cancers)

Question 32

what is the effect of colchicine and colcemid

Answer 32

binds tubulin dimers and prevents their polymerization

Question 33

what drugs have the same effect as colchicine, colcemid

Answer 33

vinblastine and vincristine (childhood hematologic malignancies)

Question 34

what drug prevents cell division during mitosis

Answer 34

colchicine (for gout)

Question 35

most differentiated cells are polarized. what does this mean

Answer 35

one end of the cell is structurally and functionally different from the other

Question 36

true or false, organelles travel slower by diffusion than by microtubules

Answer 36

false. it can take years for their diffusion whereas in microtubules it takes seconds

Question 37

what are the two families of motor proteins

Answer 37

dynein and kinesin

Question 38

what do motor proteins do

Answer 38

move vesicles along microtubules

Question 39

how do dynein and kinesin move along the microtubules

Answer 39

using their globular heads

Question 40

what directions do dynein and kinesin move

Answer 40

dynein moves towards the minus end and kinesin moves towards the plus end

Question 41

what determines the cargo type when moving along the microtubule

Answer 41

depends on the tail of the dynein or kinesin

Question 42

what are the repetitive movements cilia makes

Answer 42

power stroke and recovery stroke

Question 43

how are microtubules in cilium and flagella arranged

Answer 43

9+2

Question 44

what causes the flagella with dynein to bend

Answer 44

linking protein

Question 45

what does dynein do in an isolated doublet microtubule

Answer 45

producing microtubule sliding with help of ATP

Question 46

what does cell crawling depend on

Answer 46

cortical actin

Question 47

what decreases stability of the actin filament

Answer 47

ATP hydrolysis

Question 48

how do actin filaments regulate filament length

Answer 48

Treadmilling

Question 49

what does phalloidin (drug) do

Answer 49

binds and stabilizes filaments

Question 50

which drug caps plus end and prevents polymerization in actin filaments

Answer 50

cytochalasin

Question 51

what does latrunculin (drug) do

Answer 51

binds actin monomers and prevents polymerization

Question 52

what are types of actin binding proteins (name 6)

Answer 52

``` myosin motor protein side-binding protein cross linking protein (cortex) severing protein nucleating protein bundling protein (filopodia) ```

Question 53

what proteins regulate filament formation

Answer 53

thymosine and profilin (prevent their polymerization)

Question 54

what protein promote polymerization of actin filaments

Answer 54

formin

Question 55

what help move a cell forward

Answer 55

Forces generated in the actin-filament-rich cortex

Question 56

which direction does myosin I move across the microtubule

Answer 56

from negative to positive ends

Question 57

what has a dramatic effect on the organization of actin | filaments in fibroblasts

Answer 57

Activation of Rho family GTPases

Question 58

name two regulators in actin dynamics

Answer 58

Rac and cdc42

Question 59

what triggers muscle contraction

Answer 59

Ca ion increase

Question 60

what is the bare region

Answer 60

where the heads and tails of myosin meet (confirm this)

Question 61

what defines the boundaries of the sarcomere

Answer 61

Z-disc

Question 62

what surrounds the myofibrils

Answer 62

T tubules and the sarcoplasmic reticulum

Question 63

what controls skeletal muscle contraction

Answer 63

troponin and tropomyosin (blocks myosin binding sites) complexes

Question 64

what does Ca do in muscle contraction

Answer 64

exposes myosin binding site

Question 65

what is an example of a capping protein

Answer 65

gelsolin, which prevent polymerization of the filament

Question 66

what are the three classes of actin

Answer 66

α-actin of muscle, β-actin, and γ-actin of non-muscle cells.

Question 67

what proteins other than myosin bind to actin to perform essential cellular functions

Answer 67

α-actinin, spectrin, fimbrin, filamin, gelsolin, and talin

Question 68

what are the three types of association in actin filaments

Answer 68

Contractile bundles Gel-like networks Parallel bundles

Question 69

what types of association in actin usually has myosin

Answer 69

Contractile bundles

Question 70

what structure maintains focal contacts of the cell with extracellular matrix

Answer 70

actin filaments

Question 71

what is the relationship between integrin, talin, vinculin, fibronectin and the actin filaments

Answer 71

integrin (a transmembrane protein) binding to fibronectin and talin, which contacts both vinculin and the actin filament

Question 72

what is the function of gel-like connection

Answer 72

provide the structural foundation of much of the cell cortex

Question 73

what provides stiffness in gel-like networks

Answer 73

protein filamin

Question 74

what are fimbrin and villin responsible for

Answer 74

forming actin filaments into closely packed parallel bundles that form the core of microspikes and microvilli, respectively

Question 75

what does spectrin do

Answer 75

assists in structural integrity of cortex

Question 76

where are bundles of actin filaments anchored

Answer 76

terminal web

Question 77

what structures anchor the nucleus

Answer 77

intermediate filaments

Question 78

how many tetramers form an intermediate filament

Answer 78

8

Question 79

what is the head and the tail of each monomer called

Answer 79

N-terminus (head) and C-terminus (tail)

Question 80

what is the central domain composed of

Answer 80

elongated alpha helix

Question 81

what type of isoforms are keratin fibers

Answer 81

family of acidic and basic isoforms

Question 82

what is Epidermolysis bullosa simplex (EBS) characterized by

Answer 82

skin blisters after minor trauma (keratin 5 and 14 mutant genes)

Question 83

what conditions leads to excessive keratinization of the epidermis

Answer 83

Epidermolytic hyperkeratosis (EH) ((mutations of keratin 1 and 10 genes)

Question 84

fragmentation of the epidermis of the palms and soles is caused by what disease

Answer 84

Epidermolytic plantopalmar keratoderma (EPPK) (keratin 9 mutation)

Question 85

what is most common intermediate filament protein

Answer 85

vimentin

Question 86

what is vimentin derived from

Answer 86

mesenchyme

Question 87

what binds keratin filaments into bundles

Answer 87

flaggrin

Question 88

what do Synemin and plectin bind

Answer 88

desmin and vimentin, respectively

Question 89

what do plakins assist in

Answer 89

assist the maintenance of contact between the keratin intermediate filaments and hemidesmosomes of epithelial cells as well as actin filaments with neurofilaments of sensory neurons

Question 90

describe centriole structure

Answer 90

composed of nine highly organized microtubule triplets.

Question 91

which of the following do microtubules not do a) axoplasmic transport in neurons b) melanin transport in pigment cells c) movement of RNA along the nucleus d) vesicle movements among different cell compartments

Answer 91

c

Question 92

what are the main side effects of taxol

Answer 92

neurotoxicity and suppression of hematopoiesis (production of all of the cellular components of blood and blood plasma)

Question 93

what is Kartagener’s syndrome

Answer 93

autosomal recessive ciliary dyskinesia frequently associated with bronchiectasis and sterility in men

Question 94

what is Kartagener’s syndrome a result of

Answer 94

structural abnormalities in the axoneme (defective or absent dynein) that prevent mucociliary clearance in the airways (leading to persistent infections) and reduce sperm motility and ovarium transport in the oviduct (leading to sterility)

Question 95

where are the microtubules not dynamic

Answer 95

axonemes

Question 96

what are the monomeric proteins in intermediate filaments

Answer 96

alpha helical rod like protein

Question 97

what is the overall structure of intermediate filaments

Answer 97

cable of 4 intertwined protofibrils, each consisting of bundled tetramers associated end to end