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Cell Bio > Ch 17 - Cytoskeleton > Flashcards

Ch 17 - Cytoskeleton Flashcards

1
Q

what is the function of the cytoskeleton?

A

provides support, structure, and movement

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2
Q

what are intermediate filaments?

A

strong and rope like
strengthen cells against mechanical stress
support nuclear envelope

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3
Q

what are intermediate filaments composed of?

A

fibrous proteins

ropelike fibers

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4
Q

how do you tell the ends of intermediate filaments apart?

A

based on the proteins that bind to the ends

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5
Q

Do intermediate filaments have polarity?

A

no

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6
Q

what are desmosomes?

A

anchoring junctions
where cells connect
strengthen by intermediate filaments

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7
Q

what are the types of intermediate filaments?

A

cytoplasmic and nuclear

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8
Q

what are the cytoplasmic intermediate filaments?

A

keratin
vimentin & vimentin-related
neurofilaments

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9
Q

what are the nuclear intermediate filaments?

A

nuclear lamins

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10
Q

where are keratin intermediate filaments found?

A

epithelial cells

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11
Q

where are vimentin & vimentin-related intermediate filaments found?

A

connective tissue, muscle cells, and glial cells

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12
Q

where are nuclear lamins intermediate filaments found?

A

in all animal cells

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13
Q

where are nerve cell intermediate filaments found?

A

neurofilaments

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14
Q

how do proteins help filaments?

A

proteins help filaments bind, support, and transport things

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15
Q

What is plectin?

A

protein that helps stabilize intermediate filaments

it helps intermediate filament anchor to microtubules

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16
Q

what happens when there is a defect in plectin?

A

it can causes symptoms of: epidermolysis bullosa, muscular dystrophy, neurodegeneration

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17
Q

what do nuclear lamins do for intermediate filaments?

A

phosphorylation regulates filaments

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18
Q

what happens to intermediate filaments when nuclear lamins are phosphorylated?

A

destabilizing the structure

the phosphates start to loosen the lamin

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19
Q

what happens to intermediate filaments when nuclear lamins are dephosphorylated?

A

reassembly for structure

no phosphates allow tighter formation of the lamin

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20
Q

what causes progeria in terms of intermediate filaments?

A

defects in the nuclear lamin

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21
Q

what are the symptoms of progeria?

A

premature aging

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22
Q

what causes epidermolysis bullosa in terms of intermediate filaments?

A

mutation of keratin gene in plectin

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23
Q

what are the symptoms of epidermolysis bullosa?

A

skin easily blisters and damages

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24
Q

a defect in which type of intermediate filament would cause a phenotype in all tissue types?

A

nuclear lamins

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25
Q

what are microtubules?

A

hollow tubes with distinct ends

provides centrosome and cell interior organization

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26
Q

____ drive intracellular transport

A

motor proteins

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27
Q

what are microtubules composed of?

A

tubulin

alpha and beta subunits

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28
Q

how do microtubules grow?

A

alpha units are added to the plus end (alpha)

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29
Q

how do microtubules disassemble?

A

remove beta subunits from the minus end (beta end)

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30
Q

Do microtubules have polarity?

A

yes

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31
Q

what are microtubules anchored to?

A

centrosomes

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32
Q

what do centrosomes control in terms of microtubules?

A

length, number, and orientation

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33
Q

what is found on the surface of the centrosome?

A

gamma tubulin rings

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34
Q

what does gamma tubulin do?

A

it directly binds to microtubule and allows growth

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35
Q

what is dynamic instability?

A

microtubules grow and shrink very rapidly from one end

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36
Q

what controls dynamic instability?

A

GTP hydrolysis

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37
Q

what happens to a GTP associated tubulin?

A

it elongates

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38
Q

what happens to a GDP associated tubulin?

A

it disassembles

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39
Q

what does capping of microtubules do?

A

prevents disassembly

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40
Q

what does taxol do to microtubules?

A

binds to microtubules, prevents disassembly

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41
Q

what does colchicine do to microtubules?

A

binds free tubulin, prevents polymerization (growth)

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42
Q

what do drugs that prevent normal microtubules turnover do?

A

they inhibit mitosis

anti-cancer drugs

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43
Q

which cell would have the longest microtubules?

A

one treated with taxol

prevents disassembly

44
Q

what do microtubule motor proteins rely on?

A

ATP hydrolysis

45
Q

what are the microtubule motor proteins?

A

kinesins and dyneins

46
Q

what do kinesins do?

A

microtubule motor proteins that move towards the plus end (away from the cell body)

47
Q

what do dyneins do?

A

microtubule motor proteins that move towards the minus end (towards the cell body)

48
Q

how do nerve cells use microtubules?

A

as railroad tracks for motor proteins

49
Q

what is the “9+2” arrangement?

A

2 microtubules in the center
9 pairs of microtubules around the center microtubules
creates cilia and flagella

50
Q

what does ciliary dynein do?

A

generate movement

51
Q

what is the difference between cilia and flagella?

A

Cilia are shorter and more numerous. Flagella are longer and fewer on cells.

52
Q

what can mutations in ciliary dynein cause?

A

male infertility

mucus

53
Q

what happens to cilia when there is a mutation in ciliary dynein?

A

they have normal shape and structure but abnormal movement because there is a mutation in motor proteins

54
Q

What are actin filaments?

A

thin and flexible filaments

occur in bundles

55
Q

what do actin filaments do?

A

support the plasma membrane

56
Q

what are actin filaments responsible for?

A

membrane crawling

57
Q

what does it mean that actin filaments are dynamic?

A

they have rapid restructuring

58
Q

what does the rapid rearrangement of actin filaments depend on?

A

the proteins interacting with it

59
Q

what do actin/myosin do?

A

help form the contractile ring

60
Q

what type of hydrolysis does actin depend on?

A

ATP hydrolysis

61
Q

what is the orientation of actin filaments?

A

plus end

minus end

62
Q

what end does actin filaments grow from?

A

plus end

63
Q

what end do actin filaments dissemble from?

A

minus end

64
Q

Do actin filaments have polarity?

A

yes

65
Q

what does it mean that actin treadmill?

A

they grow from one end and shrink from the other

66
Q

how does actin grow and shrink?

A

they grow from one end and shrink from the other

67
Q

what is the difference between treadmilling and dynamic instability?

A

treadmilling - movement of monomers through filament; uses ATP hydrolysis; actin

dynamic instability - growth and disassembly from one end; GTP hydrolysis; microtubules

68
Q

what do actin binding proteins do?

A

help cell control if actin is protruding from plasma membrane or shrinking

69
Q

what does phalloidin do to actin filaments?

A

binds and stabilizes filaments

70
Q

what does cytochalasin do to actin filaments?

A

caps actin filament plus ends, preventing polymerization (growth)

71
Q

what does latrunculin do to actin filaments?

A

binds to actin monomers and prevents their polymerization

72
Q

which of the actin drugs would cause actin filaments to elongate?

A

phalloidin; stabilizes the filament allowing growth

73
Q

how do actin filaments promote cell crawling?

A

they extend lamellipodia
they contract the distal end
and they form attachments to the substratum

74
Q

what must happen to extend lamellipodia?

A

actin polymerization and contraction

75
Q

what does the contraction of actin depend on?

A

actin/myosin

76
Q

in cell crawling, what does actin polymerization do?

A

pushes leading edge forward with ARPs and formins

77
Q

what does a capping protein do on actin filaments?

A

stop growth

78
Q

what does the motor protein myosin do with actin filaments?

A

hydrolyze ATP

move towards plus end of actin filament

79
Q

where is type I myosin found?

A

all cells

80
Q

where is type II myosin found?

A

muscle cells

81
Q

what do Rho proteins do in actin filaments?

A

control various processes (cytoskeletal reorganization

82
Q

what activates Rho proteins in actin filaments?

A

extracellular signals

83
Q

what helps Rho proteins in cytoskeletal reorganization?

A

monomeric GTPases

84
Q

in general, what causes muscle contraction?

A

interactions between actin and myosin

actin slides against myosin

85
Q

what triggers muscle contraction in muscle tissues?

A

cytosolic increase in Ca2+

86
Q

what are the types of muscle cells?

A

skeletal
cardiac
smooth

87
Q

which muscle cells has voluntary contraction?

A

skeletal

88
Q

what muscle cells have involuntary contraction?

A

cardiac and smooth

89
Q

what is myosin II?

A

a dimer of two inter-twined myosin subunits

it has a globular ATPase head with coiled tail

90
Q

what happens to the head of Myosin II during ATPase activity?

A

it goes through a conformational change during ATP hyrdolysis

91
Q

what happens as myosin contracts?

A

actin slides toward each other

92
Q

what are myofibrils composed of?

A

sarcomeres

93
Q

what do z disks do?

A

they anchor actin and myosin filaments

94
Q

what is a sarcomere?

A

contractile unit of muscle cells

95
Q

where is the actin found in sarcomeres?

A

thin filaments

96
Q

where is the myosin found in sarcomeres?

A

thick filaments

97
Q

how does muscle contraction occur?

A
  1. an increase in cytosolic Ca2+ binds to troponin
  2. moves tropomyosin
  3. reveals myosin binding site
  4. myosin hydrolyzes ATP
  5. actin and myosin bind
  6. muscle contracts
98
Q

what does myosin movement depend on?

A

ATP hydrolysis

99
Q

you give a medication that prevents the reabsorption of calcium by sarcoplasmic reticulum. What would be the expected effect of this treatment on a contracting muscle?

A

continual muscle contraction.

Muscle cannot relax

100
Q

Use the image of a sarcomere to answer the following question. Which letter is labeling the Z disc?

A

c

101
Q

Use the image of a sarcomere to answer the following question. Which letter is labeling the myosin?

A

B

102
Q

Use the image of a sarcomere to answer the following question.

Which letter indicates where actin filaments can be found?

A

A

103
Q

where are intermediate filaments found?

A

extending from a ring surrounding the nucleus to the plasma membrane

104
Q

where are microtubules found?

A

the centrosome, adjacent to the nucleus

105
Q

where are actin filaments found?

A

cell cortex, microvilli, near the outside of the cell/plasma membrane

Cell Bio (9 decks)

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