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The Human Cell > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

1
Q

what is the cytoskeleton

A

a network of interconnected filaments and tubules

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2
Q

list four functions of the cytoskeleton

A

cell structure and mechanics
force generation for motility
cell division
intracellular transport

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3
Q

what are the three major structural elements making up the cytoskeleton

A

microtubules, microfilaments and intermediate filaments

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4
Q

out of the three major structural elements making up the cytoskeleton which is the largest and which is the smallest

A

the largest are the microtubules and the smallest are the microfilaments

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5
Q

what are the monomers making up the microtubules called

A

alpha tubulin and beta tubulin

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6
Q

how many protofilaments are in the wall of a microtubule

A

13

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7
Q

what is the outer diameter of a microtubule

A

25nm

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8
Q

what is the inner diameter of a microtubule

A

15nm

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9
Q

one end of a microtubule is usually attached to a single microtubule organising centre which is the

A

centrosome

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10
Q

microtubules have a +ve and a -ve end so they are said to have

A

polarity

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11
Q

microfilaments are the thinnest of the three types of fibres, what is the size

A

7nm

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12
Q

what are microfilaments made up of

A

actin

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13
Q

what is the free monomer making up the microfilaments called

A

g-actin

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14
Q

what is the linear polymer making up the microfilaments called

A

f-actin

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15
Q

do microfilaments have polarity

A

yes, one side is -ve one is +ve

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16
Q

what are microfilaments involved in

A

muscle movement, intracellular transport, maintenance of animal cell shape

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17
Q

do intermediate filaments have polarity

A

no

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18
Q

describe the structure of intermediate filaments

A

eight protofilaments joined end to end with staggered overlaps

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19
Q

what is the size of intermediate filaments

A

8-12nm

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20
Q

what are the two types of microtubules

A

cytoplasmic microtubules and axonemal microtubules

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21
Q

list the four functions of the cytoplasmic microtubules

A

regulation of cell shape, maintaining axons, formation of mitotic spindle and vesicle transport

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22
Q

list the two functions of the axonemal microtubules

A

cell motility and act as a signalling hub

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23
Q

what are axonemal microtubules and where are they found

A

they are organised and stable microtubules found in cilia, flagella and basal bodies - to which cilia and flagella attach

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24
Q

microtubules can have different types of microtubules, what are the three

A

singlet, doublet, triplet

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25
Q

how do microtubules form

A

by the addition of tubulin dimers at their ends

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26
Q

what are the three stages of microtubule polymerisation

A

nucleation, aggregation into oligomers and elongation

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27
Q

what charge does the beta end of a microtubule have

A

positive

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28
Q

what charge does the alpha end of a microtubule have

A

negative

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29
Q

describe the nucleation stage of microtubule formation

A

slow, also called the lag phase

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30
Q

describe the elongation phase of microtubule formation

A

occurs at a faster rate than the lag phase/nucleation,

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31
Q

the microtubule assembly is balanced by the microtubule _____ at the plateau phase/ elongation phase

A

disassembly

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32
Q

microtubule growth is dependent upon what factor

A

concentration

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33
Q

what is the critical concentration

A

the tubulin concentration at which microtubule assembly is exactly balanced with disassembly

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34
Q

when would a microtubule grow in terms of concentration

A

when the tubulin concentration exceeds the critical concentration

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35
Q

when would a microtubule depolymerise in terms of concentration

A

when the tubulin concentration falls blow the critical concentration

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36
Q

microtubules undergo polarised growth, at which pole do they grow at a faster rate

A

at the positive end compared to the negative end which is slower

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37
Q

define treadmilling

A

the addition of subunits at the plus end and the removal from the minus end

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38
Q

list two microtubule inhibitors

A

colchicine and nocodazole

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39
Q

how does colchicine act as a microtubule inhibitor

A

by promoting microtubule disassembly

40
Q

how does nocodazole act as a microtubule inhibitor

A

by inhibiting microtubule assembly

41
Q

how do antimitotic drugs work

A

by interfering with spindle assembly they inhibit cell division

42
Q

antimitotic drugs are useful in the treatment of what disease

43
Q

how does taxol work and what is it useful for

A

stabilises microtubules, causes dividing cells to arrest during mitosis, used in cancer treatment

44
Q

what is the dynamic instability model

A

one population of microtubules grows by polymerisation at the plus end whereas another population shrinks by depolymerisation

45
Q

individual microtubules can go through periods of growth and shrinkage, what is microtubule catastrophe

A

a switch from growth to shrinkage

46
Q

individual microtubules can go through periods of growth and shrinkage, what is microtubule rescue

A

a sudden switch back to the growth phase

47
Q

what is the function of the GTP cap

A

it is formed whenever a new tubulin dimer comes in - its function is to STABILISE

48
Q

when new tubulin is added to the plus end what form is it added in

A

the GTP form

49
Q

what happens to the GTP over time

A

over time it is hydrolysed and switches to the GDP form

50
Q

what happens at low concentrations of gtp tubulin

A

the rate of gtp hydrolysis is high so it results in shrinkage of the cap - loss of gdp bound subunits is favoured

51
Q

what happens at high tubulin concentrations

A

catastrophe is less likely because GTP is continually added

52
Q

is the gtp cap present in rescue or catastrophe

53
Q

microtubules originate from a

A

microtubule-organising center (mtoc)

54
Q

what is the mtoc in many cells

A

a centrosome near the nucleus

55
Q

which structure is the centrosome associated with

A

the centrioles

56
Q

how would you describe a centrosome

A

large ring shaped protein complexes

57
Q

what does the centrosome contain

A

gamma-tubulin along with gamma tubulin ring proteins GRiPs

58
Q

what part of the centrosome nucleate microtubule assembly

A

gamma tubulin ring complexes nucleate the assembly

59
Q

what are centrioles and what are they involved in

A

9 pairs of triplet microtubules involved in basal body formation e.g. cilia and flagella

60
Q

cells without centrioles have poorly organised…

A

mitotic spindles

61
Q

microtubule growth is regulated by proteins, list three proteins that are involved in microtubule stabilising

A

tau, Map2, +-TIP proteins

62
Q

microtubule growth is regulated by proteins, list three proteins that are involved in microtubule destabilising

A

Stathmin, Catastrophins and katanins

63
Q

list four roles of the microfilaments

A

muscle contraction, intracellular tension and cell shape, cell migration - lamellar and amoeboid movement, cytoplasmic transport

64
Q

actin is a single polypeptide consisting of how many amino acids

65
Q

actin is divided into two sub groups, muscle specific actins and nonmuscle actins, name the muscle actins and the non muscle actins

A

alpha actins - muscle actins. non-muscle actins - beta and gamma

66
Q

what can g actin monomers reversibly polymerise into

67
Q

what is f actin

A

two linear strands of polymerised g-actin

68
Q

what is the minus end of a microfilament also called

A

the pointed end

69
Q

what is the plus end of a microfilament also called

A

the barbed end

70
Q

where does rapid addition of g actin take place on a microfilament

A

at the plus end

71
Q

actin binding proteins are responsible for converting actin filaments from one form to another, what protein binds GTP actin and promotes polymerisation

72
Q

actin binding proteins are responsible for converting actin filaments from one form to another, what protein binds g actin and f actin and also severs filaments

A

adf/cofilin

73
Q

actin binding proteins are responsible for converting actin filaments from one form to another, which protein promotes nucleation and branching

74
Q

actin binding proteins are responsible for converting actin filaments from one form to another, which protein binds g actin

A

thymosin beta 4

75
Q

actin binding proteins are responsible for converting actin filaments from one form to another, what role do formins have

A

bind actin filaments and promote elongation

76
Q

actin binding proteins are responsible for converting actin filaments from one form to another, what role do capping proteins have

A

bind the ends of a filament, prevent further loss/addition of subunits

77
Q

give two examples of capping proteins

A

capZ and tropomoduins

78
Q

list three drugs that affect the polymerisation of microfilaments

A

cytochalasin, latrunculin a and phalloidin

79
Q

what affect does cytochalasin have on the polymerisation of microfilaments

A

prevents the addition of new monomers to existing microfilaments

80
Q

what affect does latrunculin a have on the polymerisation of microfilaments

A

sequesters actin monomers and prevents their addition to microfilaments

81
Q

what affect does phalloidin have on the polymerisation of microfilaments

A

stabilises microfilaments and prevents their depolymerisation

82
Q

describe intermediate filaments in four points

A

the most stable, the most diverse, the least soluble and are not polarised

83
Q

what is the diameter of intermediate filaments

84
Q

describe how a dimer goes to form an intermediate filament

A

dimer -> tetramer -> protofilaments -> intermediate filament

85
Q

give four examples of intermediate filaments

A

keratin, vimentin f actin, lamin f actin, desmin

86
Q

what are plakins

A

plakins are linker proteins that connect intermediate filaments, microfilaments and microtubules

87
Q

give an example of a plakin

88
Q

the cytoskeleton physically links to the external environment by

A

adhesion receptors

89
Q

what do integrin receptors link to the extracellular matrix

A

integrin receptors link f-actin and intermediate filaments to the extracellular matrix

90
Q

what do cadherin receptors link f actin and intermediate filaments to

A

to other cells

91
Q

what are hemi-desmosomes

A

dense, stable cluster of intergrins that link to keratins via plectin

92
Q

what do cadherin receptors do

A

form homotypic interactions with other cadherions on adjacent cells

93
Q

what do cadherin receptors such as e-cadherin link in the cytoplasm

A

link to f actin or keratin filaments in the cytoplasm

94
Q

what do adherens junctions bind

95
Q

what do desmosomes bind

The Human Cell (11 decks)

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