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The Human Cell > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

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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
how do microtubules form
by the addition of tubulin dimers at their ends
26
what are the three stages of microtubule polymerisation
nucleation, aggregation into oligomers and elongation
27
what charge does the beta end of a microtubule have
positive
28
what charge does the alpha end of a microtubule have
negative
29
describe the nucleation stage of microtubule formation
slow, also called the lag phase
30
describe the elongation phase of microtubule formation
occurs at a faster rate than the lag phase/nucleation,
31
the microtubule assembly is balanced by the microtubule _____ at the plateau phase/ elongation phase
disassembly
32
microtubule growth is dependent upon what factor
concentration
33
what is the critical concentration
the tubulin concentration at which microtubule assembly is exactly balanced with disassembly
34
when would a microtubule grow in terms of concentration
when the tubulin concentration exceeds the critical concentration
35
when would a microtubule depolymerise in terms of concentration
when the tubulin concentration falls blow the critical concentration
36
microtubules undergo polarised growth, at which pole do they grow at a faster rate
at the positive end compared to the negative end which is slower
37
define treadmilling
the addition of subunits at the plus end and the removal from the minus end
38
list two microtubule inhibitors
colchicine and nocodazole
39
how does colchicine act as a microtubule inhibitor
by promoting microtubule disassembly
40
how does nocodazole act as a microtubule inhibitor
by inhibiting microtubule assembly
41
how do antimitotic drugs work
by interfering with spindle assembly they inhibit cell division
42
antimitotic drugs are useful in the treatment of what disease
cancer
43
how does taxol work and what is it useful for
stabilises microtubules, causes dividing cells to arrest during mitosis, used in cancer treatment
44
what is the dynamic instability model
one population of microtubules grows by polymerisation at the plus end whereas another population shrinks by depolymerisation
45
individual microtubules can go through periods of growth and shrinkage, what is microtubule catastrophe
a switch from growth to shrinkage
46
individual microtubules can go through periods of growth and shrinkage, what is microtubule rescue
a sudden switch back to the growth phase
47
what is the function of the GTP cap
it is formed whenever a new tubulin dimer comes in - its function is to STABILISE
48
when new tubulin is added to the plus end what form is it added in
the GTP form
49
what happens to the GTP over time
over time it is hydrolysed and switches to the GDP form
50
what happens at low concentrations of gtp tubulin
the rate of gtp hydrolysis is high so it results in shrinkage of the cap - loss of gdp bound subunits is favoured
51
what happens at high tubulin concentrations
catastrophe is less likely because GTP is continually added
52
is the gtp cap present in rescue or catastrophe
rescue
53
microtubules originate from a
microtubule-organising center (mtoc)
54
what is the mtoc in many cells
a centrosome near the nucleus
55
which structure is the centrosome associated with
the centrioles
56
how would you describe a centrosome
large ring shaped protein complexes
57
what does the centrosome contain
gamma-tubulin along with gamma tubulin ring proteins GRiPs
58
what part of the centrosome nucleate microtubule assembly
gamma tubulin ring complexes nucleate the assembly
59
what are centrioles and what are they involved in
9 pairs of triplet microtubules involved in basal body formation e.g. cilia and flagella
60
cells without centrioles have poorly organised...
mitotic spindles
61
microtubule growth is regulated by proteins, list three proteins that are involved in microtubule stabilising
tau, Map2, +-TIP proteins
62
microtubule growth is regulated by proteins, list three proteins that are involved in microtubule destabilising
Stathmin, Catastrophins and katanins
63
list four roles of the microfilaments
muscle contraction, intracellular tension and cell shape, cell migration - lamellar and amoeboid movement, cytoplasmic transport
64
actin is a single polypeptide consisting of how many amino acids
375
65
actin is divided into two sub groups, muscle specific actins and nonmuscle actins, name the muscle actins and the non muscle actins
alpha actins - muscle actins. non-muscle actins - beta and gamma
66
what can g actin monomers reversibly polymerise into
filaments
67
what is f actin
two linear strands of polymerised g-actin
68
what is the minus end of a microfilament also called
the pointed end
69
what is the plus end of a microfilament also called
the barbed end
70
where does rapid addition of g actin take place on a microfilament
at the plus end
71
actin binding proteins are responsible for converting actin filaments from one form to another, what protein binds GTP actin and promotes polymerisation
profilin
72
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
adf/cofilin
73
actin binding proteins are responsible for converting actin filaments from one form to another, which protein promotes nucleation and branching
arp2/3
74
actin binding proteins are responsible for converting actin filaments from one form to another, which protein binds g actin
thymosin beta 4
75
actin binding proteins are responsible for converting actin filaments from one form to another, what role do formins have
bind actin filaments and promote elongation
76
actin binding proteins are responsible for converting actin filaments from one form to another, what role do capping proteins have
bind the ends of a filament, prevent further loss/addition of subunits
77
give two examples of capping proteins
capZ and tropomoduins
78
list three drugs that affect the polymerisation of microfilaments
cytochalasin, latrunculin a and phalloidin
79
what affect does cytochalasin have on the polymerisation of microfilaments
prevents the addition of new monomers to existing microfilaments
80
what affect does latrunculin a have on the polymerisation of microfilaments
sequesters actin monomers and prevents their addition to microfilaments
81
what affect does phalloidin have on the polymerisation of microfilaments
stabilises microfilaments and prevents their depolymerisation
82
describe intermediate filaments in four points
the most stable, the most diverse, the least soluble and are not polarised
83
what is the diameter of intermediate filaments
8-12nm
84
describe how a dimer goes to form an intermediate filament
dimer -> tetramer -> protofilaments -> intermediate filament
85
give four examples of intermediate filaments
keratin, vimentin f actin, lamin f actin, desmin
86
what are plakins
plakins are linker proteins that connect intermediate filaments, microfilaments and microtubules
87
give an example of a plakin
plectin
88
the cytoskeleton physically links to the external environment by
adhesion receptors
89
what do integrin receptors link to the extracellular matrix
integrin receptors link f-actin and intermediate filaments to the extracellular matrix
90
what do cadherin receptors link f actin and intermediate filaments to
to other cells
91
what are hemi-desmosomes
dense, stable cluster of intergrins that link to keratins via plectin
92
what do cadherin receptors do
form homotypic interactions with other cadherions on adjacent cells
93
what do cadherin receptors such as e-cadherin link in the cytoplasm
link to f actin or keratin filaments in the cytoplasm
94
what do adherens junctions bind
f actin
95
what do desmosomes bind
keratin

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