Cytoskeleton I Flashcards

1
Q

What form the microvilli?

A

actin microfilaments

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2
Q

Besides forming microvilli on the apical surface of epithelium what is a major job of actin filaments?

A

Maintaining cell-cell junctions

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3
Q

What type of filaments extend from the nuclear envelope to the periphery of the cell?

A

intermediate filaments

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4
Q

T or F: intermediate filaments are very important in maintaining integrity of epithelial cells and muscle cells.

A

T

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5
Q

What filaments originate in a perinuclear fashion and extend to the periphery of the cell?

A

Mictotubules

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6
Q

Explain the structure of the microtubule?

A

alpha and beta dimers combine at ± end to make 13 protofilaments that join to make a hollow tube

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7
Q

T or F: in vitro tubulin can be placed into a tube and when it reaches a certain threshold concentration it polymerizes from positive and negative ends.

A

True - but growth at the + end proceeds much faster

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8
Q

What is always present in cells to induce microtubule formation?

A

some type of organizing center (site of nucleation)

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9
Q

Why are nucleation sites needed in vivo?

A

Because cellular concentrations of tubulin are not high enough to induce spontaneous microtubule formation

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10
Q

What part of the microtubule always inserts in the nucleation site and where on the nucleation site does it insert?

A

Negative (alpha) side of the tubule enters the gamma tubulin ring complexes on the centriole

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11
Q

T or F: in the absence of any other chemicals as well as in the cellular environment, tubulin will sponaneously assemble and disassemble at the - end?

A

False, it will assemble and disassemble at the + end

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12
Q

What happens in a growing microtubule?

A
  • tubulin with bound GTP add to the end of the microtubule
  • addition of dimers proceeds faster than GTP hydrolysis
  • creates a GTP cap
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13
Q

What happens in a shrinking microtubule?

A
  • Protofilaments containing GDP tubulin peel away from the microtubule wall
  • GDP tubulin is released to the cytosol
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14
Q

T or F: in the absence of any stimulation tubulin will undergo dynamic instability

A

True

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15
Q

What family of motor proteins moves toward the positive end of microtubules?

A

Kinesins

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16
Q

What family of motor proteins moves to the minus end of microtubules?

A

Dyenins

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17
Q

What is the movement of globular heads in both motor proteins dependent on?

A

ATP

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18
Q

What is the determining factor for what type of cargo can be transported b motor proteins?

A

Their tale

19
Q

What situation garuntees and in tact microtubule?

A

GTP bound tubulin binding, exceeds the rate of tubulin hydrolysis

20
Q

T or F: bidirectional vesicles contain both dyeinin and kinesin?

21
Q

What feature of kinesin and dyeinin insures that they won’t fall off the microtubule track?

A
  • They have processive movement driven by ATP hydrolysis

- They always have one globular domain in contact with the MT

22
Q

What controls expansion and contraction of the ER?

A

Microtubules

ER follows them

23
Q

Explain the movement and motor proteins used in transport of proteins out of the ER, into the golgi and out of the cell

A

Kinesin - moves protein transport vesicle to ER exit site

Dynein - pulls vesicle into the Golgi

Kinesin - pushes the vesicles out of the golgi and out of the cell

24
Q

How does the golgi maintain its perinuclear position?

25
Explain the arrangment of mircrotubules in cilia and flagella
9 (doublets) surrounding 2 singlets
26
What do the 9 cytoplasmic doublets have?
- ciliary dynein arms - nexin links - radial spokes
27
What do the accessory proteins (those other than dynein and tubulin) do for the cilia?
They prevent sliding between microtubules and turn it into bending
28
What is kartagener syndrome?
Defect of dynein heads
29
T or F: defects in any of the ciliary proteins can cause defective cillia
T
30
What is the roles of primary cilia?
- chemo and mechanosensors - vital to embyonic development - COMPLETELY Immotile
31
Where can primary cillia be found and what is their structure like?
- Single ones are present on cells | - They contain no motor proteins, only 9 doublets and axoneme membrane
32
What is the major check check point in mitosis?
Spindle attaches to chromosome on two different sides
33
What happens to microtubules in interphase before mitosis, what is this dependent on?
they must shorten -Action is dependent on catastrophins that destabilze and MAPs that stabilize microtubules
34
What is the kinetochore?
Differentiated part of the centromere where kinetochore microtubules attach -2 and both must be engaged for mitosis
35
What protein joins sister chromatids?
cohesin
36
What protein degrades cohesin?
separase
37
What is anaphase A, what type of spindles are responsible?
Poleward movement of chromosomes that is depedent on shortening of KINETOCHORE mictrotubules
38
What are the two phases of anaphase B?
Interpolar microtubules slide and lengthen using kinesin aster microtubules pull using dynein at the same time
39
What drugs bind the tubulin dimer and block assembly?
Vinblastin and vincristine
40
What is anaphase A dependent on?
depolymerization of kinetochore microtubules of mitotic spindle
41
T or F: taxol will have an effect on the ER in cells other than cancer.
True
42
What classes of microtubules contribute to chromosome segregation?
interpolar, kinetochore, astral
43
What is the most common type of mutation that effect dynamic instability?
Missence mutations Other mutations are too detrimental