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CTO 1 > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

1
Q

What are the 2 main types of actin filaments how do they form actin fibers?

A

Globular actin (g-actin) and fibrullar actin (f-actin). F-actin is composed of ATP bound g-actin, which automatically assemble with the addition of ATP. F-actin is polarized, with a + and a - end. Only the + end grows, and only the - end comes apart.

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2
Q

Describe F-actin disassembly.

A

F-actin is composed of g-actin bound to ATP. When ATP is hydrolyzed to ADP and P, the g-actin disassociates. This happens at the - end.

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3
Q

What factors mediate whether G-actin forms F- actin?

A

The presence of ATP, Mg, and K.

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4
Q

List 6 functions of actin filaments.

A
  1. Terminal web
  2. intracellular movement
  3. microvilli
  4. filipodia,lamellapodia
  5. structural attachment (zonula adherens)
  6. contractile rings (during cytokinesis)
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5
Q

Describe the distribution of actin throughout the cell.

A

Actin is much more prevalent towards the borders of the cell, forming the terminal web.

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6
Q

How does actin facilitate cellular movement?

A

Actin forms the terminal web. When the actin filaments in the terminal web grow, they push the plasma membrane out and form extensions extracellularly.

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7
Q

List 7 actin binding proteins.

A

myosin, tropomyosin, gelsolin, villin, alpha-actinin, fibrinin, formin

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8
Q

What does myosin do?

A

A motor protein that moves actin. It can move vesicles/organelles or, it bound to the membrane, it will move the actin filament itself.

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9
Q

What does tropomyosin do?

A

Important in muscular contraction, it binds to and stabilizes actin. Certain subtypes may act to shield the actin binding sites from myosin.

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10
Q

What does gelsolin do?

A

Cuts actin filaments in the middle.

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11
Q

What does villin do?

A

It is an actin bundling protein.

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12
Q

What does alpha-actinin do?

A

It is an actin bundling protein.

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13
Q

What does fimbrin do?

A

It is an actin bundling protein.

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14
Q

What does formin do?

A

It is an actin branching protein.

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15
Q

List 3 substances that disrupt the normal functioning of actin filaments and describe how they do this.

A

Cytochalisin B and C- prevent the polymerization of g-actin into f-actin.
Palloidin- found in mushrooms- prevents the depolymerization of f-actin into g-actin

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16
Q

How thick is f-actin?

A

7 nm

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17
Q

What does MTOC stand for and why is it important?

A

Microtubule organizing center- MTs are organized in such a way that they all begin at a MTOC (usually a basal body;cilia or a centrosome) and radiate outwards

18
Q

Describe how a MT is made and its structural composition.

A

each strand is comprised of alternating alpha and beta tubulin monomers. They rely on the presence of GTP and will spontaneously polymerize. 13 of these alpha/beta strands will H-bond together to form a MT. Growth occurs at the + end.

19
Q

Describe the disassembly of a MT.

A

Disassembly occurs with the conversion of GTP to GDP and P. MTs also disassociate from the + end. The - end, comprised of g-tubulin, does not dissociate from GTP and therefore is quite stable.

20
Q

Describe the relative functions of a/b/g-tubulin

A

a and b tubulin alternate to create single strands of tubulin polymer, 13 of which will go on to form a MT.

g-tubulin is found near the MTOC and forms the base for the entire MT

21
Q

List 5 MT functions

A
  1. Intracellular Transport- via dyneins and kinesins
  2. Cilia
  3. Mitosis- chromosome movement
  4. Organelle/vesicle movement
  5. shape/structure of the cell- via extended MTs w/ capping proteins
22
Q

What are dyneins and kinesins?

A

Motor proteins on MTs that are important in cell transport. Kinesins move towards the + end and dyneins move towards the - end.

23
Q

Describe the structure of a motile cilia.

A

Have a 9+2 MT organization and powered by dyneins that move along the inside 2 MTs. Dyneins cause the MT to bend and then passively “snap” back. Cilia MTOCs are basal bodies and can often be seen as a dark layer underneath the cell membrane on slides.

24
Q

What does vinblastine do?

A

drug disrupting MT polymerization

25
Q

What does taxol do?

A

drug disrupting MT depolymerization

26
Q

was does cholchicine do?

A

disrupts MT polymerization

27
Q

How thick are MTs?

A

25 nm

28
Q

Describe the structure of an Intermediate filament.

A

composed of staggered tetramers of coiled dimers. two short chains will coil around each other to form a dimer (has polarity). The two dimers will then associate in an antiparallel manner to form a tetramer, destroying the polarity. These tetramers will associate in a staggered way, and 8 strands of staggered tetramers will coil to form an IF.

29
Q

What is a major distinguishing factor between IF, actin, and MTs in terms of their dynamic nature?

A

Actin and MTs are dynamic and remodel constantly. IFs do not dynamic, making them strong and stable.

30
Q

The primary function of IFs is what?

A

Strength/stability/structure of the cell

31
Q

Why can IFs be important in cancer cases?

A

Every type of cell has a different type of IF. If you can identify the IF in the cancerous cell, you can identify where the cell came from.

32
Q

What is the IF found in skin cells?

A

keratin

33
Q

What is the IF found in connective tissue/mesenchyme?

A

Vimentin

34
Q

What is the IF found in muscle?

A

Desmin

35
Q

What is the IF found at the nucleus?

A

Lamins

36
Q

What is the IF found in neural cells?

A

neurofilament

37
Q

What is the IF found in glial cells?

A

GFAP

38
Q

Where do different types of IFs differentiate themselves?

A

proteins at the end. middles are conserved usually

39
Q

What determines the transport speed of kinesins and dyneins?

A

The affinity for the cargo. If it is dropped more often, it will take longer to move.

40
Q

What are the 3 main components of the cytoskeleton in ascending order of size?

A

Actin filaments, intermediate filaments, microtubules

CTO 1 (8 decks)

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