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Cell/Histo - MV > Lecture 3 - Cytoskelton & Cell Memb. > Flashcards

Lecture 3 - Cytoskelton & Cell Memb. Flashcards

1
Q

List and describe components of the cytoskelton?

A

Micro filaments: (7nm thick) - G and F actin
Intermediate Filaments (10nm thick) The most stable of the 3, protein monomer of a central alpha helical rod flanked by head and tail domains.
Microtubules: (25nm thick) alpha and beta tubulin dimers

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2
Q

Describe functions of the cytoskeleton

A
  1. Scaffolding - define cell shape and resilency
  2. Structure - distribute forces betweens adjacent cells and between cell and basement membrane.
  3. Division and movement - Mitosis, microvilli, cilia, phagocytosis , intercellular trafficking
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3
Q

Which of the 3 components of the cytoskeleton are abundant in eukaryotic cells? and what is it comprised of?

A

Microfilaments

Actin

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4
Q

F actin present where in the body?

A

in microvilli: intestinal and renal epithelial (brush border).
in stereocillia: hair cells of inner ear.

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5
Q

What is unique about the evolution of actin and its conservation?

A

It has been Highly conserved, Yeast actin 90% similar to ours.

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6
Q

what are the 2 general structural forms of Actin?

A

F and G for filamentous and Globular

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7
Q

Actin must be bound to what in the cell?

A

Specific Transmembrane proteins

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8
Q

alpha actin is found in the?

A

muscle tissues

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9
Q

What is constant about microfilaments?

A

That they are never constant, but they are always assembling and disassembling

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10
Q

Actin is structurally made up by what?

A

F-acting is a double helical chain of G-actin subunits, that are constantly added and removed from the ends

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11
Q

What is crucial about the make up of F actin?

A

That it is polar, a + and - end.

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12
Q

The plus end contains what? is called what? and is where what occurs?

A

ATP
Barbed
Polymerization only , fastest growing,

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13
Q

The minus end contains what? is called what? and is where what occurs?

A

ADP
Pointed
poly and depolymerization occur, shortening or slowly growing.

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14
Q

What are the 3 proteins from other species used to experiment with altering the typical mechanisms of actin growth and movement?

A

Cytochalasins, Phalloidin, and Latrunculins

inhibit polymerization, inhibit depolymerization, promote depolymerization respectively.

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15
Q

What are the 4 actin binding proteins controlling the assembly and disassembly of F-actin? what is this called?

A 
Profilin, Cofilin, Thymosin and Gelsolin
polymerizes to + end, 
Depoly to - end, 
sequesters G actin, 
cuts/caps and prevents depoly.
Treadmilling
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16
Q

What is the dynamic equilibrium of an ever elongation/shortening F-actin dimer termed?

A

Treadmilling

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17
Q

The assembly and disassembly is directly related to what in the cell?

A

the concentration of the G actin. Low conc = disassembly, high conc = poly, growth.

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18
Q

Which protein in the F-actin assembly catalzes the exchange of ADP for ATP on a G actin.

A

Profilin. IMPORTANT!! that you know, G Actin can nucleate or come together and form globular proteins, instead of Filamentous ones. When EXchange and not hydrolysis occurs, by profilin, F actin can be created.

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19
Q

despite the fact that Actin has pretty much the same structure in all cells, it is involved in

A

many various throughout the body.

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20
Q

The diversity in function of Actin is Determined by what?

A

The binding proteins of Actin, NOT, actin itself.

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21
Q

Which Actin binding protein prevents actin monomers from being polymerized?

A

Thymosin and Profilin

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22
Q

Which Actin binding protein promotes F actin growth at the barbed end?

A

Profilin

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23
Q

Which Actin binding protein cuts and caps F actin?

A

Gelsolin

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24
Q

What is needed for Cutting of F Actin?

A

the presence of Calcium ions

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25
Q

Which Actin binding protein initiates growth on the sides of an existing F actin? whats this called?

A

Arp2/3

branching

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26
Q

When the ADP bound G Actin is converted to ATP bound G actin, is this hydrolysis or exchange?

A

Exchange

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27
Q

When the ATP bound F actin is converted to ADP bound F actin, is this hydrolysis or exchange?

A

Hydrolysis.

28
Q

Which Actin binding protein stimulates the dissociation of ADP bound G Actin from F actin? Where does this occur?

A

Cofilin

at the minus or pointed end of F actin

29
Q

Actin binding proteins, can also be called Actin ______ proteins?

A

Actin related proteins

30
Q

Like ARP2/3, Which Actin binding protein regulates elongation of the Actin Filament? where oin the filiament? and is associated with what structure?

A

Formin Forms a cap on
the barbed end of nonbranching actin filaments of
Microvilli

31
Q

nucleation is where what happens?

A

Site of adding more G actin to F actin. Ie. the production of filaments.

32
Q

Why does nucleation occur?

A

typically due to force or stress, or change in conc. of Actin.

33
Q

2 types of actin bundles?

A

Parallel, which are closely spaced.

Contractile, which are further apart so myosin can interact, and alpha actinin can crosslink the actin filaments.

34
Q

Intermediate filaments thickness? sturcture?

A

10nm

2 antiparallel Dimers form a staggerd tetramer and non polar tetramers bind end to end and form a helical filament.

35
Q

I.F.s Provide tensile strenth in what types of cells?

A

Neurons and Muscle cells

36
Q

I.F.s Provide strengthening to which CAM’s?

A

Hemidesmosomes and macula Adherens

37
Q

I.F.s have a common monomer that consists of?

A

central alpha helical rod flanked by head and tail domains.

38
Q

are I.F.s polar like microfilaments?

A

no, ends are the same.

39
Q

the major function for I.F.s is to proved?

A

mechanical support

40
Q

I.F.s are unique in their formation in that they?

A

form spontaneously

dont require Atp or Gtp

41
Q

which type of IF, is • Associated with plaques of desmosomes and hemidesmosomes?

A

Acidic Keratins

42
Q

•Type V , Provide mechanical support for inner membrane of nuclear envelope and bind chromatin, Name them?

A

• Nuclear lamins

43
Q

Are microtubules polar like microfilaments or non polar like IF’s?

A

They are Polar like microfilaments.

44
Q

what are 3 reasons why microtubules polarity so important?

A
  1. So they can assemble and disassemble
  2. for the separation of chromosomes during mitosis
  3. for organelles to know which way to move throughout the cell
45
Q

What are microtubules alternate phases of slow growth and rapid polymerization called?

A

dynamic instability

46
Q

5 characteristics of microtubules

A
  1. 25 nm diameter
  2. composed of alpha beta tubulin dimers
  3. 13 vertical dimers form the tube, stacked vertical dimers form protofilament
    • and minus end like actin with Beta orientated toward the + end
  5. GTP required for polymerization
47
Q

What is the ABP - actin binding protein that helps, (from actins perspective, so not cadhenins) to bind Actin to certain Cam’s and Cadherins?

A

Alpha Actin, there are a couple others mentioned in the book, see fig 1-8, like Vinculin, Formin-1 that are only to be aware of.

48
Q

What is a Heptad? which part of the cytoskeleton is it found? whats it responsible for?

A

it is a 7 aa chain of repeated aa’s
found in IF’s. intermed filaments.
Its the reason for the formation and structure of IF’s, dimers and there parallel twisted formation. key to IF’s is that they are nonpolar, as a whole, but in their most basic structure the dimer, you still have polarity, It’s lost in the next phase of the tetramer.

49
Q

Whats the difference between tubulin and tubules?

A

Tubilin is alpha and Beta units that form dimer and most basic polymer/structure in formation of microtubule.
Tubules is actual form of MT, alpha and beta tubule that form axoneme (9+2 arrangement in cilia and flaggelum)

50
Q

1 The ubiquitous cell membrane is also referred to as the?
2 the cell membrane or plasma membrane is also called the?
3 the membranes of the individual organelles is called the ?

A

unit membrane. refers to both cell memb. & organelles memb.
plasmalemma
cytomembranes

51
Q

•Most plasma membranes are made up of about ____%lipid and ___% protein by weight.

A

50% of each

52
Q

how many tails on a phospholipid?

A

2

53
Q

long or short chained fatty acids create space in which other chains can move? whats this create?

A

short chains, therefore increase fluidity of membrane.

54
Q

Saturation of fatty acid tail, means what?

A

There are no double bonds = no kinks = tightly packed = less fluidity of membrane

55
Q

of the Phospholipid bilayer what are 3 components of the Outer leaflet?

A

Cholesterol
Phosphatidylcholine
Sphingomyelin

56
Q

4 Components of Inner leaflet of Phospholipid bilayer?

which one is only found in the inner leaflet?

A

Cholesterol
Phosphatidylethanolamine
Phosphatidylserine: - charged
Phosphatidylinositol: - charged & *Important in cell signaling
- ..Nositol is Found only in inner leaflet

57
Q

•Cholesterol Moderates membrane fluidity at low OR high temps?

A

Both it actually
makes PM
Less fluid at high temps
Maintains fluidity at low temps - prevents from freezing.
I suppose you can say it really never makes it more fluid directly. But it doesn’t make it less fluid at cold temps.

58
Q

Glycolipids, are found in which leaflet? and responsible for ?

A

Outer leaflet only

provide energy and cell recognition markers

59
Q

•Lipid rafts are ?

A

Small patches of:
• Cholesterol
• Sphingolipids (sphingomyelin and glycolipids)

60
Q

•Glycocalyx? Which CAM recognizes this?

A

• Not an integral part of the membrane
• Carbohydrate coat on the extracellular surface of the cell membrane composed of carbohydrate portions of glycolipids and glycoproteins.
-Selectins

61
Q

Are peripheral proteins found mostly on outer or inner leaflet?
How can they be removed?

A

They are found on both

by altering pH or Ionic content of the environment

62
Q

What type of protein is a transmembrane protein? How can these types of proteins removed from the PM?

A
  • An integral protein - Which means its part of its intrinsic structure, basically it crosses a Hydrophillic portion and interacts with the hydrophobic region, but not necessarily goes all the way through.
  • only with detergent
63
Q

Transmembrane proteins must have what 3 basic regions? and one of them is made up of 20+ AA. of which type? are these latter portions sheets, strands or helices?

A

2 hydrophillic regions and 1 hydrophobic

Hydrophobic portion, made of Alpha helices of 20-25 AA

64
Q

The extracellular portion of integral and peripheral membrane prots, are generally ____________? why?

A

Glycosylated for recognition/communication

65
Q

Is it true that MOST integral proteins, are transmembrane prots?

A

yes and its the Alpha helical regions that span the membrane.

66
Q

2 Types of “Pass” transmembrane proteins?
examples of each? and
whats important about the type?

A

Single and multiple pass
Single: Glycophorin and Enzyme linked receptors.
Multiple: Porin, G protein Linked, GLUTs
Odd # of passes, have N and C terminus on opposite sides
Even have N and C on same side

Cell/Histo - MV (8 decks)

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