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cell bio cytoskeleton composition > cytoskeleton features > Flashcards

cytoskeleton features Flashcards

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Biology 101 flashcards
1
Q

the cytoskeleton is made up of 3 structures, which are…

A

Microfilaments (7nm), intermediate filaments (8-10 nm), and microtubules (25 nm)

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2
Q

Actin: how many genes do I have? What are my varieties?

A

6.
4 are expressed in muscle cells and 2 in non-muscle cells.

alpha-actin (found in muscle)
beta-actin (non-muscle actin)
gamma (non-muscle actin)

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3
Q

T/F: Actin does not bind directly to transmembrane proteins?

A

False: it binds directly or indirectly

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4
Q

Actin monomers = ___? Actin filaments = ____ ?

A

G-actin and F-actin

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5
Q

“Treadmilling” refers to-

A

equilibrium between polymerization and depolymerization of G-actin to F-actin

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6
Q

Low concentrations of G-actin favor what process?

A

depolymerization

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7
Q

High concentrations of G-actin favor what process?

A

polymerization

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8
Q

What end of F-actin does G-actin polymerize most quickly?

A

the plus (+) end, barbed

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9
Q

the “slow” moving end of F-actin is called the

A

minus ( - ) end, the pointed end

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10
Q

Cytochalasins

A

Prevents elongation, interrupts mitotic spindle: does job by binding to + end of f-actin

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11
Q

Phalloidin

A

Binds to actin filaments and prevents their depolymerization

Fluorescent-labeled phalloidin is used to stain actin filaments in cells

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12
Q

Latrunculins

A

Disrupts actin polymerization by binding to g actin and inducing f-actin depolymerization

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13
Q

Profilins

A

Has two functions: can exchange ADP for ATP on G-actin, favoring polymerization at barbed end OR it can prevent G-actin from polymerization by holding on to molecule monomer

“Suppresses nucleation”

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14
Q

Cofilin

A

An actin depolymerization factor: stimulates dissociation of ADP bound g-actin

Triggers depolymerization at the minus end

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15
Q

Thymosin

A

Sequesters pools of g-actin monomers within a cell.

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16
Q

Gelsolin

A

Dual role: capping protein to prevent loss and addition of actin monomers; a severing protein

Destabilizes f actin and caps actin filaments, preventing loss and addition of g actin

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17
Q

Spectrin

A

RBC relation actin binding protein, connects cytoskeleton to plasma membrane

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18
Q

Dystrophin

A

Connects cytoskeleton to plasma membrane

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19
Q

Villin and fimbrin

A

Cross connecting proteins in microvilli

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20
Q

Calmodulin

A

Cross links actin filaments to microvilli cytoplasm

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21
Q

Myosin 1

A

Cross links actin filaments to microvilli cytoplasm

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22
Q

Alpha actinin

A

Cross links stress fibers and connects actin to cytoplasm complexes

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23
Q

Filamin

A

Cross links actin at wide angles to form screen like gels

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24
Q

Parallel bundles

A

Closely spaced f-actin fibers with the same polarity

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25
Q

Contractile bundles

A

Utilizes alpha actinin: actin fibers spaced widely apart, cross connected by alpha actinin

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26
Q

What causes nucleation?

A

Random collisions, which explains the high rate of polymerization when concentrations of actin are high

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27
Q

What stabilizes actin as formins nucleate along unbranched stretches of f-actin?

A

tropomyosin

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28
Q

Intermediate filaments are ___ thick, and are ___ in all cells subject to ___________

A

8-10 nm, abundant, mechanical stress

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29
Q

What do intermediate filaments do per say?

A

Provide tensile strength in cells such as neurons and muscle

30
Q

IF: All have a common monomer consisting of-

A

a central alpha helical rod flanked by a head and tail domain

31
Q

I consist of repeating amino acid segments: what am I, what’s my name?

A

intermediate filament, “heptads”

32
Q

Coiled-coil alpha helix dimers OR parallel _________. What am I?

A

intermediate filaments

33
Q

Structure of the intermediate filaments (5 levels)

A

a. polar filament monomer (N end/C end) align like polar groups, forming a DIMER
b. dimers align in antiparallel fashion, forming a TETRAMER
c. tetramers coil around one another to form PROTOFILAMENTS
d. protofilaments align to form PROTOFIBRILS
e. 4 protofibrils coil together to form a 10 nm thick intermediate filament

34
Q

What aspect of intermediate filaments allow them to bind to other elements in the cytoskeleton?

A

the N terminal and C terminals

35
Q

T/F

The formation of a nonpolar helical structure consisting of two nonpolar antiparallel tetramer requires ATP to occur.

A

F, no ATP involved. Spontaneous.

36
Q

IFAPS: What am I, what is my role, and how might I operate?

A

Intermediate filament associated proteins (IFAPS)

Stabilize filaments by cross linking adjacent filaments or by linking to other cytoskeletal elements

May cap filaments to prevent further elongation

37
Q

IFAPS: list ‘em

A 
Filaggrin (associated with keratin)
Epinemin
Paranemin
Plectin
Synemin
38
Q

Synemin

A

IFAP

39
Q

Epinemin

A

IFAP

40
Q

Filaggrin

A

IFAP, associated with keratin

41
Q

Plectin

A

IFAP

42
Q

Paranemin

A

IFAP

43
Q

Type I IF Type

A

Acidic Keratins

along with basic to neutral keratins, these form the intermediate filaments of the epithelial cell cytoskeleton

44
Q

Acidic Keratins

A

form the intermediate filaments of the epithelial cell cytoskeleton

associated with plaques of desmosomes and hemidesmosomes

45
Q

Type II

A

Basic Keratins, along with acidic keratins they form the intermediate filaments of the epithelial cell cytoskeleton

46
Q

Vimentin

A

Type III IF, found in mesenchymal cells

47
Q

Desmin

A

Type III IF, associated with sarcomeric Z-discs

48
Q

Glial fibrillary acidic protein

A

Type III IF associated with astrocytes and Schwann cells (glial cells)

49
Q

Peripherin

A

Type III IF associated with neurofilaments

50
Q

Neurofilaments

A

Type IV IF, found in axons and dendrites

51
Q

Nuclear Lamins

A

Type V nuclear lamins: provide mechanical support for inner membrane of nuclear envelope and bind chromatin

52
Q

Nestin

A

Type VI IF associated with CNS stem cells

53
Q

Microtubules are ____ in width, and composed of ____ and _____

A

25 micrometers

alpha (negatively charged end) and beta (positively charged)

54
Q

A “protofilament” in the microtubulin category consists of

A

a longitudinal row of tubulin

55
Q

Microtubules are composed of

A

alpha and beta tubulin dimers strung together to form long rows of them

56
Q

A microtubule is composed of

A

13 protofilaments arranged parallel to form a cylinder with a hollow core

57
Q

13 is the magic number for what molecule?

A

microtubules: the number of protofilaments in a “microtubule”

58
Q

Dynamic instability refers to

A

“alternating phases of slow growth and rapid depolymerization”

59
Q

What causes dynamic instability?

A

the hydrolysis of GTP tubulin dimers, which release GDP dimers subunits

60
Q

MAPs —->

A

microtubule associated proteins: increase stability of microtubules

61
Q

Factors that inhibit microtubule polymerization—>

A

colchicines, colcemid, vincristine, and vinblastin: bind to tubulin monomers and inhibits polymerization

62
Q

Factors that inhibit depolymerization and stabilize microtubules

A

taxol: binds to microtubule and inhibits depolymerization

63
Q

Cilium: structure

A

9 peripheral doubles + central pair of microtubules

64
Q

Each doublet consists of

A

alpha tubule: this consists of 13 protofilaments, radial spokes extending to sheath around central pair, and pairs of dynein arms projecting to beta unit of next doublet

65
Q

alpha tubule

A

consists of 13 protofilaments, radial spokes extending to sheath around central pair, and pairs of dynein arms projecting to beta unit of next doublet

66
Q

beta tubule

A

10-11 protofilaments

67
Q

13 protofilaments = the

A

alpha tubule

68
Q

10-11 protofilaments = the

A

beta tubule

69
Q

which protofilament has the dynein arm stretching to its neighbor?

A

the alpha

70
Q

which protofilament contains spokes which radiate toward the sheath around the central pair?

A

the alpha

71
Q

rod like portion refers to what cytoskeletal component and what is it called

A

IF, formed by polymerization of long, rod like elements

coiled-coil alpha helix dimers or parallel intermediate filament proteins

referred to as “heptad”

cell bio cytoskeleton composition (2 decks)

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