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DEN 7101F - Human Structure and Function > Exam 1 9/8 Kingsley > Flashcards

Exam 1 9/8 Kingsley Flashcards

1
Q

3 major components of the cytoskeleton

A
  1. microfilaments
  2. intermediate filaments
  3. microtubules
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2
Q

Synonymous names for microfilaments

A

thin filaments, actin filaments

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3
Q

Describe the structure of microfilaments (actin filaments)

A

G-actin monomers polymerize –> coil to form F-actin (filamentous form)

2 chains of globular protein, 6-8 nm thick

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4
Q

G-actin makes up how much of cellular actin content?

A

Half

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5
Q

Critical concentration of free actin is 0.2 micromoles, is lower than actual intracellular concentration. It should all polymerize, but why doesn’t it?

A

G-actin is bound by profilin and beta thymosin. Prevents polymerization until needed

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6
Q

Actin polymerization requires:

A

ATP

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7
Q

What is hydrolyzed during actin polymerization?

A

ATP; ADP becomes trapped in polymer

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8
Q

What monovalent cation is required during actin polymerization?

A

K+

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9
Q

What divalent cation is required during actin polymerization?

A

Mg2+

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10
Q

What terminates f-actin elongation?

A

capping proteins that attach to + end. gelsolin, cofilin, and severin are the capping proteins listed

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11
Q

What regulates f-actin capping proteins?

A

ADP, ATP, Ca2+

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12
Q

What removes f-actin capping proteins?

A

Polyphosphoinositide. This facilitates f-actin lengthening

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13
Q

Examples of actin-binding proteins

A

myosin, gelsolin, fimbrin, spectrin, talin, alpha-actinin

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14
Q

What are 3 main functions of actin-binding proteins?

A

capping, forming actin bundles, motility/adhesion

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15
Q

Actin filaments form:

A

bundles

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16
Q

Actin filaments vary in ____, which is determined by _____

A

length; function (non-muscle)

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17
Q

What are 3 main types of actin bundling?

A
  1. contractile bundling
  2. gel-like networks
  3. parallel bundles
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18
Q

What are some functions of contractile bundles?

A
  1. movement of organelles and vesicles
  2. endocytosis/exocytosis
  3. filapodia
  4. mitotic division (contractile rings)
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19
Q

contractile bundles are associated with:

A

myosin

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20
Q

How are contractile bundles arranged?

A
  1. loosely arranged and branched
  2. parallel to each other
  3. alternating + and - ends (myosin binding helps determine polarity)
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21
Q

Myosin I function

A

formation and retraction of cell protrusions

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22
Q

Myosin II function

A

forms thick filaments (15 nm), moves actin filaments (muscle)

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23
Q

Myosin V

A

participates in vesicle movement along actin

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24
Q

Describe gel-like bundles

A

membrane and cytoplasmic actin-rich network, maintains cell shape and structure, linked with other proteins

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25
Q

Parallel bundles have closely packed F-actin associated with:

A

fimbrin and villin proteins, which assemble f-actin to form microvilli

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26
Q

Villin

A

actin binding protein that stays pushed out due to gel like bundle. increases surface area in the intestines

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27
Q

Focal adhesion two main components

A

P-face ABP form attachments to cytoskeleton
E-face integrins link to ECM

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28
Q

Integrins are:

A

transmembrane glycoproteins

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29
Q

Integrins bind:

A

ECM to cytoskeleton; alpha/beta subunits bind ECM; beta subunits bind ABP; bind f-actin

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30
Q

What are filopodia?

A

actin rich membrane protrusions. Made of contractile bundles

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31
Q

Lamellipodia

A

leading edge of migrating cell, made of gel-like bundles

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32
Q

Filapodia and lamellipodia are anchored by:

A

focal adhesions; integrin mediated

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33
Q

Phalloidins

A

toxins from amanita mushroom

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34
Q

What do phalloidins do, and what is the remedy?

A

binds actin filament and prevents depolymerization (disturbs membrane flow and liver cell function). Remedy is eat raw meat to allow actin/myosin to bind phalloidin and reduce the toxicity

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35
Q

Size of intermediate filaments

A

8 to 10 nm

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36
Q

Desmosomes are a type of what kind of filament?

A

intermediate filament

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37
Q

Desmosomes function

A

anchor cell-cell junctions

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38
Q

Hemidesmosomes are a type of what kind of filament?

A

intermediate filaments

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39
Q

Hemidesmosomes function

A

anchor cell-matrix junctions

40
Q

Desmosomes and hemidesmosomes together maintain:

A

cell shape and polarity

41
Q

Structure and assembly of intermediate filaments

A
  1. monomers form coiled dimers
  2. anti-parallel dimers form tetramers
  3. Tetramer is non-polar unit of IF
  4. tetramers form protofilaments –> form protofibrils –> thus forms IF
42
Q

Tetramer subunit varies upon type of:

A

IF

43
Q

Types of IF

A

keratins, desmin, vimentin, neurofilaments, flial fibrillary acidic protein, nuclear lamins

44
Q

Why is DNA methylation mitotically heritable?

A

to maintain tissue differentiation

45
Q

DNMT I

A

DNA methyltransferase; maintains tissue differentiation during replication; active in normal, differentiated tissues

46
Q

DNMT I recognizes:

A

hemi-methylated DNA –> keeps cellular identity

47
Q

____ is highly activated in aggressive tumors

A

DNMT 3 (moves DNA methyl marks, turns of methylation genes, methylated cpg island)

48
Q

What does DNMT3 cause?

A

may expose (turn on) other genes, dysplasia

49
Q

What is a tumor marker in carcinomas

A

Cytokeratin (type of IF)

50
Q

Zona occludens another name

A

tight junctions

51
Q

Primary intercellular diffusion barrier

A

zona occludens

52
Q

Zona occludens allows for what between tissues?

A

physiochemical separation

53
Q

Where is zona occludens found?

A

apical surface between adjoining epithelial cells (ex: mucosal epithelial cells, skin cells)

54
Q

major proteins associated with zona occludens:

A

claudins, occludins –> function as seal/zipper between cells

55
Q

How to tight junctions interact?

A

Via ZO-1 (zona occludens-1) with actin in the cytoskeleton

56
Q

What is zonula adherens?

A

network of additional cell-cell junctions

57
Q

Zonula adherens is mediated via transmembrane glycoprotein _____, which is located on the E face

A

cadherins

58
Q

How do cadherins form cell-cell junctions/bind cytoskeleton?

A
  1. link to catenin, vinculin found on actin filaments
  2. alpha-actinin links adjacent actin filaments together
59
Q

Cadherins are responsible for _____ and ____ cell-cell adhesion and are _____ dependent

A

homotypic; heterotypic; Ca2+ dependent

60
Q

What do cadherins link to, and where?

A

actin filaments on neighboring cells

61
Q

Another name for desmosomes

A

macula adherens

62
Q

Function of desmosomes

A

Strong cell-cell adhesion, links intermediate filaments, provide mechanical structure

63
Q

What proteins make up desmosomes

A

Desmoglein, desmocollin (E face)
Desmoplakins, plakoglobins (P face)

64
Q

Desmoglein and desmocollin are ___ dependent

A

Ca2+

65
Q

Hemidesmosomes

A

cell-to-ecm junctions

66
Q

How do hemi-desmosomes bind cell to ECM?

A
  1. integrin heterodimers bind ECM extracellularly
  2. integrins anchored to cytoplasmic proteins, which connect to intermediate filaments
67
Q

Regarding hemidesmosomes, which proteins stabilize integrin-cytoskeleton attachment?

A

BPAG, erbin

68
Q

Focal adhesions function

A

mediates adhesion and migration

69
Q

Focal adhesions link with:

A

stress fibers

70
Q

What are two main components of focal adhesion?

A
  1. P-face ACP form attachments to cytoskeleton
  2. E-face integrins link to ECM
71
Q

How do focal adhesions bind to ECM?

A

Through integrins
- a, b subunits of integrins bind ECM
- b subunits binds ABP
- a-actinin, vinculin
- bind F- actin

72
Q

Contractile bundles function

A

movement of vesicles, organelles, cell adhesion and migration

73
Q

Filopodia

A

actin rich membrane protrusions; feet of moving cells

74
Q

Filopodia have

A

contractile bundles

75
Q

Lamellipodia

A

leading edge of migrating cell; sheet of actin mesh

76
Q

Lamellipodia have

A

gel-like bundles

77
Q

Filopodia and lamellipodia are anchored by:

A

focal adhesions

78
Q

What are microtubules/their function?

A
  1. largest cytoskeletal elements
  2. structural component of centrioles
  3. structural component of cilia, flagella
  4. intracellular vesicle transport
79
Q

Microtubule structure

A

13 circular arrays of dimerized tubulin (parallel protofilaments) - alpha/beta tubulin dimer with GTP

80
Q

Microtubule polarity is established by:

A

gamma tubulin (MTOC)

81
Q

Microtubules require both ___ and ____

A

GTP and Mg2+

82
Q

Microtubules exhibit:

A

dynamic instability

83
Q

How is dynamic instability regulated?

A

MAPs (microtubule associated proteins)
- one listed in red is tau

84
Q

Where are MAPs found? (microtubule associated proteins)

A

regular intervals along polypeptide

85
Q

Two primary functions of MAPs

A

polymerization/depolymerization assist in organelle/vesicle movement

86
Q

MAPs move ____ using ___ and ____

A

cargo; dynein(-) and kinesin (+)

87
Q

What direction does kinesin travel?

A
  • to + (anterograde)
88
Q

What direction does dynein travel?

A

+ to - (retrograde)

89
Q

______ are a primary site of MT nucleation

A

Centrosomes

90
Q

Centrioles structure

A

Nine triplets of microtubules

91
Q

What is the kinetochore?

A

complex of proteins where microtubules attach during cell division

92
Q

Where is kinetochore located?

A

centromere of chromosome

93
Q

Microtubules form ____ in cilia and flagella

A

doublets

94
Q

Microtubules form ____ in basal bodies and centrioles

A

triplets

95
Q

Flagella are powered by:

A

ATP

96
Q

Cilia are powered by:

A

ATP

97
Q

Where are cilia found?

A

mucociliary escalator (immune system); fallopian tubes

DEN 7101F - Human Structure and Function (23 decks)

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