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

Exam 1 9/8 Kingsley Flashcards

(97 cards)

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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
Parallel bundles have closely packed F-actin associated with:
fimbrin and villin proteins, which assemble f-actin to form microvilli
26
Villin
actin binding protein that stays pushed out due to gel like bundle. increases surface area in the intestines
27
Focal adhesion two main components
P-face ABP form attachments to cytoskeleton E-face integrins link to ECM
28
Integrins are:
transmembrane glycoproteins
29
Integrins bind:
ECM to cytoskeleton; alpha/beta subunits bind ECM; beta subunits bind ABP; bind f-actin
30
What are filopodia?
actin rich membrane protrusions. Made of contractile bundles
31
Lamellipodia
leading edge of migrating cell, made of gel-like bundles
32
Filapodia and lamellipodia are anchored by:
focal adhesions; integrin mediated
33
Phalloidins
toxins from amanita mushroom
34
What do phalloidins do, and what is the remedy?
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
35
Size of intermediate filaments
8 to 10 nm
36
Desmosomes are a type of what kind of filament?
intermediate filament
37
Desmosomes function
anchor cell-cell junctions
38
Hemidesmosomes are a type of what kind of filament?
intermediate filaments
39
Hemidesmosomes function
anchor cell-matrix junctions
40
Desmosomes and hemidesmosomes together maintain:
cell shape and polarity
41
Structure and assembly of intermediate filaments
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
Tetramer subunit varies upon type of:
IF
43
Types of IF
keratins, desmin, vimentin, neurofilaments, flial fibrillary acidic protein, nuclear lamins
44
Why is DNA methylation mitotically heritable?
to maintain tissue differentiation
45
DNMT I
DNA methyltransferase; maintains tissue differentiation during replication; active in normal, differentiated tissues
46
DNMT I recognizes:
hemi-methylated DNA --> keeps cellular identity
47
____ is highly activated in aggressive tumors
DNMT 3 (moves DNA methyl marks, turns of methylation genes, methylated cpg island)
48
What does DNMT3 cause?
may expose (turn on) other genes, dysplasia
49
What is a tumor marker in carcinomas
Cytokeratin (type of IF)
50
Zona occludens another name
tight junctions
51
Primary intercellular diffusion barrier
zona occludens
52
Zona occludens allows for what between tissues?
physiochemical separation
53
Where is zona occludens found?
apical surface between adjoining epithelial cells (ex: mucosal epithelial cells, skin cells)
54
major proteins associated with zona occludens:
claudins, occludins --> function as seal/zipper between cells
55
How to tight junctions interact?
Via ZO-1 (zona occludens-1) with actin in the cytoskeleton
56
What is zonula adherens?
network of additional cell-cell junctions
57
Zonula adherens is mediated via transmembrane glycoprotein _____, which is located on the E face
cadherins
58
How do cadherins form cell-cell junctions/bind cytoskeleton?
1. link to catenin, vinculin found on actin filaments 2. alpha-actinin links adjacent actin filaments together
59
Cadherins are responsible for _____ and ____ cell-cell adhesion and are _____ dependent
homotypic; heterotypic; Ca2+ dependent
60
What do cadherins link to, and where?
actin filaments on neighboring cells
61
Another name for desmosomes
macula adherens
62
Function of desmosomes
Strong cell-cell adhesion, links intermediate filaments, provide mechanical structure
63
What proteins make up desmosomes
Desmoglein, desmocollin (E face) Desmoplakins, plakoglobins (P face)
64
Desmoglein and desmocollin are ___ dependent
Ca2+
65
Hemidesmosomes
cell-to-ecm junctions
66
How do hemi-desmosomes bind cell to ECM?
1. integrin heterodimers bind ECM extracellularly 2. integrins anchored to cytoplasmic proteins, which connect to intermediate filaments
67
Regarding hemidesmosomes, which proteins stabilize integrin-cytoskeleton attachment?
BPAG, erbin
68
Focal adhesions function
mediates adhesion and migration
69
Focal adhesions link with:
stress fibers
70
What are two main components of focal adhesion?
1. P-face ACP form attachments to cytoskeleton 2. E-face integrins link to ECM
71
How do focal adhesions bind to ECM?
Through integrins - a, b subunits of integrins bind ECM - b subunits binds ABP - a-actinin, vinculin - bind F- actin
72
Contractile bundles function
movement of vesicles, organelles, cell adhesion and migration
73
Filopodia
actin rich membrane protrusions; feet of moving cells
74
Filopodia have
contractile bundles
75
Lamellipodia
leading edge of migrating cell; sheet of actin mesh
76
Lamellipodia have
gel-like bundles
77
Filopodia and lamellipodia are anchored by:
focal adhesions
78
What are microtubules/their function?
1. largest cytoskeletal elements 2. structural component of centrioles 3. structural component of cilia, flagella 4. intracellular vesicle transport
79
Microtubule structure
13 circular arrays of dimerized tubulin (parallel protofilaments) - alpha/beta tubulin dimer with GTP
80
Microtubule polarity is established by:
gamma tubulin (MTOC)
81
Microtubules require both ___ and ____
GTP and Mg2+
82
Microtubules exhibit:
dynamic instability
83
How is dynamic instability regulated?
MAPs (microtubule associated proteins) - one listed in red is tau
84
Where are MAPs found? (microtubule associated proteins)
regular intervals along polypeptide
85
Two primary functions of MAPs
polymerization/depolymerization assist in organelle/vesicle movement
86
MAPs move ____ using ___ and ____
cargo; dynein(-) and kinesin (+)
87
What direction does kinesin travel?
- to + (anterograde)
88
What direction does dynein travel?
+ to - (retrograde)
89
______ are a primary site of MT nucleation
Centrosomes
90
Centrioles structure
Nine triplets of microtubules
91
What is the kinetochore?
complex of proteins where microtubules attach during cell division
92
Where is kinetochore located?
centromere of chromosome
93
Microtubules form ____ in cilia and flagella
doublets
94
Microtubules form ____ in basal bodies and centrioles
triplets
95
Flagella are powered by:
ATP
96
Cilia are powered by:
ATP
97
Where are cilia found?
mucociliary escalator (immune system); fallopian tubes

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

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