Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

bio 428 > lec 11- intermediate filaments > Flashcards

lec 11- intermediate filaments Flashcards

(74 cards)

Start Studying
1
Q

what are intermediate filaments?

A

-strong, but flexible cytoskeletal components that provide mechanical support for multicellular animals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

are intermediate filaments found in plants?

A

no, but are seen in prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what was the original reason behind the name intermediate filament?

A

-had an intermediate size based on its thickness, it being between that of myosin and actin in skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the new reason behind the name intermediate filament?

A

it is based on its size (10 nm) in diameter being between actin (6 nm) and microtubules (25nm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are intermediate filaments involved in? how do they do it?

A

-mechanical support for cells
-done by attaching to 2 different types of cellular junctions known as desmosomes (between cells) and hemidesmosomes (between cells and extracellular matrix)
-them attaching to the junctions provides tissues their mechanical integrity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

are intermediate filaments also found in the nucleus, lining the inside of the nuclear envelope?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how many intermediate filament protein genes are there?

A

70 in humans, grouped into 6 classes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

are intermediate filaments expressed selectively in different cells types?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the structure of IF?

A

-they all have an alpha helical coiled coil rod-like core and variable N and C terminal domains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what makes an apolar protofilament?

A

-2 monomers form polar coiled-coil dimers
-antiparallel staggered tetramers from 2 coiled coil dimers form Apolar protofilaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what makes protofibril?

A

2 protofilaments make a protofibril

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what makes an intermediate filament?

A

4 protofibrils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

is it known how IFs form in vivo?

A

no, because there are no known nucleating, capping, sequestering, or severing proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why are IFs stable?

A

because their subunits exchange very slowly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

are IFs highly resistant?

A

yes, resist high temp, salt concentrations, and detergents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

can IFs act as tracks for cargo?

A

no, but can be cargo travelling on microtubules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what do post translational modifications (mainly phosphorylation) do to IFs?

A

-often destabilizes them and blocks their assembly
-occurs during mitosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what does the specific protein kinase Cdk-1CyclinB do to IFs?

A

phosphorylates 2 sites flanking the rod domain of one of the nuclear IFs causing the disruption of the head to tail overlap needed for elongation and lateral association of the IF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what does phosphorylation cause in Nuerofilaments (IFs in the nucleus)?

A

phosphorylation stabilizes the filaments by binding their large C-terminal ends

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what IF proteins do epithelial, muscle, and mesenchymal cells have?

A

-epithelial cells: class 1 and 2 keratins
-muscle cells: desmins
-mesenchymal cells: vimentin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

do tumor cells express a lot of intermediate filament protein based off of the differentiated cells that they arose from?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is hair made of?

A

keratin intermediate filaments that are chemically crosslinked to each other and associated with matrix proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

14% of hair is what?

A

cysteine residues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

when hair burns, what makes the smell?

A

disulfide bonds, the burning of the bonds causes a tough material to be formed that can be modified

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
what are the 2 classifications of keratin?
alpha and beta keratin
26
what is the structure of alpha and beta keratin?
-alpha keratin: primarily alpha helices -beta keratin: primarily beta sheets
27
what causes keratin to become stronger or flexible?
1. different structures of keratin being used 2. disulfide bridges 3. the amount of water absorbed 4. other matrix proteins
28
do hagfish shoot out IFs that are packed and then unravel when in water to disrupt predators?
yes
29
how was the function of IFs discovered in 1991?
-a mutant mouse that had a shortened form of keratin-14 in the basal layers of its skin was made by Elaine Fuchs - it resulted in the mouse to have extreme blistering and mild trauma -the phenotype resembled EBS -sewuencing of keratin-14 in EBS patients showed a mutation in the conserved arginine 125 residues
30
can IFs stretch 33% of their size and then return to their native state without breaking?
yes
31
what happens when an IF stretches more than 33% of their size?
the a helices turn into B sheets and it cant recoil
32
what is the max an IF can be stretched before breaking?
250%
33
what is the max an IF can be stretched to where it can still return to its native state?
133%, beyond that they buckle
34
what's the largest family of IF binding proteins?
-Plakins: BPAG, Plectin, Desmoplakin, Envoplakin, and more
35
what does Plectin do?
-found in most tissues but not neurons, binds to IFs, actin, and microtubules
36
what do vimentin based intermediate filaments in embryonic tissue do?
-stabilize the positions of organelles and enhance the elastic behaviour of cells
37
what do cytoplasmic IFs associate with in cells?
-nucleus -mitochondria -golgi apparatus
38
IFs binding to organelles can control what?
the organelle's shape and position
39
cytoplasmic IFs bind to the nuclear envelope through what?
envelope proteins
40
what do the envelope proteins with cytoplasmic IFs that bind to the nuclear envelope form?
the LINK complex
41
can IFs also bind indirectly to the nucleus through microtubules or actin associated proteins that bind to the LINK complex?
yes
42
what does Nesprin3 do?
binds to IFs through plectin
43
what binds to mitochondria?
-keratin, vimentin, desmins, and neurofilaments
44
what do the IF binding proteins and neurofilaments do to mitochondria?
influence its distribution and their metabolic functions
45
how does vimentin bind to mitochondria?
through plectin 1b
46
vimentin KO mice have mitochondria that are?
-more motile and mitochondrial shape, membrane potential and ATP production are altered -odd shaped mitochondria but normal functions
47
what happens to different keratins when intermediate filaments are altered during actin based motility?
-keratins 6, 16, and 17 are increased -keratins 1 and 10 are decreased
48
do invasive tumours have an increased number of IF proteins ?
yes
49
what is an EMT?
when an epithelial transforms from a cell in tissue to one that will migrate during cancer that is an epithelial to mesenchymal transformation (EMT)
50
what is a marker for EMT?
vimentin
51
IF depletion usually causes what?
a decrease in the speed of cell movement
52
what does keratin 14 do?
increases the migration of breast cancer cells
53
are the effects of keratins cell type specific?
yes
54
what does keratin 19 do?
increases invasion of hepatocellular cancers, but decreases invasion by breast cancer
55
are IFs also in lamellipodia?
yes, but lamellipodia are mainly actin-rich structures
56
mutations to IFs or the junctions they dock to cause what?
blistering diseases
57
what does Epidermis bullosa simplex result in?
extensive blistering and sensitivity to mechanical stress, skin rips off during birth
58
do most animals without keratin 8 or 18 die embryologically, but if they survive they have a few problems?
yes
59
what happens to Desmin KO mice?
they survive but will die with vigorous exercise
60
what happens to humans with Desmin mutations?
they have muscle failure
61
do most organisms have genes for actin and tubulin? do actin and microtubules both use nucleotides for polymerization that evolved independently?
yes for both
62
is it thought that the ancestral actin precursor is half the size of current actin?
yes
63
how was the actin of today made?
a gene duplication of the actin precursor
64
do prokaryotes have genes for actin?
yes
65
how is actin in prokaryotes different and similar?
-their sequences have diverged, but are structurally similar -while eukaryotic actin is formed by 2 strands aligned in the same direction and form a helix, prokaryote actin is single stranded but with strands in the opposite direction
66
eukaryote actin came from what organism?
an orgnanism related to the archaeans known as Lokiarchaeota
67
has lokiarchaeota also been thought to have given rise to eukaryotes?
yes
68
has duplication of actin genes given rise to actin related proteins?
yes
69
what is the protein in bacteria and Archaean that is similar in function to tubulin but has essentially no sequence similarities?
Fts-Z
70
what is Fts-Z? what does it do?
-a protein that has the same fold as tubulin -monomers of GTP-Fts-Z do not form tubulin, but do form protofilaments
71
GTP hydrolysis by Fts-Z causes the protofilaments to?
disassemble
72
do eukaryotes have the Fts-Z gene?
yes, from symbiosis
73
what does Fts-Z in chloroplasts do?
it is involved in the division of chloroplasts but not mitochondria
74
what is known about the evolution of IFs?
-the genes of IFs are scattered throughout the phylogenetic tree and have been aquired and lost over the past billion years -some bacteria have IFs

bio 428 (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions