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BIOL 2030 > Ch. 17 Cytoskeleton, Intermediate Filaments, Microtubules > Flashcards

Ch. 17 Cytoskeleton, Intermediate Filaments, Microtubules Flashcards

1
Q

list the functions of the cytoskeleton

A
  • strength
  • structure
  • organization
  • movement
  • participates in cellular division
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2
Q

describe the cytoskeleton

A

internal network of proteins that helps to organize the cell and its organelles

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3
Q

is the cytoskeleton rigid/fixed in place. briefly explain

A
  • no!
  • dynamic in nature
  • rapidly-changing
  • it is integral for cells to have movement to be able to interact with their environments, therefore it would not make sense for the cytoskeleton to be fixed in place
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4
Q

how are organelles able to move around the cell due to the cytoskeleton

A

“tracks” are laid which allow for the movement

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5
Q

how does the cytoskeleton help with cellular division

A
  • able to move chromosomes around the cell **
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6
Q

what are the types of protein filaments making the cytoskeleton

A
  • intermediate filaments
  • microtubules
  • actin filaments
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7
Q

what is an alternative name for actin filaments

A

microfilaments (actin = thin filament)

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8
Q

list the protein filaments from highest to lowest size

A

microtubules, intermediate filaments, micro/actin-filaments

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9
Q

describe the general role of intermediate filaments

A

strengthens the cells against mechanical force (esp pressure on skin)

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10
Q

define a desmosome

A

structural connection between intermediate filaments in adjacent cells

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11
Q

what would happen to the skin if it did not have intermediate filaments

A

any type of stretch would rupture the cells

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12
Q

compare sheets of cells with and without intermediate filaments through a drawing to show how stretching affects each case

A

….

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13
Q

the top outside layer of the skin is able to withstand a lot of stimulation, stretching, pressure, and manipulation whilst still remaining intact. what is the top layer of the skin therefore referred to and how is this “resistance” possible

A
  • (dead) keratinocytes
  • keratin fibres (a type of IF) are able to remain there through connection by desmosomes
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14
Q

for most people, the skin is the last organ that people think to take care of, especially due to its “resistance” to manipulation. some people unfortunately are faced with problems with their skin that oppose this, such as epidermolysis bullosa simplex. those facing this condition suffer from large, painful blisters with even the slightest bit of heat or friction. why do you think that this condition happens?

A
  • genetic mutation of the intermediate filaments prevents their correct formation
  • this makes the skin extremely fragile in which the cells lyse even with gentle pressure
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15
Q

what is the main type of role for the intermediate filaments, why?

A
  • structure/strength providing
  • greater stability than microtubules and microfilaments
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16
Q

describe the appearance of an intermediate filament

A

ropelike (8 long tetramers), filaments twining to make one larger structure, 10nm in diameter

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17
Q

describe the structure of a monomer

A

alpha helical region in between amine and carboxylic acid groups at opposing ends

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18
Q

describe the structure of a dimer

A

two alpha-helices coiled around one another, with two amines and two carboxylic acids at opposing ends

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19
Q

describe the structure of a tetramer

A
  • two coils coiled around one another
  • two amines from a dimer and two COOH groups from the other dimer will be one end on both sides (opposing polarities)
  • staggered
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20
Q

what is the importance of tetramers being staggered dimers

A

improves their strength

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21
Q

what bonds are involved in dimers and tetramers

A

non-covalent bonding

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22
Q

what are the types of intermediate filaments

A
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23
Q

what remains relatively constant in all types of intermediate filaments and what does this help with

A
  • alpha-helix region (size and amino acid sequence)
  • allows for different types of monomers to bind with one another and make composite intermediate filaments
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24
Q

what varies between the intermediate filaments and what does this cause for the functions

A
  • globular head and tail regions
  • allows for different functions in different cell types
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25
Q

what are the main categories of intermediate filaments

A

cytoplasmic and nuclear

26
Q

what are the types of intermediate filaments, and what category are they part of

A
  • keratins, vimentin/vimentin-related, neurofilaments (cytoplasmic)
  • nuclear lamins (nuclear)
27
Q

where are keratin IFs predominantly present

A

epithelia (sheet tissues)

28
Q

where are vimentin/vimentin-related IFs present

A

connective tissue, muscle cells, neuroglial/neural support cells

29
Q

where are neurofilament IFs predominantly present

A

nerve cells

30
Q

where are nuclear lamin IFs present

A

all animal cells (they line inside of nuclear membrane)

31
Q

what are laminins

A

proteins found on extracellular matrix** db check

32
Q

what type of support does the nuclear envelope receive

A

meshwork of nuclear lamins

33
Q

aside from their relative location, what is the main difference between cytoplasmic IFs and nuclear IFs

A

cytoplasmic IFs are ropelike (random pattern) whereas nuclear IFs have a meshwork structure (organized)

34
Q

describe the meshwork structure of nuclear IFs

A
  • 2D
  • on inner nuclear membrane
  • strong (able to dissemble and reassemble during each cell division thru (de)phosphorylation of lamins)
35
Q

describe progeria

A
  • rare genetic disorders due to mutation of the lamins (collective term is progeria)
  • extremely fast aging starting within first 2 years of life
  • not fully understood
  • causes nuclear instability
36
Q

what may nuclear instability cause

A

interference with body’s ability of cellular division and repair

37
Q

what is the main role of microtubules

A

organization for cell interior

38
Q

describe microtubules

A
  • thickest cytoskeletal fibres
  • ability to move organelles, chromosomes, molecules around (motility)
  • present in cytoplasm of all eukaryotic cells (including cilia and flagella when present)
  • dynamic instability
39
Q

what types of roles does the microtubule have

A

structural (some) and organizational (main)

40
Q

draw out how microtubules are able to transport cargo along a nerve cell (indicate the “polarity” of the microtubules)

A

main points: all microtubules are oriented in the same direction based on the polarity which allows for directional protein transport

41
Q

for cargo transport along nerve cells, we can consider ________ as the tracks and ___________ as the engines

A

microtubules; motor proteins

42
Q

in reference to microtubule polarity what direction is inward transport, outward transport?

A
  • negative end of MT (toward end of cell body)
  • positive end of MT (toward axon terminal)
43
Q

describe tubulin structure

A

dimer of alpha and beta tubulin subunits

44
Q

describe the structure of microtubules

A
  • hollow tubes of tubulin
  • made of 13 protofilaments
  • 20-25nm
45
Q

what is a protofilament

A

ordered row of tubulin dimers

46
Q

what is a tubulin heterodimer

A

microtubule subunit (one alpha and one beta subunit)

47
Q

draw out tubulin heterodimer, protofilament, and microtubules

A

….

48
Q

what subunit of microtubules is associated with plus ends

A

beta

49
Q

what subunit of microtubules is associated with minus ends

A

alpha

50
Q

what is the major organizing center in animal cells

A

centrosome

51
Q

describe centrosomes

A
  • membrane-free organelle that organizes microtubules
  • close to nucleus
  • have gamma tubulin ring complexes
52
Q

most microtubules emanate from what region of the cell

A

nucleus

53
Q

what is the purpose of the gamma tubulin ring complexes in the centrosome

A

to act as nucleation sites for polar microtubule growth initiation from centrosome region

54
Q

which charge end of the microtubules is closest to the centrosome; furthest?

A

negative; positive

55
Q

what does it mean when we say that microtubules are dynamically unstable

A

they are constantly growing and shrinking (in a rapid and independent manner)

56
Q

what does it mean when we say that microtubules are growing and shrinking independently on the same centrosome

A

not all microtubules will shrink at the same time nor will they all grow at the same time (asynchronous)

57
Q

how is dynamic instability of microtubules foundationally possible

A

ability of tubulin molecules to hydrolyze GTP

58
Q

what is a GTP-cap

A

packed GTP-bound dimers on a growing microtubule, which help to stabilize it

59
Q

disassembly (i.e. shrinkage) of a microtubule is favoured by which bound tubulin dimer

A

GDP

60
Q

stable microtubules (growing) are able to express capping proteins on themselves. they can be further stabilized by attaching to

A

proteins in the cell thru “plus” ends

61
Q

why are microtubules in mature neurons stable

A

they have caps which can allow for permanent transport route

BIOL 2030 (16 decks)

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