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Intro. to Microbiology - Part 1 > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

- Characteristics & Function - structure & function of microtubules - dynamic instability - MT - organizing center - MT - associated proteins - Structure & function of actin filaments - structure & function of intermediate filaments

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Biology 101 flashcards
1
Q

cytoskeleton determines

A
  • organization

- polarity

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2
Q

a cell has to:

A
  • be correctly shaped
  • be physically robust
  • be internally structured
  • change its place and move from place to place
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3
Q

3 different types of filaments that compose the cytoskeleton

A
  1. Actin filaments
  2. Intermediate filaments
  3. Microtubules
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4
Q

Actin filaments

A
  • determine shape of cell

- necessary for cell locomotion

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5
Q

Microtubules

A
  • determine positions of membrane-bound organelles
  • direct intracellular transport
  • form mitotic spindle
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6
Q

Intermediate filaments

A
  • provide mechanical strength
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7
Q

tubulin

A
  • protein polymers that makeup MT

- subunit that is a heterodimer (alpha and beta)

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8
Q

alpha-tubulin

A
  • has a binding site that holds GTP

- GTP that is bound is never hydrolyzed or exchanged

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9
Q

beta-tubulin

A
  • has a binding site that can hold either GTP or GDP

- exchangable

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10
Q

MT characteristics

A
  • hollow cylindrical structures made out of protofilaments
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11
Q

protofilaments

A
  • composed of alpha-beta tubular heterodimers
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12
Q

How do microtubules grow and shrink?

A

process: dynamic instability

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13
Q

dynamic instability

A
  • binding and hydrolysis of GTP that occurs only in the beta subunit of tubular dimer
  • addition of GTP-containing tubular to end of protofilament -> growth
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14
Q

Microtubules originate from a specific cellular location

A

microtubule organizing center (MTOC)

- e.g. in animal cells -> centrosome is major MTOC

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15
Q

MT function during cell division

A

when cell divides, MT rearrange to form a bipolar mitotic spindle
- this is responsible for aligning and segregating the chromosomes

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16
Q

Microtubule-associated proteins (MAPs)

A
  • move along MT bringing transport vesicles to target organelles in the cell
  • can move organelles and vesicles in the cell
  • can move vesicles with pigments in the skin
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17
Q

kinensin

A

travels toward plus end

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18
Q

dynein

A

travels toward minus end

19
Q

melanosomes

A

pigments

20
Q

flagella

A

used to move cells in a liquid environment

- e.g. spermatozoids

21
Q

cilia

A

move fluid above a cell

- e.g. mucus in respiratory epithelium

22
Q

MT- Specific Drugs

A
  • Taxol: binds & stabilizes MTs

- Colchicine, colcemid, vinblastine, vincristine, nocodazole: binds subunits and prevents their polymerization

23
Q

Taxol (Paclitaxel)

A
  • anticancer chemotherapy
  • blocking Mts to kill cancer cells
  • blocks depolimerization
24
Q

Colchicin

A
  • alkaloid of the autumn crocusses
  • binds free tubular -> prevents MT polymerization and cell division
  • anti-inflammatory effects
25
Q

Vinca alkaloids

A
  • binds free tubulin -> prevents MT polymerization and cell division
26
Q

Actin

A
  • form a tight, right-handed helix called filamentous actin (F-actin)
  • consists of 2 parallel protofilaments
  • helix
  • flexible structure
27
Q

Actin filament

A
  • polymerize to grow
  • depolymerize
  • ATP bound actin has higher affinity for neighboring subunit and remains stable in the filament
  • ADP bound actin can more easily dissociate from filament
28
Q

Actin crosslink

A

villin, fimbrin

29
Q

Stress fiber

A

contractile bundle

30
Q

Cell Cortex

A

gel-like network

31
Q

Filopodium

A

tight-parallel bundle

32
Q

Actin-associated proteins & muscle contraction

A
  • kinesin
  • myosin
  • dynein
33
Q

tropomyosin

A
  • blocks myosin-binding site
34
Q

myosin-binding site

A
  • exposed by Ca2+-mediated tropomyosin movement

- a lot of Ca2+ present in sarcomere

35
Q

ATP + Ca2+

A
  • needed to walk along actin filament (movement)
36
Q

Phalloidin

A
  • toxin of the death cap - toxic esp. to liver cells
  • binds actin filaments & blocks depolimerisation
    • stabilization
    • cell not able to move or maintain homeostasis
  • alpha-amanitin inhibits RNA-Polymerase II
    • main toxicity of the death cap
37
Q

Intermediate filaments

A
  • no polarity (+/-)
  • subunits don’t contain ATP or GTP
  • don’t play a role in cell movement
  • no motor proteins associated
  • BUT, associated with:
    • cell-cell junctions
    • strengthening cells and epithelia
    • giving tissues mechanical stability
      • mechanical resistance: prevents separation of skin
38
Q

monomer

A

one protein

39
Q

in final intermediate filament

A
  • there are 16 dimers of IF monomers = 32 coiled coils
  • very strong structure
  • network of noodles in cell
40
Q

keratin filaments

A
  • intermediate filament
  • produced by keratinocytes in the epidermis
  • made up of keratin (subunit)
  • formation of horns, nails, hair
  • anchoring of epithelial cells via desmosomes/hemidesmosomes
41
Q

cytoskeleton components of MICROFILAMENTS

A
  • 2 helical crossed ACTIN strands
  • thinnest diameter
  • subunit: ACTIN
  • functions:
    • maintains cells shape
    • changes cells shape
    • muscle contraction
    • cell movement
  • in periphery of cell, sometimes running parallel
42
Q

cytoskeleton components of MICROTUBULES

A
  • tubes of strands per MT
  • thickest in diameter (has a lumen)
  • subunit: alpha and beta-tubulin
  • functions:
    • maintains cell shape
    • cell movement
    • chromosome movement during cell division
    • movement of organelles
  • comes from organizing center (centrosomes) and spreading towards cell periphery
43
Q

cytoskeleton components of INTERMEDIATE FILAMENTS

A
  • long molecules polymers
  • subunit: keratin, lain, vimentin (all proteins)
  • functions:
    • maintains cell shape
    • mechanical shape
    • formation of nuclear lamina
  • distributed along whole cytoplasm of cell, building NETWORK of filaments in cytosol

Intro. to Microbiology - Part 1 (11 decks)

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