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Microbiology MCM unit 1 > Cytoskeleton > Flashcards

Cytoskeleton Flashcards

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1
Q

cytoskeleton components

A

microtubules
microfilaments
intermediate filaments

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2
Q

Actin

A
  1. monomeric - globular, binds ATP and Mg2+, ATP hydrolyzed when actin assembles into filaments
  2. Filamentous - actin monomers assemble into 2 stranded helical filament
    - makes polar + and - end
    - treadmilling: ATP binding and hydrolysis at + end happening different rate than ADP release at - end
  3. Actin binding proteins - for length, force, motility, cross linking, bundling, capping, anchoring
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3
Q

microfilament distribution and function

A

membrane associated proteins bind microfilaments toPM for contraction, extension, stabilization

  • assemble actin from these nucleation points
    1. lamellipodia: branched array of actin. Actin related protein makes actin extend from branch points
    2. filopodia - unbranched, parallel protrusions of actin
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4
Q

actin function in non-muscle cell

A

Myosin I - walk along actin toward + end
- a motor for vesicles
Myosin II - assemble into bipolar filaments
- interact with actin to form thick filaments
need actin for protrusion and myosin for contraction

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5
Q

skeletal muscle fibers

A

long, multinucleated cells, contain many myofibrils which are divided into sarcomeres

    • end actin bound to z disc, - end away
  • myosin in the middle of sarcomere, centered by titin
  • myofibrils bound together by desmin intermediate
  • whole fiber bound to plasma membrane by dystrophin
  • SR surrounds each myofibril, stores Calcium
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6
Q

regulation of skeletal muscle contraction

A

Ca release -> Ca binds troponin -> troponin moves tropomyosin to expose myosin binding site on actin

ATP binding - myosin release actin = relaxation
ATP hydrolysis - myosin head cocks
phosphate release - actin binds myosin and power stroke

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7
Q

intermediate filament structure

A
  • monomeric rods coil into dimers, then tetramers, then large bundle
  • no polarity, not for motility
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8
Q

keratin

A
  • epithelial cells, hair, nails
  • for strength and a barrier
  • form desmosomes
  • can detect epithelial cancer
  • deficiency causes skin blisters
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9
Q

classes of intermediate filaments

A
  1. keratin
  2. vimentin, desmin, glial fibrillary acidic protein
  3. neurofilaments
  4. nuclear lamins
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10
Q

vimentin, desmin, glial fibrillary acidic protein

A
  • connective tissues, muscle and neurological cells

- form desmosomes for cell to cell attachment

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11
Q

neurofilaments

A
  • in nerve cells

- 3 subunits combine and extend along axons for tensile strength

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12
Q

nuclear lamins

A
  • meshwork on nuclear envelope
  • make nuclear lamina
  • dissociate at mitosis
  • mutations cause laminopathies, like Progeria (early aging)
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13
Q

microtubule structure

A
  • alpha and beta tubulin form dimers
  • tubulin bound to GTP. when dimer forms Alpha GTP is locked in and B GTP is hydrolyzed
  • GDP is released from - end
  • add in head –> tail to make it polar
    clinical: can stop the assembly/disassembly to treat gout
  • can arrest dividing cells to treat cancer
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14
Q

Microtubule Dynamic Instability

A
  • when all GTP is hydrolyzed, MTs disassamble from + end
  • continual assembly and reassembly
  • makes it easy to change direction and find areas that need MTs
  • distribution regulated by organizing centers (MTOC) to stabilize - ends of MT in centrosome
  • stable once they mature and are acetylated
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15
Q

MT associated ATPase motors

A
  1. Dynein - 2 headed in cytoplasm, moves in - direction
    - 1 or 3 heads in cilia/flagella
  2. Kinesins - 2 headed ATPases, + end motility
    important in organelle and vesicle transport and segregation of chromosomes at mitosis
    -disruption can cause neurodegenerative disease
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16
Q

cilia sliding doublet

A
  • cylia form cylinders with 9 doublets
  • cylinders have 2 extra single MTs if for motility
  • 2 rows of dynein, radical spokes, nexin holds it together
  • MT sliding forms a bend, becomes a wave of propagation
  • need dynein for bending
17
Q

Cilia Roles

A
  1. Motile
    - found in airways, fallopian tubes, brain ventricles
    - kartageners syndrome/primary ciliary diskenesia = lack motility in cilia. causes infertile sperm, respiratory disease, left/right asymmetry
  2. sensory/primary
    - do not have dynein arms or central MTs
    - found in mechanoreceptors in kidney and cartilage
    - ear, eye, nose
    - for sensing during embryogenesis
    - Polycystic kidney disease - abnormal growth of epithelial cells causes cysts due to mutation in gene for primary cilia

Microbiology MCM unit 1 (4 decks)

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