Cytoskeleton Flashcards

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1
Q

3 cytoskeleton filaments

A
  • intermediate filaments
  • microtubules
  • actin filaments
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2
Q

Actin filament examples

A
  • microvilli
  • cytoplasmic contractile bundles
  • lamellipodia & filopodia
  • cell division contractile ring
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3
Q

Actin filament structure and 2 forms of actin

A
  • 2-stranded helical polymers of actin protein
  • 2 forms:
  • —-G (globular) - inactive
  • —-F (filament) - active
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4
Q

Treadmilling

A

process of de/polymerisation of actin filaments

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5
Q

ATP-bound actin associated with

A

polymerisation

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6
Q

ADP-bound actin associated with

A

depolymerisation

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7
Q

Proteins that stimulate actin behaviour changes

A
  • Rho
  • Cdc42
  • Rac
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8
Q

Actin & Myosin interaction seen in:

A

muscle contraction

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9
Q

Cytoskeleton functions (4)

A
  • shape alteration
  • internal organisation
  • motility
  • mechanical interaction with environment
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10
Q

Intermediate filaments basics

A
  • rope-like fibres
  • diameter of 10nm
  • composed of fibrous protein
  • flexible
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11
Q

Intermediate filaments function

A
  • provide tensile strength

- protect against mechanical stress

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12
Q

Intermediate filaments properties

A
  • tough and durable
    survive concentrated salt solutions and nonionic detergents
  • extend across cytoplasm
  • anchored to plasma membrane at cell-cell junctions (desmosomes)
  • found in nucleus (lamina)
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13
Q

Intermediate filaments structure

A

alpha-helical monomers with N and C ends coil antiparallel to each other creating dimers which then associate to form tetramers and then lateral associations of 8 tetramers

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14
Q

Intermediate filaments types

A
  1. cytoplasmic: keratin, vimentin, neurofilaments

2. nuclear: nuclear lamins

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15
Q

Keratins composition

A

equal mixture of type 1 (acidic) and type 2 (neutral/basic) keratin chains

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16
Q

Keratin structure

A

form heterodimers and then fundamental tetrameric subunits held together by disulphide bonds

17
Q

Keratin disease

A

epidermolysis bullosa simplex (EBS):

  • mutation in K5 or 14 gene
  • defective keratins expressed in basal cell layer of epidermis
  • skin highly sensitive to mechanical stress
  • no cure
18
Q

Nuclear lamins structure and function

A
  • form a meshwork lining the inner membrane of nuclear envelope
  • provide anchorage sites for chromosomes and nuclear pores
  • assemble and disassemble during cell division
  • degradation controlled by phosphorylation
19
Q

Nuclear lamins disease

A

Progeria:

  • lamin A mutation
  • cell nucleus unstable and mis-formed
  • children age prematurely
  • no cure
  • brain development and function isn’t affected because that’s controlled by lamin C
20
Q

Microtubule basic properties

A
  • stiff hollow tubules
  • radiate from centrosome
  • rapid dis/assembly
21
Q

Microtubule functions

A
  • intracellular transport with help of kinesins and dyenins
  • organelle positioning
  • power mechanical beat of cilia and flagella
  • separate sister chromatids during mitosis
  • form mitotic spindle
22
Q

Kartagener’s syndrome

A

cilia defect causing respiratory infections and infertility

23
Q

Microtubule structure

A
  • formed from alpha and beta-tubulin heterodimers
  • dimers stack to form wall of cylindrical tube
  • 13 parallel protofilaments make tubule
  • structural polarity
24
Q

MTs

  • alpha-tubulin at ___ end
  • beta-tubulin at ___ end
A
  • alpha: -ve

- beta: +ve

25
Q

Microtubules extend from:

A

centrosomes which consist of perpendicularly paired centrioles

26
Q

Nucleation site of microtubules

A

Hundreds of ring like structures made from gamma-tubulin

27
Q

Which form of tubulin is tightly bound to GTP and which one has an exchangeable end of GDP/GTP

A
  • bound: alpha

- exchange: beta

28
Q

dynamic instability in MTs

A

process of rapid polymerisation and depolymerisation

29
Q

GTP cap

A

favours growth of microtubules

30
Q

drug inhibiting MT assembly

A

colchicine

31
Q

drug inhibiting MT disassembly

A

taxol

32
Q

modification of dynamic instability during:

A
  • mitotic spindle formation

- cell differentiation

33
Q

motor protein transport using MT ‘tracks’ powered by:

A

repeat cycles of ATP hydrolysis

34
Q

Kinesins direct traffic to:

A

+ve end

35
Q

Dyneins direct traffic to:

A

-ve end