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BIOL*1090 > The Cytoskeleton > Flashcards

The Cytoskeleton Flashcards

1
Q

What is the cytoskeleton?

A

A dynamic network of interconnected filaments and tubes that extend throughout the cytosol (and some organelles) of eukaryotes

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2
Q

T or F: All eukaryotes and prokaryotes have microtubules and microfilaments.

A

False. Only eukaryotic cells have them

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3
Q

What do animal cells have in addition to microtubules and microfilaments?

A

Intermediate filaments

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4
Q

What are the four primary functions of the cytoskeleton?

A
  • Structural support
  • Spatial organization within the cell
  • Intracellular transport
  • Contractility and motility
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5
Q

What is the structure of a microtubule?

A

Hollow and tube-like

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6
Q

What are microtubules made up of?

A

Tublin dimers

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7
Q

What are tublin dimers composed of?

A

Alpha- and beta- tubulin

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8
Q

What are alpha/beta heterodimers composed of?

A

An alpha-tublin polypeptide chain and a beta-tublin polypeptide chain

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9
Q

How are heterodimers aligned to create structural polarity?

A

In the same direction (head to tail)

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10
Q

What are protofilaments in microtubules composed of?

A

alpha/beta heterodimers

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11
Q

How many protofilaments create the hollow cylinder of a microtubule?

A

13

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12
Q

What is structural polarity important for in microtubules?

A

Microtubule growth and the direction of movement of material along it

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13
Q

Which of the three cytoskeleton fibres have the largest diameter?

A

Microtubules

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14
Q

What is the primary function of microtubules?

A

Help maintain the cell shape and internal structure

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15
Q

What are the two types of microtubules?

A
  • Axonemal microtubules
  • Cytoplasmic microtubules
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16
Q

How do axonemal microtubules and cytoplasmic microtubules differ in terms of their organization?

A
  • Axonemal: highly organized and stable
  • Cytoplasmic: loosely organized and very dynamic
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17
Q

Which type of microtubule is part of structures involved in cell movement?

A

Axonemal microtubules

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18
Q

Which type of microtubule is found in cilia?

A

Axonemal microtubules

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19
Q

What are cilia?

A

Hair-like structures that extend from the surface of cells

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20
Q

What are the two types of cilia?

A
  • Motile
  • Nonmotile
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21
Q

What function do motile cilia often perform?

A

Propel the movement of cells of the fluid surrounding them

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22
Q

What function do nonmotile cilia often perform?

A

Often serve a sensory function

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23
Q

Which type of microtubule is located in the cytosol?

A

Cytoplasmic microtubules

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24
Q

T or F: Microtubules and microfilaments undergo dynamic assembly and disassembly.

A

True

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25
Q

T or F: The formation of microtubules isn’t regulated/controlled.

A

False. It is regulated/controlled

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26
Q

What is the difference between the plus and minus end of microtubules and microfilaments?

A
  • Plus end: fast-growing
  • Minus end: slow-growing
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27
Q

What is the term used to describe the rapid shrinkage at the plus end of a microtubule?

A

Catastrophe

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28
Q

What is the microtubule-organizing centre?

A

The central site of microtubule assembly

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29
Q

T of F: The microtubule-organizing centre is found in both prokaryotes and eukaryotes.

A

False. MTOC is only found in eukaryotic cells

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30
Q

What are the two most important microtubule-organizing centres?

A

Basal bodies and centrosomes

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31
Q

What is the microtubule-organizing centre for animal cells?

A

Centrosomes

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32
Q

What is involved with dynamic instability?

A

Cycles of rapid depolymerization followed by slower polymerization in the plus end of microtubules

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33
Q

What does the dynamic instability of microtubules allow for during cell division?

A

Allows spindle microtubules to quickly find and attach to chromosomes

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34
Q

What are the two classes of microtubule-associated proteins (MAPs)?

A
  • Non-motor
  • Motor
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35
Q

Which type of microtubule-associated protein controls microtubule organization in the cytosol?

A

Microtubule-associated non-motor proteins

36
Q

What type of microtubule-associated protein often contribute to the growth and disassembly of microtubules?

A

Microtubule-associated non-motor proteins

37
Q

Defective Tau protein in neurons causes neurofibillary tangles and leads to what?

A

Alzheimer’s and other forms of neurodegenerative disorders

38
Q

Which type of microtubule-associated protein powers intracellular transport?

A

Microtubule-associated motor proteins

39
Q

What are microtubule-associated motor proteins able to generate between microtubules?

A

A sliding force

40
Q

What are the two main types of microtubule-associated motor proteins?

A
  • Kinesin
  • Dynein
41
Q

What is the difference between kinesin and dynein in terms of the direction of their movement?

A
  • Kinesin: Plus end directed (moves to plus end)
  • Dynein: Minus end directed (moves to minus end)
42
Q

What occurs during the force-generating step when motor MAPs cause movement?

A

ATP binds to the leading head and induces a conformation change that swings the training head 180 degrees toward the (+) end of the microtubule

43
Q

What is the difference between the leading head and the training head during movement along a microtubule?

A
  • Leading head: Whichever head is closest to the (+) end
  • Trailing head: Whichever head is closest to the (-) end
44
Q

What are melanophores?

A

Specialized skin cells that produce the pigment melanin

45
Q

What type of organism possesses melanophores?

A

Some vertebrates

46
Q

What do melanophores do with the pigment they have produced?

A

They keep it in granules and move them around inside in response to hormones or neuronal signals

47
Q

What does the redistribution of melanin in vertebrates with melanophores allow them to do?

A

Change colours

48
Q

How do melanin granules in melanophores move back and forth along microtubules?

A

They are transported by kinesin and dynein

49
Q

What happens to melanin granules in melanophores in the dark?

A

They are dispersed outwards, causing the organism to be darkly coloured

50
Q

Which motor MAP is responsible for dispersing melanin granules?

A

Kinesin

51
Q

What happens to melanin granules in melanophores in the light?

A

They are aggregated to the centre of the organism, causing it to be lightly coloured

52
Q

What are intermediate filaments composed of?

A

intermediate filament protein subunits

53
Q

Intermediate filaments are exclusive to which type of cell?

A

multicellular animal cells

54
Q

What does it mean for intermediate filaments to be non-polar?

A

They have no plus or minus ends

55
Q

Why are intermediate filaments not used for transport?

A

Because they are non-polar

56
Q

Karatins compose intermediate filaments in which cell type?

A

Epithelial cells

57
Q

Viementins compose intermediate filaments in which cell type?

A

Fibroblasts

58
Q

Neurofilaments compose intermediate filaments in which cell type?

A

Neurons

59
Q

Where are intermediate filaments composed of lamins located?

A

The nucleus

60
Q

Which fibre of the cytoskeleton is composed of a double helix of actin monomers?

A

Microfilaments

61
Q

Which fibre of the cytoskeleton is the thinnest?

A

Microfilaments

62
Q

Which of the three cytoskeleton fibres are involved in muscle contraction and cytokinesis?

A

Microfilaments

63
Q

What is the central component of microfilaments?

A

Actin

64
Q

What are the two ways in which actin can exist within a cell?

A
  • As a monomer (G-actin)
  • As a polymer (F-actin)
65
Q

What is G-actin?

A

A single unit/monomer of actin

66
Q

What is F-actin?

A

An actin filament/polymer

67
Q

T or F: F-actin appears as a single strand of subunits.

A

False. F-actin appears as TWO strands of subunits

68
Q

How many subunits of G-actin does one F-actin unit have?

A

28

69
Q

What is phalloidin?

A

A class of toxins (phallotoxins)

70
Q

What is a major symptom of phalloidin poisoning?

A

Acute hunger

71
Q

How does phalloidin affect F-actin?

A

It binds to and stabilizes F-actin and prevents the depolymerization of actin fibres

72
Q

Are F-actin filaments polar or non-polar?

A

Polar (have plus and minus end)

73
Q

In terms of microfilament growth, what occurs once a stable actin trimer has been established?

A

There is rapid elongation

74
Q

What regulates the organization of F-actin microfilaments?

A

Actin-binding proteins

75
Q

What is the Arp 2/3 complex?

A

A branching facilitator

76
Q

What does the Arp 2/3 complex do?

A

Helps create branching points for the polymerization of new actin fibres

77
Q

What does the polymerization and branching of microfilaments play a central role in?

A

Directed cell motility

78
Q

What is a lamellipodium?

A

An actin projection on the leading edge of a cell

79
Q

What is profilin?

A

An actin-binding protein that enhances the growth of filaments

80
Q

What is cofilin?

A

An actin-binding protein that disassembles actin filaments

81
Q

What does a capping protein do to a microfilament?

A

Prevents the exchange of a subunit at the plus end

82
Q

What are myosins?

A

A superfamily of motor proteins associated with microfilaments

83
Q

Which direction do mysoins move along microfilaments?

A

Toward the plus end

84
Q

What are the two broad groups myosins can be divided into?

A
  • Conventional myosins
  • Unconventional myosins
85
Q

Which type of myosin is the primary motor for muscle contraction?

A

Conventional myosins

86
Q

Which type of myosin generates force and contributes to motility in non-muscle cells?

A

Unconventional myosins

BIOL*1090 (15 decks)

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