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BIOL*1090 > The Cytoskeleton > Flashcards

The Cytoskeleton Flashcards

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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
T or F: The formation of microtubules isn't regulated/controlled.
False. It is regulated/controlled
26
What is the difference between the plus and minus end of microtubules and microfilaments?
- Plus end: fast-growing - Minus end: slow-growing
27
What is the term used to describe the rapid shrinkage at the plus end of a microtubule?
Catastrophe
28
What is the microtubule-organizing centre?
The central site of microtubule assembly
29
T of F: The microtubule-organizing centre is found in both prokaryotes and eukaryotes.
False. MTOC is only found in eukaryotic cells
30
What are the two most important microtubule-organizing centres?
Basal bodies and centrosomes
31
What is the microtubule-organizing centre for animal cells?
Centrosomes
32
What is involved with dynamic instability?
Cycles of rapid depolymerization followed by slower polymerization in the plus end of microtubules
33
What does the dynamic instability of microtubules allow for during cell division?
Allows spindle microtubules to quickly find and attach to chromosomes
34
What are the two classes of microtubule-associated proteins (MAPs)?
- Non-motor - Motor
35
Which type of microtubule-associated protein controls microtubule organization in the cytosol?
Microtubule-associated non-motor proteins
36
What type of microtubule-associated protein often contribute to the growth and disassembly of microtubules?
Microtubule-associated non-motor proteins
37
Defective Tau protein in neurons causes neurofibillary tangles and leads to what?
Alzheimer's and other forms of neurodegenerative disorders
38
Which type of microtubule-associated protein powers intracellular transport?
Microtubule-associated motor proteins
39
What are microtubule-associated motor proteins able to generate between microtubules?
A sliding force
40
What are the two main types of microtubule-associated motor proteins?
- Kinesin - Dynein
41
What is the difference between kinesin and dynein in terms of the direction of their movement?
- Kinesin: Plus end directed (moves to plus end) - Dynein: Minus end directed (moves to minus end)
42
What occurs during the force-generating step when motor MAPs cause movement?
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
What is the difference between the leading head and the training head during movement along a microtubule?
- Leading head: Whichever head is closest to the (+) end - Trailing head: Whichever head is closest to the (-) end
44
What are melanophores?
Specialized skin cells that produce the pigment melanin
45
What type of organism possesses melanophores?
Some vertebrates
46
What do melanophores do with the pigment they have produced?
They keep it in granules and move them around inside in response to hormones or neuronal signals
47
What does the redistribution of melanin in vertebrates with melanophores allow them to do?
Change colours
48
How do melanin granules in melanophores move back and forth along microtubules?
They are transported by kinesin and dynein
49
What happens to melanin granules in melanophores in the dark?
They are dispersed outwards, causing the organism to be darkly coloured
50
Which motor MAP is responsible for dispersing melanin granules?
Kinesin
51
What happens to melanin granules in melanophores in the light?
They are aggregated to the centre of the organism, causing it to be lightly coloured
52
What are intermediate filaments composed of?
intermediate filament protein subunits
53
Intermediate filaments are exclusive to which type of cell?
multicellular animal cells
54
What does it mean for intermediate filaments to be non-polar?
They have no plus or minus ends
55
Why are intermediate filaments not used for transport?
Because they are non-polar
56
Karatins compose intermediate filaments in which cell type?
Epithelial cells
57
Viementins compose intermediate filaments in which cell type?
Fibroblasts
58
Neurofilaments compose intermediate filaments in which cell type?
Neurons
59
Where are intermediate filaments composed of lamins located?
The nucleus
60
Which fibre of the cytoskeleton is composed of a double helix of actin monomers?
Microfilaments
61
Which fibre of the cytoskeleton is the thinnest?
Microfilaments
62
Which of the three cytoskeleton fibres are involved in muscle contraction and cytokinesis?
Microfilaments
63
What is the central component of microfilaments?
Actin
64
What are the two ways in which actin can exist within a cell?
- As a monomer (G-actin) - As a polymer (F-actin)
65
What is G-actin?
A single unit/monomer of actin
66
What is F-actin?
An actin filament/polymer
67
T or F: F-actin appears as a single strand of subunits.
False. F-actin appears as TWO strands of subunits
68
How many subunits of G-actin does one F-actin unit have?
28
69
What is phalloidin?
A class of toxins (phallotoxins)
70
What is a major symptom of phalloidin poisoning?
Acute hunger
71
How does phalloidin affect F-actin?
It binds to and stabilizes F-actin and prevents the depolymerization of actin fibres
72
Are F-actin filaments polar or non-polar?
Polar (have plus and minus end)
73
In terms of microfilament growth, what occurs once a stable actin trimer has been established?
There is rapid elongation
74
What regulates the organization of F-actin microfilaments?
Actin-binding proteins
75
What is the Arp 2/3 complex?
A branching facilitator
76
What does the Arp 2/3 complex do?
Helps create branching points for the polymerization of new actin fibres
77
What does the polymerization and branching of microfilaments play a central role in?
Directed cell motility
78
What is a lamellipodium?
An actin projection on the leading edge of a cell
79
What is profilin?
An actin-binding protein that enhances the growth of filaments
80
What is cofilin?
An actin-binding protein that disassembles actin filaments
81
What does a capping protein do to a microfilament?
Prevents the exchange of a subunit at the plus end
82
What are myosins?
A superfamily of motor proteins associated with microfilaments
83
Which direction do mysoins move along microfilaments?
Toward the plus end
84
What are the two broad groups myosins can be divided into?
- Conventional myosins - Unconventional myosins
85
Which type of myosin is the primary motor for muscle contraction?
Conventional myosins
86
Which type of myosin generates force and contributes to motility in non-muscle cells?
Unconventional myosins

BIOL*1090 (15 decks)

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