Cytoskeleton Flashcards
1
Q
Why do cells need a cytoskeleton
A
Cells need to be strong and dynamic
2
Q
Why don’t plant cells move
A
Because they have a cell wall
3
Q
What are the 3 core filament proteins in the cytoskeleton
A
Actin microfilaments
microtubules
Intermediate filaments
4
Q
What is this a cross section of
A
Actin microfilament
5
Q
What is this a cross section of
A
Microtubule
Around 25nm in diameter
6
Q
What is this a cross section of
A
Intermediate filaments
7
Q
What are the characteristics of actin microfilaments
A
8
Q
What are the characteristics of microtubules
A
9
Q
What are the characteristics of intermediate filaments
A
10
Q
Label this diagram of an actin microfilament
A
11
Q
Actin Microfilaments :
A
12
Q
Mictrotubules:
A
13
Q
Intermediate filaments:
A
14
Q
Why are filaments used for strength in a cell
A
15
Q
Why are filaments made up of subunits
A
16
Q
What is the structure of intermediate filaments and how is its structure formed
A
17
Q
What happens if something goes wrong with intermediate filaments
A
Lead to disease e.g amyotrophic lateral sclerosis
18
Q
What are the characteristics of the bacterial cytoskeleton
A
19
Q
What are some different examples of microfilaments in a cell and what do they do
A
20
Q
What are the characteristics of actin
A
21
Q
What characteristic does microfilaments have
A
They are dynamic
22
Q
What are the phases of dynamic filament
A
23
Q
What is the critical concentration
A
24
Q
What is nucleation needed for
A
Neede to facilitate growth
It brings G actin together to form oligomers
25
Using a diagram, describe the process of treadmilling
26
What is treadmilling
27
What happens when ATP vinds to actin
The conformation of actin changes
This changes the affinity in the filament
28
What is the rate of ATP/ADP addition at the plus and minus ends of the microfilament
Rate of ADP addition is slower than ATP addition at both ends of the microfilament
ADP not readily added to the plus end
The rate if loss of ADP actin is greater than the rate of addition of ATP at the minus end, but at the plus end loss of ADP actin is faster than at the minus end
29
Where does ADP actin tend to end up in a microfilament
Tends to end up in older parts of the filament
30
Using a diagram, explain the concept of critical concentration
Treadmilling occurs when the concentration of free subunits is between the critical concentrations for the two ends
Plus End Critical Concentration :The concentration of monomers required for polymerization at the plus end.
Minus End Critical Concentration : The concentration of monomers required for polymerization at the minus end
Is above Cc+, the filament will grow at the plus end.
Is below Cc- , the filament will shrink at the minus end.
Is between Cc+ and Cc- , treadmilling can occur, where the filament grows at the plus end and shrinks at the minus end.
Critical Concentration: Describes the equilibrium concentration of free monomers required for no net growth or shrinkage at a filament end.
31
What are nucleators and why are they needed
Nucleators are proteins or complexes that facilitate the formation of new actin filaments or microtubules, a process known as nucleation
They are needed because spontaneous nucleation takes too long (as it relies on diffusion)
32
What are the two main types of nucleators and what are their main roles
33
What is the role of ARP 2/3
ARP= actin related proteins
They can act as a starting point for nucleation as they have a similar structure to Actin
34
How does ARP 2/3 help produce microfilaments
It holds the minus ends and allows the plus ends to grow
35
Why is growth of the branches (daughter filaments) important for a cell
They produce a force that pushes the plasma membrane forward at the leading edge of motile cells
(Cells need it to move)
36
What is the role of formins
They provide a template for the growing plus ends of microfilaments
2 actin subunits are held by formin
37
How does formin work to help nucleation/ filament formation
38
What are actin binding proteins and what do they do
39
What are the proteins involved in controlling the growth of microfilaments
40
What are filament severing proteins and what do they do
41
What is the role of filamin
42
What do filament binding proteins do. Name two types and what they do
43
What is the role of microtubules
44
What is the structure of microtubules
45
How does microtuble nucleation occur
46
What is the microtubule organising centre
47
How are microtubules organise themselves from the centrosome
48
What do centrosomes contain
-they contain a centriole pair
49
What are microtubules able to do if they are severed from their centriole
50
How does microtubule treadmilling work
51
What is dynamic instability and how does it occur
involves the rapid switching between phases of microtubule growth (polymerization) and shrinkage (depolymerization).
Beta tubulin binds GTP before polymerizing onto the growing end of a microtubule.
The β-tubulin subunit of the dimer hydrolyzes GTP to GDP after incorporation into the microtubule lattice.
Tubulin bound to GTP (GTP-tubulin) is more stable and promotes microtubule growth, while tubulin bound to GDP
(GDP-tubulin) is less stable and promotes depolymerization
A growing microtubule typically has a "GTP cap" at its plus end (the rapidly growing end), where GTP-tubulin dimers are added faster than GTP is hydrolyzed to GDP.
The presence of this GTP cap stabilizes the microtubule and promotes further growth.
If the rate of GTP hydrolysis exceeds the rate of GTP-tubulin addition, the GTP cap is lost, exposing GDP-tubulin. This destabilizes the microtubule and leads to rapid depolymerization or shrinkage.
Rescue: The switch from shrinkage to growth can occur if enough GTP-tubulin dimers are incorporated to re-establish the GTP cap, stabilizing the microtubule and allowing it to start growing again.
52
Draw a diagram to represent how dynamic instability and catastrophe occurs
53
Draw a graph to show how length of the microtubule varies over time
54
Why may dynamic instability be useful for a cell
55
What are 2 types of microtubule binding proteins and what do they do
56
What does MAP2 and tau do
57
How is tau targeted in Alzheimer's
58
What are microtubule stabilising proteins and give an example
59
What do katanins do
Makes disassociation of microtubules more likely
60
How does katanin work
61
What drugs can be used to perturb the cytoskeleton
62
How can cell wall formation be guided by microtubules - draw a diagram to help explain this
63
What is the role of microtubules in cell division
64
Why is diffusion not enough for transport around the cell
65
What are the 3 main classes of motor proteins
66
How are energy and force produced for motor proteins
67
What kind of motor protein does prokaryotes have
They have a bacterial flagella
68
What are the 2 ways in which motor proteins are anchored
If elastic force exceeds resistance the track or motor will move (depending on which is anchored)
So if motor is anchored the track will move and vice Vera’s
69
What structures are conserved in motor proteins
70
Which class of motor protein is this
Kinesin
71
What class of motor protein is this
Cytoplasmic dynein
72
What class of motor protein is this
Myosin V
73
How do kinesins and dyneins work
74
Describe the structure of kinesins
75
Describe the structure of dynein
76
How do dyneins move across microtubules
As dynein-1 moves along an MT, ATP hydrolysis in the AAA+ ring of each monomer generates a series of conformational changes, which detach the monomer from the MT and reorient its linker domain to produce a net step toward the minus end
77
What is the function of dyneins
78
What is this a cross section of
79
How do ciliary dyneins cause the cilia to bend
80
How does dynein and Kinesin work together
81
Draw a diagram to show how kinesins and dyneins work in a cell
82
How does influenza hijack the cytoskeleton
83
What are the characteristics of the myosin superfamily
84
What is the structure of myosin
85
How do myosin motors produce force and move along the actin filament
86
What is the structure of actin and myosin in muscles
87
What happens when myosin goes wrong
88
What is the role of myosin motors in cell division
