Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MBB 231 > lec 11- the cytoskeleton cont. > Flashcards

lec 11- the cytoskeleton cont. Flashcards

1
Q

what do intermediate filaments (IF) do?

A

provide support and mechanical strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are IF made of?

A

70 different genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how many types of IF are there?

A

5 based off of the cells where they are found in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how do IF’s interconnect to other cytoskeletal filaments?

A

via cross bridges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the cross bridges called?

A

plectin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what connects at the ends of plectin?

A

on one end there is a binding site for intermediate filament, and a binding site for any other cytoskeletal filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how does labelled keratin act when in a cell with IF’s?

A

it gets scattered in the IF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is keratin?

A

an IF that provides strength for epithelial cells, most diverse IF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what does actin filament do?

A

provides motility, shape, structural support, and does muscle contractions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the most abundant types of actin in the cell?

A

G-actin = globular
F-actin = filamentous
With ATP, they form into a helical filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what do the minus and plus end of the actin filament do?

A

minus end: the end with an exposed binding cleft which binds to the plus end in a filament
plus end: the other end where the minus end of a G-actin binds too

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what regulates polymerization and depolymerization of actin filament?

A

actin binding protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is myosin?

A

an actin based motor protein that has a “head or motor domain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are the groups of myosin?

A

conventional and unconventional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what type of myosins are the best studied?

A

type II (conventional) myosins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is an example of an unconventional myosin?

A

a myosin that transports vesicles and organelles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how many polypeptide chains does a myosin II molecule have?

A

one pair of heavy chains and two pairs of light chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what does myosin II consist of?

A
  1. a pair of globular heads that contain the catalytic site of the molecule
  2. a pair of necks, each consisting of a single, uninterrupted alpha-helix and two associated light chains
  3. a single, long, rod-shaped tail formed by the intertwining of long a-helical sections of the two heavy chains

forms into a fiber with heads pointing out and tails pointing in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is a muscle?

A

bundles of parallel muscle fibres joined by tendons to the bones that the muscle must move

20
Q

what are muscle fibres?

A

each fiber is a multinucleate cell formed during embryogenesis and specialized for contraction

21
Q

what is myofibril?

A

thinner cylindrical strands that make up muscle fiber

22
Q

what is a sarcomere?

A

the contractile unit of myofibrils each which has a very specific organization

23
Q

what is a sarcomere made of?

A

thin filaments (actin)
thick filaments (myosin)
and Z lines at the ends

24
Q

what side of the actin is anchored to the Z lines?

A

the plus end

25
Q

what does CapZ do?

A

caps actin to the Z end

26
Q

what is nebulin?

A

repeating actin binding motifs that binds actin filament to Z line

27
Q

what is myomesin?

A

bundles the myosin filaments

28
Q

what is titin?

A

extends through the myosin filament and attaches to the Z line-helps to prevent tearing of muscle

29
Q

do multiple myosins work at the same time?

A

no, individually

30
Q

explain the contractile cycle of actin and myosin:

A
  1. ATP binds to myosin head, causing release of myosin from actin
  2. ATP is hydrolyzed to ADP and Pi, causing nech to straighten and head to pivot which causes a weak binding to a new actin, myosin head is cocked and ready for power stroke
  3. Pi releasing causes neck to go back to original conformation, tighter binding to actin, and creating a power stroke which moves thin filament
  4. ADP is released and new ATP can now bind to repeat cycle
31
Q

what does calcium, tropomyosin and troponin do?

A

-tropomyosin blocks myosin binding sites on actin
-troponin forms a complex with tropomyosin
-motor neuron excitation signal, signal transduction pathway leads to calcium release from the SR, calcium binds to troponin, the troponin-tropomyosin complex moves opening binding sites, when signal stops calcium goes back to SR and muscle relaxes

32
Q

what does cofilin do?

A

binds ADP actin and severs filaments promoting depolymerization at minus end

33
Q

what does profilin do?

A

functions as an adenine nucleotide exchange factor, binds ADP actin at plus end changing conformation and allowing binding of ATP, binding results in dissociation of profilin, ATP actin then either joins growing filament at plus end or is bound by thymosin

34
Q

what does thymosin do?

A

sequesters G-actin preventing polymerization, displacement of thymosin allows binding of G-actin to the plus end

35
Q

are both ends of F-actin capped?

A

yes, it stabilizes the sarcomere by preventing plus end further growth or minus end loss of subunits

36
Q

can actin be linked to other actin filaments and the cell membrane?

A

yes

37
Q

what is the network of actin filaments and accessory proteins that underlies the plasma membrane called?

A

cell cortex

38
Q

what promotes actin branching and growth?

A

Arp2/3 complex: nucleates new branches off the side of existing filaments

39
Q

what activates Arps?

A

WASPs

40
Q

what are the steps in cell motility?

A

1 and 2. extracellular signal recognized and signal transduction cascade initiated
3 and 4. WASP activates Arp complex and Arp nucleates new actin filaments
5. The result is branch formation at plus end
6. membrane is pushed forward
7. caps terminate elongation
8. oldest part of filament at the minus end
9. F-actin severed and depolymerized at minus end
10. profilin exchanges GDP to GTP

41
Q

what does GDI do?

A

prevents Rho-GTPase from putting its tail into the membrane and interacting with GEF

42
Q

what does GEF do?

A

turns the GDP on the Rho into GTP turning it “on”

43
Q

how does Rho with GTP turn back into GDP?

A

GAP removes the phosphate on GTP, making it into GDP “off”

44
Q

what does Rho-GTPase do?

A

regulates actin nucleators

45
Q

What is tropomodulin?

A

Caps negative end and regulates the length of actin filament

MBB 231 (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions