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MBB 231 > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

The basics of microtubules structure

A
  • largest of the cytoskeletal components
  • 13 straight, hollow, noncovalently bonded globular dimers to form a heterodimer
    (a-tublin and B-tublin)
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2
Q

what are MAP’s?

A

Microtubule Associated Proteins
- increase the stability and promote stability

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3
Q

Energy Source of the Tublin

A

alpha tublin (NEGATIVE END)
- has a GTP trapped in its monomer that can never be hydrolyzed
Beta tublin (POSITIVE END)
- has a GDP or GTP in its monomer that can be hydrolyzed

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4
Q

What is a microtubules organizing centre and what does it do?

A

MTOC’s is where they microtubules grow from
they also control these aspects of their assembly
- polarity
-number of MT
- location
- timing

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5
Q

dynamic of microtubules

A

the process of growing and shrinking is called dynamic instability
- the dislocation rate of GDP tublin dimer is more rapid than GTP tublin dimer

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6
Q

What are motor proteins and what do they do?

A

they convert ATP into mechanical energy making them able to move unidirectionally on the cytoskeletal track in a stepwise manner

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7
Q

What are the 3 types of molecular motor

A
  • kinesin and dynein move along the microtuble track
  • myosin moves along the microtubule track
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8
Q

Function and directionality of Kinesin

A

-anterograde microtubule motor (moves forward (positive direction))
- walks progressive in a hand over hand manner
- each step is the length of one tublin dimer

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9
Q

Function and directionality of Dynein

A

retrograde microtubule motor (moves back to nucleus (negative direction))
- walks progressive in a hand over hand manner
- each step is the length of one tublin dimer

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10
Q

How can motor proteins be regulated?

A

Melanomsome aggregation is done by dynein
Melanosome diapered is done by kinesin

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11
Q

What are the stages the cell cycle

A
  • Go
  • G1
  • S
  • M phase
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12
Q

What is Go phase

A

the resting phase

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13
Q

What is G1 phase

A

growth phase: RNA and protein synthesis (6-12 hours)

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14
Q

What is S phase

A

synthesis phase : DNA synthesis doubles the amount of DNA in the cell and RNA and protein sysnthsis still occur (6-8h)

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15
Q

What is the G2 phase

A

growth phase 2: more RNA and protein synthesis. DNA synthesis seizes (3-4h)

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16
Q

What is the M phase

A

Mitosis and Cytokinsis occurs (1h)

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17
Q

What is interphase

A

The stage when the cell is not dividing (G1, S & G2)

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18
Q

What is cytokinesis

A

when the cell spilts into 2 daughter cells

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19
Q

What is a centrosome

A

is the best studied microtubule organization centre and its where they microtubules grow from

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20
Q

What is a centriole

A

short cylinders of modified microtubules

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21
Q

What is the nucleation of microtubules by gamma TURC

A

growth of the microtublues: subunits are added to the plus end of them

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22
Q

What are the 3 types of microtubules and roles

A
  • Kinetochores: attach to the chromosomes
  • Astral microtubules : orient and stabilize the spindle during cell divison
  • polar microtubules: pushing the cells away from each other by pushing on the opposite MT
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23
Q

What are the microtubules doing in prophase?

A
  • the centrosomes form a MTOC and the MT beginning to elongate
  • the nuclear envelope dissembles
24
Q

What are the microtubules doing in prometaphase?

A
  • Kinetochore attach to the centromeres of the chromosomes
    one side’s microtubules will grow and the other shrinks
25
Q

What are the microtubules doing in metaphase?

A

the kinteochores are equal length on both sides

26
Q

What are the microtubules doing in anaphase?

A

the polar MT are pushing apart the cells by a four headed kinesin family motor protein
-tublin is lost at the minus ends to be added to the plus ends

27
Q

What are the microtubules doing in telophase?

A

the mitotic spindle disassembles

28
Q

What’s the characteristics of intermediate filaments

A
  • strong flexible ropelike fibres that give ,mechanical strength to cells that are in physical stress
29
Q

Role of plectin

A

they are elongated dimeric proteins that create cross bridges in intermediate filaments

30
Q

Role of Lamins

A

to create the nuclear lamina

31
Q

what regulates the assembly an disassembly of intermediate filaments

A

they are controlled by subunit phosphorylation and dephosphorylation

32
Q

What is the structure of G-actin?

A

globular (when no ATP is present)

33
Q

What is the structure of F-actin?

A

filamentous (in the presence of ATP it becomes flexible)

34
Q

structure of actin

A

it is polar and it has
- Minus End (pointed end) where the binding cleft is exposed to bind with the plus end
- Plus end (barded end)

35
Q

Actin Disassembly and assembly

A

in vitro - plus and minus ends have different polymerization rates

in vivo- polymerization only occurs at the plus ends by ATP-actin (the minus end is probably anchored)

36
Q

What is myosin?

A

molecular motor that has a binding spot to ATP and actin
- there’s 2 classes called conventional (found in the muscle cells) and unconventional

37
Q

Structure of myosin 2

A

1) pair of globular head with catalytic site
2) a pair of necks each with a pair of light chains
3) 2 intertwining heavy chains

38
Q

The role of myosin 2 in muscle contraction

A

conventional, to pull the actin making cross bridges that help the muscle contract

39
Q

Role and polarity of Cap Z in muscle contraction

A

caps the act an the plus end

40
Q

Role and polarity of tropomodulin in muscle contraction

A

caps the - end of actin and regulates the length of the actin filament

41
Q

Role and polarity of myomesin in muscle contraction

A

bundles the myosin filaments

42
Q

Role and polarity of titan in muscle contraction

A

extends through the myosin bundle and attaches to the z line (helps prevent tearing)

43
Q

Role and polarity of nebulin in muscle contraction

A

binds actin filament to z line

44
Q

What is the structure of G-actin in vivo

A
45
Q

Role and polarity of troponin in muscle contraction

A

when Ca2= binds on it, it allows it to move tropomyosin off of the myosin binding site.

46
Q

Role and polarity of tropomyosin in muscle contraction

A

it covers the myosin binding site on the actin filament when there is not activity in cell

47
Q

What is the assembly of F-actin in vivo

A
48
Q

What is profilin

A

Polymerization: it functions as adenine nucleotide exchange
- it bind to the plus end of ADP actin changing t into ATP actin so it can join the growing filament

49
Q

what is cofilin

A

Depolymerization: it binds to ADP actin and severs filaments promoting depolymerization

50
Q

what is thymosin

A

Storage or Pause of Polymerization: binds to ATP actin prevent them from polymerizing

51
Q

role of the Arp complex

A

not considered a true actin fitment but shares characteristics of it

it helps polymerize by binding to the side of it along with an activating protein called WASP (Wiskott-Aldrich syndrome protein)

52
Q

The fundamentals of the branching and elongation of the Arp complex (relation to cell mobility)

A

1) signal for case to initiate
2) WASP activates Arp and new filaments grow at plus end
3) then causes membrane to put up
4) Coflin depolymerizes old filament
5) Profile will exchange the GDP for GTP

53
Q

What is Rho

A

regulates the actin skeleton

54
Q

What is GDI and its role

A

guanine nucleotide dissociation inhibitor
- prevent rho from interacting with its GEF

55
Q

compare and constrast microtubules, actin and intermediate filaments

A

MBB 231 (11 decks)

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