Lecture 05

Question 1

Cytoskeletal filament necessary for whole-cell locomotion

Answer 1

Actin filaments

Question 2

Cytoskeletal filament that provides mechanical strength

Answer 2

Intermediate filaments

Question 3

Cytoskeletal filament that determines the position of organelles

Answer 3

Microtubules

Question 4

Cytoskeletal filament that drives the pinching of one cell into two

Answer 4

Actin filaments

Question 5

Cytoskeletal filament that directs intracellular transport

Answer 5

Microtubules

Question 6

Microtubules are attached to a single point called _________________.

Answer 6

MTOC - Microtubule Organizing Center

Question 7

T or F. The centrosome is the MTOC.

Answer 7

True

Question 8

The centrosome is made up of _________________.

Answer 8

a pair of centrioles

Question 9

Why are the subunit interactions of the filaments non-covalent?

Answer 9

Rapid assembly and disassembly

Question 10

During cytokinesis, actin filaments form a ___________ that pinches the cell in two.

Answer 10

contractile ring

Question 11

T or F. Actin uses GTP for assembly while microtubules use ATP.

Answer 11

False. The other way around

Question 12

ODD MAN OUT:
Actin, Microtubules, Intermediate filament

Forms a hollow cylinder

Answer 12

Actin

Actin forms a double helix

Question 13

ODD MAN OUT:
Actin, Microtubules, Intermediate filament

Aids in cell motility

Answer 13

Intermediate filament

Question 14

ODD MAN OUT:
Actin, Microtubules, Intermediate filament

Strenghtens cellular structure

Answer 14

Microtubules.

Intermediate filaments strengthen the nucleus and overall structural integrity, while actin filaments strengthen the cell cortex and periphery.

Question 15

Phases of actin assembly

Answer 15

Nucleation, Elongation, Steady State

Question 16

In which phase of actin assembly does the treadmilling occur?

Answer 16

Steady state (equilibrium phase)

Question 17

T or F. During elongation, monomers can bind at the pointed end of the actin filament.

Answer 17

True. While monomers preferentially bind to the barbed end, they can still bind reversibly at each end.

Question 18

The rapid elongation at a filipodia is regulated by which elongation factor?

Answer 18

Formin

Question 19

Small cross-linking proteins that bind to the parallel actin bundles to strengthen it.

Answer 19

alpha-actinin

Question 20

Small cross-linking protein : alpha-actinin
Large cross-linking protein : _____________

Answer 20

Filamin

Question 21

Binding protein that nucleates branching in actin filament

Answer 21

Arp 2/3

Question 22

What common proteins are found in filopodia?

Answer 22

Formin and alpha-actinin

Question 23

What common proteins are found in lamellipodia?

Answer 23

Filamin and Arp 2/3

Question 24

Difference/s and similarity between tropomodulin and capping protein

Answer 24

They both prevent disassembly and assembly of actin.

Tropomodulin = at the pointed end
Capping protein = at the barbed end

Question 25

T or F. Profilin prevents assembly while thymosin promotes assembly.

Answer 25

False. The other way around.

Question 26

Accelerates disassembly of actin filament

Answer 26

Cofilin

Question 27

T or F. ATP is needed to attach myosin to the actin.

Answer 27

False. ATP is needed to release myosin from the actin.

Question 28

Microtubules are hollow cylindrical structure built from __(a)__ parallel ___(b)___. The (b) are composed of tubulin ________.

Answer 28

13; protofilaments; dimers

Question 28

Which tubulin monomer is always bound to GTP? Which tubulin monomer can be bound to GTP or GDP?

Answer 28

a-tubulin; b-tubulin

Question 29

Differentiate the (-) ends and the (+) ends of actin filaments vs microtubules

Answer 29

In ACTIN FILAMENTS, the (+) end grows more rapidly and the (-) end grows more slowly. In MICROTUBULES, the (+) end GROWS AND SHRINKS more rapidly than the (-) end.

Question 30

Actin filaments: treadmilling effect Microtubules: _______________

Answer 30

dynamic instability

Question 31

Explain dynamic instability

Answer 31

Good job :D KEYWORDS: Catastrophe & Rescue

Question 32

Two polymer forms of microtubules

Answer 32

T form - more energy to polymerize G form - less energy; tends to depolymerize

Question 33

T or F. The GTP cap is also known as the less stable region of the microtubule.

Answer 33

False. The region with GDP-tubulin dimers is the less stable region.

Question 34

Actin: Arp 2/3 Microtubule: _______

Answer 34

Augmin. Both nucleates branching.

Question 35

How does stathmin prevent rescue of microtubles? What protein has the same function in actin filaments?

Answer 35

It binds to subunits to prevent assembly of tubulin dimers. Thymosin.

Question 36

Motor proteins for vesicular transport.

Answer 36

Kinesin and Dynein

Question 37

Facilitates anterograde movement (to + end).

Answer 37

Kinesin

Question 38

Facilitates retrograde movement (to - end)

Answer 38

Dynein