9.2.16 Lecture Flashcards Preview

MCBG > 9.2.16 Lecture > Flashcards

Flashcards in 9.2.16 Lecture Deck (99)
Loading flashcards...
1

The cytoskeleton involves a dynamic array of what three interacting filaments?

1. Actin (smallest, 5-7nm diameter)
2. Microtubules (largest, 25 nm diameter)
3. Intermediate filaments (medium, 10 nm diameter)

2

What are the 6 major functions of actin?

1. Dictate cell shape
2. Mediate cell adhesion
3. Polarization
4. Phagocytosis
5. Muscle contraction
6. Cell migration

3

Actin is localized below the ___.

Cell membrane

4

What determine cell shape and surface area?

Cortical actin and actin arrays

5

What are the two types of cell adhesion mediated by actin?

1. Cell-cell, through adherens junctions
2. Cell-matrix through focal contacts

6

Actin arrays partition polarized cells into ___ and ___ compartments.

Apical; basal

7

The ___ is an actin-based structure.

Phagosome

8

Bundles of actin filaments are used by ___ for muscle contraction.

Myosin motors

9

What are the four general instances needing cell migration?

1. Development
2. Wound healing
3. Immune system
4. Cancer metastasis

10

What is the soluble subunit of actin?

Actin monomer

11

Describe the structure of the actin monomer.

Globular, contains ATP when in the cytosol, ADP when in the filament, has + and - end (polar)

12

What is the actin filament made of?

Flexible helix of 2 protofilaments

13

Actin monomers and filaments are ___. This gives it ___. Which end is more dynamic?

Polar; directionality; +

14

___ regulate actin filament assembly and disassembly.

Accessory proteins

15

Small soluble actin subunits are in ___ with large filamentous polymers.

Equilibrium

16

A signal can lead to disassembly of filaments and rapid ___ of subunits, followed by reassembly at a ___ site.

Diffusion; new

17

What are the three phases to actin filament assembly?

1. Nucleation (lag phase)
2. Elongation (growth phase)
3. Steady state equilibrium (equilibrium phase)

18

What is the rate limiting step to actin filament assembly?

Nucleation

19

What is the critical concentration?

The concentration of actin monomers at steady state

20

What happens to the kinetics of actin formation if actin "nuclei" are added directly?

Removes the nucleation/lag phase

21

Actin is nucleated at the ___ end.

Minus

22

Nucleation occurs preferentially at the ___, which allows for cell surface structures to form.

Cell membrane

23

Nucleation occurs via what protein(s)?

Actin related proteins (ARP) -> ARP2 and ARP3

24

ARP binds pre-existing filaments at a ___ angle.

70 degree

25

What modulates filament growth and localization? What do each of these do?

End binding proteins (ARP and Cap Z) - ARP caps and nucleates the minus end, CapZ binds and stabilizes the + end.

26

___ modulate filament elongation. These are ___ (less or more) efficient than end binding proteins.

Subunit binding proteins; less

27

___ modulate filament stability and orientation. This includes what protein?

Filament binding proteins; cofilin (actin depolymerization factor that preferentially binds to ADP subunits in existing actin filaments.)

28

Filamentous actin contains enzymes to...

...hydrolyze ATP present in subunits.

29

ATP hydrolysis converts ___ form to ___ form.

T (stabilizes + end of filament); D

30

Nucleotide hydrolysis results in treadmilling. What is this?

+ end addition is fast and hydrolysis lags behind. - end addition is slow and hydrolysis catches up. This creates a flux of subunits.