Brainscape's Knowledge GenomeTM

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


See full index

BI 338 Cells > Microfilaments (Lecture 18) > Flashcards

Microfilaments (Lecture 18) Flashcards

1
Q

True or False: Cells differ in internal organization, shape, and motility while the cytoskeleton supports its needs.

A

True

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

True or False: Distribution and organization of cytoskeleton filaments structurally polarizes different cells.

A

True

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

In epithelial cells, core bundles of actin ______ support the apical microvilli.

A

Microfilaments

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

What are the four parts that make up the cytoskeleton?

A

Microfilaments, microtubules, intermediate filaments, nucleus

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

In the macrophage cytoskeleton, migrating cells polarized with leading edge oriented in the direction of locomotion.

A

True

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

True or False: Cytoskeletons components contain at least 3 of the 4 parts that make up the cytoskeleton.

A

False, only need to contain one or more

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

Order microtubules, microfilaments and intermediate filaments from shortest to longest.

A

Microfilament, Intermediate, microtubule

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

______ is organized into functional bundles by actin-binding proteins and may serve as tracks for ATP-powered myosin motor proteins

A

Actin microfilaments

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

______ extend through cell and provide organizational framework and may serve as tracks for ATP-powered kinesins and dyneins (motor proteins).

A

Tubulin microtubules

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

______ provide structural support for nuclear membrane, barrier functions in skin, hair, and nails and are not used as tracks by motor proteins.

A

True

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

True or False: Cells sense extracellular signals and interpret them to direct arrangement of the cytoskeleton.

A

True, Detected by cell-surface receptors that activate signal transduction pathways

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

______ is a disease that can cause dysregulation or cytoskeletal component defects.

A

Metastatic cancer, allow cells to break away from the generating tissue.

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

What are the 9 types of microfilament organizations.

A

Microvilli, cell cortex, Adherens belt, filopodia, lamellipodium/leading edge, stress fibers, phagocytosis, moving Endocytic vesicles, contractile ring.

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

The building block of microfilaments is ______ and is molded into different structures by ______ proteins.

A

Actin, actin binding

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

True or False: Microfilaments have reverse assembly.

A

True

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

True or False: Actin is not an abundant intracellular protein in eukaryotic cells.

A

False

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

True or False: Actins from amoebae and animals are 80% identical.

A

True

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

How many actin genes do yeast and humans have?

A

2 and 6

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

What are the 3 different groups of actin based on charge.

A

a-actin, b-actin, y-actin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

______ are enriched in cell cortex & leading edge of motile cells.

A

b-actin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

______ are found in some stress fibers.

A

y-actin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

______ are associated with contractile .

A

a-actin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Each actin molecule contains an ______ ion complexed with either ______.

A

Mg2+, ATP or ADP

24
Q

True or False: Actin is a ATPase that hydrolyzes ATP to ADP and Pi.

A

True

25
Q

What are the two forms of actin?

A

Globular polymer, G-actin
Filamentous polymer. F-actin
F-actin is a linear chain of G-actin subunits

26
Q

______ actin is separated into two lobes by a deep cleft, denatures quickly without a bound nucleotide, and addition of cations Mg2+, K+, Na+ to G-actin induces filament formation.

A

G-actin

27
Q

______ actin is arranged in helical structures of one another and the ATP binding clefts are all oriented to the - end.

A

F-actin

28
Q

When does F actin repeat itself?

A

72nm or 14 actin subunits`

29
Q

What end of the F-actin filament is favoured for the addition of actin sub units and what side is favoured for subunit dissociation of ATP.

A

+, -

30
Q

True or False: Electron microscopy can’t detect the ATP-binding cleft when looking at microfilaments

A

True

31
Q

When myosin binds to actin, the arrow heads are pointing towards the ______ end and the barbed end is pointing towards the ______ end.

A

-, +

32
Q

True or False: Actin filaments are dynamic with polymerization and depolymerization.

A

True

33
Q

True or False: Actin-binding proteins contribute to the stability and disassembly of filaments.

A

True

34
Q

True or False: G-actin cannot be purified at high concentration without forming filaments if the buffer has ATP and low levels of cation.

A

False, it can

35
Q

What are the 3 phases of actin polymerization.

A

Nucleation, elongation, steady state

36
Q

The Lag period in which G-actin subunits combine into an oligomer of 2-3 subunits is known as the.

A

Nucleation phase

37
Q

True or False: In the elongation phase, actin is being added to both the + and - end.

A

True

38
Q

What is the critical concentration of actin polymerization?

A

Below which filaments cannot assemble and above which filament form

39
Q

What is the steady state of actin polymerization?

A
  •   Concentration of monomeric actin remains at the critical concentration\
  •   Rate of assembly and dissociation are equal
  •   Mixture of filaments and monomers
40
Q

True or False: Actin grows 10x faster at + end then negative end.

A

True

41
Q

True or False: Dissociation of ATP-G-actin subunits is favoured at the (-) end.

A

False, similar at both ends

42
Q

What is the Cc of subunits at the + end?

A

0.12 µM

43
Q

What is the Cc of subunits at the - end?

A

0.60 µM

44
Q

During actin treadmiling, at the steady state the + and - end adds and dissociated at the same rate.

A

False, + adds and - dissociates at the same rate.

45
Q

What is the actin treadmill powered by?

A

ATP hydrolysis

46
Q

What are the 3 types of actin binding proteins?

A

Cofilin, Profilin, Thymosin-B4

47
Q

______ binds G-actin on the side opposite of the ATP-binding cleft (+ end?) and keeps essentially all free G-actin in ATP-bound state

A

Profilin

48
Q

______ specifically binds ADP-F-actin and allows the filament to break into short pieces with more (-) ends that can be disassembled simultaneously.

A

Cofilin

49
Q

What two ATP binding proteins enhance treadmilling by 10x.

A

Profilin and Cofilin

50
Q

______ is a actin monomer sequestering protein that binds excess ATP-G-actin and will be released when ATP-G-actin becomes low

A

Thymosin-B4

51
Q

What is an example of Thymosin-B4

A

Platelets rich in actin and thymosin-β4; allows burst of actin assembly during blood clotting

52
Q

—______ helps nucleotide exchange so ATP-actin ready for (+) end — 

______ fragments ADPactin filament regions, enhancing depolymerization — 

______ provides buffered reservoir of ATP-G-actin for polymerization

A

Profilin

Cofilin

Thymosin-B4

53
Q

What is the function of capping proteins?

A

Prevent continual growth and disassembly in an uncontrolled manner

54
Q

What are the two classes of capping protein at each end of the filament.

A

CapZ + end

Tropomodulin - end

55
Q

The capping protein ______ blocks assembly and ______ blocks disassembly.

A

CapZ

Tropomodulin

BI 338 Cells (21 decks)

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