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BIOL 3040: Cell Structure and Function > Actin Filaments (Microfilament) - Cytoskeleton > Flashcards

Actin Filaments (Microfilament) - Cytoskeleton Flashcards

1
Q

What is the most important components of Action that make microfillaments unique in the cytoskeleton?

A

Actin makes microfillaments:
The smallest
The most flexible

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2
Q

What are microfilaments made up of?

A

monomers (G-actin)

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3
Q

What is microfilaments plymerized to?

A

polymer (F-actin)

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4
Q

What is the monomers of microfilaments?

A

G-actin

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5
Q

What is the polymer of microfilaments?

A

F-actin

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6
Q

What do two polymers of F-actin form in a microfilament?

A

double-helix

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7
Q

What makes up a double- helix in a microfilament?

A

two polymers of F-actin

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8
Q

Explain the formation of a microfilament.

A

A microfilament is made up of monomer G-actin, that polymerize to an F-actin, creating a polymer. Two F-actin polymers twisted together create a double-helix, creating a microfilament.

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9
Q

What are the 3 main key functions of the cytoskeleton?

A

1) maintain cell shape
2) allow key movements
3) adapt to compressive forces

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10
Q

How are microfilaments involved in cell migration?

A

microfilaments can polymerize, squeeze in, and changes morphology to fit through tiny spaces

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11
Q

What is Diapedesis and actins associates?

A

white blood cells change shape through actins to squeeze through the tiny intracapillary clefts

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12
Q

Why would a white blood cell want to perform cell migration?

A

to move out of the blood stream and into interstial spaces to fight pathogens

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13
Q

What is microfilaments role in cell division?

A

microfilaments seperate one cell by forming a constriction ring, allowing actin to pinch the cell in half producing two daughter cells.

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14
Q

What stage of mitosis does actin form a constriction ring?

A

during cytokinesis

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15
Q

How are microfillaments related to cell extension?

A

Actin are involved in the formation of Microvilli and Stereocilia.

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16
Q

What are the two main parts of the cell membrane in microvilli and stereocilia?

A

Apical: top portion
Basal: bottom portion

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17
Q

What occurs on the Apical surface of microvilli and stereocilia?

A

Actin forms a core of fingerlike projections or extensions, allowing movement

18
Q

Which cell has a a smaller extension on apical surface?

Microvilli
Stereocilia

A

Microvilli

19
Q

Which cell has a larger extension on apical surface?

Microvilli
Stereocilia

A

Stereocilia

20
Q

What is Microvilli’s role in the gastrointestinal tract?

A

food passing through GI tract come into contact with microvilli, increasing surface area for digestion

21
Q

What is Stereocilias role in the inner ear?

A

the stereocilia movement opens up channels in the inner ear for balance (vestibular) and hearing (cochlear)

22
Q

What is microfilaments role in muscle contraction?

A

microfilaments in muscles are know as Myofilaments (Actin + Myosin). The mysion clicks on with action, pulling the actin strans closer to other actin strands, causing shortening of myofilaments. = muscle contraction and relaxation.
(heavily involved in ATP production)

23
Q

What is a myofilament?

A

the microfilament of a muscle cell, made up of actin and myosin

24
Q

What does mysosin do in a muscle cell?

A

clickes on actin to pull actin strands closer together (shortening myofilaments) to cause muscle contraction/ reflaxation

25
Q

What role does microfilaments play in cell junctions?

A

prevents cell seperation through tight junctions and adheren junctions

26
Q

Whar are actin filaments key in the cell function formation?

A

actin strands help stick cells together and prevents seperation.

27
Q

What role does microfilamanets play in membrane transport?

A

actin responsible for invagination/ fuses on cell membrane allowing endosomes to perform endocytosis or extocytosis.

28
Q

What is actin assembled into filaments called?

A

F-actin

29
Q

Which has an ATP inding site?

G-actin
F-actin

A

G-actin

30
Q

Where is the ATP binding site located in a monomer G-protein?

A

between domains II and IV

31
Q

Actin filaments are:

non-polar
polar

A

polar

(-) end: ATP binding cleft (gobular heads of myosin)
(+) end: Barbed end (gobular heads of myosin)

32
Q

What end of actin filaments is pointed, where ATP binding cleft is located?

A

(-) end

33
Q

What end of actin filaments is the barbed end?

A

(+) end

34
Q

G-actin has intrinsic ATPase activty, thus is usually bound to:

ATP
ADP
both

A

both ATP and ADP

35
Q

Where does polymerization and depolymerization occur in microfilaments?

A

at the ends of the filaments (not the middle)

36
Q

What are the three phases of polymerization?

A

1) nucleation
2) elongation
3) steady-state

37
Q

Which phase of polymerization occurs slowly?

A

nucleation

38
Q

Which phase of polymerization occurs relatively rapidly?

A

elongation

39
Q

When does elongation occur?

A

Only when g-protein concentration is above a critical concentration. (Cc)

40
Q

What phase of actin polymerization does elongation occur?

A

when G-actin concentration in above a Cc

BIOL 3040: Cell Structure and Function (49 decks)

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