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Cell Biology > Microfilaments > Flashcards

Microfilaments Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

components of the cytoskeleton

A

microfilaments, intermediate filaments, microtubules

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2
Q

microfilament

A

smallest component of cytoskeleton; dynamic structure involved in movement

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3
Q

intermediate filament

A

midsized component, static structure involved in stabilization

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4
Q

microtubules

A

largest component, dynamic structure involved in movement

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5
Q

epithelial cell polarity

A

apical domain w/ microvilli and cell junctions; basolateral domain with cortical band & attached to basal lamina

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6
Q

motile cell polarity

A

leading edge w/ filopodium; lagging edge

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7
Q

cellular structures containing actin

A

microvilli, cell cortex, circumferential belt, leading edge, filopodia, contractile ring, stress fibers

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8
Q

types of actins

A

α actin, ß actin, gamma actin

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9
Q

α actin

A

involved in muscle contraction (circus. belt and contractile ring)

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10
Q

ß actin

A

part of the leading edge/lamellipodium

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11
Q

gamma actin

A

makes up stress fibers

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12
Q

4 states of actin

A

G-Actin ATP, G-Actin ADP, F-Actin ATP, F-Actin ADP

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13
Q

most common states of actin

A

G-Actin ATP and F-Actin ADP

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14
Q

actin polymerization

A

nucleation, elongation, steady state

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15
Q

How do the plus and minus ends of microfilaments differ?

A

ATP binding site of a G-Actin align to the - end of the filament; Monomers add preferentially to the + end of the microfilament.

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16
Q

critical concentration

A

Concentrations of monomers needed to add to the +/- end of the microfilament; Higher conc. needed to add to - end of microfilament.

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17
Q

treadmilling

A

Monomers add preferentially to one end and dissociate at the other.
Accelerated by profilin and cofilin.

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18
Q

Cofilin

A

severing factor

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19
Q

Profilin

A

exchange factor; removes ADP and adds ATP to encourage polymerization

20
Q

Thymosin ß4

A

provides a reservoir of ATP G-actin by binding and preventing its addition to the microfilament

21
Q

CapZ

A

binds + end of microfilament to prevent subunit addition/loss

22
Q

Tropomodulin

A

binds - end of microfilament to prevent subunit addition/loss

23
Q

Formins

A

create a dimer at the end of the filament and guides the addition of G-actin to prevent branching

24
Q

Arp 2/3

A

(protein machine) binds to the side of the actin filament and binds a new nucleus to form branch at 70 degree angle

25
Q

regulatory proteins

A

profilin, thymosin ß4, cofilin

26
Q

capping molecules

A

capZ, tropomodulin

27
Q

molecules influencing microfilament structure

A

formins, arp2/3

28
Q

How do actin cross linking proteins stabilize actin structures?

A

They have 2 actin binding domains that bind to the microfilament and stabilize in various arrangements.
The type of cross linking depends on the distance between the actin binding domains.

29
Q

actin crosslinking proteins

A

fimbrin, α actinin, spectrin, filamin

30
Q

fimbrin

A

2 actin binding domains with short tail; stabilizes microvilli, filopodia, and focal adhesions

31
Q

α actinin

A

actin binding domain with short tail, arranged head to tail; stabilizes stress fibers, filopodia, & muscle Z band

32
Q

spectrin

A

actin binding domain with longer tail, arranged head to tail; stabilizes cell cortex

33
Q

filamin

A

actin binding domain with medium tail, connected at the tail end; stabilizes leading edge, stress fibers, and filopodia

34
Q

myosin structure

A

globular (ATP binding) head, long coiled tail, flexible neck; myosin I is a monomer, others are dimers

35
Q

How does myosin II move actin filaments?

A

Binds ATP, head released from actin.
Hydrolysis of ATP to ADP + P, myosin head rotates into “cocked” state.
Myosin head binds actin filament.
“Power stroke” - release of P and elastic energy straightens myosin & moves actin filament toward (-) end.
ADP released; ATP bound; head released from actin

36
Q

How does myosin V move vesicles?

A

Binds microfilament with head.

Tail interacts with receptor or molecule in the membrane of a vesicle/organelle.

37
Q

directional movement of myosin

A

all myosin EXCEPT myosin VI move toward the positive end

38
Q

actin-containing contractile structures in nonmuscle cells

A

polarized epithelial cells: circumferential belt (structural)
motile cells: stress fibers, focal adhesions w/ integrins
cleavage furrow: contractile ring

39
Q

describe how cells move

A

Extension - sensing the environment and reaching out with the leading edge (signalling activates Cdc42 and Rac).
Adhesion - formation of new focal adhesion (integrin binds to ECM and interacts with internal microfilaments); gives leverage to start moving forward.
Translocation - nucleus will orient near front of the cell; mass of the cell will move forward toward leading edge as actin filaments rearrange.
De-adhesion - rear focal adhesion releases to allow cell to propel forward (in some cells, Rho promotes de-adhesion).

40
Q

members of the Rho family of GTPases

A

Rho, Rac, and Cdc42

41
Q

Rho

A

found in stress fibers; activates actin and myosin activity

42
Q

Rac

A

found in the lamellipodia; activates WAVE > Arp 2/3

43
Q

Cdc42

A

found in filopodia; activates WASP > Arp2/3 and sets polarity

44
Q

How do intermediate filaments differ from microfilaments and microtubules?

A

do not hydrolyze ATP or GTP, more rigid, rod-like structure, made of lamins and keratins

45
Q

lamins

A

give nuclear structure and strength (found in all cells but red blood cells)

46
Q

keratins

A

found outside of the nucleus; give structure to cell and the placement of the nucleus

Cell Biology (16 decks)

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