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MMD1042: Module 1 > Cytosquelette 1: Actin & Questions > Flashcards

Cytosquelette 1: Actin & Questions Flashcards

1
Q

What are the three main components of cytosqeleton?

A

Microtubules

Filament Intermediates

Actine

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2
Q

Where does the adition of G-Actin occur?

A

Actin is polarized:

The ends are not the same

  • and + side

+ side will bind G-Actin

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3
Q

What is the role of profilin?

A

Inhibits spontaneous nucleation

Accelerated (promotes) polymerization once nucleation is done

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4
Q

What is the role of cofilin?

A

Promotes depolymerization

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5
Q

How do you explain muscle stiffness in relation to ATP?

A

Myosine: Motor protein to pull two filaments together

Myo: Contractile

Has two mobile heads

Uses ATP as energy to move:

Each head of the myosin will use ATP

ATP binding will detach the head from its bound position

Hydrolysis of the ATP will move the head to another site of attachment

This is why lack of ATP leads to muscle stiffness → rigid cadaver

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6
Q

What are sacromeres?

A

A sarcomere is the functional unit of striated muscle. This means it is the most basic unit that makes up our skeletal muscle.

Each sarcomere is composed of protein filaments (myofilaments) that include mainly the thick filaments called myosin, and thin filaments called actin

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7
Q

What makes up microvilli?

A

Actin
@ parallel actin

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8
Q

What is Arp2/3 and Formine?

A

Arp2/3: Promotes Branched Filaments

Activation always begins at the membrane

Always at 70° angle

Formine: Promotes Non-branched Filaments

Always attached at the positive extremity

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9
Q

What is the role of CapZ ?

A

Used in actin to stabilize the structure

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10
Q

Where do you find most of actin nucleation?

A

At the phospholipid membrane of the cell

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11
Q

What is the difference between contractive fibers and lamelopode and filopode in their location, morphology and constituant?

A

Location:
FC at the cytoplasm
Lamellipode and filopode and the Conducting extremety

Morphology:
Lamellopods are branched, filopods are non branched

Constituatiant: actin

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12
Q

What is the main molecule for cell migration? What does it involve?

A

Actin!!!!

Portrusion of the leading end
Contraction of the tail end and re-building of the actin cell cortex

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13
Q

What are the main molecules involved in cell splicing during cell division?

A

Actin and Myosin

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14
Q

What is chemotaxis?

A

Using chemical gradient along with actin to move

For example neutrophils hunting bacteria

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15
Q

What are the main constituents of Ceinture adherent?

A

Formed by actin and myosin

Form the zonula adherents

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16
Q

What is the function of profilin in actin polymerization?
a. Inhibits spontaneous nucleation
b. Promotes depolymerization
c. Accelerates polymerization once nucleation is done
d. Stabilizes actin filaments

A

Inhibits spontaneous nucleation
Accelerates polymerization once nucleation is done

17
Q
  1. Lack of ATP leads to muscle stiffness because:
    a. Actin filaments cannot bind to myosin
    b. Actin filaments cannot detach from myosin
    c. Actin filaments cannot polymerize
    d. Actin filaments cannot depolymerize
A

. Actin filaments cannot detach from myosin

18
Q

The nucleation of actin filaments can occur through which mechanisms?
a. Arp2/3 and Formine
b. Arp2/3 and Profilin
c. Cofilin and Formine
d. Cofilin and CapZ

A

a. Arp2/3 and Formine

19
Q

What is the role of cofilin in actin dynamics?
a. Inhibits spontaneous nucleation
b. Promotes depolymerization
c. Accelerates polymerization once nucleation is done
d. Stabilizes actin filaments

A

b. Promotes depolymerization

20
Q
  1. How does ATP binding affect the movement of myosin heads?
    a. ATP binding detaches the head from its bound position
    b. ATP binding stabilizes the head in its bound position
    c. ATP binding promotes polymerization of actin filaments
    d. ATP binding promotes depolymerization of actin filaments
A

a. ATP binding detaches the head from its bound position

21
Q

Which structure is important for parallel filament creation?
a. Fimbrin
b. Myosin
c. Profilin
d. Cofilin

A

Fimbrin

22
Q

Which nucleation mechanism is responsible for branched actin filaments?
a. Arp2/3
b. Formine
c. Profilin
d. Cofilin

A

Arp2/3

23
Q

Which structure is responsible for cellular division?
a. L’anneau contractile
b. Lamellipodia
c. Filopodia
d. Microvilli

A

a. L’anneau contractile

24
Q

How do actin and myosin contribute to cell migration?
a. Actin forms lamellipodia and filopodia for movement, while myosin changes the cell cortex
b. Actin stabilizes the cell membrane, while myosin promotes cell division
c. Actin forms stress fibers for migration, while myosin promotes cell adhesion
d. Actin and myosin work together to form the adherence belt for cellular movement

A

a. Actin forms lamellipodia and filopodia for movement, while myosin changes the cell cortex

MMD1042: Module 1 (21 decks)

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