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MSDF > Myosin II > Flashcards

Myosin II Flashcards

1
Q

What is the repeating unit of myofibrils?

A

Sarcomere

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2
Q

Why does actinomyosin have semicrystalline properties?

A

Repeating sarcomere structure

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3
Q

What is the structure of myosin II?

A
  • Dimer of 2 heavy chains
  • Long coiled-coil domain
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4
Q

Does myosin II have a cargo binding domain?

A

No

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5
Q

How many IQ motifs does the lever arm of myosin have?

A

2

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6
Q

What regulates the powerstroke in myosin II?

A

The lever arm

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7
Q

Which direction does myosin II move?

A

towards the plus end of actin

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8
Q

Does myosin II have a high or low duty ratio?

A

Low

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9
Q

What forms the core of myosin filaments?

A

interaction of coiled-coil domains

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10
Q

When muscle contraction occurs what happens to the length of the sarcomere?

A

It gets shorter

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11
Q

When muscle contraction occurs what happens to the size of the dark band?

A

It remains the same

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12
Q

Are the 2 heads of myosin independent?

A

Yes

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13
Q

When does the pre-stroke position occur in myosin II?

A

Once ATP hydrolysis has occurred

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14
Q

Does myosin II move hand-over-hand?

A

No as the heads are independent from each other

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15
Q

How many ATP are consumed per step on myosin II?

A

1

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16
Q

What is the purpose of CapZ?

A

Protects the plus ends of actin filaments

17
Q

What is the role of Z-discs?

A

In muscle hold plus ends of actin filaments coming from adjacent sarcomeres

18
Q

What is the function of alpha-actinin?

A

In muscle helps to attach actin filaments to the Z-lines

19
Q

What is the function of tropomodulin?

A
  • Binds and caps minus ends of actin
  • Helps regulate length of actin filaments
20
Q

How does tropomodulin help regulate actin filament length?

A

By blocking dissociation of ADP-bound actin monomers for minus end

21
Q

Which protein acts as a molecular ruler to set the length of actin filaments?

A

Nebulin

22
Q

What is the largest known protein?

A

Titin

23
Q

What is the function of Titin?

A

Functions as a passive molecular spring responsible for muscle elasticity

24
Q

What is the function of tropomyocin?

A

Controls the binding of myosin

25
Q

What does troponin bind?

A

Ca2+

26
Q

How do troponin and Ca2+ regulate muscle contraction?

A
  • Ca2+ triggers muscle contraction
  • Ca2+ binds to troponon which shifts conformation and moves tropomyosin, exposing myosin binding sites

MSDF (30 decks)

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