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Animal Phys > The cross-bridge cycle > Flashcards

The cross-bridge cycle Flashcards

1
Q

during contraction, thick filaments bind to thin filaments and pull them toward the M line. what is this movement called?

A

filament sliding

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2
Q

during filament sliding, it shortens the _________ and increases the _________.

A

sarcomere; amount of overlap within the sarcomere

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3
Q

during contraction, where does filament sliding occur?

A

in all sarcomeres within every myofibril in a muscle fiber

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4
Q

the process by which the cross-bridge pulls the thin filament

A

cross-bridge cycle

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5
Q

how does the cross-bridge cycle generally work?

A

individual cross-bridges bind to g-actin in the thin filament
- cross-bridge then applies force to thin filament
- drawing thin filament towards M line

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6
Q

How much does each cross-bridge pull the thin filament to the M line?

A

10nm

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7
Q

only some of the cross-bridges within the muscle fiber undergo cross-bridge cycles during contraction.

A

No, all cross-bridges undergo the cycle

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8
Q

cross-bridges go thru each cycle ___________ of other cross-bridges, so cycles are _______ ____________

A

independently; not synchronous

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9
Q

the cross-bridge is connected to the tail by a

A

flexible hinge region

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10
Q

What are the two positions the cross-bridge can shift into?

A

the cocked and uncocked position

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11
Q

Which angle is smaller? the cocked or uncocked position?

A

uncocked

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12
Q

movement to the cocked position is called

A

cocking

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13
Q

occurs when ATP binds to the ATPase site on the cross-bridge
-converts ATP to ADP and Pi

A

ATP hydrolysis

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14
Q

increases the affinity of myosin for actin

A

ATP hydrolysis

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15
Q

What causes cocking within the cross-bridge?

A

energy storage within the cross-bridge

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16
Q

ATP binding to the ATPase site does what to the affinity of myosin to actin?

A

decreases affinity

17
Q

the cross-bridge cycle is dependent on ________ ________ and only occurs if the concentration of this in the sarcoplasm is high.

A

calcium ions

18
Q

-the ATPase site is empty
- no stored energy in cross-bridge
- has high affinity for actin
- bound to thin filament

A

rigor

19
Q

when does rigor end?

A

when ATP bind to the ATPase site

20
Q

What does binding of ATP cause?

A

decreases affinity of cross-bridge for actin, causing the cb to unbind from thin filament

21
Q

-ADP and Pi are now in the ATPase site
- energy is now stored in the cb
-cocking occurs
-affinity for actin increases

A

ATP hydrolysis

22
Q

Pi is released from ATPase site causing

A

power stroke

23
Q

-energy is released from the cb, moving it to the uncocked position
-movement to the uncocked position pulls thin filament towards M line
-only point in cycle where filament sliding occurs

A

power stroke

24
Q

What is the last thing to be released from ATPase site?

A

ADP

25
Q

What is the last thing to occur in the cb cycle?

A

cb is in rigor, and a new cycle begins

26
Q

true or false. during muscle fiber contraction, the amount of overlap bw thick and thin filaments increases in each sarcomere.

A

true

27
Q

thin filaments shorten during muscle fiber contraction (t or f? )

A

false

28
Q

during muscle fiber contraction, a cb pulls a thin filament toward the Z disk (t or f? )

A

false

29
Q

during muscle fib contraction, all cross-bridges go thru the cb cycle (t or f? )

A

true

30
Q

the angle bw the cb and the tail is greater when the cb is in the cocked position (t or f? )

A

true

31
Q

During rigor, the ATPase site is (bound or empty?)

A

empty

32
Q

the affinity of myosin for actin decreases when

A

ATP binds to the cb

33
Q

the cb moves to the cocked position when

A

ATP is hydrolyzed to ADP and Pi

34
Q

the power stroke occurs when

A

Pi is released from the cb

35
Q

energy becomes stored in the cb during

A

ATP hydrolysis

Animal Phys (16 decks)

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