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Block II > Contractile Proteins and Motors > Flashcards

Contractile Proteins and Motors Flashcards

1
Q

What are the major protein players in muscle contraction

A

Myosin
Microfilaments (actin)
Tropomyosin
Troponin

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2
Q

Myosin II structure

A

2 heads - ATP, binds actin
neck
Tail - forms a filament

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3
Q

Who are the thick and thin filaments

A

Myosin - thick
Actin - thin

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4
Q

What does tropomyosin do

A

Controls myosin binding sites

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5
Q

Where does tropomyosin bind

A

In the groove between actin strands

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6
Q

How does tropomyosin do its job

A

In low Ca state –> blocks myosin binding site on actin
in high Ca state –> moves to reveal myosin binding site on actin

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7
Q

How does tropomyosin do its job

A

In low Ca state –> blocks myosin binding site on actin
in high Ca state –> moves to reveal myosin binding site on actin

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8
Q

Who is troponin

A

Complex that can bind with Ca, associated with tropomyosin

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9
Q

Who doesn’t have troponin

A

Smooth muscle

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10
Q

What does troponin do

A

controls tropomyosin position in response to Ca levels

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11
Q

Run down of the basic relationship between the 4 proteins

A

Troponin binds to Ca controls –> tropomyosin position - controls –> myosin binding to actin

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12
Q

What is the sarcoplasm filled with

A

repeating arrays of filaments (myofibrils) made of actin and myosin

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13
Q

Where does the intercellular Ca live

A

The SR

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14
Q

What are t-tubules

A

Transverse invaginations in the sarcolemma (plasma membrane)
They transmit the action potential to the myofilaments

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15
Q

What is the area where the sarcolemma and T-tubules come into proximity called

A

Terminal cisterna

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16
Q

What is a sarcomere

A

The contractile unit if the muscle cell

17
Q

Why does skeletal (and cardiac) muscle look striated

A

Ordered, repeating arrangements of actin and myosin –> myofilaments

18
Q

What do thick filaments contain

A

Myosin

19
Q

What do thin filaments contain

A

Actin, tropomyosin, troponin

20
Q

Dark bands:

A

A bands, thick filaments and overlapping thin filaments

21
Q

Light bands

A

i bands, thin filaments

22
Q

M line:

A

H band , connection between adjacent mysosin filaments

23
Q

z discs:

A

Define the ends of the sarcomere, site of attachment of plus end of actin filaments

24
Q

How are the myofilaments arranged in the sarcomere

A

6 actin around 1 myosin

25
Q

In basic terms, what makes muscles contract

A

Sarcomeres shortening as myosin walks along actin

26
Q

Basics of the cross-bridge cycle:

A

ATP binding releases myosin head from actin –>
ATP –> ADP rotates myosin head —>
Myosin head binds actin filament –>
“Power stroke” - release of P and stored elastic energy moves actin filament left –>
ADP –> ATP - myosin released

27
Q

What is happening in rigor mortis

A

Myosin head is attached to actin, no ATP available to release it

28
Q

What regulates contraction

A

Ca ions

29
Q

How does Ca regulate contraction (low Ca)

A

Low Ca: myosin binding site is blocked by tropomyosin which is held in place by troponin

30
Q

How does Ca regulate contraction (high Ca)

A

High Ca in cytoplasm –>
Ca binds to troponin –>
Conformational change –>
Tropomyosin moved off of myosin binding site on actin

31
Q

What controls the release of Ca

A

Action potentials - stimulate release of Ca from the SR

32
Q

What protein does smooth muscle lack

A

Troponin

33
Q

What binds sarcoplasmic Ca in smooth muscles

A

Calmodulin

Block II (28 decks)

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