Muscle 3 + 4

Question 1

What are Thin filaments tethered to at one end?

Answer 1

The Z disk

Question 2

What is the thin filament of actin composed of?

Answer 2

A double stranded α helical polymer of actin molecules (F actin)

Question 3

What is F actin?

Answer 3

The backbone of the thin filament actin composed of α helical polymer of actin molecules

Question 4

What is F actin associated with?

Answer 4

Two actin regulatory binding proteins: Tropomyosin and troponin

Question 5

Which regulatory binding proteins is actin associated with?

Answer 5

Tropomyosin and troponin

Question 6

What is each thin filament formed by?

Answer 6

The polymerization (combination) of many single molecules of globular actin

Question 7

What are thin filaments composed of?

Answer 7

• Two globular strands of actin
• Two smaller strands of tropomyosin
• Troponin

Question 8

What do Tropomyosin molecules consist of?

Answer 8

Two identical α helices that shadow the actin double helix

Question 9

Where does the Tropmyosin sit?

Answer 9

In the grooves of the helical actin strands

Question 10

What are the three components of Troponin?

Answer 10

TnT
TnC
TnI

Question 11

What can Troponin be described as because of its three components?

Answer 11

Heterotrimer

Question 12

What does TnT of troponin bind to?

Answer 12

Tropomyosin

Question 13

What does TnC of Troponin bind to?

Answer 13

Calcium

Question 14

What does TnI of troponin bind to and what does it do?

Answer 14

Binds to actin and inhibits contraction

Question 15

What does the coordinated actions of the troponin complex allow for?

Answer 15

Actin and Myosin interactions to be regulated by calcium

Question 16

Aside from Actin, Troponin and Tropomyosin what do the thin filaments also contain?

Answer 16

Nebulin

Question 17

What is Nebulin and what does it do?

Answer 17

An inelastic protein which helps to anchor the thin filaments to the Z disk

Question 18

What are Thick filaments generally made of?

Answer 18

Intertwined complexes of proteins

Question 19

What is the meaning of Myosin being a double trimer?

Answer 19

It means that there are a total of 6 chains in each myosin

Question 20

What does each Myosin consist of?

Answer 20

• Two intertwined heavy chains
• Two regulatory light chains
• two alkali (essential) light chains

Question 21

What are the three regions of the the two heavy chains of Myosin?

Answer 21

• Rod (tail)
• Hinge
• Head region

Question 22

What is the description of the Rod (tail) region of mysoin?

Answer 22

They are α helices that wrap around each other

Question 23

What occurs at the hinge region of Myosin?

Answer 23

the Tail region begins to unwind and open to form two globular heads

Question 24

What are the Globular heads for Myosin?

Answer 24

The cross bridges between the thick and thin filaments of the sarcomere

Question 25

What do the Globular heads of actin and myosin contain binding sites for?

Answer 25

* Actin | * Binding and Hydrolyzing ATP

Question 26

What does the head portion of each myosin form a complex with?

Answer 26

Two light chains •One regulatory •One alkali

Question 27

What does the Alkali light chain on the Myosin play a role in?

Answer 27

Stabilizing the myosin head region

Question 28

What does the Regulatory light chain on the Myosin do?

Answer 28

Regulates the ATPase activity of myosin

Question 29

What is a thick filament made up of?

Answer 29

Many molecules of myosin

Question 30

What does a cross bridge refer to?

Answer 30

The attachment of myosin with actin within the muscle cell

Question 31

What is Cross-Bridge Cycling?

Answer 31

Repeated attachment of actin and myosin within the cell

Question 32

Where is ATP of muscle cells split?

Answer 32

In the region where actin and myosin heads can make contact

Question 33

What is the energy generated by the splitting of ATP converted into?

Answer 33

Small movement

Question 34

What are the thick and thin filaments held in place by?

Answer 34

Plates of accessory proteins

Question 35

What do the accessory proteins that hold the thick and filaments in place divide the myofibrils into?

Answer 35

Sarcomeres

Question 36

What is Titin?

Answer 36

A large elastic protein that anchors the thick myosin filament to the Z disc

Question 37

What does Titin attach to?

Answer 37

The Z disc and the myosin

Question 38

What do C protein and myomesin do?

Answer 38

Hold the thick filament in precise alignment at the M line

Question 39

What holds the thick filament at the M line?

Answer 39

C protein and Myomesin

Question 40

What is α-actinin important for?

Answer 40

The attachment of actin filaments to the Z disk

Question 41

What attaches the actin filaments to the Z disc?

Answer 41

α-actinin

Question 42

What does Nebulin do?

Answer 42

Helps to anchor actin to Z disks