Muscle 3 + 4 Flashcards
What are Thin filaments tethered to at one end?
The Z disk
What is the thin filament of actin composed of?
A double stranded α helical polymer of actin molecules (F actin)
What is F actin?
The backbone of the thin filament actin composed of α helical polymer of actin molecules
What is F actin associated with?
Two actin regulatory binding proteins: Tropomyosin and troponin
Which regulatory binding proteins is actin associated with?
Tropomyosin and troponin
What is each thin filament formed by?
The polymerization (combination) of many single molecules of globular actin
What are thin filaments composed of?
- Two globular strands of actin
- Two smaller strands of tropomyosin
- Troponin
What do Tropomyosin molecules consist of?
Two identical α helices that shadow the actin double helix
Where does the Tropmyosin sit?
In the grooves of the helical actin strands
What are the three components of Troponin?
TnT
TnC
TnI
What can Troponin be described as because of its three components?
Heterotrimer
What does TnT of troponin bind to?
Tropomyosin
What does TnC of Troponin bind to?
Calcium
What does TnI of troponin bind to and what does it do?
Binds to actin and inhibits contraction
What does the coordinated actions of the troponin complex allow for?
Actin and Myosin interactions to be regulated by calcium
Aside from Actin, Troponin and Tropomyosin what do the thin filaments also contain?
Nebulin
What is Nebulin and what does it do?
An inelastic protein which helps to anchor the thin filaments to the Z disk
What are Thick filaments generally made of?
Intertwined complexes of proteins
What is the meaning of Myosin being a double trimer?
It means that there are a total of 6 chains in each myosin
What does each Myosin consist of?
- Two intertwined heavy chains
- Two regulatory light chains
- two alkali (essential) light chains
What are the three regions of the the two heavy chains of Myosin?
- Rod (tail)
- Hinge
- Head region
What is the description of the Rod (tail) region of mysoin?
They are α helices that wrap around each other
What occurs at the hinge region of Myosin?
the Tail region begins to unwind and open to form two globular heads
What are the Globular heads for Myosin?
The cross bridges between the thick and thin filaments of the sarcomere
What do the Globular heads of actin and myosin contain binding sites for?
- Actin
* Binding and Hydrolyzing ATP
What does the head portion of each myosin form a complex with?
Two light chains
•One regulatory
•One alkali
What does the Alkali light chain on the Myosin play a role in?
Stabilizing the myosin head region
What does the Regulatory light chain on the Myosin do?
Regulates the ATPase activity of myosin
What is a thick filament made up of?
Many molecules of myosin
What does a cross bridge refer to?
The attachment of myosin with actin within the muscle cell
What is Cross-Bridge Cycling?
Repeated attachment of actin and myosin within the cell
Where is ATP of muscle cells split?
In the region where actin and myosin heads can make contact
What is the energy generated by the splitting of ATP converted into?
Small movement
What are the thick and thin filaments held in place by?
Plates of accessory proteins
What do the accessory proteins that hold the thick and filaments in place divide the myofibrils into?
Sarcomeres
What is Titin?
A large elastic protein that anchors the thick myosin filament to the Z disc
What does Titin attach to?
The Z disc and the myosin
What do C protein and myomesin do?
Hold the thick filament in precise alignment at the M line
What holds the thick filament at the M line?
C protein and Myomesin
What is α-actinin important for?
The attachment of actin filaments to the Z disk
What attaches the actin filaments to the Z disc?
α-actinin
What does Nebulin do?
Helps to anchor actin to Z disks
