Skeletal Muscle Flashcards
Draw a model of skeletal muscle including I-band + H-band and their components.
In contracted SkM, what ∆s? What stays the same?
H zone + I bands decrease, distance btwn Z-lines decrease
A band stays the same
What microfilaments are in the I-band? A-band? H-zone?
I-band: actin
A-band: actin + length of myosin
H-zone: myosin
What are the 3 components of the I-band?
F-actin, Tropomyosin, Troponin
What is the function of F-actin in the I-band?
Binding sites for myosin
What is the function of Tropomyosin in the I-band?
Covers myosin binding site
What is the function of Troponin in the I-band? What molecule is needed for this action? What forms as a result?
Troponin bound to Ca = conformational-∆ forces tropomyosin into groove, allows cross bridge formation
What are the 3 types of Troponin and their functions?
Troponin I: bind actin
Troponin T: at end of Tropomyosin
Troponin C: bind Ca
What is the A-band?
Length of myosin
What are the 2 components of the H-zone? What are these components made of?
Myosin tail: 2 heavy chains
Myosin head: 4 light chains contain the ATPase activity
Name the accessory proteins of SkM, where do they attach/what are their functions?
Nebulin: adjacent to actin filaments, attaches to Z-line
Titin: in elastic protein which attaches ends of the myosin molecules to the Z-line
What are the 4 steps of Sliding Filament Theory?
- Relaxed state
- Cross bridge formation
- Power stroke
- Termination / End of Contraction
What is the 1st step of Sliding Filament Theory?
Relaxed state: ATP bound to myosin head
What is the 2nd step of Sliding Filament Theory?
Cross bridge formation: ATPase converts ATP —> ADP + Pi
- allows “high energy” / ready position
- if Ca present, myosin binds to actin
What is the 3rd step of Sliding Filament Theory?
Power stroke: release ADP + Pi, actin slides over myosin
