Protein Function: Contractile Proteins
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23 Terms
What are the thick filaments of a sarcomere mainly composed of?
Myosin.
What three parts of myosin should you be able to identify?
Heavy chains, actin-binding sites, and light chains.
Where are the actin-binding sites on myosin?
On the myosin heads.
What other binding sites are found on the myosin heads?
ATP-binding sites.
What memory aid is given for the actin-binding sites?
The "mouth of the snake."
How many myosin heavy chains are there?
Two.
What do the myosin heavy chains contain?
Heads and alpha-helical tails.
What memory aid is given for the heavy chains?
The "body of the snake."
How many myosin light chains are there?
Four.
Where are the light chains located?
On the neck regions, with two on each neck.
What memory aid is given for the light chains?
"Collars on the neck."
What does the review compare the overall structure of myosin to?
Intertwined snakes with heads, mouths, and collars.
What are the thin filaments of a sarcomere mainly composed of?
Actin.
What three components should you identify on the thin filament?
F-actin filament, troponin, and tropomyosin.
What memory aid is given for F-actin?
"BIG BEADS."
What is the first step after a power stroke has ended?
Myosin remains bound to actin; ATP binds to the myosin head and causes it to release actin.
What causes myosin to detach from actin?
ATP binding to the myosin head.
What happens to ATP after myosin releases actin?
ATP is hydrolyzed into ADP and phosphate.
What is the energy from ATP hydrolysis used for?
To "cock" the myosin head and prepare it to bind the next actin bead.
What happens after the myosin head is cocked?
The myosin head binds to the next actin bead and phosphate is released.
What happens during the power stroke?
Myosin pulls on the actin strand, causing the muscle fiber to contract a little more.
What is released during the power stroke?
ADP.
What is the correct order of the cross-bridge cycle?
1) ATP binds and myosin releases actin. 2) ATP is hydrolyzed to ADP + phosphate and the myosin head is cocked. 3) Myosin binds actin and phosphate is released. 4) The power stroke occurs and ADP is released.