BIO 330 Lecture Notes - Lecture 22: Intermediate Filament, Myosin, Cytoskeleton

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24 May 2018
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BIO 330 Lecture notes 22:
How does the cell directly use a cytoskeleton
Provide and maintain shape
Protect against mechanical stress by combine tension and compression
How does a cell use motors in conjunction with the cytoskeleton
Organize compartments
Transport materials
Why does a cell actively remodel their cytoskeleton?
Move through their environment (migrate)
Respond to intracellular & extracellular signals
What are the three components of cytoskeleton?
intermediate filaments
microtubules
actin filaments
What is actin also known as?
the building block of the cytoskeleton
Are actin filaments polar or non polar?
polar - barbed end = plus
pointed end = minus
Which side of actin adds actin monomers?
+ adds, - loses
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What is the term for when filament length stays the same but the filament is changing
monomers
treadmilling
What is the first step in actin production
nucleation (lag phase)
actin subunits begin to form into oligomers
What is the second step in actin production?
elongation (growth phase)
grows on both sides
What is the third step in actin production?
steady state equilibrium phase
actin filaments add to the to plus end and comes off the negative end
What is the braiding of multiple myosins called?
thick filaments
What is the middle part of a thick filament called and what is it?
the bare zone
zone that is free of myosin head domains
What is included on a myosin head?
IT IS A DIMER
2 catalytic cores
2 lever arms connected to thick filaments via coil-coil rod
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Explain the steps in myosin cross-bridge cycle
ADP + Pi bound myosin head binds to actin, Pi kicked off to maintain contact
Power stroke activated, ADP falls off (now in RIGOR conformation)
ATP binds to release myosin head from actin
ATP hydrolyzed to re-cock the arm
Where are actin filaments anchored?
the Z disk
Which side of the actin filament interfaces with the z disk?
+ end
What is the building block of muscle?
sarcomere
What is a bunch of sarcomeres together called?
myofibril
What are a bunch of myofibrils together called?
muscle fiber
What two things distribute calcium in sarcomeres?
Transverse tubules form invaginations in plasma membrane, and the sarcoplasmic
reticulum further distributes
How does the sarcoplasmic reticulum release calcium into the cytosol?
Via a voltage-gated Ca2+ channel in the T-tubule membrane
When the t-tubule membrane is depolarized, the voltage-gated channel opens, which
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