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