Module 3- Lesson 1 Flashcards
What are the three main components of the cytoskeleton?
Actin microfilaments, microtubules, and intermediate filaments.
What is the monomeric form of actin called?
G-actin (globular actin).
What molecule is required for actin polymerisation?
ATP.
What protein complex nucleates branched actin filaments?
Arp2/3 complex.
What motor proteins move along actin filaments?
Myosins.
Why does the cytoskeleton need to strike a balance between stability and flexibility?
To maintain cellular structure while allowing dynamic processes like movement, shape change, and division.
How does polarity affect the dynamics of actin filaments?
The + end grows faster than the - end, allowing for directional treadmilling.
What is the significance of actin treadmilling?
It allows for dynamic remodeling of the cytoskeleton for processes like cell movement and shape changes.
Compare the roles of formins and Arp2/3 in actin assembly.
Formins nucleate unbranched filaments; Arp2/3 nucleates branched filaments.
Why don’t intermediate filaments serve as tracks for motor proteins?
They lack polarity and are mostly static, making them unsuitable for directional transport.
What are the three steps of actin polymerisation?
Nucleation, elongation, and steady-state (treadmilling).
Outline the cycle of a myosin II motor interacting with actin.
Binds ATP → releases actin
Hydrolyses ATP → cocked state
Binds actin
Releases Pi → power stroke
Releases ADP → binds ATP → cycle restarts
How does profilin regulate actin polymerisation?
It promotes the formation of ATP-G-actin by catalyzing nucleotide exchange.
What is the role of cofilin in actin filament dynamics?
It destabilizes ADP-actin in filaments, enhancing disassembly at the - end.
How does thymosin β4 affect actin filament dynamics?
It sequesters ATP-G-actin, acting as a buffer for filament growth.
