Lecture 5 Flashcards
What is the function of the cytoskeleton?
It allows movement, organization, and gives shape to the cell and organelles
What are the three filament types in the cytoskeleton?
Microfilaments, intermediate filaments, and microtubules
What are some subcellular structures that microfilaments organize into?
Microvilli, cell cortex, adherens belts, stress fibres, and contractile rings
What are microfilaments made of?
Actin monomers
What are the two states of actin?
G-actin (globular) and F-actin (filaments)
What occurs at the (-) end and the (+) end of an actin filament?
Depolymerization occurs at the (-) end and polymerization occurs at the (+) end
What does ATP bound actin favor?
Polymerization
What is the rate limiting step of actin polymerization?
Nucleation
What is a steady state?
When polymerization = depolymerization due to the concentrations of G-actin and F-actin being at equilibrium
How does the treadmilling of microfilaments generate force in the cell?
Treadmilling means that the microfilament is not changing in length, but it is moving in one direction. This movement is what generates the force.
What are actin sequestering proteins?
Proteins that bind at actin to prevent spontaneous polymerization.
What is profilin?
It enhances the loss of ADP off G-actin to increase the concentration of ATP-G actin
What is cofilin?
It binds to ADP-F actin and increases destabilization
What are myosins?
Myosins are ATP dependant proteins that can bind actin, undergo a conformational change, and move against the rigid actin CSK
What do all myosins contain?
An actin binding head domain, a flexible neck, and a tail domain