lecture 14 (cytoskeleton) Flashcards
What is the function of Actin filaments?
provides mechanical support, determines cell shape, and allows movement of the cell surface, thereby enabling cells to migrate, engulf particles, and divide.
True or False: actin filaments are always stable
False, they are unstable but can be stable when associated with other proteins.
What are actin binding proteins?
They are proteins that interacts with actin filaments to enable it to function
What is the difference in length in microtubules and microfilaments?
Microfilaments is Shorter than microtubules but the total length of microfilaments is greater than microtubules
what is polymerization of actin?
it is t a process, in which actin monomers both associate with and dissociate from the ends of actin filaments.
the actin filaments grow by the addition of actin in both ends however the —– end will grow faster
plus end
the rate of actin addition on both ends are proportional to:
the concentration of G-actin (unpolymerized actin)
the rate of disassemble of actin is:
independent of G-actin (nearly constant)
which type of nucleoside triphosphate does the actin monomers carry?
ATP
what is the consequences of ATP hydrolysis in actin filament?
it reduces the strength of binding between the monomers and decreases the overall stability
when the concentration of free actin is very high actin filament will —— at both ends.
will grow rapidly adding monomers at both ends
what happens to the actin filments when the concentration of free actin is intermediate?
the filament will lose the subunit from the - end and at the same time adds them to the + end (treadmilling) a stable overall length
what happens to the actin filments when the concentration of free actin is low?
lead to filament depolymerization.
what happens to the actin filments when the concentration of free actin is high?
actin filaments will grow rapidly adding to both ends (polymerization)
what are the three phases of G-actin polymerization?
1) nucleation
2) elongation
3) steady state
nucleation:
when G-actin combine needs specifc concentration to start elongation
elongation:
addition of actin to both ends and rate of loss is constant
steady state:
the balance in addition and leaving rate (treadmilling)
the rate of addition is —— greater than the negative end
12x
if the concentration is less than —- it will shrink
0.12 micrometer
if the concentration is more than —– it will grow
0.6 micrometer
what is the name of the two protein that bind to actin monomers to prevent polymerization?
1) thymosin
2) profilin
what is the name of the two protein that bind to actin monomers to promote polymerization?
1) formins
2) actin-related proteins (ARPs)
types of actin-related proteins:
1) Actin-bundling proteins
2) cross linking protein
3) severing protein
4) capping protein (plus end blocking)
