Lecture 8: Cytoskeleton I: Microfilaments

Question 1

Actin is an ____ and ____ binding protein

Answer 1

ATP an Mg++

Question 2

What are microfilaments comprised of?

Answer 2

Actin

Question 3

Once actin is assembled into microfilaments, what happens to ATP

Answer 3

hydrolyzed to ADP

Question 4

how are different tissues made from different forms of actin (alpha, beta, gamma)?

Answer 4

different genes, different promoters for each type of tissue

Question 5

Do microfilaments, comprised of actin, have structural polarity?

Answer 5

Yes

Question 6

What is the result of structural polarity?

Answer 6

Treadmilling - different rates of polymerization at + and - ends

Question 7

what are the 2 ways to determine structural polarity?

Answer 7

growth rate at each end (electron microscopy) and binding to myosin (+ end)

Question 8

what are the two classes of actin monomer binding proteins? what do they regulate?

Answer 8

thymosins, profilins

actin assembly

Question 9

what is the cell cortex?

Answer 9

plasma membrane + underlying mesh of crosslinked actin filaments (microfilaments)

Question 10

microfilaments can allow stretching and contracting of the plasma membrane to form __________

Answer 10

filopodia and lamellipodia

Question 11

which membrane structures do microfilaments help to stabilize?

Answer 11

microvilli, stress fibers, lamellipodia, contractile ring of dividing cell

Question 12

what does capping protein do?

Answer 12

limit length of growing microfilaments (lamellipodia)