16B Assignment

Question 1

As we will see, F-actin can be built into strong and substantial structures, however, an individual filament is ______ and the _____ in the cytoskeletal system.

rigid, thinnest
rigid, thickest
flexible, thinnest
flexible, thickest

Answer 1

flexible, thinnest

Question 2

G-actin has a stable, compact, and globular shape. How would you characterize the relative location of the C- and N- termini? (Why do you think actin’s stability and compactness is useful to the cell)

Close to each other
Distant from each other

Answer 2

Close to each other

Question 3

For a newly translated and folded G-actin protein monomer to optimally join a growing F-actin (filament) it would first need to obtain a molecule of _____, and then approach the _____ end of an elongating filament.

ATP, plus
ADP, plus
GTP, plus
ATP, minus
GTP, minus

Answer 3

ATP, plus

Question 4

After a relatively brief time incorporated into a stable filament a(n) _____ would be released from position “C.”

Pi
ADP
ATP

Answer 4

Pi

Question 5

Upon removal from a filament, _____ would be extracted from “C.”

Pi
ADP
ATP

Answer 5

ADP

Question 6

Profilin is a part of the amazing apparatus that can replenish position “C” with _____.

Pi
ADP
ATP

Answer 6

ATP

Question 7

Latrunculin is most like what actin binding protein?

A. Thymosin
B. Fimbrin
C. Profilin
D. Filamen
E. Tropomyosin

Answer 7

A. Thymosin

Question 8

Phalloidin is most like what actin binding protein?

A. Thymosin
B. Tropomyosin
C. Profilin
D. Filamen
E. Fimbrin

Answer 8

B. Tropomyosin

Question 9

Proteins (e.g. fimbrin, filamen, alpha-actinin, etc.) that manipulate actin filaments into useful multi-filament structures generally utilize _____ actin binding domains.

2
4
6
8
10

Answer 9

2

Question 10

Arp2 and Arp3 proteins facilitate the lateral assembly of a new filament on an existing filament. The regular angle formed by these complexes enables their use in:

diffuse cell membrane pressure (all directions)
focused cell membrane pressure (directional)

Answer 10

focused cell membrane pressure (directional)

Question 11

Arp2 and Arp3 enhance localized actin polymerization by overcoming the major rate-limiting step of:

ATP generation
G-actin translation
ATP hydrolysis
G-actin transcription
Nucleation

Answer 11

Nucleation

Question 12

Formin associates with the _____ end of a _____ actin filament.

+, shinking
+, growing
-, shrinking
-, growiing
-, steady

Answer 12

+, growing