A cytoskeletal filament has rapid assembly at one end with equally rapid disasse

Question

A cytoskeletal filament has rapid assembly at one end with equally rapid disassembly at the other end. The process being described is called__________________.
A. Dynamic Stability
B. Structural Polarity
C. Treadmilling
D. Nucleation
E. Contraction

What would happen in the absence of filament-binding proteins?
A. Actin filaments would not polymerize
B. Actin filaments would polymerize more efficiently
C. Actin filaments would not nucleate
D. Actin filaments would not form crisscrossed meshworks (gels) or linear bundles
E. All of the above

An actin filament is forming. Which step will take the longest?
A. The step mediated by formin
B. The step mediated by ARP2/3
C. The step mediated by profilin
D. The step mediated by filament-binding proteins
E. A and B are both correct

What would happen in a cell lacking profilin?
A. g-actin bound to ADP would exchange it for ATP more efficiently
B. Actin would not nucleate
C. Actin filament polymerization would be much slower
D. Actin filament polymerization would be much faster
E. A and C are both correct

If you wanted to breakdown a microtubule, which of the following should you do?
A. Phosphorylate Stathmin
B. Dephosphorylate Stathmin
C. Express catastrophe Factors
D. A and C only
E. B and C only

Which of the following are true of the MTOC?
A. It is composed of gamma tubulin, not alpha or beta tubulin
B. it is the site of microtuble nucleation
C. it associates with the plus end of microtubles
D. All of the above
E. A and B only

Which of the following statements is correct?
A. Intermediate filaments are dynamic
B. Intermediate filaments are structurally polar
C. Intermediate filaments are conserved in all eukaryotes
D. Intermediate filaments depolymerization is required for cell division
E. none of the above are correct

Instructions - Fill in the blank with one of the following three answers: There are 6 Blanks to be filled:
A. Actin Filament
B. Microtubule
C. Intermediate Filament

Please just type the letter (a, b, or c) that corresponds to the correct answer (lower case, no period).

_______usually nucleate near the cell periphery.
_______ have the smallest diameter of the three cytoskeletal filaments, _______ have the largest diameter.
_______forms the contractile ring that pinches cells apart during cell division, while________form the mitotic spindle that pulls chromosomes apart during cell division.

_______are composed of a heterogenous group of proteins and are not dynamic.

Explanation / Answer

1. D. Nucleation

2. A. Actin filaments would not polymerize

3. E. A and B are both correct , The step mediated by formin and The step mediated by ARP2/3

4. A. Phosphorylate Stathmin

5. D. All of the above are true , It is composed of gamma tubulin, not alpha or beta tubulin , it is the site of microtuble nucleation , it associates with the plus end of microtubles

6. A. Intermediate filaments are dynamic

Microtubules usually nucleate near the cell periphery

Actin filaments have the smallest diameter of the three cytoskeletal filaments and largest diameter is Microtubules

Actin Filament forms the contractile ring that pinches cells apart during cell division while Microtubules form the mitotic spindle that pulls chromosomes apart during cell division.

Intermediate filaments are composed of a heterogenous group of proteins and are not dynamic

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