Question

Which of the following statements about actin is correct?

a. If the actual amount of available ATP-bound G-actin is below the critical concentration at both ends of a filament, then the actin filament will depolymerize.
b. Actin monomers are called G-actin because they have a nucleotide binding site that accommodates a molecule of GTP.
c. The plus end of an actin monomer has a net positive charge.
d. Actin generally polymerizes more rapidly at the pointed end.
e. Polymerization of an actin filament will only occur at the plus end.

Answer 1

The correct answer is option a. "If the actual amount of available ATP-bound G-actin is below the critical concentration at both ends of a filament, then the actin filament will depolymerize".

Step-by-step explanation:

Actin is the monomeric subunit of most filaments in cells, constituting the the cytoskeleton that brings support and maintains the cells' structure. Actin filament depolymerization is a process that allows for the creation of turnovers in the cytoskeleton and ensures that enough actin subunits are available to produce the filaments. One signal that starts actin filament depolymerization occurs when the actual amount of available ATP-bound G-actin is below the critical concentration at both ends of a filament. This occurs in the opposite direction as well, because the ability of a solution of G-actin to polymerize is given when the available ATP-bound G-actin is above the critical concentration.

Answer 2

Option C

Step-by-step explanation:

The G actin are Actin monomers have a nucleotide binding site which accommodates a molecule of ATP where ATP is hydrolyzed after polymerization. The plus end of an actin monomer has a net positive charge. Polymerization of an actin filament occur at the both ends but elongation is faster to about 4-5 times at the plus end than at the minus end. Actin generally polymerizes more rapidly at the barbed end than the pointed end.