BIOL 4100 EXAM 4 QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED

BIOL 4100 EXAM 4 QUESTIONS AND ANSWERS WITH

COMPLETE SOLUTIONS VERIFIED

Globular (G) actin

Actin monomer with tight binding sites that mediate head-to-tail interactions with two

other actin monomers

Filamentous (F) actin

Microfilament formed by polymerization of actin monomers

Barbed (+) end

End to which assembly is favored in actin polymerization

Pointed (-) end

End to which assembly is disfavored in actin polymerization

Treadmilling

Phenomenon in which one end of a filament grows in length while the other end shrinks,

resulting in a section of filament seemingly moving across a stratum or the cytosol

T form

Form of actin that is ATP bound

D form

Form of actin that is ADP bound

Nucleation

First stage of actin polymerization in which dimers and trimers form, then monomers are

added to either end

Oligomer instability

, Tendency of actin oligomers to fall apart

Arp2/3

Nucleating complex that is used for initial nucleation of actin filaments and for nucleation

of side branches

Nucleation promotion factor

Activates the Arp2/3 complex to produce branched actin filaments

Formin

Functions as a dimer and interacts with terminal actin subunits

Profilin

Binds actin subunits and speeds elongation by binding to formin monomers and

stimulating ADP to ATP exchange

Tropomodulin

Prevents assembly and disassembly at minus end of actin

Capping protein

Prevents assembly and disassembly at plus end of actin

Cofilin

Stimulates disassembly at minus end of actin

Gelsolin

Severs actin filaments along with cofilin and destrin

Cortex

Dense region of crosslinked actin networks underlying the plasma membrane

Stress fiber