BIOL313 Exam 4
Cytoskeleton ANS: Network of microfilaments, intermediate filaments, and microtubules that organize
cell shape, internal organization, and motility.
Microfilaments ANS: Cytoskeletal elements (8 nm) made of actin, involved in cell shape, movement,
and contraction.
Intermediate Filaments ANS: Cytoskeletal elements (8-11 nm) providing mechanical strength; less
dynamic and not polarized.
Microtubules ANS: Cytoskeletal elements (24 nm) made of tubulin dimers, involved in organelle
positioning, cell division, and motility.
Signal Transduction ANS: External signals that cause changes in the cytoskeleton, affecting movement,
contraction, and organization.
G-Actin ANS: Globular actin monomer that can bind ATP or ADP.
F-Actin ANS: Filamentous, polymerized actin forming microfilaments.
Nucleation ANS: First step of actin polymerization where G-actin monomers form a stable seed for
filament growth.
Elongation ANS: Rapid addition of actin monomers at both ends of the nucleated filament.
Steady State ANS: Phase when the rate of actin monomer addition equals the rate of loss; filament
length is stable.
, Critical Concentration (Cc) ANS: The actin monomer concentration at which filament growth and
shrinkage are balanced.
Formin ANS: Protein that promotes actin filament nucleation and stays associated with the plus end
during elongation.
Plus End (of Actin) ANS: Faster-growing end of the actin filament; lower critical concentration.
Minus End (of Actin) ANS: Slower-growing/shrinking end of the actin filament; higher critical
concentration.
Profilin ANS: Protein that catalyzes the exchange of ADP for ATP on G-actin, making it competent for
polymerization.
Tropomodulin ANS: Protein that caps the minus end of actin filaments, preventing disassembly.
Cap Z ANS: Protein that caps the plus end of actin filaments, regulating filament growth.
Cofilin ANS: Protein that binds ADP-actin within filaments, promoting filament severing and
disassembly.
Gelsolin ANS: Protein that severs actin filaments and caps the newly exposed plus ends.
Tropomyosin ANS: Protein that stabilizes actin filaments by binding along their sides.
Thymosin β4 ANS: Protein that binds G-actin-ATP, temporarily preventing it from polymerizing.
Cytoskeleton ANS: Network of microfilaments, intermediate filaments, and microtubules that organize
cell shape, internal organization, and motility.
Microfilaments ANS: Cytoskeletal elements (8 nm) made of actin, involved in cell shape, movement,
and contraction.
Intermediate Filaments ANS: Cytoskeletal elements (8-11 nm) providing mechanical strength; less
dynamic and not polarized.
Microtubules ANS: Cytoskeletal elements (24 nm) made of tubulin dimers, involved in organelle
positioning, cell division, and motility.
Signal Transduction ANS: External signals that cause changes in the cytoskeleton, affecting movement,
contraction, and organization.
G-Actin ANS: Globular actin monomer that can bind ATP or ADP.
F-Actin ANS: Filamentous, polymerized actin forming microfilaments.
Nucleation ANS: First step of actin polymerization where G-actin monomers form a stable seed for
filament growth.
Elongation ANS: Rapid addition of actin monomers at both ends of the nucleated filament.
Steady State ANS: Phase when the rate of actin monomer addition equals the rate of loss; filament
length is stable.
, Critical Concentration (Cc) ANS: The actin monomer concentration at which filament growth and
shrinkage are balanced.
Formin ANS: Protein that promotes actin filament nucleation and stays associated with the plus end
during elongation.
Plus End (of Actin) ANS: Faster-growing end of the actin filament; lower critical concentration.
Minus End (of Actin) ANS: Slower-growing/shrinking end of the actin filament; higher critical
concentration.
Profilin ANS: Protein that catalyzes the exchange of ADP for ATP on G-actin, making it competent for
polymerization.
Tropomodulin ANS: Protein that caps the minus end of actin filaments, preventing disassembly.
Cap Z ANS: Protein that caps the plus end of actin filaments, regulating filament growth.
Cofilin ANS: Protein that binds ADP-actin within filaments, promoting filament severing and
disassembly.
Gelsolin ANS: Protein that severs actin filaments and caps the newly exposed plus ends.
Tropomyosin ANS: Protein that stabilizes actin filaments by binding along their sides.
Thymosin β4 ANS: Protein that binds G-actin-ATP, temporarily preventing it from polymerizing.
