Unit 1- Actin and Intermediate Filaments Flashcards
Cytoskeleton Areas:
Microfilaments (actin): Involved in movement and structure.
Intermediate Filaments: Provide mechanical support.
Microtubules: Maintain cell shape and transport.
Actin Location & Function:
Found just beneath the plasma membrane; supports cell shape, enables motility, and aids in cell division.
G Actin to F Actin:
G actin (globular) polymerizes to form F actin (filamentous). Polymerization is favored by ATP-bound G actin, while dissociation is favored by ADP-bound G actin.
Nucleation:
The initial step in actin polymerization where actin monomers aggregate to form a stable base for filament growth.
Treadmilling in Actin Filaments:
G actin adds at the plus end while dissociating from the minus end, maintaining a constant length. Essential for actin’s role in cell motility.
Actin-Binding Proteins:
Profilin: Promotes actin polymerization.
Cofilin: Disassembles actin filaments.
Fimbrin/Villin: Organizes filaments in microvilli.
Microvilli vs. Stereocilia
Both are actin-based structures.
Microvilli: Increase surface area for absorption.
Stereocilia: Involved in sensory functions like hearing.
Rho Proteins:
Regulate actin cytoskeleton dynamics, controlling cell shape, motility, and adhesion.
Intermediate Filament Function:
Provide tensile strength, help maintain cell shape, and anchor organelles.
Intermediate Filament Polymerization:
Monomers form dimers, which associate into tetramers and eventually assemble into strong, rope-like structures.
Intermediate Filament Locations:
Keratins: Epithelial cells.
Vimentin: Connective tissue.
Neurofilaments: Neurons.
Hemidesmosomes vs. Desmosomes:
Hemidesmosomes: Attach cells to the extracellular matrix.
Desmosomes: Link cells together, providing mechanical stability.
