Cytoskeleton Flashcards
What are actin filaments composed of?
Polymer of actin monomers, 7nm in diameter
Actin filaments are globular proteins arranged in a helix found in all eukaryotic cells.
What is the diameter of intermediate filaments?
8-12nm in diameter
Intermediate filaments serve as structural proteins in eukaryotic cells.
What is the primary role of microtubules?
Cell structure, organization, mitosis, and movement
Microtubules are filaments of tubulin monomers, 25nm in diameter.
What is the organization of actin in cells?
Organized in bundles and may form meshed networks
Actin defines the shape of cells and cellular substructures.
What are stress fibers?
Contractile actin-myosin bundles in the cytoplasm
Stress fibers play a role in cell movement and shape.
What are filopodia?
Finger-like protrusions with loose bundles of actin
Filopodia ensure the cell is moving in the right direction.
How abundant is actin in eukaryotic cells?
15 percent of total protein, with 10 percent being actin-binding proteins
Actin is the most abundant protein in eukaryotic cells.
What is the structure of G-actin?
Globular protein with hydrophilic R groups on the outside
G-actin binds ATP/ADP and has a pointed end (minus) and a barbed end (plus).
What is actin treadmilling?
Monomers added at both ends, faster at the barbed end
Actin appears to have a trail due to this dynamic polymerization.
What do actin-binding proteins regulate?
Microfilament dynamics such as severing, annealing, and branching
Approximately 60 actin-binding proteins are involved in this regulation.
What role do intermediate filaments play in cells?
Provide stability and cohesion against stretch
They include keratin, vimentin, and neurofilaments.
What are keratin monomers?
Fibrous proteins that mesh in the cytoplasm
Keratin allows cells to adhere to the basement membrane and each other.
What mutations can cause epidermolysis bullosa?
Mutations in intermediate filaments such as keratin
This condition affects the integrity of skin and mucous membranes.
What is the composition of microtubules?
Heterodimers of alpha and beta tubulin
This composition generates polarity with beta tubulin as the plus end.
Where do microtubules originate?
In the centrosome (microtubule organizing center, MTOC)
The centrosome duplicates during mitosis.
What are microtubule-associated proteins (MAPs)?
Proteins that stabilize microtubules and regulate their dynamics
MAPs are crucial for maintaining microtubule structure.
What is the role of kinesins and dyneins?
Kinesins carry cargo from minus to plus end; dyneins move cargo from plus end to minus end
These motor proteins use energy from ATP hydrolysis to transport cargo.
True or False: Microtubules are responsible for transport within the cell.
True
They transport cargo along the cell and are components of cilia.
What happens to tau protein in Alzheimer’s disease?
It mutates and becomes hyperphosphorylated, leading to neuronal tangles
These tangles are associated with neuronal death.
What are Lamins?
Are intermediate filaments that support nuclear envelope?
What factor destabilizes microtubules?
Nocadazole, Colchicine, Vinblastine
What factor binds to and stabilizes actin filaments?
Phalloidin
Order subcellular structures by diameter (small = big for DNA double helix, intermediate filaments, microtubule, actin filament and mitosis chromosome
DNA double helix - actin filament - intermediate filament - microtubule - mitosis chromosome
