Cytoskeleton questions Flashcards
Mutations in the actin protein would affect cellular shape, muscle contraction and cell division
True
The microvilli lining intestinal epithelium are composed of plasma membrane covering a
microtubule cytoskeleton
False
Microtubules and microfilaments have a capacity to self-assemble and their subunits possess
enzymatic activity
True
Microtubules are highly dynamic but unstable structures sensitive to temperature and GTP levels
True
Microtubules with tubulin dimers containing GTP tend to stop growin
False
Centrosomes duplication is required for the formation of a mitotic spindle
True
Cell in mitosis contain cilia to sense and receive signals from the external environment
False
Centrosomes are required in all animal cells to organize microtubules.
True
Treatment of a cancer patient with taxol would NOT directly affect muscle contraction, DNA
replication and cilia formation.
False
Explain the principle of actin treadmilling?
Continous turnover of actin filaments growth at plus end is the same as shrinkage at minus end of the filament -> moves cells forward
Why are microtubules particularly important in neurons?
How could you stabilize microtubules?
What are the consequences of altered microtubule dynamics?
maintaining neuronal structure, facilitating intracellular transport
Stabilizing by Taxol / Tau
Alterring Microtubule dynamics: Neuronal degeneration / Transport deficencies
What is extracellular matrix and why do cells produce ECM?
Structural suppoprt, Signaling, Adhesion
Gylcoproteins; Filaments, Proteoglycans and polysaccharides
Briefly describe/compare the organization of actin filaments in lamellipodia, filopodia and stress
fibers and explain how actin cytoskeleton generates force that can be utilized for intracellular
movement or motility of the entire cell. You can use drawing.
Lamellipodia:
Lamellipodia are broad, flat protrusions found at the leading edge of migrating cells.
Actin filaments in lamellipodia are arranged in a branched network with fast turnover rates.
The branching actin network generates pushing forces against the plasma membrane, facilitating cell protrusion and leading-edge advancement during cell migration.
Filopodia:
Filopodia are thin, finger-like protrusions extending from the cell surface.
Actin filaments in filopodia are bundled together in parallel arrays, typically organized with their plus ends oriented toward the tip of the protrusion.
These bundled actin filaments provide structural support and enable filopodial extension, allowing cells to explore their environment and sense extracellular cues.
Stress Fibers:
Stress fibers are contractile bundles of actin filaments found in the central region of the cell.
Actin filaments in stress fibers are organized in parallel bundles, interspersed with myosin II motor proteins.
Myosin II motors generate contractile forces by sliding adjacent actin filaments past each other, leading to the contraction of stress fibers and cell retraction or tension generation.
Force generation:
Actin Polymerization: Actin filaments undergo polymerization at the leading edge of protruding structures like lamellipodia. This polymerization pushes against the plasma membrane, generating protrusive forces that drive cell migration.
Myosin-Mediated Contraction: In regions like stress fibers, myosin II motors bind to actin filaments and utilize ATP hydrolysis to generate contractile forces. Myosin II motors pull on actin filaments, causing them to slide past each other and leading to the contraction of stress fibers. This contraction results in cell retraction or tension generation, which is crucial for cell adhesion, traction, and overall cell motility.
