VO 4 cell biology

• Filopodia are one-dimensional structures formed by migrating growth cones of neurons and some fibroblasts, containing long, bundled actin filaments
• Lamellipodia are two-dimensional, sheetlike structures formed by epithelial cells, fibroblasts, and some neurons, containing a cross-linked mesh of actin filaments
• Cells initiate movement through actin polymerisation driving plasma membrane protrusion
• Invadopodia and podosomes extend in three dimensions and are important for cells to cross tissue barriers
• Microtubules determine the positions of organelles, direct intracellular transport, and form the mitotic spindle during cell division.
• The cytoskeleton undergoes continuous turnover and rearrangement, which is essential for cell morphology and migration.
• The cytoskeleton is composed of three major filaments: microtubules, actin, and intermediate filaments.
• Intermediate filaments provide mechanical strength to the cell and form rope-like fibers.
• Actin filaments determine the shape of the cell's surface, are necessary for whole-cell movement, and drive cell division.
• Cells use cell adhesion and traction to pull themselves forward, with actin monomers assembling on the barbed end of actin filaments at the leading edge.
• Actin polymerization drives plasma membrane protrusion.
• If there is no interaction between the actin filament and focal adhesions, the actin filament is driven rearward by newly assembled actin.
• The ARP complex nucleates filaments efficiently when bound to the side of a preexisting actin filament, resulting in a treelike web of actin filaments.
• Actin at the leading edge forms dense cores of filamentous actin in lamellipodia.
• Microtubules are structurally more complex than actin filaments and play diverse roles in the cell.
• The Arp2/3 complex helps actin to nucleate and form a web configuration.
• Microtubules are polymers of the protein tubulin, consisting of α-tubulin and β-tubulin heterodimers.
• Each α or β tubulin monomer has a binding site for one molecule of GTP or GDP.
• Co filin binds actin filaments and accelerates their disassembly.
• Actin-binding proteins regulate actin filament dynamics and organization in cells.
• Cell migration is facilitated by filaments of the cytoskeleton.
• The cytoskeleton is analogous to ligaments, bones, and muscles in our own bodies.
• The cytoskeleton is made up of actin filaments, intermediate filaments, and microtubules.
• The cytoskeleton provides strength, shape, and movement to a cell.
• Intermediate filaments have a diameter of 10nm and can be visualized using electron microscopy.
• The cytoskeleton is composed of three families of protein filaments: actin filaments, microtubules, and intermediate filaments.
• Microtubules have a diameter of 25nm and are found in a loose network with actin filaments.
• Small subunits allow for rapid diffusion in the cytosol, while assembled filaments cannot diffuse rapidly.
• Properties of individual subunits influence filament behavior and contribute to the stability and mechanical properties of each type of filament.
• Actin subunits assemble head-to-tail to create flexible, polar filaments.
• Helices can have different numbers of subunits per helical turn, such as two, three, or six.
• A helix forms when a series of subunits bind to each other in a regular way.
• A helix can be either right-handed or left-handed.
• Covalent linkages hold together the backbones of biological polymers, while weak non-covalent interactions hold together cytoskeletal polymers.
• The actin filaments are shown in red, with arrowheads pointing toward the minus end.
• Filopodia are spike-like projections of the plasma membrane that allow a cell to explore its environment.
• Lecture topics include cell components, membrane structure and function, cytoskeleton and cell migration, cell death and cell senescence, meiosis, cell cycle, chromosome segregation and cell division.
• Extracellular signals can activate the three Rho protein family members.
• The cortex underlies the plasma membrane.
• Rho family GTPases are molecular switches that control actin organization.