F11 Cytoskelettet Flashcards
Essential concepts
- The cytoplasm of a eukaryotic cell is supported and organized by a cytoskeleton of intermediate filaments, microtubules, and actin filaments.
- Intermediate filaments are stable, ropelike polymers—built from fibrous protein subunits—that give cells mechanical strength. Some intermediate filaments form the nuclear lamina that supports and strengthens the nuclear envelope; others are distributed throughout the cytoplasm.
- Microtubules are stiff, hollow tubes formed by globular tubulin dimers. They are polarized structures, with a slow-growing minus end and a fast-growing plus end.
- Microtubules grow out from organizing centers such as the centrosome, in which the minus ends remain embedded.
- Many microtubules display dynamic instability, alternating rapidly between growth and shrinkage. Shrinkage is promoted by the hydrolysis of the GTP that is tightly bound to tubulin dimers, reducing the affinity of the dimers for their neighbors and thereby promoting microtubule disassembly.
- Microtubules can be stabilized by localized proteins that capture the plus ends, thereby helping to position the microtubules and harness them for specific functions.
- Kinesins and dyneins are microtubule-associated motor proteins that use the energy of ATP hydrolysis to move unidirectionally along microtubules. They carry specific organelles, vesicles, and other types of cargo to particular locations in the cell.
- Eukaryotic cilia and flagella contain a bundle of stable microtubules. Their rhythmic beating is caused by bending of the microtubules, driven by the ciliary dynein motor protein.
- Actin filaments are helical polymers of globular actin monomers. They are more flexible than microtubules and are generally found in bundles or networks.
- Like microtubules, actin filaments are polarized, with a fast-growing plus end and a slow-growing minus end. Their assembly and disassembly are controlled by the hydrolysis of ATP tightly bound to each actin monomer and by various actin-binding proteins.
- The varied arrangements and functions of actin filaments in cells stem from the diversity of actin-binding proteins, which can control actin polymerization, cross-link actin filaments into loose networks or stiff bundles, attach actin filaments to membranes, or move two adjacent filaments relative to each other.
- A concentrated network of actin filaments underneath the plasma membrane forms the bulk of the cell cortex, which is responsible for the shape and movement of the cell surface, including the movements involved when a cell crawls along a surface.
- Myosins are motor proteins that use the energy of ATP hydrolysis to move along actin filaments. In nonmuscle cells, myosin-I can carry organelles or vesicles along actin-filament tracks, and myosin-II can cause adjacent actin filaments to slide past each other in contractile bundles.
Show how A cilium beats by performing a repetitive cycle of movements, consisting of a power stroke followed by a recovery stroke
show how A single molecule of kinesin moves along a microtubule
Show how Actin filaments allow animal cells to adopt a variety of shpes and perfor a variety of functions
Show how actin filaments allow animal cells to migrate
Show how Actin filaments are thin, flexible protein threads
Show how actin filaments can undergo treadmiling
Show how Actin-binding proteins control the behavior of actin filaments in vertebrate cells
Show how Activation of Rho-family GTPases can have a dramatic effect on the organization of actin filaments in fibroblasts
Show how Defects in a nuclear lamin can cause a rare class of premature aging disorders called progeria
Show how Different motor proteins transport different types of cargo along microtubules
Make a table over drugs that affect filaments
Make a table over Drugs that affect microtubules
Show how Each microtubule grows and shrinks independently of its neighbors
show how Forces generated in the actin-filament-rich cortex help move a cell forward
Show how GTP hydrolysis controls the dynamic instability of microtubules
Show how Intermediate filaments are divided into four major classes
Show how Intermediate filaments are like ropes made of long, twisted strands of protein
Show how Intermediate filaments support and strenghten the nuclear envelope
Show how Kinesin causes microtubule glinding in vitro
Show how Microtubules are hollow tubes made of glbular tubulin subunits
Show how Microtubules can be stabilized by attachment to capping proteins
Show how Microtubules guide the transport of organelles, vesicles, and macromolecules in both directions along a nerve cell axon
show how Microtubules help position organelles in eukaryotic cell
Show how Microtubules in a cilium or flagellum are arranged in a 9 + 2 array
Show how Microtubules usually grow out from an organizing
Show how motor proteins move along microtubules using their globular heads
Show how Myosin-I is the simplest myosin
Show how Myosin-II molecules can associate with one another to form myosin filaments
Show how Protein complexes bridge the nucleus and cytoplasm through the nuclear envelope
Show how the movement of dynein causes the flagellum to bend
Show how The three types of protein filaments that form the cytoskeleton differ in their composition, mechanical properties, and roles inside the cell.
show how tubulin polymerizes from nucleation sites on a centrosome
