In each blank, try to type in the
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If your not sure what answer should be entered, press the space bar and the next missing letter will be displayed. When you are all done, you should look back over all your answers and review the ones in red. These ones in red are the ones which you needed help on. Question: cytoskeletonAnswer: spatially organizes the cytoplasm of eucaryotic . Network of protein filaments Question: cytoskeletal Answer: form helical assembleis of subunits that self-associate using of end-to-end and side-to-side protein contacts. Question: mechanical properties of filamentsAnswer: differences in the structure of the subunits and of their self-assembly Question: 3 main filaments that are fundamental to spatial organizationAnswer: actin, microtubules, and filaments Question: are the cytoskeletal effective on their own?Answer: no Question: cytoskeletal usefulness to the cell depends on...Answer: a large number of accessory proteins that link the filaments to other cell , as well as each other. Question: why are proteins essential in cytoskeletal filamentsAnswer: for the controlled assembly of the cytoskeletal filaments in particular locations, including the motor proteins that either move organelles along the filaments of move the filaments themselves Question: function of filamentsAnswer: determine the shape of the cell's surface and are for whole-cell locomotion Question: function of filamentsAnswer: provide mechanical and resistance to shear stress Question: function of Answer: determine the positions of membrane-enclosed and direct intracellular transport Question: long, hollow cylinders made of subunits; outer diameter of 25 nmAnswer: microtubules Question: strong, tubes; more rigid than actin filamentsAnswer: Question: microtubules are long and straight, typically with one end attached to a single microtubule-organizing center (MTOC) called a ____________Answer: Question: What are the three principal types of cytoskeleton ?Answer: microtubules, filaments, and intermediate filaments Question: two-stranded helical polymers of actin protein Answer: filaments (microfilaments) Question: as flexible structures but are easy to breakAnswer: filaments (microfilaments) Question: organized into bundles, 2-D networks, and 3-D gelsAnswer: filaments (microfilaments) Question: of 5-9 nm; thinnest of the three filamentsAnswer: filaments (microfilaments) Question: dispersed throughout the cell, but most concentrated in the cortex, just beneath the plasma membraneAnswer: filaments (microfilaments) Question: rope-like with diameter around 10 nm;Answer: intermediate filaments made of intermediate filament proteins (easy to bend but hard to ) Question: one type of intermediate filament forms a meshwork called the ________ ________ just beneath the inner nuclear membraneAnswer: nuclear Question: types of this cytoskeleton filament extend across the cytoplasm gining cells mechanical strengthAnswer: filaments Question: in epithelial tissue, they span the cytoplasm from one cell to another, strengthening the entire epitheliumAnswer: filaments Question: a _______ _______ is stabilized by multiple contacts between adjacent subunitsAnswer: helical Question: addition of a third actin monomer to form a ______ makes the entire group more stableAnswer: which actss a a nucleus for polymerization Question: for ______ nucleation tthe nucleus is larger and has a more complicated structure consisting of a ring of 13 or more moleculesAnswer: Question: this type of binds relatively weakly in nucleationAnswer: Question: what are the phases of Answer: assembly of a nucleus (slow "lag phase"), "growth phase" from addition of monomers to nucleus (elongation), and a "steady state" or "equilibrium" when growth and shrinkage of polymer is Question: actin filaments and microtubules assemble (__________) and disassembly by the addition and removal of subunits (_______) at the end of the polymerAnswer: (polymerize); (monomers) Question: the rate of addition of monomers is given by the rate constant ______ which has units of _______Answer: Kon; M-1 sec-1 Question: the rate of loss is given by ____ which has units of ____Answer: Koff; sec-1 Question: what is the concentrationAnswer: the number of monomers that add to the polymer per second is proportional to the concentration of the free (konC) Question: As the polymer grows, subunits are used up, and C is observed to _____ until it reaches a constant value called the _____ _____Answer: drop; concentration Question: Does the subunits leaving the polymer end at a rate depend on C (koff)?Answer: Question: the two ends of an actin filament or microtubule at different ratesAnswer: true Question: the plus end is the slow-growing Answer: false Question: the difference in rates of growth at the two ends of an actin filament is made possible by changes in the ________ of each subunit as it enters the polymer. The ________ change affects the rates at which subunits add to the two ends.Answer: conformation; Question: the ratio kon/koff and Cc must be the same at both ends for a polymerization reaction (no ATP or GTP hydrolysis).Answer: Question: Different subunit inretactions are broken when a is lost at either endAnswer: false (exactly the same ) Question: the final stat of the subunit after is identicalAnswer: Question: Delta G for the subunit loss is different at both ends and determines the equilibrium constant for its association with the Answer: false (loss is ) Question: the _______ _______ _______ that accompanies polymerization removes the constraint that keeps then ends growing and shrinking at an identical rateAnswer: nucleotide phosphate Question: eacg actin molecule carries a tightly bound ____ that is ydrolyzed to ___ soon after assembly into the polymerAnswer: ATP; Question: each molecule carries a tightly bound ___ that is hydrolyzed to ___Answer: GTP;GDP Question: ________ of the bound nucleotide reduces the binding affinity of the subunit for neighboring subunits making it more likely to dissociate from each end of the filamentAnswer: Question: usually the ______ form of nucleotide adds to the filament and the ______ form leavesAnswer: ; diphosphate Question: ATP or GTP that is hydrolyzed must be replenished by a _____ _____ _____ of the free subunit creating a steady state. diphosphate --> triphosphateAnswer: nucleotide exchange Question: _____ and _____ bind and hydrolyze nucleoside triphosphatesAnswer: tubulin and Question: binds ___Answer: Question: actin ___Answer: Question: what are the two behaviors associated with nucleoside triphosphate hydrolysis observed in polymers?Answer: dynamic instability and Question: dynamic instability predominates in _______Answer: Question: ________ predominates in actin filamentsAnswer: Question: what is ?Answer: a filament assembles at one end while disassembling at the other end Question: Microtubules depolymerize about 100 times faster from an end containing ____ tubulin that from one containing ____ tubulinAnswer: GDP; Question: A GTP cap favors growth, but if it is lost, then ________ ensuesAnswer: Question: what is instabilityAnswer: when individual microtubules alternate between a period of slow growth and a period of dissassembly Question: At the apical (upper) surface, facing the intestinal lumen, bundled actin filaments form ______ that increase the cell surface area available for absorbing nutrients from foodAnswer: Question: just below the microvilli, a circumferential band of actin filaments contributes to forming _______ _________ that prevent the contents of the intestinal lumen from leaking into the body.Answer: cell-cell Question: ____________ run vertically from the top of the cell to the bottom, and provide a global coordinate system that enables the cell to direct newly synthesized components to their proper locationsAnswer: Question: _________ __________ are anchored to other kinds of adhesive structures including desmosomes and ____________ that connect the epithelial cells into a sturdy sheet and attach them to the underlying extracellular matrix on the basal side of the cell.Answer: filaments; hemidesmosomes Question: the formation of ______ _______ from much smaller protein subunits allows regulated filament assembly and disassembly to reshape the cytoskeletonAnswer: filaments Question: how is polymerization ?Answer: by raising the salt concentration in a solution of pure actin subunits or with preformed fragments of filaments present to act as nuclei for filament growth. Question: what are the tissue-specific forrms of intermediat filaments found in the of animal cells?Answer: keratin filaments in epithelial cells, neurofilaments in nerve cells, and desmin in muscle cells. Question: what is the primary function of intermediate ?Answer: to mechanical strength Question: phalloidinAnswer: -specific drug that binds and stabilizes filaments Question: Answer: actin-specific drug that caps filaments plus Question: Answer: actin-specific drug that filaments Question: latrunulinAnswer: actin-specific drug that subunits and prevents their polymerization Question: taxonAnswer: microtubule-specific drug that and stabilizes microtubules Question: what are the microtubule-specific drugs that binds subunits and prevents polymerization?Answer: colchicine, ; vinblastine, vincristine; and nocodazole Question: Bacterial cells also contain of tuulin, actin and intermediate filaments which function to...Answer: form dynamic filamentous structures, determine cell , and function in cell division Question: the varied forms and functions of sytoskeletal filament structues in eucaryotic cells depend of a versatile repertoire of ____ _____Answer: accessory Question: a primary determinant of the sites of cytoskeletal structures is the regulation of the processes that initiate the ___________ of new filamentsAnswer: Question: in most animal cells ________ are nucleated at the centrosome, a complex assembly located near the center of the cellAnswer: Question: most actin filaments are nucleated near the ____ ______Answer: membrane Question: the kinetics of filament assembly and disassembly can be slowed or accelerated by ______ _____ that bind to free subunits or the filaments themselvesAnswer: proteins Question: some accessory proteins alter filament dynamics by _____ to the ends of filaments or _____ the filaments into smaller fragmentsAnswer: binding; Question: some ________ ______ assemble filaments into larger ordered structures by cross-linking them to one another in geometrically defined waysAnswer: accessory Question: what happens when the concentration of is less than critical concentration?Answer: both ends Question: ______ rearranges cytoskeltal elements to pursue targetAnswer: Question: what is Answer: actin subunit that nucleates assembly and remains associated with the growing plus Question: what is ARP Answer: actin subunit that nucleates assembly to form a web and associated with the minus end Question: actin filament , cross linking, and attachment to membranes creates...Answer: fimbrin and -actin Question: this microtubule filament nucleates and remains associated with the minus endsAnswer: -TuRC Question: microtubule that stabilizes tubules by binding along sidesAnswer: Question: filament that stabilizes plus ends and accelerates assemblyAnswer: XMAP215 Question: What are the two of actin filament bundles and what are they composed of?Answer: 1. contractile bundly- loose packing allows myosin-II to enter bundle (actin and alpha-actinin)
2. Parallel bundle- tight packing prevents myosin-II from entering bundle (actin filaments and fimbrin) Question: a bundle of parallel actin filaments cross-linked by the actin-bundling proteins villin and fimbrin forms the core of a _______Answer: Question: Lateral side arms of a microvillus are composed of ______ and ______. They connect the sides of the actin filament bundle to the overlying plasma membraneAnswer: I and the Ca2+ binding protien in calmodulin Question: All the _____ ends of the actin filaments are at the tip of the microvillus, where they are embedded in an amorphous, densely staining substance of unknown compositionAnswer: Question: These proteins use energy of ATP hydrolysis to move along microtubules or actin filaments, mediate the sliding of flilaments, and the transport of cargo along filamentsAnswer: motor Question: all known motor proteins that move on actin filaments are members of the ______ ______Answer: superfamily Question: the motor protiens that move on microtubules are either members of the _____ _____ or the _____ _____Answer: kinesin superfamily or the dynein Question: the only structural element shared among all members of each superfamily is the motor _____ domainAnswer: Question: the tails of motor help to perform different functions in the cell including...Answer: transportation and localization of specific proteins, membrane-enclosed organelles, and Question: what are the two distinct types of specialized structures in cells that are formed from highly ordered arrays of motor proteins that move on stabilized filament tracks?Answer: the myosin-actin of the sarcomere, and the dyenin-microtubule system of the axoneme Question: function of the -actin system of the sarcomereAnswer: powers the contraction of various types of muscle such as skeletal, smooth, and cardiac Question: function of the dyenin-microtubule system of the Answer: powers the beating of and the undulations of flagella Question: whole-cell movements and the -scale shaping and structuring of the cells require:Answer: coordinated of all three basic filament systems and a large variety of cytoskeletal accessory proteins, including motor proteins Question: of the microtubule-based mitotic spindle during cell division requires spatial and temporal cooperation between...Answer: dynamic cytoskeletal filaments, active molecular motor proteins, and a wide of accessory factors Question: what are the main of myosin?Answer: I (located in microvilli) and myosin II ( motor head for muscle contraction) Question: huge multinucleated cells form by the fusion of many muscle cell precursors, called ________Answer: Question: in an adult human, a muscle cell is typically ____ mm in diameter and can be up to several centimeters longAnswer: 50 Question: what are the two type of motor proteins?Answer: and dyneins Question: _____ is a motor protein that moves along microtubules. the fastest of this protein can move their microtubules at about 2-3 mm/secAnswer: Question: ________ are the largest of the known molecular motors, and they are also among the fastest. They are independently evolved and have distinct structure and mechanism of action. (can move microtubules in test tube 14 mm/sec)Answer: Question: in isolated doublet microtubules dynein produces ______ ______Answer: microtubule Question: in normal flagellum dynein causes ________ _______Answer: microtubule Question: Dyenin movement is from ________ to _________Answer: to negative Question: What are the three classes of dynamic microtubules in the spindle at metaphase?Answer: kinetochore microtubules (attach each chromosome to the spindle pole), interpolar (hold the two halves of the spindle together), astral microtubules (can interact with the cell cortex) Question: All of the microtubules are oriented with their _______ ends at the spindle poles where the centrosomes reside, and their ______ ends projecting away.Answer: minus; Question: ______ _______ undergo dynamic instability, growing and shrinking at their plus endsAnswer: microtubules Question: _________ _______ and _________ __________ both undergo continuous flux toward the spindle polesAnswer: kinetochore and interpolar microtubules Question: Cell is important in?Answer: embryonic development, healing, tissue maintenance, immune system function Question: How does the cell cytoskeletal actions?Answer: protrusion at the leading edge( of new actin filaments) and adhesion of newly protruded part to substratum signals forces generated by molecular motors to bring the cell body forward Question: Actin-polymerization is dependent protrusion and firm attachment of a _________ at the leading edge of the cell moves the edge forward and stretches the actin cortexAnswer: Question: Contraction at the rear of the cell propels the body cell ___________ to relax some of the tensionAnswer: Question: Complex cells the coordinated assembly of:Answer: Microtubules, , action filaments, and action of dozens of highly specilized molecular motors that transport subcellular components to their appropriate destinationd |
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