RR Final 2 Microtubules.1

  1. structure
    compoentns of __.
    • hollow, relatively rigid, tubuluar structures in nearly every eukaryotic cell
    • structures like the mitotic spindle, cilia, etc
    •                                                               i.      Outer diameter of 25 nm and a wall thickness of about 4 nm, and may extend across the length or breadth of a cell
  2.                                                               i.      The wall is composed of _- arranged in __, called __, that are aligned __to the long axis of the tubule
    1.       __ between adjacent ones are important in maintaining structure
    2.       Each __is assembled from __building blocks consisting of one __ and __.
    • globular proteins
    • longitudinal rows
    • protofilaments
    • parallel 
    • Noncovalent interactions
    • protofilament
    • dimeric 
    • alpha-tubulin and one beta-tubulin subunit.
  3. a.       The two types have a similar 3D structure and fit tightly together
                                                                                                                                          i.      __ organized in a linear array along the length of each __, which is __due to each assembly unit having two nonidentical components (__)
    • tubulin dimers
    • protofilament
    • asymmetric 
    • heterodimer
  4. 1.       all __have the same __; and the entire polymer has __
    a.       one end of a microtubule is called the __and is terminated by a __
    b.      opposite end is the __ and is terminated by a row of __
    • protofilaments 
    • polarity x2
    • plus end 
    • row of Beta-tubulin subunits

    • minus end
    • alpha-tubulin subunits
  5. a.       Microtubules have additional proteins, called __                                                              i.      __comprise a __collection of proteins
    1.       first ones identified= “__” and have one domain that what and another domain that does what?
    • microtubule-associated proteins (MAPs)
    • MAPs 
    • heterogeneous 
    • classical MAPs
    • attaches to the side of a microtubule 
    • projects outward as a tail from the microtubule’s surface
  6.                                                               i.      some MAPs arranged as __ connecting microtubules, thus maintaining their __
                                                                ii.      MAPs generally increase the __ of microtubules and promote their __
    1.       the __ of the various MAPs is controlled primarily by the __ and __  of __from particular __
    • cross-bridges
    • parallel alignment
    • stability
    • assembly
    • microtubule-binding activity
    • addition and removal
    • phosphate groups 
    • amino acid residues
  7.                                                               i.      abnormally high level of __of one particular MAP, called __, has been implicated in the development of several fatal __, like Alzheimer’s
    • phosphorylation 
    • tau
    • neurodegenerative disorders
  8. a.       Microtubules are stiff enough to do what?

                                                                  i.      __helps determine __
    resist forces that might compress or bend the fiber, enabling mechanical support


  9.                                                               i.      cultured animal cells: microtubules extend in a __ outward from nuclear area, giving round, flattened shape
                                                                ii.      in columnar epithelial cells: __ __ to the __ of the cell= support elongated shape
    • radial array
    • long axis parallel
    • long axis
  10.                                                               i.      plant cells: indirect role in maintain cell shape by forming __
    1.       during __, most of a plant cell’s microtubules are located just beneath the plasma membrane, forming a __
    2.       microtubules influence the movement of __ located in the plasma membrane
    3.       as a result, the __ of the cell wall are assembled in an __that is parallel to the underlying microtubules of the __
    • cell wall
    • Interphase
    • distinct cortical zone
    • cellulose-synthesizing enzymes
    • cellulose microfibrils
    • orientation 
    • cortex
  11. a.       the orientation of these __ plays an important role in determining the __characteristics of the cell and thus its __
                                                                                                                                i.      in most cells, newly synthesized __ and __ are arranged __to the long axis of the cell (transversely), because the cellulose microfibrils resist __, the __ exerted by the fluid in the cell vacuole is directed to the ends of the cell, causing __
    • cellulose microfibrils
    • growth 
    • shape
    • newly synthesized cellulose microfibrils
    • coaligned microtubules 
    • perpendicular 
    • lateral expansion
    • turgor pressure
    • cell elongation
  12. a.       microtubules also maintain __ of cells, which drugs can affect
                                                                  i.      ex: Golgi usually in center of mammal cellà treatment with __disperses Golgi until the drug is gone
    b.      __ depends on presence of microtubules because specific disruption of these __ brings the movements to a halt
    • internal organization
    • colchicines 
    • transport of materials from one membrane compartment to another
    • cytoskeletal elements
  13.                                                               i.      __: axon of motor neuron may stretch from spinal cord to tip of finger or toe and contains a cell body
    1.       __allows view of labeled proteins into axons and down its length
    • axonal transport
    • injecting amino acids into cell body
  14. a.       many different materials are __within membranous vesicles in the ER and Golgi complex of the cell body and transported down the length of the axon
    b.      non-membrane-bound cargo, like __, are also transported along this vast stretch of __
    2. different materials move at __

    • compartmentalized 
    • RNAs
    • extended cytoplasm
    • different rates
  15.                                                               i.      structures and materials traveling from the cell body toward the terminals of a neuron are said to move in an __
    1.       other structures, including __ that form at the axon terminals and carry regulatory factors from target cells, move in opposite, or __, directions—from the synapse toward the cell body
    • anterograde direction
    • endocytic vesicles
    • retrograde
  16.                                                               i.      axons are filled with __, including __interconnected in various ways
    1.       using __, investigators can follow individual vesicles as they move along the __of an axon, either toward or away from the cell body
    • cytoskeletal structures
    • bundles 
    • video microscopy
    • microtubules
  17. a.       these movements are mediated primarily by __, which serve as what?
    • microtubules
    • tracks for a variety of motor proteins that generate the forces required to move objects within a cell
  18. a.       the __ of a cell convert __energy into __energy, which is used to generate __, as occurs when a muscle cell contracts, or to move cellular cargo (ex: vesicles, mitochondria, etc.) attached to the motor
    • motor proteins
    • chemical 
    • mechanical 
    • force
  19.                                                               i.      a single cell can have hundreds of __, each with a specialized function
                                                                ii.      __ can be grouped into __, __, and __
    1.       __ and __ move along microtubules, whereas __move along microfilaments
    2.       no motor protein is known that uses __, which aren’t __, not causing directional cues to the motor
    • motor proteinsx2
    • kinesins, dyneins, and myosins
    • kinesins and dyneins
    • myosins
    • intermediate filaments
    • polarized
  20.                                                               i.      motor proteins move __along their cytoskeletal trancks in a stepwise manner, from one __ to the next
    1.       as it moves along, it goes htorugh a series of __ that constitute a __, which includes steps that are coupled to a __, which provides energy necessary to fuel the motor’s activity
    • unidirectionally 
    • binding site
    • conformational changes
    • mechanical cycle
    • chemical (catalytic) cycle
  21. What are the steps
    •                                                                                                                                       i.      binding of ATP to motor
    •                                                                                                                                     ii.      hydrolysis of ATP
    •                                                                                                                                   iii.      release of products from motor
    •                                                                                                                                    iv.      binding of new ATP
  22. a.       binding and hydrolysis of a single ATP at the catalytic site is used to do what?
    2.       as the motor protein moves to successive sites along the cytoskeletal polymer, the __ and __ are repeated over and over again, pulling the cargo over considerable distances
    drive a power stroke that moves the motor a precise number of nanometers along its track

    mechanical and chemical cycles
  23.                                                               i.      __ (1985) isolated a motor protein from the cytoplasm of squid axons using microtubulesà called __
                                                                ii.      __ is only one member of a superfamily of related proteins, called __
    • Robert Vale
    • kinesin
    • Kinesin-1
    • KRPs (kinesin-related proteins)
  24. Structure of kinesins
    tetramer constructred from two identical heavy chains and two identical light chains
  25. Structure of kinesins cont. 

    a.       contains several parts, including a pair of __ that bind a __and act as __
                                                                                                                                          i.      each head (or __) is connected to a __, a __, and a __ that binds cargo to be hauled
    • globular heads
    • microtubule 
    • ATP-hydrolyzing, force-generating engines
    • motor domain
    • neck
    • rodlike stalk
    • fan-shaped tail
  26. 1.       the motor  proteins of all __have related __, reflecting their common evolutionary ancestry and their similar role in moving along microtubules
    a.       in contrast, the tails have __, reflecting the variety of cargo these motors haul
    • KRPs 
    • amino acid sequences
    • diverse sequences,
  27. 1.       __ of kinesins are similar to that of __, despite the fact that kinesins are much smaller proteins and the two types of motors operate over different tracks
    a.       __ and __ almost certainly evolved from a common ancestral protein present in a primitive eukaryotic cell
    • motor domains
    • myosins
    • kinesins and myosins
  28.                                                               i.      when purified kinesin molecules are observed, the motor proteins move along microtubules toward their __ = __
    1.       in an axon, where all of the microtubules are oriented with their __ facing the cell body, kinesin transports vesicles and other cargo toward the synaptic terminals 
    • plus end
    • plus end-directed microtubular motor
    • minus ends
  29.                                                               i.      a single kinesin molecule moves along a single __of a microtubule at a velocity proportional to the __

    1.       low ATP concentration: Explain what was observed
    • protofilament 
    • ATP concentration
    • kinesin molecules travel slowly enough for observers to conclude that the protein mvoes in distinct steps
  30. a.       each step is about 8 nm in length, which is also the lengths of one __ in a __, and requires the __= __mechanism
    • tubulin dimer
    • protofilament
    • hydrolysis of a single ATP molecule
    • hand over hand
  31. Explain the hand-over-hand mechanism
                                                                                                                                          i.      in this mechanism, the two heads alternate in taking the leading and lagging positions without an accompanying rotation of the stalk and cargo at every step
  32.  i.      the movement of kinesin molecules, both in vitro and in vivo, is highly __, meaning what
    1.       a two-headed kinesin molecule can accomplish this feat because what?
    • processive
    • motor protein tends to move along an individual microtubule for considerable distances without falling off
    • at least one of the heads is attached to the microtubule at all times
  33. a.       a motor protein with this capability is well adapted for __
                                                                ii.      the two heads of a kinesin molecule behave in a __manner, so that they are always present at different stages in their __ at any given time
    • independent, long-distance transport of small parcels of cargo
    • coordinated 
    • chemical and mechanical cycles
  34. 1.       when one head binds to the microtubule, what happens?
    the resulting conformational changes in the adjacent neck region of the motor protein cause the other head to move forward toward the next binding site on the protofilament
  35. a.       the forward-moving head probably finds its precise binding site on the __through a __ search
    2.       __ of the head leads to a __movement of the neck which is attached to a molecule of GFP rather than to a stalk and the partner head in a __
    • protofilament 
    • rapid, diffusional (random)
    • catalytic activity
    • swinging 
    • dimer
  36. a.       the microtubule is not simply a passive track in these events but plays an active role in __
                                                                                                                                          i.      freely soluble kinesins adopt a __ conformation and require interaction with __and a __
    • stimulating certain steps int eh mechanical and chemical cycles of the kinesin molecule
    • folded, self-inhibited
    • cargo 
    • microtubule to become activated
  37.                                                               i.      like kinesin-1, most KRPs move toward the __ to which they are bound
    1.       one small family (__) moves in the opposite direction, toward the __
    a.       possible because the heads of the two proteins are __; it’s the differences in __ that cause differences in the __ of the two proteins 
    • plus end of the microtubule
    • kinesin-14
    • minus end
    • indistinguishable
    • directional movement
    • adjacent neck regions
  38. 1.       even though the __ that normally would move toward the __of a microtubule, as long as it is joined to the neck of a __, it moves in the __
    • catalytic domain
    • minus end 
    • plus end motor
    • plus direction
  39.                                                               i.      a third family,__, are incapable of movement
    1.       bind to either end and bring about __rather than move along its length; called __

    • kinesin-13
    • depolymerization 
    • depolymerases
  40.                                                               i.      routes followed by __ and __are called __, and members of the __ are strongly implicated as __that drive the movement of this membrane-bounded cargo
    • cytoplasmic vesicles
    • organelles 
    • microtubules

    • kinesin superfamily
    • force-generating agents
  41. 1.       in most cells, microtubules are aligned with their plus ends pointed __
    a.       therefore, members of the __ tend to move vesicles and organelles in an __ toward the cell’s __
    • away from the center of the cell
    • kinesin superfamily
    • outward direction
    • plasma membrane
Card Set
RR Final 2 Microtubules.1