Functions Of Cytoskeletal Elements

52 Questions | Total Attempts: 96

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Functions Of Cytoskeletal Elements - Quiz

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Questions and Answers
  • 1. 
    In a pulse-chase procedure, if the chase is longer, whichstatement below correctly describes the location of theradioactively labeled proteins in the cell?
    • A. 

      Closer to the synthesis site

    • B. 

      Farther from the nucleus

    • C. 

      Farther from the synthesis site

    • D. 

      Closer to the nucleus

    • E. 

      Farther from the mitochondria

  • 2. 
    You incubate liposomes with a series of purified proteinsnormally found in the coats of cell transport vesicles. Afteradding one of them to the liposome mixture, budding ofvesicles from the liposomes began. What does thismean?
    • A. 

      Liposomes cause the protein to denature

    • B. 

      The protein is involved in the initiation of vesicle formation.

    • C. 

      The protein is involved in liposome denaturation

    • D. 

      The protein triggers protein synthesis.

    • E. 

      The protein causes the entry of water into the liposomes

  • 3. 
    How and where is the asymmetry of the phospholipidbilayers initially established?
    • A. 

      It is initially established in the Golgi complex during lipid and protein modification

    • B. 

      It is initially established in the ER during lipid and protein synthesis.

    • C. 

      It is initially established in the secretory vesicles during lipid and protein modification

    • D. 

      It is initially established in the mitochondria by random insertion into the membranes.

    • E. 

      All of the above

  • 4. 
    Which type of cytoskeletal element is described as a solid,thinner structure, often organized into a branchingnetwork, and composed of actin subunits?
    • A. 

      Microfilaments

    • B. 

      Microtubules

    • C. 

      Intermediate filaments

    • D. 

      All of the above

    • E. 

      Macrofilaments

  • 5. 
    Which of the following is (are) made on free ribosomes?
    • A. 

      Proteins that are to remain in the cytosol

    • B. 

      Peripheral proteins of the inner cell membrane surface

    • C. 

      Peripheral proteins of the outer cell membrane surface

    • D. 

      Proteins to be transported to the nucleus

    • E. 

      A, b and d

  • 6. 
    Which molecule below is a GTP-binding protein that isrequired for the release of a clathrin-coated vesicle fromthe membrane on which it was formed?
    • A. 

      AP2

    • B. 

      GGA

    • C. 

      Clathrin

    • D. 

      Dynamin

    • E. 

      Opsonin

  • 7. 
    Which endosome serves as a sorting station that directsdifferent types of receptors and ligands along differentpathways?
    • A. 

      Medial endosomes

    • B. 

      Late endosomes

    • C. 

      Early lysosomes

    • D. 

      Medial lysosomes

    • E. 

      Early endosomes

  • 8. 
    What determines the sequence of sugar addition toglycoproteins traveling through the Golgi complex?
    • A. 

      Nothing - the sequence is random

    • B. 

      The spatial arrangement of specific glycosyltransferases that contact proteins as they pass through the Golgi complex

    • C. 

      The concentration of sugars in the Golgi complex

    • D. 

      The sequence of sugars in the Golgi complex

  • 9. 
    Which model of Golgi complex formation suggests that thecisternae of a Golgi stack remain in place as stablecompartments held together by a protein scaffold while thecargo is shuttled through the Golgi via vesicles that budfrom one compartment and fuse with a neighboring one?
    • A. 

      The cisternal maturation model

    • B. 

      The cargo carrying model

    • C. 

      The vesicular transport model

    • D. 

      The secretory transport model

    • E. 

      The chemiosmotic model

  • 10. 
    Why is the ER so well-suited and ideally constructed for itsrole as a port of entry for secretory proteins?
    • A. 

      It has a large surface area allowing the attachment of many ribosomes

    • B. 

      The ER cisternae lumen favors the folding and assembly of proteins.

    • C. 

      The RER segregates secretory, lysosomal and plantcell vacuolar proteins from other newly made proteins, allowing their modification, and sends them to their destination.

    • D. 

      A and c

    • E. 

      A, b and c

  • 11. 
    A small subfamily of kinesins moves toward the minus end of amicrotubule, while the rest move toward the plus end. Whenthe neck and stalk of a minus-directed kinesin is joined to thehead of a plus-directed kinesin, in what direction will
    • A. 

      In a retrograde direction

    • B. 

      Toward the plus-end of the microtubule

    • C. 

      In an anterograde direction

    • D. 

      Towards the fastest growing end of the microtubule

    • E. 

      C and d

  • 12. 
    The heads of kinesin-like proteins have fairly closely relatedamino acid sequences but diverse tail sequences. What isthe explanation for this seeming contradiction?
    • A. 

      The similarity of kinesin-like protein heads and the variation in their tails are purely random.

    • B. 

      The similarity of the heads is explained by their similar roles in interacting with microtubules; the variation in the tails reflects the variety of cargoes to which they bind.

    • C. 

      The similarity of the heads is explained by their different roles in interacting with microtubules; the variation in the tails reflects the similar cargoes to which they bind.

    • D. 

      The similarity of the heads is explained by their similar roles in interacting with microtubules; the variation in the tails reflects the similar cargoes to which they bind

    • E. 

      The similarity of the heads is explained by their different roles in interacting with microtubules; the variation in the tails reflects the variety of cargoes to which they bind

  • 13. 
    Which type of cytoskeletal element is characterized as ahollow, rigid cylindrical tube with walls composed of tubulinsubunits
    • A. 

      Microfilments

    • B. 

      Microtubules

    • C. 

      Intermediate filaments

    • D. 

      All of the above

  • 14. 
    The vesicle is targeted to the appropiate compartment by_________.
    • A. 

      Endocytosis

    • B. 

      Rabs

    • C. 

      GTP binding proteins

    • D. 

      T-snares

  • 15. 
    Most vesicles budding from the Golgi body have a fuzzy,electron-dense coat on their ______ surface. The coatappears to be made of _______.
    • A. 

      Luminal, lipid

    • B. 

      Cytosolic, lipid

    • C. 

      Cytosolic, carbohydrate

    • D. 

      Luminal,protein

    • E. 

      Cytosolic, protein

  • 16. 
    The uptake (both specific and nonspecific) of fluid,dissolved solutes and suspended macromolecules iscalled ________.
    • A. 

      Endocytosis

    • B. 

      Phagocytosis

    • C. 

      Autophagy

    • D. 

      Exocytosis

    • E. 

      Pinocytosis

  • 17. 
    What recognizes the signal sequence as it exits theribosome and of what is it made?
    • A. 

      Signal recognition particle, DNA and protein

    • B. 

      Signal recognition particle, carbohydrate and protein

    • C. 

      SRP and its components, RNA and protein.

    • D. 

      SRP and its components, RNA and protein.

    • E. 

      Signal recognition protein, carbohydrate and lipid

  • 18. 
    In addition to microtubule motor proteins, ________ arealso involved in vesicular transport.
    • A. 

      Actin

    • B. 

      Myosins

    • C. 

      Tubulin

    • D. 

      Dynein

    • E. 

      Kinesin-like proteins

  • 19. 
    All of the following statements about cellular trafficking aretrue EXCEPT
    • A. 

      COPI-coated vesicles move materials from Golgi to the secretory vesicle

    • B. 

      Tethering proteins mediate docking between target and vesicle

    • C. 

      COPII-coated vesicles move materials from ER to Golgi

    • D. 

      Movement may be mediated by microtubules

  • 20. 
    The accumulation of misfolded proteins in the ER is a potentially lethal situation and thus causes the triggering ofwhat process?
    • A. 

      The polysomal response

    • B. 

      The posttranscriptional response

    • C. 

      The unfolded protein response (UPR)

    • D. 

      The proteasomal response

  • 21. 
    How do protein coats select the contents of the vesiclesthey help to form?
    • A. 

      They electromagnetically attract the correct cargo proteins.

    • B. 

      The coats have a specific affinity for the cytosolic tails of integral membrane receptors for cargo proteins that reside in the donor membrane.

    • C. 

      The coats have a specific affinity for the luminal tails of integral membrane

    • D. 

      Receptors for cargo proteins that reside in the donor membrane.

    • E. 

      The coat proteins directly attach to the cargo proteins in the lumen of the forming vesicles.

  • 22. 
    Kinesin movement along a microtubule is said to be________ meaning that it can move long distances alongan individual microtubule without falling off
    • A. 

      Excessive

    • B. 

      Progressive

    • C. 

      Excessive

    • D. 

      Processive

    • E. 

      Aggressive

  • 23. 
    What is the supposed function of the small subfamily ofkinesins that is incapable of movement
    • A. 

      They stabilize microtubules

    • B. 

      They encourage depolymerization

    • C. 

      They cause polymerization.

    • D. 

      They block other kinesins from moving along microtubules.

    • E. 

      They add phosphate groups to tubulin

  • 24. 
    Typically, receptors for hormones or growth factors aredestroyed during endocytosis, leading to a reduction in thecell’s sensitivity to further stimulation by that particularhormone or growth factor. This is a mechanism by whichcells regulate their ability to respond to extracellular messengers. What is it called?
    • A. 

      Receptor up-regulation

    • B. 

      Receptor annihilation

    • C. 

      Endocytic assignation

    • D. 

      Receptor down-regulation

    • E. 

      Super signaling

  • 25. 
    Which of the proteins below is(are) not made on themembrane-bound ribosomes of the RER?
    • A. 

      Inner peripheral membrane proteins

    • B. 

      Soluble lysosomal proteins

    • C. 

      Vacuolar enzymes

    • D. 

      Proteins of the extracellular matrix

    • E. 

      All of the above

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