Lodish Ch 14: Vesicular Traffic and Secretion Mechanisms
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Questions and Answers

The discovery of green fluorescent protein (GFP) has greatly facilitated living cell experiments because:

  • GFP requires a jellyfish-specific cofactor.
  • GFP is green.
  • GFP sequences may be readily fused to those of other proteins. (correct)
  • wild-type GFP folding is adapted to normal seawater temperatures, 15-25 °C.
  • Endoglycosidase D is a useful reagent because it allows scientists to distinguish glycosylated proteins that:

  • remain in the cis-Golgi.
  • remain in the trans-Golgi.
  • get secreted.
  • remain in the ER. (correct)
  • Yeast sec mutations:

  • invariably affect nonessential genes.
  • affect protein transport into mitochondria but not chloroplasts.
  • all fall into the same complementation class.
  • provide little evidence regarding the mechanism, necessitating other assays or information. (correct)
  • Cell-free transport assays:

    <p>all of the above</p> Signup and view all the answers

    The first step in the secretory pathway that should be inhibited by a non-functional mutant of NSF is:

    <p>ER to Golgi transport.</p> Signup and view all the answers

    Given the wild type (normal) yeast on the left and the mutant yeast on the right, identify the defective phenotype for the mutant.

    <p>fusion of transport vesicles from the ER to the Golgi</p> Signup and view all the answers

    Vesicle budding recruits proteins that are needed for subsequent:

    <p>selective vesicle targeting and fusion.</p> Signup and view all the answers

    The presence of clathrin mediates vesicular transport:

    <p>trans-Golgi to endosome.</p> Signup and view all the answers

    Which of the following small GTPases are NOT involved in vesicle budding or docking?

    <p>ras</p> Signup and view all the answers

    If Sar1 is inserted into the membrane:

    <p>it is bound to GTP and recruits COPII coat proteins.</p> Signup and view all the answers

    Proteins that function in the ER will encounter which of the following?

    <p>anterograde transport in COPII coated vesicles</p> Signup and view all the answers

    What phenotype would be observed in a cell containing a nonhydrolyzable form of ATP with respect to the vesicles of the secretory pathway?

    <p>Coated vesicles would accumulate.</p> Signup and view all the answers

    COPI coat proteins mediate ______ transport between the Golgi apparatus and other organelles.

    <p>retrograde</p> Signup and view all the answers

    Which of the following is a forward transport sorting signal acting at the ER?

    <p>diacidic amino acid motif within the cytosolic domain</p> Signup and view all the answers

    Soluble and membrane proteins advance through the Golgi complex by:

    <p>cisternal progression.</p> Signup and view all the answers

    Protein sorting of anterograde cargo to different destinations within the Golgi complex occurs in the:

    <p>trans-Golgi network.</p> Signup and view all the answers

    In hepatocytes, the process by which apically destined proteins travel from the basolateral region across the cell before fusing with the apical membrane is called:

    <p>transcytosis.</p> Signup and view all the answers

    The mannose 6-phosphate residue is important, as it is required to target soluble enzymes to the lysosome. The two enzymes responsible for attaching this residue onto these soluble enzymes reside in the:

    <p>cis-Golgi.</p> Signup and view all the answers

    In MDCK cells, which of the following is a sorting signal that allows proteins to be targeted to the apical membrane?

    <p>GPI</p> Signup and view all the answers

    The LDL receptor is a receptor for:

    <p>apolipoprotein B and receptor-mediated endocytosis of LDL.</p> Signup and view all the answers

    Lipoproteins are effective in transporting lipid molecules in an aqueous environment because their surface layer is:

    <p>amphipathic.</p> Signup and view all the answers

    Acidification of endosomes is important in dissociating:

    <p>iron from transferrin.</p> Signup and view all the answers

    Formation of the late endosome/multivesicular endosome occurs by mechanisms similar to those of:

    <p>retrovirus budding from the plasma membrane.</p> Signup and view all the answers

    An important molecule for generating fatty acids in the cell enters via receptor-mediated endocytosis. The complex formed between the receptor on the plasma membrane and the important molecule is stable only at neutral pH. Based on this knowledge, you would predict:

    <p>both the molecule and the receptor are degraded to release the molecule from the receptor.</p> Signup and view all the answers

    The topogenic sequence of transferrin must include:

    <p>an internal signal-anchor sequence with positive charges N-terminal to the SA.</p> Signup and view all the answers

    Receptor-mediated endocytosis of iron-carrying transferrin results in:

    <p>vesicle formation at the plasma membrane mediated by COP proteins.</p> Signup and view all the answers

    The mannose 6-phosphate residue is important, as it is required to target soluble enzymes to the lysosome. The two enzymes responsible for attaching this residue onto these soluble enzymes reside in the trans-Golgi.

    <p>lysosome; cis-Golgi</p> Signup and view all the answers

    Which of the following is TRUE about lysosomes?

    <p>They are bound by a single membrane but can engulf organelles containing double membranes.</p> Signup and view all the answers

    Study Notes

    Vesicular Traffic, Secretion, and Endocytosis

    • GFP (green fluorescent protein) discovery facilitated living cell experiments due to its ability to fuse with other proteins.
    • Endoglycosidase D distinguishes glycosylated proteins that remain in the ER.
    • Yeast sec mutations provide insight into mechanisms but may affect non-essential genes.
    • Cell-free transport assays offer evidence for secretory pathway analysis, assess glycosylation status, and test protein effects.
    • VSV G protein analysis is useful due to its temperature-sensitive folding properties permitting protein synthesis and inhibitor use in experiments.
    • Vesicles' movement direction in VSV G-based systems is determined through isolating and characterizing vesicles.
    • NSF, a protein in the secretory pathway, is implicated in inhibiting ER-to-Golgi transport.
    • Identifying defective phenotype in relation to wild-type yeast.
    • Role of vesicle budding, trafficking, and membrane fusion in the secretory pathway for correct movement of proteins through the system.
    • COPI, COPII proteins, and GTPases' association in vesicle transport in various cellular locations.
    • SNARE proteins' role in membrane fusion; their pairing mechanisms for vesicle and target membrane association.
    • Protein sorting signals and how specific enzymes are targeted to particular locations.
    • Receptor-mediated endocytosis involving proteins in internalizing different molecules.
    • Autophagy process and regulation for cellular cleaning.
    • Role of pH in facilitating protein dissociation for different targets.
    • Sorting signals for proteins targeted to apical membranes in MDCK cells.
    • Clathrin-coated vesicles pinching off through a process mediated by the GTPase Dynamin.
    • LDL receptor and its role in targeting apolipoproteins for cellular use or degradation.
    • Receptor-mediated endocytosis of iron-carrying transferrin for iron release.
    • Importance of mannose 6-phosphate in targeting enzymes to the lysosome.
    • Correctly identifying and understanding the enzymes responsible for mannose 6-phosphate addition to enzymes for transport.
    • Importance of lysosomal enzymes for protein degradation/removal.
    • Processes/molecules involved in transporting proteins to and from the endoplasmic reticulum (ER).

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    Description

    This quiz covers the essential concepts of vesicular traffic, secretion, and endocytosis, focusing on the discovery and applications of GFP, yeast sec mutations, and the roles of specific proteins in the secretory pathway. Test your understanding of the mechanisms behind vesicle movement and protein glycosylation processes as they relate to cellular functions.

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