Exam 3: RR (5)

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  1. a.      Glycosylation in the RER
                                                                  i.      nearly all proteins produced on membrane-bound ribosomes—whether integral components of a membrane, soluble lysosomal or vacuolar enzymes, or parts of the ECM—become __
    1.      __ have key roles in the function of many __, particularly as bidning sites in their interactions with other __, as occurs during many cellular processes
    • glycoproteins
    • carbohydrate groups
    • glycoproteins
    • macromolecules
  2.                                                               i.      they also aid in the __ and __of the protein to which they are attached
    1.      the sequences of sugars that comprise the __ of __are highly specific; if the __are isolated from a purified protein of a given type of cell, their sequence is consistent and predictable
    • proper folding and stabilization 
    • oligosaccharides
    • glycoproteins 
    • oligosaccharides
  3.                                                               i.      the addition of sugars to an __chain is catalyzed by enzymes called __, each of which transfers a specific monosaccharide from a __sugar to the growing end of the carb chain
    1.      the sequence in which they are transferred during assembly of an oligosaccharide depends on the __ that participate in the process
    • oligosaccharide 
    • glycosyltransferases
    • nucleotide 
    • sequence of action of glycosyltransferases
  4. a.      this in turn depends on the location of specific __within the various memrbaens of the __
                                                                                                                                          i.      thus, the arrangement of sugars int eh oligosaccharide chains of a glycoprotein depends on the __ of particular __in the __
    • enzymes 
    • secretory pathway
    • spatial localization
    • enzymes 
    • assembly line
  5.                                                               i.      the initial steps in the assembly of __ of both soluble proteins and integral membrane proteins
    1.      __, or __, segment of each carb chain is not assembled on the protein itself but put together independently on a __ and then transferred, as a __, to specific __ of the polypeptide
    • N-linked oligosaccharides
    • basal
    • core
    • lipid carrier
    • block
    • asparagines residues
  6. a.      this lipid carrier, which is named __, is embedded in the ER membrane
                                                                                                                                          i.      sugars are added to the __ molecule one at a time by membrane-bound __
    • dolichol phosphate
    • dolichol phosphate
    • glycosyltransferases
  7. 1.      this part of __ process is invariant; in mammals, it begins with the transfer of __, then __ and three __units in the precise pattern, which is then transferred by the ER enzyme __from __ to certain __ in the nascent polypeptide as the polypeptide is being translocated into the eR lumen
    • glycosylation
    • N-acetylglucosamine
    • nine mannose
    • glucose 
    • oligosaccharyltransferase 
    • dolichol phosphate
    • asparagines
  8.                                                               i.      mutations that lead to the total absence of __ cause the death of embryos prior to __
    1.      mutatiosn that lead to partial disruption of the __pathway in the ER are responsible for serious inherited disorders affecting nearly every organ system
    a.      these diseases are called __ and they are usually identified through blood tests that detect abnormal __ of serum proteins 
    • N-glycosylation
    • implantation
    • glycosylation 
    • Congenital Diseases of Glycosylation
    • glycosylation
  9.                                                               i.      shortly after it is transferred to the nascent polypeptide, the __ undergoes a process of __
    1.      this modification begins int eh ER with the enzymatic removal of two of the three __
    a.      this sets the stage for an important event in the life of a newly synthesized __in which it is screened by a system of quality control that determines whether or not it is fit to move on to the next compartment of the __
    • oligosaccharide chain
    • gradual modification
    • terminal glucose residues
    • glycoprotein 
    • biosynthetic pathway
  10.                                                                                                                                       i.      to begin this __process, each __, which at this stage contains a single remaining glucose, binds to an __
    1.      removal of the remaining glucose by __ leads to release of the glycoprotein from the __
    • screening 
    • glycoprotein
    • ER chaperone
    • glucosidase II
    • chaperone
  11. a.      if a __ at this stage has not completed its folding or has misfolded, it is recognized by a __that adds a __ back to one of the __residues at the exposed end of the recently trimmed oligosaccharide
                                                                                                                                                                                                                  i.      __recognizes incompletely folded or misfolded proteins because they display exposed __ that are absent from properly folded proteins
    • glycoprotein
    • conformation-sensing enzyme (UGGT) 
    • single glucose residue
    • mannose 
    • UGGT 
    • hydrophobic residues
  12. 1.      once glucose residues added, the “__” glycoprotein is recognized by the same __, which give the protein another chance to fold properly
    a.      after some time with the __, the added glucose residue is removed and the __ checks it again to see if it has achieved its proper 3D structure
    • tagged
    • ER chaperones
    • chaperone
    • conformation-sensing enzyme
  13.                                                                                                                                                                                                               i.      if it is still partially unfolded or misfolded, another __ is added and the process is repeated until, eventually, the __has either folded correctly and continues on its way, or remains misfolded and is destroyed
                                                                                                                                                                                                                ii.      studies say the decision to destroy the defective protein begins with the __ that trims a __ from an exposed end of the __of a protein that has been in the ER for an extended period
                                                                                                                                                                                                              iii.      once one or more of these __ have been remove, the protein can no longer be recycled and, instead, is sentenced to degradation
    • glucose residue
    • glycoprotein 
    • activity of a slow-acting enzyme in the ER
    • mannose residue
    • oligosaccharide 
    • mannose resiudes
  14.                                                               i.      Mechanisms that Ensure the Destruction of Misfolded Proteins
    1.      misfolded proteins are not destroyed in the ER, but instead are __
    2.      once in the cytosol, the __ are removed, and the __are destroyed in __, which are protein-degrading machines; this process is called __
    a.      it ensures that aberrant proteins are not transported to other parts of the cell, but it can have __
    • transported into the cytosol by a process of dislocation
    • oligosaccharide chains
    • misfolded proteins 
    • proteasomes
    • ER-associated degradation (ERAD)
    • negative consequences
  15. 1.      under certain circumstances, misfolded proteins can be generated in the __ at a rate faster than they can be __to the cytoplasm
    a.      accumulation of misfolded proteins, which is potentially lethal to cells, triggers a comprehensive “__” within the cell called __
                                                                                                                                          i.      the ER contains __ that monitor the concentration of unfolded or misfolded proteins in the ER lumen
    1.      the sensors are normally kept in an __ state by molecular __, particularly __
    • ER
    • exported 
    • plan of action
    • unfolded protein response (UPR)
    • protein sensors
    • inactive
    • chaperones
    • BiP
  16.                                                                                                                                       i.      if circumstances should lead to an accumulation of __, the __ molecules in the __ are called into service as __ for the misfolded proteins, rendering them incapable of inhibiting the sensors
    • misfolded proteins
    • BiP
    • ER lumen
    • chaperones
  17.                                                                                                                                       i.      activation of the __leds to a multitude of signals that are transmitted into both the nucleus and cytosol and result in :
    1.      the __ whose encoded proteins have the potential to alleviate stressful conditions within the ER
    • sensors 
    • expression of hundreds of different genes
  18. a.      these include genes that encode:
                                                                                                                                                                                                                  i.      __ that can help misfolded proteins reach the native state
                                                                                                                                                                                                                ii.      proteins involved in the __
                   iii. proteins involved in the __ of abnormal proteins 
    • ER-based molecular chaperones
    • transport of the proteins out of the ER
    • selective destruction
  19. 1.      __of a key proiten is required for protein synthesis
    a.      this modification inhibits __ and decreases the flow of newly synthesized proteins into the ER
                                                                                                                                                                                                                  i.      this gives the cell an opportunity to remove those proteins that are already present in the __
    • phosphorylation 
    • protein synthesis
    • ER lumen
  20.                                                               i.      The __ is more than a __ mechanism; it also includes the activation of a pathway that leads to the __
    1.      it is presumed that the __provides a mechanism to relieve itself of the stressful conditions
    a.      if these corrective measures are not successful, the __ is triggered and the cell is destroyed
    • UPR
    • cell-survival
    • death fo the cell
    • UPR 
    • cell-death pathway
  21. a.      From Erà Golgi
                                                                  i.      the __ contain specialized exit sites that are devoid of ribosomes and serve as places where the__ in the __pathway are formed
                                                                ii.      soon after they bud from the ER membrane, __ fuse with one another to form larger vesicles and interconnected tubules in the region between the __ and __

    • RER cisternae
    •  first transport vesicles
    • biosynthetic 
    • transport vesicles
    • ER and Golgi complex
  22. 1.      this region is called __, and the vesicular-tubular carriers that form these are called __
    a.      once formed, the __move farther away from the ER toward the __
                                                                ii.      movement of __occurs along tracks composed of microtubules
    • ERGIC (ER Gogli intermediate compartment)
    • VTCs
    • VTCs 
    • Golgi complex
    • VTCs
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Exam 3: RR (5)
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