Exam 3: RR (10)

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Exam 3: RR (10)
2013-11-09 15:31:10
Cell Bio

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  1. a.      the fusion of a secretory vesicle or secretory granule with the plasma membrane and subsequent discharge of its contents is called __
                                                                  i.      probably occurs on a rather __basis in most cells, as proteins and other materials are delivered to both the plasma membrane and extracellular space
    1.      in some cases, __produces an __through which the contents of the vesicle or granule are released into the __
    • exocytosis
    • continual 
    • membrane fusion 
    • opening 
    • EC space
  2.                                                                                                                                       i.      in this case, __is regulated by a __present in the membrane of the __
    1.      in other types of cells, __is generally triggered by release of __ from __
    a.      __between the __ and __ is thought to lead to the formation of a small, protein-lined “__”
    • fusion 
    • calcium-binding protein (synaptotagmin) 
    • synaptic vesicle
    • exocytosis 
    • Ca2+ from cytoplasmic stores

    • contact 
    • vesicle and plasma membranes

    fusion pore
  3.                                                                                                                                                                                                               i.      some __ may simply re-close, but in most cases, the __rapidly dilates to form an opening to __of the vesicle contents
    b.      Regardless of the mechanism, when a __ fuses with the plasma membrane, the __ of the vesicle membrane becomes part of the outer surface of the plasma membrane, whereas the __ of the vesicle membrane becomes part of the inner (cytosolic) surface of the plasma membrane
    fusion pores



    cytoplasmic vesicle

    luminal surface

    cytosolic surface
  4. I.                   Posttranslational Uptake of Proteins by Peroxisomes, Mitochondria, and Chloroplasts
    a.      __ within a eukaryotic cell is governed by __ and __that recognize these signals and deliver proteins containing them to the proper compartment
    • protein trafficking
    • sorting signals
    • receptors
  5. a.      Four of the cell’s major organelles—__(4)__—import proteins through one or more outer boundary membranes
                                                                  i.      as in the case of the __, proteins that are imported by these organelles contain __ that serve as addresses that are recognized by receptors at the __
    • nucleus, mitochondria, chloroplasts, and peroxisomes
    • rough ER,
    • amino acid sequences
    • organelle’s outer membrane
  6. a.      unlike the rough ER, which generally imports its proteins __, the proteins of these other organelles are imported __, following their __ on __ in the cytosol
    • cotranslationally
    • posttranslationally
    • complete synthesis
    • free ribosomes
  7. a.      Uptake in Peroxisomes
                                                                  i.      very simple organelles with __in which an imported protein can be placed: the __

                                                                ii.      proteins destined for a __possess a __, either a __for a __ or an __for a __
    • two subcompartments 
    • boundary membrane and the internal matrix
    • peroxisome 
    • peroxisomal targeting signal
    • PTS 
    • peroxisomal matrix protein
    • mPTS 
    • peroxisomal membrane protein
  8. 1.      several different __, __, and __ have been identified
    2.      __ bind to __ in the cytosol and shuttle them to the surface of the __, where they can enter the organelle
    • PTSs, mPTSs, and PTS receptors
    • PTS receptors
    • peroxisome-destined proteins
    • peroxisome
  9. a.      evidence suggests that at least one of the __ moves from the cytosol into the __ where it formsa __ that facilitates the movement of proteins into the peroxisome
    • PTS receptors
    • peroxisomal membrane
    • transient pore
  10.                                                               i.      unlike __ and __, whose imported proteins must assume an __, __are somehow able to import __ in their native, folded conformation, even those that consist of several subunits
    • mitochondria and chloroplasts
    • unfolded state,
    • peroxisomes 

    peroxisomal matrix proteins
  11. a.      Uptake into Mitochondria

                                                                  i.      have __ into which proteins can be delivered: __ (4)__
    • four subcompartments
    • outer mitochondrial membrane (OMM), inner mitochondrial membrane (IMM), intermembrane space, and matrix
  12.                                                               i.      mitochondria synthesize a few of their own integral membrane polypeptides; but, __% of the organelle’s proteins are encoded by the __, synthesized in the __, and imported __
    • 99
    • nuclear genome
    • cytosol
    • posttranslationally
  13.                                                               i.      mitochondrial proteins contain __ that target them to their home base
    1.      most __ contain a removable __ located at the __ of the molecule
    • signal sequences
    • mitochondrial matrix proteins
    • targeting sequence
    • N-terminus
  14. a.      a __typically includes a number of __ on one face of the __and __ on the opposite face
    b.      in contrast, most proteins destined for the __contain __ that remain as part of the molecule
    • presequence 
    • positively charged residues
    • helix 
    • hydrophobic residues
    • IMM 
    • internal targeting sequences
  15.                                                               i.      before a protein can enter a mitochondrion, several events are thought to take place
    1.      first, the protein must be __ in a relatively __ state
    __prepare polypeptides for uptake into mitochondria, incluindg ones that specifically direct mitochondrial proteins to the __ of the __
    • presented to the mitochondrion
    • extended, or unfolded,
    • chaperones 
    • cytosolic surface of the OMM
  16.                                                                                                                                       i.      the __contains a __, the __, which includes
    1.      receptors that __

    2.      __ through which unfolded polypeptides are __ across the outer membrane
    • OMM 
    • protein-import complex
    • TOM complex
    • recognize and bind mitochondrial proteins
    • protein-lined channels
    • translocated
  17.                                                                                                                                       i.      proteins destined for the __or __must pass through the __ and engage a second __ located in the __, called a __

    the IMM contains two major __complexes: __ and __
    • IMM 
    • matrix 
    • intermembrane space
    • protein-import complex
    • IMM
    • TIM complex
    • TIM 
    • TIM22
    • TIM23
  18. TIM22
    a.      TIM22 binds integral proteins of the IMM that contain an internal targeting sequence and inserts them into the lipid bilayer
  19. TIM23
    • a.      TIM23 binds proteins with an N-terminal presequence, which includes all of the proteins of the matrix
    •                                                                                                                                                                                                               i.      TIM23 recognizes and translocates the matrix proteins completely through the iMM and into the inner aqueous compartment
  20.  i.      __occurs at sites where the __ and __ come into close proximity so that the imported protein can cross both membranes simultaneously
    b.      movement into the matrix is powered by the __ across the __acting on the __; if the potential is dissipated by addition of a drug such as __, translocation ceases
    • Translocation 
    • outer and inner mitochondrial membranes

    • electrical potential
    • IMM
    • positively charged targeting signal

  21. 1.      As it enters the matrix, a polypeptide interacts with __, such as __, that mediate entry into the aqueous compartment
    a.      two mechanisms proposed to explain the general action of molecular __involved in the movement of proteins across membranes, which is a widespread phenomenon:
    • mitochondrial chaperones
    • mtHsp70
    • chaperones
  22. The first view
    the chaperones act as force-generating motors that use energy derived from ATP hydrolysis to actively “pull” the unfolded polypeptide through the translocation pore
  23.    i.      the chaperones aid in the __of the polypeptide across the membrane
    1.      __ is random
    a.      if unfolded polypeptide entered __ in mitochondrial membrane and “poked head” into the matrix, the chaperone residing on the inner surface of the membrane would do what?
    diffusion x2

    • translocation pore
    • bind and block the diffusion of the polypeptide back into the cytosol, causing further travel into the matrix
  24.                                                                                                                                                                                                               i.      as the polypeptide diffused further into matrix, it would be bound repeatedly by the __and at each stage prevented from __
    This is called __, and the chaperone is said to be acting as a __
    iii. regardless of the method of entry, once in the __the polypeptide achieves its native conformation following __ of the __
    • chaperone 
    • diffusing backward
    • biased diffusion
    • Brownian ratchet
    • matrix 
    • enzymatic removal
    • presequence
  25. a.      Uptake of Proteins into Chloroplasts
                                                                  i.      chloroplasts have __subcompartments into which proteins can be delivered: __
                                                                ii.      chloroplasts and mitochondrial import mechanisms exhibit many similarities, although their translocation machineries have evolved independently
    • six 
    • an inner and outer envelope membrane and interening intermembrane space, as well as the stroma, thylakoid membrane, and thylakoid lumen
  26. iii. As in the mitochondria: (1) and (2)
    • 1.      the vast majority of chloroplast are imported from cytosol
    • 2.      the outer and inner envelope membranes contain distinct translocation complexes (Toc and Tic complexes) that work together during import
  27. iii. As in the mitochondria: (3) and (4)
    • 1.      chaperones aid in the unfolding of the polypeptides in the cytosol and folding o the proteins in the chloroplasts
    • 2.      most proteins destined for the chloroplast are synthesized with a removable N-terminal sequence that is highly variable in length and sequence
  28.                                                               i.      the __ does more than simply target a polypeptide to a chloroplast: it provides an “__” that localizes the polypeptide to one of several possible __within the organelle
    1.      all proteins __through the __ contain a __ as part of their __, which guarantees that the polypeptide will enter the stroma
    a.      once in the __, the __ is removed by a __ located in that compartment
    • transit peptide
    • address
    • subcompartments 
    • translocated 
    • chloroplast envelope
    • stroma targeting domain
    • transit peptide
    • stroma 
    • stroma targeting domain
    • processing peptidase
  29. 1.      those polypeptides that belong in a __ or __ bear an additional segment in their __, called the __, which dictate entry into the __
    • thylakoid membrane
    • thylakoid lumen
    • transit peptide
    • thylakoid transfer domains
    • thylakoids
  30. a.      several distinct pathways have been identified by which proteins are either inserted into the __ or __into the __                                                                                                                                      i.      these pathways exhibit striking similarities to transport systems in __cells, the presumed ancestors of chloroplast
    • thylakoid membrane
    • translocated 

    thylakoid lumen

  31. 1.      many proteins that reside within the __ are encoded by __ and synthesized on __of the __
    • thylakoid membrane
    • chloroplast genes
    • membrane-bound ribosomes 
    • chloroplasts