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Molec Cell > protein sorting and transport > Flashcards

protein sorting and transport Flashcards

1
Q
  1. the experiments of palade and colleagues, using incorporation of labeled amino acids, defined the pathway taken by secreted proteins as
    a. rough ER, smooth ER, Golgi, secretory vesicles, cell exterior
    b. rough ER, smooth ER, golgi, endosomes, cell exterior
    c. rough ER, golgi, endosomes, cell exterior
    d. rough ER, golgi, secretory vesicles, cell exterior
A

d. rough ER, golgi, secretory vesicles, cell exterior

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2
Q
  1. a signal sequence on the polypeptide chain targets all but ___ proteins to the rough ER surface
    a. secreted
    b. plasma membrane
    c. mitochondrial
    d. lysosomal
A

c. mitochondrial

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3
Q
  1. most eukaryotic plasma membrane proteins are synthesized on
    a. free ribosomes and inserted after translation into the plasma membrane
    b. rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the golgi apparatus
    c. rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the rough ER
    d. ribosomes associated with the plasma membrane and inserted into the membrane cotranslationally
A

b. rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the golgi apparatus

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4
Q
  1. when compared to ribosomes in free polyribosomes in the cytosol; rough ER-bound ribosomes have
    a. different large and small subunits
    b. the same large and small subunits
    c. different large subunits but the same small subunits
    d. different small subunits but the same large subunits
A

b. the same large and small subunits

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5
Q
  1. when compared to polypeptides synthesized in vitro on free ribosomes, the polypeptides synthesized from the same mRNA on microsome-bound ribosomes are
    a. the same size
    b. larger
    c. smaller
    d. more hydrophobic
A

c. smaller

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6
Q
  1. the signal sequence that targets a polypeptide to the rough ER is rich in ___ amino acids
    a. positively charged
    b. negatively charged
    c. hydrophilic
    d. hydrophobic
A

d. hydrophobic

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7
Q
  1. as they emerge from the ribosome, signal sequences are recognized and bound by a
    a. tRNA
    b. signal peptidase
    c. signal recognition particle
    d. SRP receptor
A

b. signal peptidase

c. signal recognition particle

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8
Q
  1. Which of the following is evidence for the signal hypothesis for targeting of a secretory protein to the rough ER
    a. The protein is larger when synthesized in vitro on free polysomes
    b. The secretory protein ends up in the cytosol when a short sequence is deleted by genetic engineering
    c. A normally cytosolic protein is secreted when a sequence is added to it by genetic engineering
    d. All of the above
A

d. All of the above

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9
Q
  1. If you isolate the secretory protein from secretory vesicles and inject it into the cytosol, it will
    a. Be taken up into the rough ER and follow the secretory pathway
    b. Be taken up into secretory vesicles and secreted
    c. Be secreted through channels in the plasma membrane
    d. Remain in the cytosol until it is degraded
A

d. Remain in the cytosol until it is degraded

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10
Q
  1. When the signal sequence emerges from the ribosome, it binds first to a
    a. Translocon
    b. Signal peptidase
    c. Signal recognition particle
    d. SRP receptor
A

c. Signal recognition particle

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11
Q
  1. Protein folding in the ER is assisted by a chaperone called
    a. BiP
    b. PiP
    c. Hsp60
    d. Hsp90
A

a. BiP

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12
Q
  1. Disulfide bonds within or between proteins form easily in which of the following
    a. Both cytosol and ER
    b. Neither cytosol nor ER
    c. Cytosol but not ER
    d. ER but not cytosol
A

d. ER but not cytosol

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13
Q
  1. GPI-anchored proteins are synthesized
    a. On free ribosomes and attached to the GPI group on the outside of the ER
    b. As transmembrane proteins, cleaved, and attached to the GPI group on the inside surface of the ER
    c. As transmembrane proteins, cleaved, and attached to the GPI group on the cytosolic surface of the ER
    d. Into the lumen of the ER and attached to the GPI group on the inside surface of the ER
A

b. As transmembrane proteins, cleaved, and attached to the GPI group on the inside surface of the ER

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14
Q
  1. The unfolding response involves
    a. General inhibition of protein synthesis
    b. Increased synthesis of chaperons
    c. Increased activity of proteosomes
    d. All of the above
A

d. All of the above

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15
Q
  1. Most cellular lipids are synthesized in
    a. Fat droplets
    b. Mitochondria
    c. The endoplasmic reticulum
    d. The golgi apparatus
A

c. The endoplasmic reticulum

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16
Q
  1. Newly synthesized membrane lipids are found in both halves of membrane bilayers because they are
    a. Synthesized on both surfaces
    b. Removed and transported to these locations by lipid transport proteins
    c. Synthesized on one surface and flip spontaneously to the other surface
    d. Synthesized on one surface and flipped to the other surface by proteins called flippases
A

d. Synthesized on one surface and flipped to the other surface by proteins called flippases

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17
Q
  1. The sequence Lys-Asp-Glu-Leu(KDEL) serves as an ER retention signal for proteins by binding to KDEL receptors that
    a. Hold the proteins in the rough ER
    b. Hold the proteins in the smooth ER
    c. Hold the proteins in both smooth ER and rough ER and prevent their transport to the Golgi apparatus
    d. Transports the proteins from the Golgi apparatus back to the ER
A

d. Transports the proteins from the Golgi apparatus back to the ER

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18
Q
  1. Proteins attached to the outer layer of the plasma membrane bilayer are usually attached by a
    a. Farnesyl tail
    b. Glycosylphosphatidylinositol (GPI) anchor
    c. Prenyl tail
    d. Geronyl tail
A

b. Glycosylphosphatidylinositol (GPI) anchor

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19
Q
  1. Vesicles initially enter the golgi apparatus by fusing with
    a. the cis (convex) face. They exit from the trans (concave) face
    b. the trans (concave) face. They exit from the cis (convex) face
    c. both faces. They exit from the sides of cisternae
    d. none of the above
A

a. the cis (convex) face. They exit from the trans (concave) face

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20
Q
  1. which of the following proteins do not pass through the golgi apparatus
    a. lysosomal enzymes
    b. cell surface proteins
    c. ribosomal proteins
    d. proteins secreted by exocytosis
A

c. ribosomal proteins

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21
Q
  1. N-linked oligosaccharides are added in the
    a. Cis Golgi and modified in the medial golgi
    b. ER and modified in the golgi
    c. Medial golgi and modified in the trans golgi
    d. Cis golgi and modified in the trans golgi
A

b. ER and modified in the golgi

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22
Q
  1. Lysosomal proteins are marked by adding a phosphate to a ___ group
    a. Glucose
    b. Serine
    c. GDP
    d. Mannose
A

d. Mannose

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23
Q
  1. The plasma membrane of intenstinal epithelial cells requires separate targeting of proteins to
    a. One continuous plasma membrane domain
    b. Two plasma membrane domains: the apical and basolateral domains
    c. Three plasma membrane domains: the apical, lateral, and basal domains
    d. Four plasma membrane domains: one apical, two lateral, and a basal domain
A

b. Two plasma membrane domains: the apical and basolateral domains

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24
Q
  1. Which of the following classes of lipids is synthesized in the golgi apparatus
    a. Phospholipids
    b. Glycolipids
    c. Cholesterol
    d. Ceramide
A

b. Glycolipids

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25
Q
  1. Which of the following polysaccharides is synthesized in the golgi apparatus
    a. Pectin
    b. Cellulose
    c. Amylose
    d. Glycogen
A

a. Pectin

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26
Q
  1. Which of the following does not bud directly from the trans golgi network
    a. Constitutive vesicles
    b. Regulated secretory vesicles
    c. Transport vesicles for lysosomal enzymes
    d. Lysosomes
A

d. Lysosomes

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27
Q
  1. The enzyme that modifies the mannose group on lysosomal proteins recognizes and binds to a(n)
    a.  helix
    b. signal sequence
    c. signal patch
    d. KDEL sequence
A

c. signal patch

28
Q
  1. In plant cells, vesicles transport proteins from the golgi apparatus to
    a. Lysosomes
    b. Vacuoles
    c. Chloroplasts
    d. Mitochondria
A

b. Vacuoles

29
Q
  1. Yeasts are advantageous for studying secretory pathways because
    a. They secrete more proteins per cell than animal cells
    b. one can easily isolate Golgi apparatuses.

    c. they are amenable to genetic analysis.
    d. they have only one simple pathway for secreted proteins.
A

c. they are amenable to genetic analysis.

30
Q
  1. Brain tissue is useful for studies of vesicular transport because
    a. many brain diseases involve mutant vesicular transport.

    b. synaptic vesicles are abundant in the brain and can be isolated in large quantities for biochemical analysis
    c. the mechanisms of vesicle transport and fusion are unique to neurons.
    d. All of the above
A

d. All of the above

31
Q
  1. Vesicles that carry proteins from the rough ER to the Golgi apparatus bud off as _______ vesicles.
    a. Uncoated
    b. clathrin-coated
    c. COPI-coated
    d. COPII-coated
A

d. COPII-coated

32
Q
  1. Lysosomal proteins are initially incorporated into _______ vesicles.
    a. Uncoated
    b. clathrin-coated
    c. COPI-coated
    d. COPII-coated
A

b. clathrin-coated

33
Q
  1. ARF function on vesicles is regulated by
    a. phosphorylation of serine residues
    b. phosphorylation of mannose residues
    c. binding of GTP.
    d. binding of ATP.
A

d. binding of ATP.

34
Q
  1. Clathrin coats are bound to specific receptors by a protein called
    a. adaptor protein
    b. ARF
    c. COPI
    d. NSF.
A

a. adaptor protein

35
Q
  1. Clathrin molecules are composed of
    a. four protein molecules in the shape of a cross
    b. three protein chains in the shape of a triskelion.
    c. six protein chains in the shape of a hexagon
    d. five protein chains in the shape of a pentagon
A

b. three protein chains in the shape of a triskelion.

36
Q
  1. Rothman and colleagues proposed that the specificity of a vesicle fusing with its target membrane lies in the interaction of pairs of proteins called v-(vesicle) and t-(target)
    a. SNAPs
    b. SNAREs
    c. NSFs
    d. COPs.
A

b. SNAREs

37
Q
  1. In vesicle fusion with a target membrane, ATP hydrolysis is required to
    a. bind t- and v-SNAREs together
    b. bind SNAREs to Rabs
    c. bind NSF to SNAP
    d. separate the bound t-and v-SNAREs.
A

d. separate the bound t-and v-SNAREs.

38
Q
  1. Griscelli syndrome, a disease caused by mutations in the gene encoding Rab27a, is characterized by abnormal
    a. transport of melanosomes
    b. export of neurotransmitters.
    c. export of vesicles in T lymphocytes
    d. Both a and c
A

d. Both a and c

39
Q
  1. The protein complexes where exocytosis occurs are called
    a. Exocysts
    b. Exocytocysts
    c. secretosites
    d. secretion sites
A

a. Exocysts

40
Q
  1. The pH inside lysosomes is about
    a. 7.0
    b. 6.0
    c. 5.0
    d. 4.0
A

c. 5.0

41
Q
  1. Lysosomes digest
    a. Proteins
    b. nucleic acid
    c. carbohydrates
    d. lipids
    e. All of the above
A

e. All of the above

42
Q
  1. The fate of the mannose-6-phosphate receptors that bind and take up lysosomal hydrolases into lysosomal transport vesicles is that they
    a. are transported to lysosomes and hold the lysosomal hydrolases there
    b. are transported to lysosomes and degraded there
    c. release the lysosomal hydrolases in the late endosomes and are recycled in vesicles back to the Golgi
    d. are degraded in late endosomes, allowing the release of the lysosomal hydrolases.
A

c. release the lysosomal hydrolases in the late endosomes and are recycled in vesicles back to the Golgi

43
Q
  1. Transport vesicles carrying acid hydrolases fuse with
    a. Lysosomes
    b. endocytic vesicles
    c. early endosomes
    d. late endosomes
A

a. Lysosomes

44
Q
  1. Gaucher disease is a failure of lysosomes of macrophages to hydrolyze
    a. Proteins
    b. Glucocerebrocide
    c. DNA
    d. Polysaccharides
A

b. Glucocerebrocide

45
Q
  1. All of the following are contiguous membrane domains except
    a. rough ER
    b. secretory granules
    c. smooth ER
    d. transitional ER
A

b. secretory granules

46
Q
  1. Radioactive amino acid-labeled proteins in pancreatic acinar cells were located progressively in
    a. secretory vesicles → Golgi apparatus → rough ER → nucleus.
    b. Golgi apparatus → rough ER → nucleus → secretory vesicles
    c. rough ER → Golgi apparatus → secretory vesicles
    d. rough ER → secretory vesicles → Golgi apparatus.
A

c. rough ER → Golgi apparatus → secretory vesicles

47
Q
  1. Which of the following is not a possible destination for vesicles leaving the Golgi apparatus?
    a. The plasma membrane
    b. The exterior of the cell
    c. Lysosomes
    d. Mitochondria
A

d. Mitochondria

48
Q
  1. The ribosomes of the rough endoplasmic reticulum (rough ER) are targeted to the cytoplasmic side of the membrane via
    a. a signal sequence within the 28S ribosomal RNA
    b. a sequence within the protein being synthesized
    c. the S6 ribosomal protein
    d. the cap sequence at the 5′ end of the mRNA being translated.
A

b. a sequence within the protein being synthesized

49
Q
  1. As they emerge from the ribosome, signal sequences are recognized and bound by a
    a. tRNA
    b. signal peptidase
    c. signal recognition particle (SRP)
    d. SRP receptor.
A

c. signal recognition particle (SRP)

50
Q
  1. In yeast, posttranslational translocation of proteins targeting the ER is
    a. a process affecting many newly synthesized proteins
    b. much less common than in mammalian cells
    c. rare
    d. impossible, because all translocation into the ER is driven by the process of protein synthesis.
A

a. a process affecting many newly synthesized proteins

51
Q
  1. Which of the following is true of transmembrane proteins?
    a. The signal sequences are always cleaved off
    b. They are always inserted with the amino terminus on the lumenal side and the carboxyl terminus in the cytosol
    c. They cross the membrane only once
    d. They usually have one or more α helices spanning the membrane bilayer.
A

d. They usually have one or more α helices spanning the membrane bilayer.

52
Q
  1. The lumen of the ER is equivalent topologically to
    a. the cytoplasm
    b. the cytoplasmic face of the plasma membrane
    c. the extracellular space
    d. the nucleoplasm
A

c. the extracellular space

53
Q
  1. Proteins that span the membrane multiple times have multiple _______ that alternate with multiple transmembrane stop-transfer sequences
    a. glycosylation sites
    b. internal signal sequences
    c. phosphorylation sites
    d. sulfation sites
A

b. internal signal sequences

54
Q
  1. N-linked glycosylation at an Asn-X-Ser/Thr consensus sequence adds approximately _______ sugar(s) in a single step to the protein
    a. 1
    b. 15
    c. 30
    d. 100
A

b. 15

55
Q
  1. Calnexin assists in folding glycoproteins that contain one _______ residue
    a. glucose
    b. mannose
    c. N-acetylglucosamine
    d. sialic acid
A

a. glucose

56
Q
  1. The major site at which membrane lipids are synthesized is
    a. the cytosolic side of the ER membrane
    b. the cytosol
    c. the lumenal side of the ER membrane
    d. the cytosolic side of the Golgi membrane.
A

a. the cytosolic side of the ER membrane

57
Q
  1. The sequence Lys-Asp-Glu-Leu (KDEL) serves to retain proteins in the ER by
    a. preventing their packaging into vesicles destined for the Golgi
    b. binding to receptors within the membranes of the ER and Golgi, which retain them or return them to the ER
    c. binding the SRP receptor in the ER membrane
    d. associating with the lipids in the ER membrane.
A

b. binding to receptors within the membranes of the ER and Golgi, which retain them or return them to the ER

58
Q
  1. The trans Golgi network is
    a. the intermediate compartment between the ER and the Golgi
    b. the part of the Golgi where fusion of vesicles from the ER occurs
    c. where sorting of proteins to the lysosomes, plasma membrane, and cell exterior occurs
    d. the network of vesicles that transport proteins between Golgi cisternae.
A

c. where sorting of proteins to the lysosomes, plasma membrane, and cell exterior occurs

59
Q
  1. Which of the following is not involved in the specific targeting of proteins to lysosomes?
    a. N-linked glycosylation in the ER
    b. Mannose phosphorylation
    c. The mannose-6-phosphate receptor
    d. Signal patches
A

a. N-linked glycosylation in the ER

60
Q
  1. Which of the following lipids is/are synthesized in the Golgi apparatus?
    a. Phospholipids
    b. Cholesterol
    c. Ceramide
    d. Glycolipids
A

d. Glycolipids

61
Q
  1. Clathrin-coated vesicles are involved in
    a. the retrieval of ER resident proteins from the cis-Golgi or the ER-Golgi intermediate compartment
    b. the uptake of extracellular molecules by endocytosis and the transport of molecules from the trans Golgi network to the lysosomes
    c. transport from the ER to the Golgi
    d. the process of secretion.
A

b. the uptake of extracellular molecules by endocytosis and the transport of molecules from the trans Golgi network to the lysosomes

62
Q
  1. The activity of Rab GTPases are regulated by all of the following classes of proteins except
    a. GAP (GTPase activating protein)
    b. GDI (GDP-dissociation inhibitor)
    c. GEF (Guanine nucleotide exchange factor)
    d. GTF (Guanine nucleotide trypolysis factor)
A

d. GTF (Guanine nucleotide trypolysis factor)

63
Q
  1. The major model of vesicle fusion holds that the specificity of a vesicle fusing with its target membrane lies in the interaction of pairs of proteins called v- (vesicle) and t- (target)
    a. SNAREs
    b. SNAPs
    c. COPs
    d. NSFs.
A

a. SNAREs

64
Q
  1. Which of the following would you expect to find at high concentrations in lysosomes?
    a. Proteins destined for secretion
    b. Glycosylation enzymes
    c. Degradative enzymes
    d. Proteins containing the Lys-Asp-Glu-Leu (KDEL) amino acid sequence
A

c. Degradative enzymes

65
Q
  1. The process by which cells degrade their own components by enclosure in a membrane derived from the ER is termed
    a. autophagy
    b. ER-mediated endocytosis
    c. Phagocytosisd
    d. pinocytosis.
A

a. autophagy

Molec Cell (13 decks)

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