WorksheetsChapter 12
Total questions: 60
Worksheet time: 5hrs 0mins
. Using radiolabeled amino acids, Palade and colleagues defined the pathway taken by secreted proteins. Which sequence represents that pathway?
Rough ER -> smooth ER -> Golgi -> secretory vesicles -> cell exterior
Rough ER -> smooth ER -> Golgi -> endosomes -> cell exterior
Rough ER -> Golgi -> lysosomes -> cell exterior
Rough ER -> Golgi -> secretory vesicles -> cell exterior
Most plasma membrane proteins in higher eukaryotic cells are synthesized on
free ribosomes and inserted after translation into the plasma membrane.
rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the Golgi apparatus
rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off from the rough ER
ribosomes associated with the plasma membrane and inserted into the membrane cotranslationally
A signal sequence in a polypeptide chain targets all but _______ proteins to the rough ER surface.
secreted
plasma membrane
mitochondrial
lysosomal
Free ribosomes in the cytosol and ribosomes bound to the ER membrane have
different types of large and small subunits
the same types of large and small subunits
different types of large subunits but the same small subunits
different types of small subunits but the same large subunits
When compared to polypeptides synthesized in vitro on free ribosomes, polypeptides synthesized from the same mRNA on microsome-bound ribosomes often are
the same size
larger
smaller
more hydrophobic
As they emerge from the ribosome, signal sequences are recognized and bound by
a tRNA
a signal peptidase
a signal recognition particle (SRP)
an SRP receptor
Which statement describes evidence that supports the signal hypothesis as an explanation for how secretory proteins are targeted to the rough ER?
The protein is larger when synthesized in vitro on free polysomes
The secretory protein ends up in the cytosol when a short sequence is deleted by genetic engineering
A normally cytosolic protein is secreted when a specific sequence is added to it by genetic engineering
All the above
If secretory proteins are isolated from secretory vesicles and injected into the cytosol, they will
be taken up into the rough ER and follow the secretory pathway
remain in the cytosol until they are degraded
be secreted through channels in the plasma membrane
be taken up into secretory vesicles and secreted
The signal sequence that targets a nascent polypeptide and its mRNA to the rough ER is rich in _______ amino acids.
positively charged
negatively charged
hydrophilic
hydrophobic
Protein folding in the ER is assisted by a chaperone called
BiP
PiP
Hsp60
Hsp90
Disulfide bonds within or between proteins form easily
in the ER but not the cytosol
in neither the cytosol nor the ER
in the cytosol but not the ER
in both the cytosol and the ER
GPI-anchored proteins are synthesized
on free ribosomes and attached to the GPI group on the outside of the ER.
as transmembrane proteins, then are cleaved and joined to the GPI group on the cytosolic surface of the ER
as transmembrane proteins, then are cleaved and joined to the GPI group on the lumenal surface of the ER.
on free ribosomes and attached to the GPI group on the cytosolic surface of the ER
Proteins attached to the outer half of the plasma membrane bilayer are usually attached by a
farnesyl tail
prenyl tail
geranyl tail
glycosylphosphatidylinositol (GPI) anchor
The unfolded protein response involves
translation of most proteins
increased synthesis of chaperones
decreased proteasome activity
all of the above
Most cellular lipids are synthesized in
fat droplets
mitochondria
the endoplasmic reticulum
the golgi apparatus
Newly synthesized membrane lipids are found in both halves of a membrane bilayer because they are
synthesized on one surface and flipped to the other surface by flippases.
removed and transported to these locations by lipid transport proteins.
synthesized on one surface and flipped spontaneously to the other surface
synthesized on both surfaces
The sequence Lys-Asp-Glu-Leu (KDEL) serves as an ER retention signal for proteins by binding to KDEL receptors that
hold the proteins in the rough ER
hold the proteins in the smooth ER
hold the proteins in both the smooth ER and rough ER and prevent their transport to the Golgi apparatus.
transport the proteins from the Golgi apparatus back to the ER.
Vesicles enter the Golgi apparatus by fusing with _______, and they exit from the _______.
the cis (convex) face; trans (concave) face
the trans (concave) face; cis (convex) face
both the cis (convex) and the trans (concave) faces; sides of cisternae
the sides of the cisternae; cis (convex) face
N-linked oligosaccharides are added in the _______ and modified in the _______
ER; golgi
cis Golgi; medial Golgi
medial Golgi; trans golgi
cis golgi; trans golgi
Which of the following polysaccharides is synthesized in the Golgi apparatus?
pectin
cellulose
amylose
glycogen
Which of the following proteins do not pass through the Golgi apparatus?
lysosomal enzymes
cell surface proteins
ribosomal proteins
proteins secreted by exocytosis
Which of the following vesicle types does not bud directly from the trans-Golgi network?
Vesicles transporting plasma membrane receptors
Vesicles that form regulated secretory vesicles
Vesicles carrying lysosomal enzymes
Lysosomes
Lysosomal proteins are marked by the addition of a phosphate to a _______ group
glucose
serine
GDP
mannose
Plasma membrane proteins of intestinal epithelial cells require separate targeting to
one continuous plasma membrane domain
two plasma membrane domains: the apical and basolateral
three plasma membrane domains: the apical, lateral, and basal
four plasma membrane domains: one apical, two lateral, and a basal
In plant cells, vesicles transport proteins from the Golgi apparatus to
lysosomes
vacuoles
chloroplasts
mitochondria
In polarized epithelial cells, membrane proteins containing a dileucine (LL) motif in their cytoplasmic domain are
retained in the golgi apparatus
targeted to lysosomes
targeted to the basolateral plasma membrane
targeted to the apical plasma membrane
Clathrin coats are bound to specific receptors by a protein called
an adaptor protein
ARF
COPI
NSF
Arf function on vesicles is regulated by
phosphorylation of serine residues
phosphorlyation of mannose residues
binding of GTP
binding of ATP
The pinching off of budding clathrin-coated vesicles is driven by the action of
dynamin and GTP hydrolysis
dynamin and ATP hydrolysis
GDP bound ARF
GTP bound ARF
Which coat protein(s) would you expect to be recruited for vesicle formation by a KDEL receptor?
COPI
COPII
clathrin
COPI and clathrin
Which coat protein directs retrograde vesicular transport from the ERGIC or Golgi to the endoplasmic reticulum?
COPII
COPI
clathrin
both COPI and COPII
Vesicles that carry proteins from the rough ER to the Golgi apparatus bud off as _______ vesicles.
uncoated
clathrin-coated
COPI-coated
COPII-coated
. Lysosomal proteins are initially incorporated into _______ vesicles
uncoated
clathrin-coated
COPI-coated
COPII-coated
How many Rab proteins have been shown to play a specific role in vesicular transport?
fewer than 10
about 25
about 50
60 or more
Lysosomes digest
proteins only
nucleic acids and proteins only
carbohydrates only
proteins, nucleic acids, and carbohydrates
The pH inside lysosomes is about
7.0
6.0
5.0
4.0
Gaucher disease results from the failure of macrophage lysosomes to hydrolyze
proteins
glycolipids
DNA
polysaccharides
Transport vesicles carrying acid hydrolases fuse with
lysosomes
endocytic vesicles
early endosomes
late endosomes
Which of the following is not a contiguous membrane domain?
Rough ER
Secretory granules
Smooth ER
ER exit site (ERES)
In the “pulse-chase” experiment, Palade and colleagues studied the pathway taken by newly secreted proteins in pancreatic acinar cells by labeling them with radioactive amino acids, removing unused label, and determining their location within the cells at various time points. Which sequence represents the correct order in which the proteins were identified?
secretory vesicles -> golgi apparatus -> rough ER -> nucleus
golgi apparatus -> rough ER -> nucleus -> secretory vesicles
rough ER -> secretory vesicles -> golgi apparatus
rough ER -> golgi apparatus -> secretory vesicles
Proteins with a C-terminal transmembrane sequence are
cotranslationally brought to the ER by SRP, where they are inserted into the ER lumen
posttranslationally brought to the ER by TRC40, where they remain in the ER membrane with their N-terminal domain facing the lumen
posttranslationally brought to the ER by SRP, where they remain in the ER membrane with their N-terminal domain facing the lumen
posttranslationally brought to the ER by TRC40, where they remain in the ER membrane with their C-terminal domain facing the lumen
The ribosomes of the rough endoplasmic reticulum are targeted to the cytoplasmic side of the membrane via
a signal sequence within the 28S ribosomal RNA
a sequence within the protein being synthesized
the S6 ribosomal protein
the cap sequence at the 5' end of the mRNA being translated
As they emerge from the ribosome, signal sequences are recognized and bound by a(n)
tRNA
signal peptidase
signal recognition particle (SRP)
signal receptor
In yeasts, posttranslational translocation of proteins targeting the ER is
a process affecting many newly synthesized proteins
much less common than in mammalian cells
rare
impossible because translocation into the ER requires the energy of protein synthesis
Which statement about transmembrane proteins is true?
they cross the membrane only once
the signal sequences are always cleaved off
they usually have one or more a helices spanning the membrane bilayer
they are always inserted with the amino terminus on the lumenal side and the carboxyl terminus in the cytosol
Which statement about transmembrane proteins is true?
by flippases
through an aqueous channel created by the Sec61 protein
by being pushed by translation through the lipid bilayer of the ER membrane
by being pulled by BiP across the lipid bilayer of the ER membrane
In some proteins, the only transmembrane sequence is located C-terminally in the protein. These proteins are recognized by
the SRP
the Sec61 translocon
TRC40 (GET3)
the GET1-GET2 complex embedded in the ER membrane
In proteins being made on rough ER, short spans of hydrophobic amino acids that form helices
induce a conformational change in the translocon, allowing them to exit into the ER membrane
are posttranslationally inserted into the ER membrane by BiP
are ubiquitinated and transferred into the cytosol for proteasomal degradation
cause premature termination of translation, leading to the unfolded protein response
The lumen of the ER is equivalent topologically to the
cytoplasm
cytoplasmic face of the plasma membrane
extracellular space
nucleoplasm
N-linked glycosylation at an Asn-X-Ser/Thr consensus sequence adds _______ sugar(s) to the protein in a single step
1
14
30
100
The major site at which membrane lipids are synthesized is the
cytosolic side of the ER membrane
cytosol
lumenal side of the ER membrane
cytosolic side of the golgi membrane
Which of the following is not a destination for vesicles leaving the Golgi apparatus?
the plasma membrane
the exterior of the cell
lysosomes
mitochondria
The sequence Lys-Asp-Glu-Leu (KDEL) serves to retain proteins in the ER by
preventing their packaging into vesicles destined for the Golgi.
binding to receptors within the membranes of the ERGIC and Golgi, which retain them or return them to the ER
binding the SRP receptor in the ER membrane
associating with the lipids in the ER membrane
Cargo proteins are transported through the Golgi apparatus by
forward (anterograde) moving vesicles
backward (retrograde) moving vesicles
cisternal maturation in which the cisternae themselves are the carriers for cargo transport through the Golgi apparatus.
some process that remains controversial and may include elements of both vesicular transport and cisternal maturation
The trans-Golgi network is the
intermediate compartment between the ER and the Golgi
part of the Golgi where fusion of vesicles from the ER occurs
exit part of the Golgi where sorting of proteins to the lysosomes, plasma membrane, and cell exterior occurs
network of vesicles that transport resident Golgi proteins between cisternae.
Which of the following lipids is(are) synthesized in the Golgi apparatus?
phospholipids
chloresterol
ceramide
glycolipids
Clathrin-coated vesicles are involved in
retrieval of ER resident proteins from the cis Golgi or the ER-Golgi intermediate compartment
uptake of extracellular molecules by endocytosis and the transport of molecules from the trans-Golgi network to the lysosomes
transport from the ER to the Golgi
recycling of Golgi resident proteins during cisternal maturation
The major model of vesicle fusion holds that actual fusion of a vesicle with its target membrane is driven by the interaction of pairs of proteins called vesicle and target
SNAREs
Rab proteins
COPs
tethers
Which of the following would you expect to find at high concentrations in lysosomes?
proteins destined for secretion
glycosylation enzymes
degradative enzymes
recycling endosomes
The process by which cells degrade their own components by enclosing them in ER membrane is
autophagy
ER-mediated endocytosis
phagocytosis
pinocytosis
