Chapter 10 Flashcards
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.
d. rough ER, Golgi, secretory vesicles, cell exterior
A signal sequence on the polypeptide chain targets all but _________ proteins to the rough ER surface
a. secreted
b. plasma membrane
c. mitochondria
d. lysosomal
c. mitochondrial
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
c. rough ER ribosomes and carried to the plasma membrane by vesicles that punch off from the rough ER
d. ribosomes associated with the plasma membrane and inserted into the membrane cotranslationally.
b. rough ER ribosomes and carried to the plasma membrane by vesicles that pinch off
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
b. the same large and small subunits
When compared to polypeptides synthesized in vitro on free ribosomes, the polypeptides synthesized from the same mRNA on microsomes-bound ribosomes are
a. the same size
b. larger
c. smaller
d. more hydrophobic
c. smaller
The signal sequence that targets a polypeptide to the rough ER is rich in ______ amino acids
a. positively charged
b. negatively cahrged
c. hydrophilic
d. hydrophobic
d. hydrophobic
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
c. signal recognition particle
Which of the following is evidence for the signal hypothesis from targeting of a secretory protein in 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
d. All of the above
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 path
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. be taken up into the rough ER and follow the secretory path
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
c. signal recognition particle
Protein folding in the ER is assisted by a chaperone called
a. BiP
b. PiP
c. Hsp60
d. Hsp90
a. BiP
Disulfide bonds within or between proteins form easily in which of the following?
a. Both cytosol and ER
b. Neither cytosol or ER
c. Cytosol but not ER
d. ER but not cytosol
d. ER but not cytosol
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 attacked to the GPI group on the inside surface of the ER
c. as transmembrance 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
c. as transmembrance proteins, cleaved, and attached to the GPI group on the cytosolic surface of the ER
The unfolding response involves
a. general inhibition of protein synthesis
b. increased synthesis of chaperones
c. increased activity of proteosomes
d. All of the above
d. all of the above
Most cellular lipids are synthesized in
a. fat droplets
b. mitochondria
c. the ER
d. Golgi apparatus
c. the ER
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
d. synthesized on one surface and flipped to the other surface by proteins called flippases
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 the smooth and rough ER and prevent their transport to the Golgi apparatus.
d. transport the proteins from the Golgi apparatus back to the ER
d. transport the proteins from the Golgi apparatus back to the ER
Proteins attached to the outer layer of the plasma membrane bilayer are usually attached by a
a. farnesyl tail
b. GPI anchor
c. prenyl tail
d. geronyl tail
b. GPI anchor
A signal sequence in ER does?
determines destination of proteins
A signal recognition particle (SRP) in ER does?
recognizes a signal sequence of a protein and binds it to the ribosome
A signal peptidase in ER does?
cleaves off the signal sequence
a KDEL sequence does?
marks proteins which are suppose to remain in the ER lumen, if the proteins are exported, they are recognized and returned to the ER
Protein disulfide isomerase does?
facilitates the disulfide bond formation
What happens to a glycoprotein in the ER lumen if it fails to fold correctly?
the folding sensor will try to refold and if that fails, the misfolded protein is transfered to the cytosol where they are ubiquitinated.
Vesicles initially enter the Golgi 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 cisternac
d. None of the above
a. the cis (convex) face. They exit from the trans (concave) face.
Which of the following proteins do not pass through the Golgi?
a. Lysosomal enzymes
b. Cell surface proteins
c. Ribosomal proteins
d. Proteins secreted by exocytosis
c. Ribosomal proteins
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.
b. ER and modified in the Golgi
Lysosomal proteins are marked by adding a phosphate to a _____ group
a. glucose
b. serine
c. GDP
d. mannose
d. mannose
The plasma membrane of intestinal 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.
b. two plasma membrane domains: the apical and basolateral domains
Which of the following classes of lipids is synthesized in the Golgi apparatus?
a. Phospholipids
b. Glycolipids
c. Cholesterol
d. Ceramide
b. Glycolipids