Biol 309
Question Bank
Intracellular Transport
Multiple Choice
1. Which of the following statements is NOT TRUE of "cotranslational” protein transport.
A. Proteins are produced on ribosomes.
B. The protein eventually will move through the vesicular pathway.
C. This occurs when proteins are transported into chloroplasts and mitochondria.
D. The signal peptide is cleaved after the protein enters its target destination.
E. transport requires the action of a “membrane transport complex.”
2. A "signal peptide" would be best described as a:
A. short sequence of amino acids located on the N-terminus of a protein.
B. small protein that binds to another protein as it passes through a membrane.
C. special receptor protein that occurs on the surface of membranes.
D. short sequence of bases in a mRNA molecule that is not translated on the ribosome.
3. All of the following statements correctly describe “nuclear transport”, EXCEPT:
A. It involves relatively large pores in the membrane.
B. Allow small molecules to pass freely, but restrict passage of macromolecules.
C. Allow movement of molecules into and out of the nucleus.
D. Transport of proteins through pores is passive; i.e., does not require an energy source.
E. Recognize ‘signal patch’ sequences that are not subsequently removed from the protein.
4. Which one of the following statements is NOT true of the ER?
A. Synthesis of phospholipid molecules occurs here.
B. Glycosylation of proteins occurs within the ER.
C. The appearance of rough ER is due to vesicles bound to the surface.
D. The smooth ER is where proteins are packaged for transport to the Golgi apparatus.
E. In some places the ER membrane is linked to that of the nucleus.
5. Which one of the following statements INCORRECTLY describes lysosomes.
A. Hydrolytic enzymes move to the lysosomes via vesicular transport.
B. Materials phagocytosed into the cell go to the lysosomes.
C. The pH of lysosomes is more acidic than that of the cytoplasm.
D. Lysosomes are the principal site of cellular degradation.
E. Hydrolytic enzymes are transported to lysosomes directly from the cytosol.
6. Clathrin and COPI are examples of:
A. membrane receptors.
B. membrane transport proteins.
C. vesicle coating proteins.
Biol 309
D. phospholipid head groups.
E. None of the above answers are correct.
Question Bank
Intracellular Transport
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7. In an “in vitro translation” experiment:
A. DNA must be purified from the cell and used to make mRNA.
B. a signal peptide is transferred to a new protein.
C. purified mRNA is used to produce proteins outside of a cell.
D. mRNA must be isolated from chloroplasts and transcribed into DNA.
E. None of the above answers are correct.
8. Exocytosis is said to be ‘regulated’ when?
A. vesicles from the ER travel to the cell surface.
B. binding to a fusion protein must occur first.
C. vesicles travel from the Golgi to the lysosomes.
D. a signal is required to trigger membrane fusion.
E. All of the above answers are correct.
9. Golgi-associated vesicles transport:
A. ER resident proteins back to the ER.
B. Golgi resident proteins in both retrograde and anterograde directions
C. cargo proteins in an anterograde direction
D. All of the above statements are correct.
10. Which one of the diagrams to the right correctly shows the process of exocytosis?
11. Protein transport is said to be post-translational when:
A. binding to a membrane transport receptor is required.
B. transport begins after the peptide is released from the
ribosome.
C. it occurs from the cytoplasm into an organelle.
D. a signal peptide carries the membrane targeting information.
12. The function of chaperone proteins is:
A. stabilizing the structure of proteins during translation.
B. guiding proteins through the golgi apparatus.
C. proteolyzing proteins that have begun to denature.
D. targeting membrane vesicles for fusion with specific
membranes.
13. Which of these processes occurs within the cisternae of the Golgi apparatus?
A. hydrolysis of proteins, lipids and carbohydrates
B. synthesis of lipids for membranes
C. synthesis of oligosaccharides on dolichol-P
D. covalent modifications of proteins
Biol 309
Question Bank
Intracellular Transport
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14. What is the role of the nuclear localization sequence in a nuclear protein?
A. It is a hydrophobic sequence that enables the protein to enter the nuclear membranes.
B. It aids protein unfolding in order for the protein to thread through nuclear pores.
C. It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.
D. It prevents the protein diffusing out of the nucleus via nuclear pores.
15. After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the
RNAs attached to it. Which of the following proteins do you expect the RNA from the rough
endoplasmic reticulum to encode? Circle all correct answers.
A. Soluble secreted proteins
D. Plasma membrane proteins
B. ER membrane proteins
E. Ribosomal proteins
C. Mitochondrial membrane proteins
16. An individual transport vesicle
A. will fuse with only an appropriate target membrane.
B. remains permanently covered with coating proteins.
C. is endocytic if it is traveling toward the plasma membrane.
D. has a membrane with the same protein composition as the membrane of the donor organelle.
True or False
1. Materials phagocytosed through the cell membrane first pass into a membrane compartment called
the endosome.
2. Acid hydrolases are examples of “Golgi-resident proteins”.
3. Pinocytosis refers to the uptake of membrane and solutes by the cell in small vesicles.
4. In general, signal peptides are permanent structural components of a protein.
5. The trans-face of the Golgi apparatus is the site of protein sorting and packaging into vesicles.
6. A "signal patch" is the receptor to which a "signal peptide" binds.
7. Glycosylation is a form of protein covalent modifications that occurs in ER and Golgi.
8. A signal peptide is necessary for proteins following a cytosolic pathway but not to enter
the vesicular pathway of transport. (think about this carefully)
9. T-SNARES are necessary for the process of “cotranslational transport.”
10. Complex oligosaccharides are preassembled in their final form before being transferred to a
protein.
Biol 309
Question Bank
Intracellular Transport
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11. Membrane vesicles combine to form an endosome before fusing with a lysosome.
12. The pH of an endosome is likely to be lower than that of a lysosome.
13. Membrane fusion of neurotransmitter vesicles is an example of regulated exocytosis.
14. Clathrin coats vesicles moving to and from the cell membrane, whereas COPI coats transported to
and within the Golgi apparatus.
15. Golgi-resident proteins move in both anterograde and retrograde directions between the golgi
cisternae.
Fill-in etc
1. The “address” information for targeting of a protein to a specific organelle is contained in the
__________________ of the protein. If the targeting information, such as that for proteins destined
for the nucleus, occurs across an area of the protein surface, it is called a ______________, and
______ (is/is not) removed after the protein is imported.
2. Integral proteins of the cell membrane are inserted initially into the membrane of the
__________________ (organelle), ____-terminus first.
3. For transport of proteins into the ER, a ________________________ first binds to the signal
peptide of the protein and subsequently to a ______________________ in the ER membrane which
passes the protein into ER in a _________________ form.
4. Proteins are transported to the Golgi apparatus, lysosome and cell membrane via the
__________________ pathway.
5. Synthesis of a short, branched carbohydrate called an ____________________ begins in the lumen
of the _________________ on a lipid called __________________. The oligosaccharide is
transferred from its lipid base to a target protein by an enzyme called a ___________________.
6. A. Identify all of the components in this diagram involved in the vesicle formation and targeting.
B. Explain the statement “The sorting, packaging and
targeting of proteins of cargo proteins moving through
the vesicular transport pathway are coupled (linked).”
Biol 309
Question Bank
Intracellular Transport
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7. A. Why are large nuclear pores needed for nuclear transport but not transport into other organelles?
B. Why is retention of targeting information (signal patch) important for nuclear proteins but not
proteins entering other organelles?
8. A. Label the various constituents of the transmembrane transport process shown in this diagram.
B. Does this diagram show co- or post-translational transport? Explain.
9. A. Label the components of the vesicular transport pathway shown in this diagram, and add arrow
heads to the lines to show the direction of movement.
smooth ER
cis-golgi
membrane transport vesicles
trans-golgi network
golgi medial cisternae
lysosome
golgi transport vesicles
cell membrane
endosome
B. Transport vesicles are believed to travel
in anterograde and retrograde directions.
In which direction do ER-resident proteins
move? (Antero, Retro, or Both)
… cargo proteins?
… Golgi-resident proteins?
C. Explain the need for retrograde
transport of transport vesicles:
… from the golgi to the ER.
… from the cell surface.
… through the golgi.
D. Compare and contrast the ‘vesicular transport’ and ‘cisternal maturation’ models of golgi function.
Biol 309
Question Bank
Intracellular Transport
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10. Rubisco, the enzyme of plants that catalyzes the first
step of CO2 fixation, contains two subunits having
molecular weights of 55 Kd and 14 Kd. The large
subunit (LS) is encoded on chloroplast DNA, but the
gene for the small subunit (SS) is nuclear, necessitating
import of the protein from the cytosol. If purified SS
mRNA is in vitro translated in the presence of 35S
methionine, and the labeled protein is then incubated
with purified chloroplasts, the peptide will be imported.
If gel electrophoresis and autoradiography are performed
for the original in vitro translated peptide and for
homogenized chloroplasts after incubation with the
peptide, the results shown in this figure are obtained. In one of the samples appears a band
corresponding to a 18Kd peptide, whereas in the other sample is found a 14Kd peptide band.
A. Which of the samples (A or B) represents the original in vitro translated peptide, and which
the chloroplast homogenate? Explain the change.
B. Why is it necessary to use a radiolabeled peptide to demonstrate import? In other words, what
would be the result if the same experiment were performed except that the in vitro translated
peptide was not radiolabeled, and the translated protein and homogenized chloroplasts were
subjected to gel electrophoresis with staining for total protein with Coomassie blue instead of
autoradiography? What would be the banding pattern expected for the two samples?
11. The diagram below shows the arrangement of transfer start and stop sequences in a transmembrane
protein.
A. Label each region of the peptide as being either an intracellular (IC) or an extracellular (EC)
domain.
B. Draw the protein in the membrane
diagrammed to the right, correctly
showing the orientation of the IS
and EC domains, and the COOH
and NH3 termini.
Biol 309
Question Bank
Intracellular Transport
Page 6
12. Drin et al. (2008) studied how the protein GMAP-210 participates in the transport of ER vesicles
to the cis-Golgi, and the effects of membrane curvature on the process. GMAP-210 has three
domains: the ALPS domain, an extended string-like domain, and the GRAB domain. The GRAB
domain can bind to a membrane by associating with Arf1GTP (a Golgi membrane protein) but not if
the GTP of Arf1-GTP is hydrolyzed to GDP by a GTPase called arfGAP1. The picture below models
how GMAP-210 may contribute to vesicle fusion.
In their experiments Drin et al. used truncated forms of the GMAP-210 that consisted of either only
the ALPS domain or the GRAB domain. These were combined with large or small liposomes and
other proteins of the system. After a period of incubation, the presence of GRAB or ALPS bound to
the liposomes were determined by gel electrophoresis. Results are summarized below.
Large liposomes
Small liposomes
GRAB domain
ALPS domain
Arf1GTP
arfGAP1
Binding of GRAB
Binding of ALPS
Components added to binding assay
+ + +
+ + +
+ + +
+ +
+ + + + + +
+ + + + +
+ +
+ +
+ +
+
+
+
+
N Y N N Y N
N N N Y Y
+
+
+
+
Y
Answer the following questions.
A. Why are large and small vesicles used in this study? Why were separated GRAB and ALPS
domains used?
B. Do ALPS and GRAB domains show preferences for more or less curved membranes? Explain.
C. What has happened in Frame C to cause release of the GRAP domain? What would need to
happen for it to reattach to the Golgi membrane?
D. What has happened in Frame D to cause release of the ALPS domain?
E. In your own words, describe the cycle of events by which GMAP-210 contributes to tethering
and fusion of membrane vesicles.
Drin G, Morello V, Casella J-F, Gounon P, Antonny B. 2008. Asymmetric Tethering of Flat and Curved Lipid
Membranes by a Golgin. Science 320 670-673.
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Question Bank
Intracellular Transport
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