Alberts Molecular Biology of Cell - Chapter 013 -
INTRACELLULAR MEMBRANE TRAFFIC Q & A
2023/2024
5. Adaptor proteins select cargo proteins that will be incorporated into clathrin-coated vesicles. An
adaptor protein such as AP2 ...
A. can induce membrane curvature even before clathrin molecules bind.
B. acts as a coincidence detector, assembling only when a number of requirements are met.
C. binds to phosphoinositides in the cytosolic leaflet of the membrane.
D. alternates between a locked cytosolic form and an unlocked membrane-bound form.
E. All of the above. correct answers E. All of the above.
6. Phosphoinositides mark different cellular membranes and play key roles in protein trafficking inside
the cell. Among them, PI(4,5)P2 is involved in receptor-mediated endocytosis as well as phagocytosis at
the plasma membrane. This phosphoinositide ...
A. is bound by the adaptor protein AP2.
B. is bound by the GTPase dynamin.
C. is depleted from clathrin-coated vesicles to promote their uncoating.
D. All of the above. correct answers D. All of the above.
8. Sort the following events to reflect the order in which they occur during the formation of vesicles from
the ER destined for the Golgi apparatus. Your answer would be a four-letter string composed of letters A
to D only, e.g. DACB.
(A) Sar1 GTP hydrolysis
(B) Sar1 GTP binding
(C) Sar1-Sec23 binding
(D) Sar1 membrane association correct answers BDCA
9. Indicate true (T) and false (F) statements below regarding intracellular vesicle transport. Your answer
would be a four-letter string composed of letters T and F only, e.g. TTTF
( ) The plasma membrane is stiffer and flatter than most intracellular membranes, and its deformation
generally requires greater force.
( ) Large molecules such as collagen fibers of about 300 µm in length are highly packed and coiled to fit
into normal COPII vesicles of about 80 nm in diameter.
( ) Rab proteins are recruited to membranes following activation by Rab-GEFs.
( ) A Rab and its effector are always on two different membranes that will then fuse. correct answers ( T )
The plasma membrane is stiffer and flatter than most intracellular membranes, and its deformation
generally requires greater force.
( F ) Large molecules such as collagen fibers of about 300 µm in length are highly packed and coiled to fit
into normal COPII vesicles of about 80 nm in diameter.
( T ) Rab proteins are recruited to membranes following activation by Rab-GEFs.
( F ) A Rab and its effector are always on two different membranes that will then fuse.
10. If this protein is unable to hydrolyze its bound GTP, invaginated clathrin-coated pits accumulate but
fail to pinch off from the plasma membrane. In neurons, long vesicle necks collared by the protein are
observed and presynaptic endocytosis is blocked. This protein ...
, A. contains a PI(4,5)P2 binding domain and a GTPase domain.
B. recruits other proteins to the neck of the vesicle.
C. may change the membrane lipid composition by recruiting lipid-modifying enzymes.
D. may directly distort the membrane using the energy from GTP hydrolysis.
E. All of the above. correct answers E. All of the above.
11. Sort the following events to reflect the order in which they occur during vesicle docking onto a target
membrane, starting with an inactive Rab in the cytosol. Your answer would be a four-letter string
composed of letters A to D only, e.g. DACB.
(A) Rab is bound to its effector (tethering protein) on the target membrane.
(B) Rab is bound to its Rab-GDI.
(C) Rab is bound to the membrane in its GTP-bound form.
(D) Rab dissociates from the membrane. correct answers BCAD
13. Indicate whether each of the following descriptions better applies to t-SNAREs (T) or v-SNAREs (V).
Your answer would be a three-letter string composed of letters T and V only, e.g. TVV.
( ) They are usually located on the target membrane.
( ) They are composed of a single polypeptide chain.
( ) They are usually associated with inhibitory proteins that can be released by Rab proteins. correct
answers ( T ) They are usually located on the target membrane.
( V ) They are composed of a single polypeptide chain.
( T ) They are usually associated with inhibitory proteins that can be released by Rab proteins.
14. The transmembrane protein Tango1 is a packaging protein that helps some secretory proteins leave
the endoplasmic reticulum (ER) after synthesis. Knocking down Tango1 by RNA interference impairs the
incorporation of collagen VII, but not collagen I, into transport vesicles destined for the Golgi apparatus.
The protein contains a lumenal N-terminal SH3 domain and a cytosolic C-terminal proline-rich domain.
Which of the following proteins would you expect to interact with the N-terminal and C-terminal
domains of Tango1, respectively?
A. Procollagen VII; COPI components
B. Procollagen VII; COPII components
C. Procollagen I; COPI components
D. Procollagen I; COPII components
E. COPI components; procollagen I correct answers B. Procollagen VII; COPII components
16. The cytoplasmic C-terminal KKXX sequence of transmembrane proteins interacts with ...
A. t-SNAREs
B. v-SNAREs
C. AP2
D. COPI coatomers
E. COPII coatomers correct answers D. COPI coatomers
18. The Golgi apparatus is made up of an ordered series of compartments. To process N-linked
oligosaccharides, different Golgi compartments carry different enzymes that alter the sugar chains
sequentially. Which Golgi cisternae are normally responsible for the addition of galactose and sialic acid,
respectively, in complex oligosaccharides?
A. cis cisterna; medial cisterna
B. cis cisterna; trans cisterna
INTRACELLULAR MEMBRANE TRAFFIC Q & A
2023/2024
5. Adaptor proteins select cargo proteins that will be incorporated into clathrin-coated vesicles. An
adaptor protein such as AP2 ...
A. can induce membrane curvature even before clathrin molecules bind.
B. acts as a coincidence detector, assembling only when a number of requirements are met.
C. binds to phosphoinositides in the cytosolic leaflet of the membrane.
D. alternates between a locked cytosolic form and an unlocked membrane-bound form.
E. All of the above. correct answers E. All of the above.
6. Phosphoinositides mark different cellular membranes and play key roles in protein trafficking inside
the cell. Among them, PI(4,5)P2 is involved in receptor-mediated endocytosis as well as phagocytosis at
the plasma membrane. This phosphoinositide ...
A. is bound by the adaptor protein AP2.
B. is bound by the GTPase dynamin.
C. is depleted from clathrin-coated vesicles to promote their uncoating.
D. All of the above. correct answers D. All of the above.
8. Sort the following events to reflect the order in which they occur during the formation of vesicles from
the ER destined for the Golgi apparatus. Your answer would be a four-letter string composed of letters A
to D only, e.g. DACB.
(A) Sar1 GTP hydrolysis
(B) Sar1 GTP binding
(C) Sar1-Sec23 binding
(D) Sar1 membrane association correct answers BDCA
9. Indicate true (T) and false (F) statements below regarding intracellular vesicle transport. Your answer
would be a four-letter string composed of letters T and F only, e.g. TTTF
( ) The plasma membrane is stiffer and flatter than most intracellular membranes, and its deformation
generally requires greater force.
( ) Large molecules such as collagen fibers of about 300 µm in length are highly packed and coiled to fit
into normal COPII vesicles of about 80 nm in diameter.
( ) Rab proteins are recruited to membranes following activation by Rab-GEFs.
( ) A Rab and its effector are always on two different membranes that will then fuse. correct answers ( T )
The plasma membrane is stiffer and flatter than most intracellular membranes, and its deformation
generally requires greater force.
( F ) Large molecules such as collagen fibers of about 300 µm in length are highly packed and coiled to fit
into normal COPII vesicles of about 80 nm in diameter.
( T ) Rab proteins are recruited to membranes following activation by Rab-GEFs.
( F ) A Rab and its effector are always on two different membranes that will then fuse.
10. If this protein is unable to hydrolyze its bound GTP, invaginated clathrin-coated pits accumulate but
fail to pinch off from the plasma membrane. In neurons, long vesicle necks collared by the protein are
observed and presynaptic endocytosis is blocked. This protein ...
, A. contains a PI(4,5)P2 binding domain and a GTPase domain.
B. recruits other proteins to the neck of the vesicle.
C. may change the membrane lipid composition by recruiting lipid-modifying enzymes.
D. may directly distort the membrane using the energy from GTP hydrolysis.
E. All of the above. correct answers E. All of the above.
11. Sort the following events to reflect the order in which they occur during vesicle docking onto a target
membrane, starting with an inactive Rab in the cytosol. Your answer would be a four-letter string
composed of letters A to D only, e.g. DACB.
(A) Rab is bound to its effector (tethering protein) on the target membrane.
(B) Rab is bound to its Rab-GDI.
(C) Rab is bound to the membrane in its GTP-bound form.
(D) Rab dissociates from the membrane. correct answers BCAD
13. Indicate whether each of the following descriptions better applies to t-SNAREs (T) or v-SNAREs (V).
Your answer would be a three-letter string composed of letters T and V only, e.g. TVV.
( ) They are usually located on the target membrane.
( ) They are composed of a single polypeptide chain.
( ) They are usually associated with inhibitory proteins that can be released by Rab proteins. correct
answers ( T ) They are usually located on the target membrane.
( V ) They are composed of a single polypeptide chain.
( T ) They are usually associated with inhibitory proteins that can be released by Rab proteins.
14. The transmembrane protein Tango1 is a packaging protein that helps some secretory proteins leave
the endoplasmic reticulum (ER) after synthesis. Knocking down Tango1 by RNA interference impairs the
incorporation of collagen VII, but not collagen I, into transport vesicles destined for the Golgi apparatus.
The protein contains a lumenal N-terminal SH3 domain and a cytosolic C-terminal proline-rich domain.
Which of the following proteins would you expect to interact with the N-terminal and C-terminal
domains of Tango1, respectively?
A. Procollagen VII; COPI components
B. Procollagen VII; COPII components
C. Procollagen I; COPI components
D. Procollagen I; COPII components
E. COPI components; procollagen I correct answers B. Procollagen VII; COPII components
16. The cytoplasmic C-terminal KKXX sequence of transmembrane proteins interacts with ...
A. t-SNAREs
B. v-SNAREs
C. AP2
D. COPI coatomers
E. COPII coatomers correct answers D. COPI coatomers
18. The Golgi apparatus is made up of an ordered series of compartments. To process N-linked
oligosaccharides, different Golgi compartments carry different enzymes that alter the sugar chains
sequentially. Which Golgi cisternae are normally responsible for the addition of galactose and sialic acid,
respectively, in complex oligosaccharides?
A. cis cisterna; medial cisterna
B. cis cisterna; trans cisterna
