TEST BANK for MOLECULAR BIOLOGY OF THE CELL, SIXTH
EDITION BRUCE ALBERTS
CHAPTER 12 INTRACELLULAR COMPARTMENTS AND PROTEIN SORTING
1 Imagine a protein that has been engineered to contain a nuclear localization signal, a
nuclear export signal, a C-terminal peroxisomal targeting sequence, and a canonical
endoplasmic reticulum (ER) signal sequence. With all of these signals, where would you
expect to find the protein after its synthesis?
A. Cytosol
B. Nucleus
C. Shuttling between the cytosol and the nucleus
D. Peroxisomes
E. Endoplasmic reticulum
2 Consider a human cell such as a hepatocyte. Which of the following compartments
occupies a larger volume in the cell?
A. Cytosol
B. Nucleus
C. Endoplasmic reticulum
D. Mitochondria
E. Peroxisomes
3 Consider a human liver hepatocyte. Among the following membranes, which one has the
largest total area?
A. Plasma membrane
B. Nuclear inner membrane
C. Mitochondrial outer membrane
D. Rough ER membrane
E. Smooth ER membrane
4 Consider two cells, A and B. Both are approximately spherical, but cell A is a bacterium
with a diameter of only about 1 µm, while the diameter of the eukaryotic cell B is about
10 µm. If the plasma membrane in the eukaryotic cell comprises only about 2% of the
total cell membrane, which cell has a higher ratio of total cell membrane to volume?
Write down A or B as your answer.
,5 Indicate whether the location of each of the following is topologically equivalent to the
cytosol (C) or the extracellular space (E). Your answer would be a five-letter string
composed of letters C and E only, e.g. CCECE.
( ) Ribosomes
( ) Chromatin
( ) Lysosomal hydrolases
( ) Calcium ions in the ER
( ) Peroxisomal catalase
6 Indicate whether each of the following transport processes occurs via the mechanisms
described as gated transport (G), transmembrane transport (T), or vesicular transport (V).
Your answer would be a five-letter string composed of letters G, T, and V only, e.g.
VTTTG.
( ) Import into nucleus
( ) Export from nucleus
( ) Import into mitochondria
( ) Return from Golgi to ER (
) Return from ER to cytosol
7 Indicate true (T) and false (F) statements below regarding the compartmentalization of
cells. Your answer would be a four-letter string composed of letters T and F only, e.g.
TTTF. ( ) Almost all eukaryotic cells have plastids, but only plant cells have chloroplasts
capable of photosynthesis.
( ) The perinuclear space is topologically equivalent to the extracellular space.
( ) The mitochondria and chloroplasts are thought to have evolved by invagination and
pinching off from the plasma membrane of the ancient eukaryotic cell.
( ) All organelles in a eukaryotic cell can be constructed de novo, which means that the
information to construct them is encoded in the genome.
8 Fill in the blank in the following paragraph. DO NOT use abbreviations.
“A significant fraction of total membrane area in a eukaryotic cell
encloses the lumen of the ..., which forms an extended netlike
labyrinth of tubules and sacs. Secretory proteins are normally
synthesized by ribosomes bound to a special type of this
compartment.”
9 A geneticist has devised a strategy to study protein translocation into the endoplasmic
reticulum (ER) in yeast cells. She is interested in two different signal sequences that are
, thought to operate via slightly different translocation mechanisms. Using genetic
engineering, she has fused the first signal sequence to a protein whose cytosolic
expression is absolutely necessary for cell survival in the selective medium, but is
inactive when in the ER. In the same cell, she has also fused the second signal sequence
to a toxic protein whose cytosolic expression leads to cell lysis but is harmless when in
the ER. Whereas wild-type cells undergo lysis upon the expression of these fusion
proteins, she has been able to identify viable mutants, each of which has a loss-of-
function mutation in a gene encoding a protein involved in membrane translocation. The
products of these genes are probably ...
A. involved in the general transport of proteins into the ER, regardless of the type of
signal sequence.
B. involved in the transport of proteins with the first signal sequence but not the second
one.
C. involved in the transport of proteins with the second signal sequence but not the first
one.
D. involved in the transport of proteins with a novel signal sequence (i.e. neither the first
signal sequence nor the second one).
10 Indicate true (T) and false (F) statements below regarding the nucleus and nuclear protein
transport. Your answer would be a four-letter string composed of letters T and F only, e.g.
TTTF.
( ) The inner and outer nuclear membranes are continuous with each other, yet maintain
distinct protein compositions.
( ) The outer nuclear membrane is studded with ribosomes engaged in protein synthesis.
( ) The endoplasmic reticulum lumen is continuous with the nuclear interior.
( ) Ribosomal proteins pass through the nuclear pore complexes twice; they are imported
into the nucleus after synthesis, and are exported from the nucleus after assembly with
ribosomal RNA.
11 In the following schematic diagram of a nuclear pore complex, on which side is the
cytosol located? What is the approximate diameter of the pore, as indicated by the
vertical bar?
EDITION BRUCE ALBERTS
CHAPTER 12 INTRACELLULAR COMPARTMENTS AND PROTEIN SORTING
1 Imagine a protein that has been engineered to contain a nuclear localization signal, a
nuclear export signal, a C-terminal peroxisomal targeting sequence, and a canonical
endoplasmic reticulum (ER) signal sequence. With all of these signals, where would you
expect to find the protein after its synthesis?
A. Cytosol
B. Nucleus
C. Shuttling between the cytosol and the nucleus
D. Peroxisomes
E. Endoplasmic reticulum
2 Consider a human cell such as a hepatocyte. Which of the following compartments
occupies a larger volume in the cell?
A. Cytosol
B. Nucleus
C. Endoplasmic reticulum
D. Mitochondria
E. Peroxisomes
3 Consider a human liver hepatocyte. Among the following membranes, which one has the
largest total area?
A. Plasma membrane
B. Nuclear inner membrane
C. Mitochondrial outer membrane
D. Rough ER membrane
E. Smooth ER membrane
4 Consider two cells, A and B. Both are approximately spherical, but cell A is a bacterium
with a diameter of only about 1 µm, while the diameter of the eukaryotic cell B is about
10 µm. If the plasma membrane in the eukaryotic cell comprises only about 2% of the
total cell membrane, which cell has a higher ratio of total cell membrane to volume?
Write down A or B as your answer.
,5 Indicate whether the location of each of the following is topologically equivalent to the
cytosol (C) or the extracellular space (E). Your answer would be a five-letter string
composed of letters C and E only, e.g. CCECE.
( ) Ribosomes
( ) Chromatin
( ) Lysosomal hydrolases
( ) Calcium ions in the ER
( ) Peroxisomal catalase
6 Indicate whether each of the following transport processes occurs via the mechanisms
described as gated transport (G), transmembrane transport (T), or vesicular transport (V).
Your answer would be a five-letter string composed of letters G, T, and V only, e.g.
VTTTG.
( ) Import into nucleus
( ) Export from nucleus
( ) Import into mitochondria
( ) Return from Golgi to ER (
) Return from ER to cytosol
7 Indicate true (T) and false (F) statements below regarding the compartmentalization of
cells. Your answer would be a four-letter string composed of letters T and F only, e.g.
TTTF. ( ) Almost all eukaryotic cells have plastids, but only plant cells have chloroplasts
capable of photosynthesis.
( ) The perinuclear space is topologically equivalent to the extracellular space.
( ) The mitochondria and chloroplasts are thought to have evolved by invagination and
pinching off from the plasma membrane of the ancient eukaryotic cell.
( ) All organelles in a eukaryotic cell can be constructed de novo, which means that the
information to construct them is encoded in the genome.
8 Fill in the blank in the following paragraph. DO NOT use abbreviations.
“A significant fraction of total membrane area in a eukaryotic cell
encloses the lumen of the ..., which forms an extended netlike
labyrinth of tubules and sacs. Secretory proteins are normally
synthesized by ribosomes bound to a special type of this
compartment.”
9 A geneticist has devised a strategy to study protein translocation into the endoplasmic
reticulum (ER) in yeast cells. She is interested in two different signal sequences that are
, thought to operate via slightly different translocation mechanisms. Using genetic
engineering, she has fused the first signal sequence to a protein whose cytosolic
expression is absolutely necessary for cell survival in the selective medium, but is
inactive when in the ER. In the same cell, she has also fused the second signal sequence
to a toxic protein whose cytosolic expression leads to cell lysis but is harmless when in
the ER. Whereas wild-type cells undergo lysis upon the expression of these fusion
proteins, she has been able to identify viable mutants, each of which has a loss-of-
function mutation in a gene encoding a protein involved in membrane translocation. The
products of these genes are probably ...
A. involved in the general transport of proteins into the ER, regardless of the type of
signal sequence.
B. involved in the transport of proteins with the first signal sequence but not the second
one.
C. involved in the transport of proteins with the second signal sequence but not the first
one.
D. involved in the transport of proteins with a novel signal sequence (i.e. neither the first
signal sequence nor the second one).
10 Indicate true (T) and false (F) statements below regarding the nucleus and nuclear protein
transport. Your answer would be a four-letter string composed of letters T and F only, e.g.
TTTF.
( ) The inner and outer nuclear membranes are continuous with each other, yet maintain
distinct protein compositions.
( ) The outer nuclear membrane is studded with ribosomes engaged in protein synthesis.
( ) The endoplasmic reticulum lumen is continuous with the nuclear interior.
( ) Ribosomal proteins pass through the nuclear pore complexes twice; they are imported
into the nucleus after synthesis, and are exported from the nucleus after assembly with
ribosomal RNA.
11 In the following schematic diagram of a nuclear pore complex, on which side is the
cytosol located? What is the approximate diameter of the pore, as indicated by the
vertical bar?
