This family of ATPases is structurally related to the turbine-like pumps that acidify
lysosomes and vesicles; however, they usually function in reverse, generating ATP from
ADP and Pi using proton gradients across membranes. What are they called?
A.P-type pumps
B.ABC transporters
C.V-type pumps
D.F-type pumps
E.Permeases
How is the activation of epidermal growth factor receptor (EGFR) different from that of
insulin receptor (IR)?
A.EGFR is a dimer in its inactive and active forms, whereas IR dimerizes only when
active.
B.EGFR activation requires dimerization, whereas IR can become activated as a
monomer.
C.EGFR is activated by transautophosphorylation, whereas IR activation is
phosphorylation-independent and is a simple consequence of receptor dimerization.
D.Unlike IR activation, EGFR activation involves an asymmetric arrangement of the
intracellular kinase domains.
E.Both C and D above.
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
Mutations in certain components of the cell-cycle machinery in Drosophila
melanogaster can be used to slow down the rate of progression through the cell cycle in
the wing imaginal discs of the fly larvae, without a major effect on the rate of cell
growth. As a result, compared to wild-type flies, the wing in the mutant flies would …
A.have a larger size (area) with a higher number of relatively normal cells.
B.have the same size, but with a higher number of relatively smaller cells.
C.have the same size, but with a smaller number of relatively larger cells.
D.have a smaller size with the same number of relatively smaller cells.
E.have a smaller size with a smaller number of relatively normal cells.
Comparing mRNA molecules from human and Escherichia coli cells, which of the
following is typically NOT true?
A.A human mRNA has a special 5′ cap, while a bacterial mRNA does not.
B.A human mRNA has a poly-A tail, while a bacterial mRNA does not.
C.A human mRNA undergoes alternative splicing, while a bacterial mRNA does not.
D.A human mRNA contains noncoding sequences, while a bacterial mRNA does not.
E.A typical human mRNA encodes one protein, while many bacterial mRNAs encode
several different proteins.
PI 3-kinase …
A.is a membrane-associated tyrosine kinase.
B.activates PDK1 by phosphorylating a serine residue on the protein.
C.is counteracted by PTEN phosphatase.
D.is only known to be activated by receptor tyrosine kinases.
E.inhibits Akt.
Integrins are single-pass integral membrane proteins in the plasma membrane of animal
cells and are involved in the interaction of the cell with the surrounding extracellular
matrix. Which of the following descriptions do you think matches the transmembrane
part of an integrin molecule?
A.It forms a barrel.
B.It is an ± helix that is bent in the middle.
C.It is about 10 amino acids long, with every other amino acid side chain being
hydrophobic.
D.It folds in a conformation with maximal intrachain hydrogen-bonding.
E.It is about 100 amino acids long.
In some adenomas of the colon, intestinal crypt cells appear to have proliferated
abnormally to form small tumors known as polyps. Studies on the familial type of such
a disease led to the identification of a major signaling pathway (which was aberrant in
the polyp cells) as being involved in the maintenance of the gut stem-cell compartment.
What signaling pathway is this? Is it upregulated or downregulated in colon cancers?
A.MAPK pathway; up-regulated
B.MAPK pathway; down-regulated
C.Wnt pathway; up-regulated
D.Wnt pathway; down-regulated
E.Hedgehog pathway; down-regulated
Which of the following scenarios does NOT normally occur on a nuclear pore
complex?
A.A protein complex is imported into the nucleus, with ONLY one of its subunits
containing a nuclear localization signal (NLS).
B.In a single pore, an NLS-containing protein is imported, while at the same time a
nuclear export signal (NES)-containing protein is exported.
C.A nuclear import receptor is exported from the nucleus through the pore.
D.A protein is imported on its own through the pore, without the need for a separate
import receptor.
E.All of the above are possible scenarios and occur naturally.
How many protons [or, more accurately, hydronium ions (H3O+)] are there in a
spherical lysosome that is about 0.6 in diameter and maintains an interior pH of
about 5.0? Recall that the volume of a sphere of radius r is calculated as V = 4/3 x x
r3, and that pH = -log [H+]. Avogadro’s constant is approximately 6 x 1023
molecules/mole.
A.About 700 ions
B.About 7000 ions
C.About 70,000 ions
D.About 700,000 ions
E.About 7,000,000 ions
In the following qualitative histogram, which two curves better correspond to human
exon and intron length distributions, respectively?
A.Curves 1 and 2
B.Curves 2 and 1
C.Curves 2 and 3
D.Curves 3 and 2
E.Curves 3 and 1
Consider the structure of a sarcomere. Which of its features does NOT shorten during
skeletal muscle contraction?
A.The dark band
B.The light band
C.The distance from the M line to the Z disc
D.The distance between two consecutive Z discs
E.The extension of the titin molecules
The cell cycle can be arrested in mitosis when a single sister-chromatid pair is
mono-oriented on the mitotic spindle. If at this point a glass microneedle is used to pull
the mono-oriented chromosome toward the pole to which it is not attached, the cell
proceeds to anaphase. This observation confirms that …
A.mono-oriented chromosomes are stable.
B.mechanical tension drives the formation of bi-oriented chromosomes.
C.bi-oriented chromosomes activate the spindle assembly checkpoint.
D.lack of mechanical tension at the kinetochore in at least one chromosome prevents
entry into anaphase.
E.mechanical tension at the kinetochore in at least one chromosome is required for
entry into anaphase.
Reference: Contractile-Ring Positioning
Three models for contractile-ring positioning in animal cells are presented in the
schematic diagrams below. Answer the following question(s) according to these models.
In classic experiments carried out in the 1960s and schematized below, an egg of the
sand dollar Echinarachnius parma was made into a torus shape using a glass bead on the
end of a needle, to study the influence of microtubules on cleavage-furrow positioning.
The cells were allowed to undergo two rounds of mitosis. After the second mitosis, an
extra furrow (indicated by a red arrowhead) was observed between the two asters that
did not have a spindle between them. Which of the models (1 to 3) is more consistent
with this observation? Write down 1, 2, or 3 as your answer.
The citric acid cycle is summarized in the following figure. Answer the following
question(s) about this cycle.
In the citric acid cycle shown above, which steps produce CO2 as a by-product? List all
such steps by their number, from the smallest number to the largest. Your answer would
be a number composed of digits 1 to 8 only, e.g. 258.
Indicate if each of the following descriptions matches lipids (1), nucleic acids (2),
polysaccharides (3), or proteins (4). Your answer would be a four-digit number
composed of digits 1 to 4 only, e.g. 1332.
( ) Their monomers contain phosphorus and nitrogen.
( ) They constitute almost half of the cell’s dry mass.
( ) They are the main constituent of all cellular membranes.
( ) They are largely hydrophobic and can store energy.
Indicate true (T) and false (F) statements below regarding the mutational landscape of
cancer cells. Your answer would be a four-letter string composed of letters T and F only,
e.g. TFFF.
( )In each cancer, usually there is one driver mutation and a large number of passenger
mutations.
( )It is estimated that about 20% of our genes are cancer-critical.
( )Cancer-critical genes can encode metabolic enzymes or components of the RNA
splicing machinery.
( )The karyotype is often severely disordered in cancer cells.
Indicate whether each of the following descriptions better applies to cDNA libraries (C)
or genomic DNA libraries (G). Your answer would be a five-letter string composed of
letters C and G only, e.g. CGCGC.
( )Their production requires use of reverse transcriptase.
( )They are enriched in protein-coding genes.
( )Different sequences are represented in them based on their transcription level.
( )They contain intronic sequences.
( )They are cell-type specific.
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
Indicate whether each of the following descriptions applies to myosins (M), kinesins
(K), or dyneins (D). Your answer would be a five-letter string composed of letters M, K,
and D only, e.g. MMMDD.
( )They have larger structures than the other two.
( )They are generally faster than the other two.
( )They are structurally unrelated to the other two.
( )They walk on a different cytoskeletal filament than the other two.
( )They are all minus-end directed.
An intracellular pathogen uses one of three major strategies to survive and replicate
once inside the host cell, as shown in the schematic drawing below. Indicate which
strategy (1, 2, or 3) each of the following pathogens employs for this purpose. Your
answer would be a three-digit number composed of digits 1 to 3 only, e.g. 332.
( )Listeria monocytogenes
( )Legionella pneumophila
( )Shigella flexneri