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WorksheetsPCB 4023 Practice Exam 1
Total questions: 85
Worksheet time: 43mins
Despite the diversity, cells resemble each other to an astonishing degree in their chemistry. For example, only four _____ are used to make DNA.
dNTP
NTP
amino acid
monosaccharide
fatty acid
The _____ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum.
nuclear envelope
plasma membrane
Golgi network
mitochondrial membrane
Ionic bonds form a ___.
Salt
Molecule
Polymer
Lipid bilayer
The side chain of the amino acid R under pH 7 is ___.
Nonpolar
Negatively charged
Positively charged
Polar but uncharged
Which of the following amino acid side chain can be phosphorylated by a protein kinase?
C
F
D
Y
Hydrogen bonds are essential to form a(n) _____
alpha-helix
lipid bilayer
salt
polypeptide
Which of the following protein is necessary to stop a mitogenic signaling by dissociating a SH2 domain containing protein (Grb2) from phosphorylated Growth factor receptor?
a lipid kinase
a protein kinase
a lipid phosphatase
a protein phosphatase
Which of the following is mainly mediated by an ionic bond?
Grb2 and SOS association
Growth factor & Receptor Tyrosine Kinase association
Phospho-tyrosine and SH2 domain association
SOS and Ras association
Protein A binds to protein B to form a complex, AB. At equilibrium in a cell, A, B, and AB concentrations are all at 10 nM. Calculate the equilibrium constant for the reaction A + B ↔ AB
107 liters/mole
109 liters/mole
10−8 liters/mole
108 liters/mole
Choose an example of a motor protein.
Myosin II
Insulin
Sodium potassium ATPase
EGFR
Choose an example of a protein that is a signaling molecule (ligand).
Insulin
Sodium potassium ATPase
Myosin II
EGFR
Choose an example of a protein of which a signaling receptor.
EGFR
Sodium potassium ATPase
Insulin
Myosin II
Which of the following is not a feature commonly observed in α helices?
left-handedness
one helical turn every 3.6 amino acids
cylindrical shape
amino acid side chains that point outward
Which of the following is not a feature commonly observed in β sheets?
coiled-coil patterns
antiparallel regions
extended polypeptide backbone
parallel regions
The α helices and β sheets are examples of protein _____.
Primary structure
Secondary structure
Quaternary structure
Tertiary structure
Domain
A protein _____ is the modular unit from which many larger single-chain proteins are constructed.
Primary structure
Secondary structure
Quaternary structure
Tertiary structure
Domain
Which of the following molecule shows a significant conformational change in response to binding to ATP?
Myosin II
Ras
Grb2
The heterotrimeric G proteins
Which of the following proteins will form a globular protein molecule?
Actin
Keratin
Elastin
Collagen
In a DNA double helix, ___
the two DNA strands are identical.
purines pair with purines.
thymine pairs with cytosine.
the two DNA strands run antiparallel.
The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation?
an increase in gene expression
gene silencing
recruitment of remodeling complexes
displacement of histone H1
Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the “histone code.” Which of the following patterns will probably lead to gene silencing?
lysine 9 trimethylation
lysine 4 methylation and lysine 9 acetylation
lysine 14 acetylation
lysine 9 acetylation and lysine 14 acetylation
22. Which of the following best describes the mechanism by which chromatin- remodeling complexes “loosen” the DNA wrapped around the core histones?
They use energy derived from ATP hydrolysis to change the relative position of the DNA and the core histone octamer.
They chemically modify the DNA, changing the affinity between the histone octamer and the DNA.
They remove histone H1 from the linker DNA adjacent to the core histone octamer.
They chemically modify core histones to alter the affinity between the histone octamer and the DNA.
Most eukaryotic cells only express 20-30% of the genes they possess. The formation of heterochromatin maintains the other genes in a transcriptionally silent (unexpressed) state. Which histone modification is associated with the formation of the most common type of heterochromatin?
H3 lysine 4 methylation
H3 lysine 9 trimethylation
H3 lysine 14 methylation
H3 lysine 27 methylation
RNA in cells differs from DNA in that ___.
it contains the base uracil, which pairs with cytosine.
it is single-stranded and cannot form base pairs.
it is single-stranded and can fold up into a variety of structures.
the sugar ribose contains fewer oxygen atoms than does deoxyribose.
Transcription is similar to DNA replication in that ___.
an RNA transcript is synthesized discontinuously and the pieces are then joined together.
it uses the same enzyme as that used to synthesize RNA primers during DNA replication.
the newly synthesized RNA remains paired to the template DNA.
nucleotide polymerization occurs only in the 5'-to-3' direction.
Which of the following statements is FALSE?
A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule’s synthesis is completed.
If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies.
RNA polymerase is responsible for both unwinding the DNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides.
Unlike DNA, RNA uses an uracil base and a deoxyribose sugar.
Which of the following statements is FALSE?
RNA polymerase can start making a new RNA molecule without a primer; DNA polymerase cannot.
RNA polymerase does not proofread its work; DNA polymerase does.
RNA polymerase catalyzes the linkage of ribonucleotides while DNA polymerase catalyzes the linkage of deoxyribonucleotides.
RNA polymerase adds bases in a 3'-to-5' direction; DNA polymerase adds bases in a 5'-to-3' direction.
Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon?
Eukaryotes have three types of RNA polymerase.
Eukaryotic RNA polymerases require general transcription factors.
The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter.
Prokaryotic genes are packaged into nucleosomes.
Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?
The ribosome binds to the mRNA.
The mRNA is polyadenylated at its 3' end.
A guanine nucleotide with a methyl group is added to the 5' end of the mRNA.
RNA polymerase dissociates.
30. The correct statement about the genetic code is correct?
All codons specify more than one amino acid.
Most of the genetic code is redundant.
All amino acids are specified by more than one codon.
All codons specify an amino acid.
A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals, while a white blood cell defends the body against infection. This is because ___
all of the proteins found in a neuron are completely different from the proteins found in a white blood cell.
the neuron and the white blood cell within an individual have the same genome.
the neuron expresses some mRNAs that the white blood cell does not.
neurons and white blood cells are differentiated cells and thus no longer need to transcribe and translate genes.
The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the ___.
replication of specific genes.
transcription of genes transcribed by RNA polymerase II.
transcription of housekeeping genes.
proteins that directly bind the TATA box of eukaryotic genes.
Approximately how many such genes does the typical differentiated human cell express at any one time?
21,000—all of them
between 18,900 and 21,000—at least 90% of the genes
between 5000 and 15,000
less than 2100
Which of the following statements about differentiated cells is TRUE?
Cells of distinct types express nonoverlapping sets of transcription regulators.
Once a cell has differentiated, it can no longer change its gene expression.
Once a cell has differentiated, it will no longer need to transcribe RNA.
Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.
Which of the following statements about transcriptional regulators is FALSE?
Transcription regulators interact only with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix.
Transcription regulators will form hydrogen bonds, ionic bonds, and hydrophobic interactions with DNA.
The DNA-binding motifs of transcription regulators usually bind in the major groove of the DNA helix.
The binding of transcription regulators generally does not disrupt the hydrogen bonds that hold the double helix together.
Which of the following is NOT involved in post-transcriptional control?
the spliceosome
Dicer
Mediator
RISC
miRNAs, tRNAs, and rRNAs all ___
do not code for proteins.
act in the nucleus.
are packaged with other proteins to form RISC.
form base pairs with mRNA molecules.
MicroRNAs _.
are produced from a precursor miRNA transcript.
are found only in humans.
control gene expression by base-pairing with DNA sequences.
can degrade RNAs by using their intrinsic catalytic activity.
Which of the following statements about miRNAs is FALSE?
One miRNA can regulate the expression of many genes.
miRNAs are transcribed in the nucleus from genomic DNA.
miRNAs are produced from rRNAs.
miRNAs are made by RNA polymerase.
Which of the following statements about RNAi is TRUE?
The RNAi mechanism is found only in plants and animals.
RNAi is induced when double-stranded, foreign RNA is present in the cell.
RISC uses the siRNA duplex to locate complementary foreign RNA molecules.
siRNAs bind to miRNAs to induce RNAi.
Which one of the followings proteins contains a single Transmembrane (TM) region?
Growth factor receptor (Receptor Tyrosine Kinase)
Sos
Ras
Which of the following events is necessary for establishing lipid anchor of a membrane protein on the extracellular side?
Myristoylation
Prenylation
Glycosylphosphatidylinositol (GPI) anchor
Ubiquitylation
Some proteins are almost as mobile as lipids, whereas others are virtually immobile. Which of the following proteins would be the fastest moving membrane protein?
fibronectin, a peripheral glycoprotein that interacts with the extracellular matrix.
Bacterial rhodopsin a 7-TM protein
E-Cadherin at the cell-cell junction linked to the F-Actin
Which of the following statement on SRP (Signal Recognition Particle) is NOT true?
An ER signal sequence and an SRP direct a ribosome to the SRP Receptor on the ER membrane.
SRP binding to the ER signal sequence on a Ribosome pauses translation
SRP receptor localizes on the ER membrane
SRP binding to the start transfer sequence will inhibit the Ribosome binding to the ER
Which of the following is one of the features of RPTK?
an intracellular ligand binding domain
seven transmembrane domain
kinase domain
GEF activity
Which of the following type of molecules associate with activated RPTK?
MAPK
an SH2 domain containing adaptor protein
Ras
heterotrimeric G proteins
MAP Kinase stands for ___?
Mitogen Activated Protein Kinase
Mono Amino Phosphate Kinase
Mitochondrial Associated Protein Kinase
Microtubule Assembly Protein Kinase
In response to mitogenic signal, cells induce immediate early response genes. Which of the following is one of them?
RPTK
GPCR
MAPK
c-Myc
Under certain situation, cells interpret the same molecular ligand to a RPTK differently through selective downstream signal transduction. For example, RPTK can activate PI3K, Ras, or PLC pathways. Which of the following pathway is most critical for RPTK to suppress programmed cell death?
PI3K/PKB(Akt)
Ras/MAPK
PLC
There are eight members of phosphatidylinositol. Which of the following is the target (or substrate) for PLC?
PIP3
PI(4,5)P2
PI(3)P
There are eight members of phosphatidylinositol. Which of the following is the target (or substrate) for PI3K?
PIP3
PI(4,5)P2
PI(3)P
In response to a survival signal, the activated PKB(Akt) phosphorylates BAD protein. Does Bad protein suppress or promote apoptosis?
suppresses
promotes
In response to a survival signal, the activated PKB(Akt) phosphorylates BAD protein. Upon phosphorylation, BAD protein does one of the following:
directly promoting apoptosis
dissociating from Bcl-2
inactivating Bcl-2
Which of the following statements is true?
Bcl2 inhibits apoptosis.
Akt kinase inhibits Bcl2.
Akt kinase activates BAD protein.
Which of the following is not regulated by the PI3K/PKB/mTOR signaling?
Stimulation of protein synthesis.
Inhibition of Protein degradation.
Inhibition of Rb phosphorylation.
______ signal transduction pathway inhibits cell cycle progression.
Mitogenic
Apoptotic
TGF-beta
p53 can induce cell cycle arrest. What is the p53 mediated cell cycle arrest?
activating ERK2
degrading E2F
stabilizing Rb
generating CDK inhibitors such as p21.
Which of the following processes occur only in S phase of the cell cycle?
Organelle replication
Cell growth
Chromosome segregation
DNA replication
The period between one M phase and the subsequent M phase is called:
S phase
anaphase
interphase
G2 phase
If the Rb protein binds to transcription regulators, the cell will move from G1 phase to S phase.
True
False
What inhibits Rb?
Ras
CyclinD/Cdk
Cdc6
Myc
Transcription factor E2F is inhibited by ____.
(a) Rb
(b) Cyclin D
(c) p53
(d) CDK2
The signal to commence DNA replication comes from:
S-Cdk.
ORC.
the destruction of Cdc25.
the destruction of M-Cdk.
RPTK can activate multiple downstream signaling pathways such as PI3K, Ras, or PLC. Which of the following pathway is usually activated for RPTK to induce cells to proliferate?
PI3K/PKB/Bcl2
Ras/MAPK/Myc
PLC/IP3/Calcium
Which of the following statements about the newly synthesized strand of a human chromosome is TRUE?
It was synthesized from a single origin solely by continuous DNA synthesis.
It was synthesized from a single origin by a mixture of continuous and discontinuous DNA synthesis.
It was synthesized from multiple origins solely by discontinuous DNA synthesis.
It was synthesized from multiple origins by a mixture of continuous and discontinuous DNA synthesis.
A telomerase is best described as a
RNA polymerase.
ligase.
topoisomerase.
DNA polymerase with its bound RNA template
exonuclease.
Where does the initiator protein bind DNA at the start of replication?
At a replication fork
At an origin of replication
At any AT-rich region
At a promoter region
At a start codon
Helicase induces DNA supercoiling as the replication fork migrates during replication. Which kind of enzyme reduces Helicase-induced supercoiling as the replication fork migrates during replication?
Telomerase
Ligase
DNA polymerase I
DNA polymerase III
Topoisomerase
Homologous recombination (HR) is an important mechanism in which organisms use a "backup" copy of the DNA as a template to fix double-strand breaks without loss of genetic information. Which of the following is NOT necessary for homologous recombination to occur?
The cell should be at the G2 phase
The cell should be at the G1 phase
3' DNA strand overhang
a long stretch of sequence similarity
Sometimes replication errors escape proofreading of DNA Polymerase and generate a DNA mismatch. Which of the following mechanism will fix this kind of error?
Mismatch Repair (MMR)
NHEJ
HR
Which of the following would promote cancer development?
upregulating telomerase
by activating DNA repair system
by activating TGF-beta signaling
by activating p53
The properties of a lipid bilayer are determined by the structures of its lipid molecules. Predict the properties of the lipid bilayers that would result if the following was the case: phospholipids had only one hydrocarbon chain instead of two.
still form bilayers
form micelles rather than bilayers.
The properties of a lipid bilayer are determined by the structures of its lipid molecules. Predict the properties of the lipid bilayers that would result if the following was the case: if all of the hydrocarbon chains were saturated, ___
Bilayers formed by lipids with saturated hydrocarbon tails would be much less fluidic.
Their fatty acid tails are trans-conformation
Where does most new membrane synthesis take place in a eukaryotic cell?
ER
Nucleus
the plasma membrane
mitochondria
A biological membrane can be solubilized with a mild detergent such as Triton X-100. The shape of the phospholipids in the mixed micelle is ____.
a cone
a cylinder
a cube
an Icosahedron
You generated a light activatable chloride channel and successfully expressed it in a mouse neuron of which function is not known. During the period of the channel activation, the mouse failed to make any memory. What can you say from the experiment?
The targeted neuron is positively involved in memory formation.
The targeted neuron is negatively involved in memory formation.
The targeted neuron is not involved in memory formation.
Which of the following ions has the highest cytosolic concentration?
Na+
K+
Mg2+
Ca2+
Which of the following ions has the lowest cytosolic concentration?
H+
K+
Mg2+
Ca2+
Cells with aquaporin channels in the plasma membrane can NOT maintain electrochemical gradient. Is this statement true or false?
True
False
If all the sodium glucose symporter and the glucose uniporter localize to the basal membrane of the intestinal epithelial cells (facing the connective tissue), what would be the happening?
Glucose molecules would flow from the epithelial cells to the connective tissue
Glucose molecules would shuttle between the connective tissue and epithelial cells
Glucose molecules would be depleted from the epithelial cells
Glucose molecules cannot be transported to the connective tissue from the epithelial cells
Macrophages remove dead cells by recognizing a signal on their targets: apoptosed cells populate phosphatidylserine on their outer leaflet, but not the healthy ones. If you have a mutant cell that is efficiently phagocytosed by macrophages, what would be the problem of the mutant cell?
The mutant cells failed to keep the Phosphatidylserine in the inner leaflet of their plasma membrane.
The mutant cells failed to keep the Phosphatidylserine in the outer leaflet of their plasma membrane.
The mutant cells have excessive flippase activity and thus the Phosphatidylserine stay exclusively at the inner leaflet of the plasma membrane.
The resting membrane potential of an animal cell ____.
has a negative value that can be changed into a positive value
is generated by the Calcium ATPase that pumps out positively charged Calcium ions from the cell
is generated by the Sodium/Potassium ATPase that pumps out positively charged ions from the cell
is generated by the sodium leak channel
Which of the following statement is true?
During the action potential propagation, the unidirectional propagation of the action potential is mediated by sodium potassium pump.
During the action potential propagation, the three distinct forms (conformations) of the voltage sensitive potassium channel spatially localize around region of the action potential.
During the action potential propagation, the three distinct forms (conformations) of the voltage sensitive calcium channel spatially localize around region of the action potential.
The sodium ions entering the axon through the voltage sensitive sodium channel diffuse randomly.
Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential?
by closing Na+ channels
by preventing the secretion of excitatory neurotransmitters
by opening K+ channels
by opening Cl- channels
p53 can induce the cell to kill itself if damage to its DNA is very severe?
True
False
