cell biol 2300
In the laboratory, you observe cells undergoing mitosis under the microscope. The sister chromatids line up at the cell equator, but they do not not separate. All of the following are possible explanations EXCEPT.
idk but not separase
In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins?
in the cytosol
What type of macromolecule helps package DNA in eukaryotic chromosomes?
proteins
What is the RNA component of a ribosome?
rRNA
Which RNA is involved in chemical modifications of RNA?
snoRNA
The DNA-binding motifs of transcription factors have an overall positive charge.
true
If allolactose is present and glucose is absent, transcription of the lactose operon _____.
----
Which of the following is true about operons?
----
An exported mRNA containing 300 nucleotides can initially be translated into a protein
100 amino acids
DNA damage is present during the G1 stage of interphase. All of the following are possible outcomes EXCEPT.
The cell immediately enters S phase.
The nucleotide consensus sequence found at the 3′ splice site of intron-exon boundaries is _____.
5'-PyPyPyPyPyPyNCAG-3'
You have a piece of DNA that includes the following sequence: 5′-ATAGGCATTCGATCCGGATAGCAT-3′ 3′-TATCCGTAAGCTAGGCCTATCGTA-5′ Which of the following RNA molecules could be transcribed from this piece of DNA?
5′-AUAGGCAUUCGAUCCGGAUAGCAU-3′
Which of the following is true about operons?
All genes in the operon are transcribed into one mRNA molecule.
Which of the following is NOT part of the process known as "oxidative phosphorylation"?
ATP molecules are produced in the cytosol as glucose is converted into pyruvate.
Binding of adrenaline to a GPCR stimulates cAMP synthesis, which can ultimately activate glycogen phosphorylase to break down glycogen to glucose. Which of the following proteins can diminish signal transduction of this pathway?
Activated cyclic AMP phosphodiesterase.
Which of the following statements about the unfolded protein response (UPR) is FALSE?
Activation of the UPR occurs when receptors in the cytoplasm sense misfolded proteins.
Which of the following conditions is likely to decrease the likelihood of skeletal muscle contraction?
Addition of a drug that blocks Ca2+ binding to troponin.
Which of the following conditions is likely to increase the likelihood of skeletal muscle contraction?
Addition of a drug that increases Ca2+ binding to troponin.
During which stage of mitosis does mitotic spindle begin to form?
prophase
Which of the following statements is TRUE?
Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes.
All of the following promote apoptosis EXCEPT _____.
Bcl2
Comparing DNA polymerase and RNA polymerase, which of the following statements is incorrect?
Both polymerases require a short RNA primer to be synthesized by primase before they can synthesize DNA or RNA.
Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do excitatory neurotransmitters cause the postsynaptic cell to fire an action potential?
By opening Na+ channels.
For Cyclin-Cdk complexes to be active, inhibitory phosphates must be removed by phosphatases such as _______.
Cdc25
In prokaryotes, which of the below underlined codons will be selected as the translation initiator codon (codon number shown in parentheses)? 5'...GAGGAGCGCACAUG(1)CGAGGAGGUAUCCAUG(2)GCUAAGCCGUCCCAUG(3)GACGCCCAUG(4)GAGGGCGGCA...3'
Codon 2
In eukaryotes, which of the below underlined codons will be selected as the translation initiator codon (codon number shown in parentheses)? 5'...AUAUGCGCACAUG(1)GCGCGCAAUG(2)AGGGCAGCCGCCAUG(3)GACGCCGCCACCAUG(4)GAGGCGGCAAC...3'
Codon 4
Which of the following statements about the cytoskeleton is FALSE?
Covalent bonds between protein monomers hold together cytoskeletal filaments.
Which of the following is not a method of epigenetic inheritance?
DNA recombination
Cell cycle progression is controlled by Cdk-cyclin activity. All of the following are methods to regulate Cdk-cyclin activity EXCEPT.
Degradation of the cyclin by separase
Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients. Which of the following is not one of the common ways to perform active transport?
Glucose transporter uniport.
Which of the following statements is TRUE?
Disulfide bonds stabilize but do not change a protein's final conformation.
Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels?
ER → Golgi → plasma membrane
Which of the following statements is TRUE?
Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.
Lamellipodia are long, thin, actin-containing extensions.
False
Which of the following statements about RNA splicing is FALSE?
For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene.
Consider two genes that are next to each other on a chromosome, as arranged below. Which of the following statements is TRUE?
Gene A and gene B can be transcribed at different rates, producing different amounts of RNA within the same cell.
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 9 methylation
Which of the following choices best describes GAP (GTPase activating protein) regulation of GTP-binding proteins?
Hydrolyzes GTP to GDP to deactivate the protein.
Which RNA is involved in RNA editing?
gRNA
Which RNA is involved in RNA silencing?
siRNA
Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed below. Which of the following statements is FALSE?
In the absence of a survival signal, Bad is phosphorylated.
Where does most new membrane synthesis take place in a eukaryotic cell?
In the endoplasmic reticulum
Genes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why?
Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus.
What is the role of the nuclear localization sequence in a nuclear protein?
It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.
How does S-Cdk help guarantee that replication occurs only once during each cell cycle?
It phosphorylates the Cdc6 protein, marking it for destruction.
Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell?
K+
Which of the following statements about the function of the centrosome is FALSE?
Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome.
Which of the following statements is TRUE?
Nonpolar amino acids tend to be found in the interior of proteins.
Which of the following methods is NOT used by cells to regulate the amount of a protein in the cell?
Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.
Which of the following statements is TRUE?
Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation.
A protein contains a KDEL ER-retention signal sequence. Which protein processing mechanism would permit the protein to transport out of the endoplasmic reticulum?
Proteolytic cleavage of the KDEL signal sequence from the protein.
Which of the following is NOT a eukaryotic transcription factor binding motif?
RING finger
Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because_______.
RNA is singlestranded
Which of the following statements is FALSE?
RNA polymerase adds bases in a 3′-to-5′ direction; DNA polymerase adds bases in a 5′-to-3′ direction.
Which of the following statements about RNAi is true?
RNAi is induced when double-stranded RNA is present in the cell.
Which family of GTPases control the organization of the actin cytoskeleton?
Rho
Which of the following statements about prokaryotic mRNA molecules is FALSE?
Ribosomes must bind to the 5′ cap before initiating translation.
Which of the following statements about the genetic code is CORRECT?
Some amino acids are specified by more than one codon.
Which of the following statements about a protein in the lumen of the ER is FALSE?
Some of the proteins in the lumen of the ER can end up in the plasma membrane.
Membrane lipids are capable of many different types of movement. Which of these rarely occurs spontaneously in biological membranes?
Switching or flip-flopping between lipid layers
You have a bacterial strain with a mutation that removes the transcription termination signal from the Abd operon. Which of the following statements describes the most likely effect of this mutation on Abd transcription?
The Abd RNA from the mutant strain will be longer than normal.
After an amino acid has been linked to a peptide chain, the large ribosomal subunit shifts forward, moving the spent tRNA to which ribosome tRNA binding site before ejecting it?
The E site
Which of the following descriptions is consistent with the behavior of a cell infected with a virus that inhibits checkpoint mechanisms that normally operates during G2?
The cell would enter M phase under conditions when normal cells would not.
You have a segment of DNA that contains the following sequence: 5′-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3′ 3′-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5′ You know that the RNA transcribed from this segment contains the following sequence: 5′-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA-3′ Which of the following choices best describes how transcription occurs?
The bottom strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′
You have a segment of DNA that contains the following sequence: 5′-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3′ 3′-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5′ You know that the RNA transcribed from this segment contains the following sequence: 5′-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA-3′ Which of the following choices best describes how transcription occurs?
The bottom strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′.
Which of the following statements about skeletal muscle contraction is FALSE?
The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction.
Which of the following statements about the genetic code is CORRECT?
The genetic code is redundant.
Which of the following statements about transport into mitochondria is FALSE?
The protein moves completely through the protein translocator in the outer membrane, then the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane.
Which of the following does NOT occur before a eukaryotic mRNA is exported from the nucleus?
The ribosome binds to the mRNA.
Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?
The ribosome binds to the mRNA.
The following happens when a G-protein-coupled receptor activates a G protein.
The α subunit exchanges its bound GDP for GTP.
Which of the following is FALSE about molecular chaperones?
They can interact with unfolded polypeptides in a way that changes the final fold of the protein.
K+ leak channels are found in the plasma membrane. These channels open and close in a random fashion. What do they accomplish in a resting cell?
They keep the resting membrane potential at slightly below zero.
Molecular chaperones can work by creating an "isolation chamber." What is the purpose of this chamber?
This chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until protein folding is completed.
Microtubules are important for transporting cargo in nerve cell axons. Notice that the two types of cargo are traveling in opposite directions. The gray cargo is attached to dynein.
True
Steroid hormones can pass through the plasma membrane to interact with intracellular receptors.
True
Which of the following statements is FALSE?
Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.
Which of the following statements about chromatin is TRUE?
chromatin remodeling affects transcription by altering chromatin structure to allow accessibility to the DNA .
Which of the following might decrease the transcription of only one specific gene in a bacterial cell?
a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site
Which of the following protein families are NOT involved in directing transport vesicles to the target membrane?
adaptins
Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called________.
active transport
Molecules to be packaged into vesicles for transport are selected by ______.
adaptins
The figure below shows how normal signaling works with a Ras protein acting downstream of an RTK. You examine a cell line with a constitutively active (always ON) Ras protein that is always signaling. Which of the following conditions will turn off signaling in this cell line?
addition of a drug that blocks protein Y from interacting with its target
The poison strychnine binds to the glycine receptor on neurons decreasing its affinity for the neurotransmitter glycine. This is an example of what type of regulation?
allosteric inhibition
The hydrolysis of GTP to GDP carried out by tubulin molecules _____.
allows the behavior of microtubules called dynamic instability.
Complete the sentence with the best option provided below. The primary structure of a protein is the
amino acid sequence
Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found?
an aquaporin
Which of the following descriptions best matches the function of a kinase?
an enzyme that catalyzes the addition of phosphate groups to other molecules
Select the best option to fill in the blanks of the following statement: Fermentation is a/an __________ process that converts __________into carbon dioxide and __________.
anaerobic, pyruvate, ethanol
Apoptosis differs from necrosis in that necrosis _____.
causes cells to swell and burst, whereas apoptotic cells shrink and condense.
Which of the following would not occur following the unfolded protein response (UPR).
cell division
In eukaryotes, which of the below underlined codons will be selected as the translation initiator codon? Codon number in parentheses after codon. 5'...AUAUGCGCACAUG(1)GCGCCGCCACCAUG(2)AGGGCAGCGGCGCCAUG(3)GACGCCCGCCACCAUG(4)GAGGCGGAC...3'
codon 2
You observe cells under a microscope undergoing mitosis. The sister chromatids have condsensed, but they are not paired up. The cell is in Prometaphase. This is likely due to a defect in which protein?
cohesion
Methotrexate, a chemotherapy drug, is structurally similar to folate. Folate binds and activates the enzyme dihydrofolate reducatase. When methotrexate is bound to dihydrofolate reducatase, it is unable to bind folate and the enzyme is inactive. This is an example of what type of regulation?
competitive inhibition
During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in __________ signaling.
contact-dependent
RNA in cells differs from DNA in that
it is single-stranded and can fold up into a variety of structures.
Peptide bonds are formed between two amino acids through a _______ reaction.
dehydration
If lactose is absent and glucose is absent, transcription of the lactose operon _____.
does not occur because the promoter is blocked by the repressor, even though CAP/cAMP is available.
If lactose is absent and glucose is present, transcription of the lactose operon _____.
does not occur because the promoter is blocked by the repressor.
Your friend has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. He wants to start designing some experiments but was not listening carefully when he was told about the molecular defect of this cell line. He is too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated vesicles but cannot dock with the target membrane. Which of the following proteins might be lacking in this cell line?
dynamin
Which factor makes direct contact with the 5' cap on mRNA at the start of translation?
eIF-4E
Signal sequences that direct proteins to the correct compartment are
encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination.
Signal sequences that direct proteins to the correct compartment are ______.
encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination.
The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is that
energy can be extracted in usable amounts.
When an action potential reaches the end of a neuron, neurotransmitters are released into the synapse. Which of the following processes could be responsible for their secretion?
exocytosis
H2O is a molecules that diffuses freely by passive transport across cell membranes.
false
In transmembrane proteins, start-transfer sequences are hydrophobic and stop-transfer sequences are hydrophilic.
false
Lysosomes mature into endosomes, which contain hydrolytic enzymes that are only active in acidic conditions.
false
The ATP-driven Na+ pump moves two Na+ ions into the cell and three K+ ions out of the cell.
false
Cells are coated with polysaccharide __________, which can improve cell motility.
glycocalyx
Which of the following processes do NOT take place in the mitochondria?
glycogen breakdown
When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is _____.
hormonal
When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a
hormone
Proteins bind selectively to small-molecule targets called ligands. The selection of one ligand out of a mixture of possible ligands depends on the number of weak, noncovalent interactions in the protein's ligand-binding site. Where is the binding site typically located in the protein structure?
inside a cavity on the protein surface
All of the following cytoskeleton components are involved in mitosis and cytokinesis EXCEPT.
intermediate filaments
During RNA splicing _____ are excised and _____ are ligated.
introns, exons
Combinatorial control of gene expression _________.
involves groups of transcription regulators working together to determine the expression of a gene.
A protein kinase can act as an integrating device in signaling if it
is activated by two or more proteins in different signaling pathways.
A protein kinase can act as an integrating device in signaling if it _____.
is activated by two or more proteins in different signaling pathways.
In the laboratory, you mutate a gene in neurons and discover that the resulting cells are unable to transport vesicles and organelles to the axon terminal, but they can still transport vesicles and organelles from the axon terminal to the cell body. The gene you mutated is most likely a _________.
kinesin motor protein.
`In the final stage of the oxidation of food molecules, a gradient of protons is formed across the inner mitochondrial membrane, which is normally impermeable to protons. If cells were exposed to an agent that causes the membrane to become freely permeable to protons, which of the following effects would you expect to observe?
less ATP would be made
During which stage of mitosis do the chromosomes line up at the cell equator?
metaphase
Which RNA is involved in regulating gene expression?
miRNA
Some chemotherapy drugs function by preventing mitotic spindle formation and function and as a result preventing cell division. Which cytoskeleton component are they targeting?
microtubules
Using genetic engineering techniques, you remove the sequences that code for the ribosome-binding sequences of the bacterial LacZ gene. The removal of these sequences will lead to _______.
no translation of the LacZ mRNA.
Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP?
oxidative phosphorylation
Irradiated mammalian cells usually stop dividing and arrest at a G1 DNA damage checkpoint. Which of the following would occur first?
p53 is phosphorylated.
Which type of lipids are the most abundant in the plasma membrane?
phospholipids
During which stage of mitosis does the nuclear envelope fragment and disappear?
prometaphase
The sigma subunit of bacterial RNA polymerase
recognizes promoter sites in the DNA.
When does DNA replication occur?
s phase
Which of the following structures shorten during muscle contraction?
sarcomeres
In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by
scanning along the mRNA from the 5′ end.
Cell membranes maintain symmetric growth by __________, which catalyzes transfer of random phospholipids from one side of the bilayer to the other.
scramblase
Transporters, in contrast to channels, work by ____________.
specific binding to solutes
The microtubules in a cell form a structural framework that can have all the following functions except which one?
strengthening the plasma membrane
Which of the following is NOT a chemical group commonly found on core histone N-terminal tails for chromatin regulation?
sulfhydryl
Involved in translation termination, eRF-1 has a structure similar to which of the following choices?
tRNA
In a DNA double helix,
the two DNA strands run antiparallel.
Which of the following is NOT a process that delivers material to the lysosome?
transcytosis
Proteins that are fully translated in the cytosol do not end up in
transport vesicles
Proteins that are fully translated in the cytosol do not end up in ______.
transport vesicles
By wobble pairing, a single tRNA is sometimes able to decode more than one codon sequence.
true
Posttranslational modification with ________ marks proteins to be located to the proteasome.
ubiquitin
Which of these pathways is not a function of an endosomal compartment?
unfolded protein response
Which of the following is required for the secretion of neurotransmitters in response to an action potential?
voltage gated Ca2+ channels
An action potential is triggered by depolarization of the plasma membrane. This causes ___________ to flicker open, rapidly furthering depolarization of the membrane.
voltage gated Na+ channels
