BIO 314 Exam 2 Atempt 1 & Atempt 2
Shown below is a diagram of how theoretical intracellular signaling pathways could integrate incoming signals to produce a coordinated cell response. Which signal(s) would lead to activation of both kinase 1 and kinase 2?
signals A and D
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 lumen of an organelle in the endomembrane system. Some of the proteins in the lumen of the ER can end up in the extracellular space. Some of the proteins in the lumen of the ER can end up in the plasma membrane. A protein in the lumen of the ER is synthesized by ribosomes on the ER membrane.
A protein in the lumen of the ER is synthesized by ribosomes on the ER membrane.
Which of the following types of cell signaling is long range and uses hormones as signals? endocrine paracrine neuronal contact-dependent
endocrine
Which of the following signaling pathways would be likely to trigger the most rapid cell response? a. Acetylcholine binds to anion-channel-coupled receptor that allows Na+ to flow down its electrochemical gradient, triggering contraction of a skeletal muscle cell. b. Adrenaline binds to a GPCR to activate a cyclic AMP signaling pathway that triggers glycogen breakdown c. Platelet-derived growth factor binds to a RTK to activate a signaling pathway that stimulates cell proliferation at the site of a wound d. Nerve growth factor binds to a receptor tyrosine kinase to activate a signaling pathway that enhances the transcription of Bcl2, a protein that suppresses cell death
Acetylcholine binds to anion-channel-coupled receptor that allows Na+ to flow down its electrochemical gradient, triggering contraction of a skeletal muscle cell.
Which of the following statements about transport into mitochondria and chloroplasts is FALSE? The signal sequence on proteins destined for these organelles is recognized by a receptor protein in the outer membrane of these organelles. Proteins that are transported into these organelles are unfolded as they are being transported. Signal peptidase will remove the signal sequence once the protein has been imported into these organelles. After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane.
After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane.
Which of the following is NOT true for the signal transduction pathway shown below: a. GTP-bound G-alpha subunit activates adenylyl cyclase to produce the second messenger cAMP. b. The trimeric G protein is kept at the membrane by the presence of lipid tails c. After binding its receptor, the odorant is internalized via receptor-mediated endocytosis. d. The second messenger Ca2+ acts to trigger opening of the chloride channel, which makes the neuron more likely to reach the threshold to send an action potential to the brain.
After binding its receptor, the odorant is internalized via receptor-mediated endocytosis.
Predict the membrane orientation of a protein that is synthesized with an uncleaved, internal signal sequence (as below in red) but did not contain a stop-transfer sequence (shown in yellow below)? Amino terminus in the ER lumen and carboxy terminus in the cytosol Both N- and C-termini in the cytosol Both N- and C-termini in the ER lumen Amino terminus in the cytosol and carboxy terminus in the ER lumen
Amino terminus in the cytosol and carboxy terminus in the ER lumen
The activated G-beta/gamma complex can be inactivated by: a. Adding a non-hydrolyzable ATP analog to the mix b. Binding to GTP-bound G-alpha c. Binding to GDP-bound G-alpha d. Adding a non-hydrolyzable GTP analog to the mix
Binding to GDP-bound G-alpha
What overcomes the translational arrest that occurs when SRP (signal recognition particle) binds to the signal peptide as it emerges from the ribosome? a. Degradation of the SRP by a cytosolic proteosome b. Phosphorylation of the SRP by an activating kinase c. Recruitment of a GEF to re-activate the translocation elongation factor d. Binding to the SRP receptor (or "docking protein") and release of SRP when the ribosome is transferred to the ER translocon
Binding to the SRP receptor (or "docking protein") and release of SRP when the ribosome is transferred to the ER translocon
Researchers studying yeast discovered that, for some mutants, when the temperature at which the cells are grown was elevated from 25 degrees Celsius to 37 degrees Celsius, their secretory pathway no longer functions and the cells grow dense with unsecreted proteins. When these cells are examined microscopically, they can be divided into groups that vary in terms of where the unsecreted proteins accumulate. In some of the mutants, proteins accumulate in the ER; in others, the Golgi; in others, they accumulate in vesicles near the plasma membrane. What is the likely explanation for this difference in appearance? a. Different temperature-sensitive mutations affect different stages of the transport process b. Different temperature-sensitive mutations disrupt protein synthesis c. The temperature-sensitive mutant proteins are targeted to different compartments d. Different temperature-sensitive mutations promote an increase in protein synthesis
Different temperature-sensitive mutations affect different stages of the transport process
Which of the following statements is FALSE? Some signal molecules can bind directly to intracellular proteins that bind DNA and regulate gene transcription. Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids. Nucleotides and amino acids can act as extracellular signal molecules. Some signal molecules are transmembrane proteins.
Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.
Which of the following statements is TRUE? Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response that is produced by that signal molecule on the same cell type. A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior. To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol.
Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.
Which of the following is NOT true? a. GAP proteins stimulate the rate of GTP hydrolysis by a G protein b. G proteins can hydrolyze GTP on their own but it is very slow c. GDIs are necessary for G proteins to release GDP so they can bind GTP d. G proteins can release GDP on their own but at an extremely slow rate
GDIs are necessary for G proteins to release GDP so they can bind GTP
What enzymatic activity does a G protein have? a. Phosphatase activity b. GTPase activity c. Kinase activity d. Translocase activity
GTPase activity
If you cloned a gene into a cell that encodes a protein with an ER signal sequence at its N-terminus and a nuclear localization sequence in its middle, where will the expressed protein be found? a. It will be degraded in the lysosome b. Half will be in the ER and half will be in the nucleus c. In the ER lumen d. in the nucleus
In the ER lumen
(Q028) Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed in Figure 16-28. Which Is FALSE a. In the presence of a survival signal, the cell-death inhibitory protein Bcl2 is active. b. In the presence of a survival signal, Akt is phosphorylated. c. In the absence of a survival signal, Bad is phosphorylated. d. In the absence of a survival signal, Bad inhibits the cell-death inhibitor protein Bcl2.
In the absence of a survival signal, Bad is phosphorylated.
Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed in Figure 16-28. In the absence of a survival signal, Bad inhibits the cell-death inhibitor protein Bcl2. In the presence of a survival signal, the cell-death inhibitory protein Bcl2 is active. In the absence of a survival signal, Bad is phosphorylated. In the presence of a survival signal, Akt is phosphorylated.
In the absence of a survival signal, Bad is phosphorylated.
In the following olfactory signal transduction pathway, what is responsible for the "adaptation" or "desensitization" that occurs after prolonged exposure to the odorant? Binding of the Ca2+ by calmodulin Inhibition of the odorant receptor by ORK and PKA Inhibition of the odorant receptor by G-alpha Degradation of the cAMP by phosphodiesterase
Inhibition of the odorant receptor by ORK and PKA
In the following olfactory signal transduction pathway, what is responsible for the "adaptation" or "desensitization" that occurs after prolonged exposure to the odorant? a. Binding of the Ca2+ by calmodulin b. Inhibition of the odorant receptor by ORK and PKA c. Degradation of the cAMP by phosphodiesterase d. Inhibition of the odorant receptor by G-alpha
Inhibition of the odorant receptor by ORK and PKA
A key function of the lysosome is: a. Intracellular degradation b. ATP synthesis by oxidative phosphorylation c. Sorting of endocytosed material d. Synthesis of new membranes
Intracellular degradation
Nitric oxide: a. Is a second messenger that rapidly diffuses through membranes b. Has a long half-life. c. Is the primary signaling molecule in plants d. Is an example of an endocrine signal
Is a second messenger that rapidly diffuses through membranes
(Q009) What is the role of the nuclear localization sequence in a nuclear protein? a. It is a hydrophobic sequence that enables the protein to enter the nuclear membranes. b. It aids in protein unfolding so that the protein can thread through nuclear pores. c. It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. d. It prevents the protein from diffusing out of the nucleus through nuclear pores.
It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.
All of the following are true about lysosomes EXCEPT:
Lysosomes contain a broad spectrum of hydrolytic enzymes that are only active in the very basic (i.e., high pH) environment of the lysosome
When the cytosolic tail of the __________ receptor is cleaved, it migrates to the nucleus and affects gene regulation. G-protein coupled Notch growth factor nuclear
Notch
(Q012) Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? a. Nuclear transport receptors would be unable to enter the nucleus. b. Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils. c. Nuclear transport receptors would be unable to release their cargo in the nucleus. d. Nuclear transport receptors would be unable to bind cargo.
Nuclear transport receptors would be unable to release their cargo in the nucleus.
(Q019) You are interested in Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which of the following statements must be TRUE? a. Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded. c. Fuzzy has a C-terminal signal sequence that binds to SRP. c. Only one ribosome can be bound to the mRNA encoding Fuzzy during translation. d. Fuzzy must contain a hydrophobic stop-transfer sequence.
Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded.
(Q026) Which of the following statements is TRUE? a. Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP. b. MAP kinase is important for phosphorylating MAP kinase kinase. c. Dimerization of GPCRs leads to Gα activation. d. PI 3-kinase phosphorylates a lipid in the plasma membrane.
PI 3-kinase phosphorylates a lipid in the plasma membrane.
Which of the following statements is TRUE? MAP kinase is important for phosphorylating MAP kinase kinase. Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP. Dimerization of GPCRs leads to Gα activation. PI 3-kinase phosphorylates a lipid in the plasma membrane.
PI 3-kinase phosphorylates a lipid in the plasma membrane.
(Q021) Which of the following statements is TRUE? a. Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation. b. Proteins destined for the ER are translated by a pool of cytosolic ribosomes that contain ER-targeting sequences that interact with ER-associated protein translocators. c. Proteins destined for the ER are translated by a special pool of ribosomes whose subunits are always associated with the outer ER membrane. d. Proteins destined for the ER translocate their associated mRNAs into the ER lumen where they are translated.
Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation.
Which of the following is not unfolded during its import? Proteins imported into the nucleus. Proteins imported into the ER Proteins imported into the chloroplast Proteins imported into the mitochondria
Proteins imported into the nucleus.
During fertilizaton: Rapid diffusion of a wave of Ca2+ across the egg inhibits polyspermy Na+ channels open to trigger an action potential to inhibit polyspermy No signaling can occur until after the sperm nucleus has fused with the egg nucleus A GPCR is activated that signals a kinase to initiate transcription to inhibit polyspermy
Rapid diffusion of a wave of Ca2+ across the egg inhibits polyspermy
A typical signaling pathway for a steroid hormone involves:
Steroid hormone crosses membrane to bind intracellular (or intranuclear) receptor --> receptor undergoes allosteric change --> receptor now acts as a transcription factor to turn on gene expression
Activated receptor tyrosine kinases contain phosphorylated tyrosines on their cytoplasmic tails which serve as docking sites for a large set of signaling proteins. These signaling proteins can interact with each other and other signaling proteins using interaction domains to assemble a large complex at the plasma membrane. What is a major advantage of forming these large aggregates? The complex is set up with the same components downstream of different receptors in every cell type The complex of proteins causes the signal to last for a long time The complex of proteins allows the receptors to signal many downstream pathways simultaneously Each of the docked proteins in the aggregate becomes phosphorylated and has enzyme activity to further activate signaling
The complex of proteins allows the receptors to signal many downstream pathways simultaneously
(Q011) Which of the following statements about G-protein-coupled receptors (GPCRs) is FALSE? a. GPCRs are the largest family of cell-surface receptors in humans. b. The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains. c. GPCRs are used in endocrine, paracrine, and neuronal signaling. d. GPCRs are found in yeast, mice, and humans.
The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.
(Q037) Which of the following statements about secretion is TRUE? a. The signal sequences of proteins destined for constitutive exocytosis ensure their packaging into the correct vesicles. b. The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior. c. Proteins destined for constitutive exocytosis aggregate as a result of the acidic pH of the trans Golgi network. d. Vesicles for regulated exocytosis will not bud off the trans Golgi network until the appropriate signal has been received by the cell.
The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior.
(Q004) Which of the following statements is TRUE? a. The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA. b. Lysosomes are believed to have originated from the engulfment of bacteria specialized for digestion. c. Chloroplasts and mitochondria share their DNA d. Because bacteria do not have mitochondria, they cannot produce ATP in a membrane-dependent fashion.
The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA.
(Q003) Which of the following statements is TRUE? a. The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling. b. The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells. c. Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal. d. Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism.
The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling.
All of the following is true about RTKs EXCEPT: a. They are receptors that, when activated will phosphorylate a serine residue on their partner b. Dimerization by other means, such as IgG antibody binding two RTKs to bring them together, can result in activation c. They are integral membrane proteins that can relay extracellular signals to the inside of a cell. c. Ligand binding causes dimerization
They are receptors that, when activated will phosphorylate a serine residue on their partner
The role of a GAP protein in a signaling pathway is: a. To generate the IP3 second messenger b. To inactivate an activated G protein c. To activate an inactivated G protein d. To generate a phosphorylated tyrosine binding site that recruits an adaptor protein
To inactivate an activated G protein
Mechanisms to target proteins to the correct compartment include all of the following EXCEPT: a. Gating through a pore. b. Transport through an aquaporin beta barrel c. Transport by protein translocators. d. Transport by vesicles.
Transport through an aquaporin beta barrel
Residues that can be phosphorylated include all of the following EXCEPT: T Y S W
W
Which of the following describes negative feedback regulation? a component acts to further activate the signaling pathway and enhance the cell's response a component late in the pathway inhibits an enzyme early in the pathway A component amplifies the signal for a more robust response A component generates an all-or-none, switch-like mechanism
a component late in the pathway inhibits an enzyme early in the pathway
(Q020) Figure 16-20 shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? a. a muscle cell that has cyclic GMP phosphodiesterase constitutively active b. a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP c. a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO d. a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO
a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP
) Figure 16-20 shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP a muscle cell that has cyclic GMP phosphodiesterase constitutively active a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO
a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP
The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization? changing the tyrosines that are normally phosphorylated on RGFR dimerization to alanines a mutation that increases the affinity of RGFR for RGF changing the tyrosines that are normally phosphorylated on RGFR dimerization to glutamic acid a mutation that prevents RGFR from binding to RGF
a mutation that prevents RGFR from binding to RGF
Which of the following is NOT required for targeting and import of a mitochondrial protein? involvement of chaperones to unfold and refold the protein before and during mitochondrial import an N-terminal amphipathic targeting signal sequence a signal recognition particle (SRP) that recognizes the signal sequence and arrests translation until the ribosome can dock at the mitochondrial translocator protein unfolding during translocation
a signal recognition particle (SRP) that recognizes the signal sequence and arrests translation until the ribosome can dock at the mitochondrial translocator
(Q002) 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. a. contact-dependent b. neuronal c. endocrine d. paracrine
a. contact-dependent
(Q026) Which of the following protein families are NOT involved in directing transport vesicles to the target membrane? a. SNAREs b. tethering proteins c. Rabs d. adaptins
adaptins
GTPase switch proteins such as ras: are active when bound to GDP but inactive when bound to GTP Are converted from the active to inactive state by a guanine nucleotide exchange factor are active when bound to GTP but inactive when bound to GDP synthesize GTP from GDP
are active when bound to GTP but inactive when bound to GDP
Proteins typically included in coated vesicles include: a. nitrous oxide b. cAMP c. adaptins d. nuclear import receptor
c. adaptins
G protein signaling can be regulated by other proteins that include all of the following EXCEPT: a. cAMP b. GAP c. GDI d. GEF
cAMP
Sorting information that directs trafficking or localization within the cell may be found on all of the following EXCEPT: a. chaperone b. NLS c. signal sequence d. SNARE protein
chaperone
(Q036) Vesicles from the ER enter the Golgi at the a. medial cisternae. b. cis Golgi network. c. trans Golgi network. d. trans cisternae.
cis Golgi network.
(Q024) Which of the following mechanisms is NOT directly involved in inactivating an activated RTK? a. dephosphorylation by serine/threonine phosphatases b. digestion of the RTK in lysosomes c. removal of the RTK from the plasma membrane by endocytosis d. dephosphorylation by protein tyrosine phosphatases
dephosphorylation by serine/threonine phosphatases
The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by diffusing into cells and stimulating the cyclase directly. activating a G protein. activating an intracellular protein kinase. activating a receptor tyrosine kinase.
diffusing into cells and stimulating the cyclase directly.
What type of cell response would take the longest amount of time (on the scale of minutes to hours) to execute? a. one that uses a phosphorylation event to activate an enzyme b. one that involves a change in gene expression c. one that involves the release of secretory vesicles d. one that involves the firing of an action potential along a neuron
one that involves a change in gene expression
The pleckstrin homology (PH) domain binds: a. phosphoserine b. phosphorylated inositol phospholipid c. proline-rich motif d. phosphotyrosine
phosphorylated inositol phospholipid
The Src homology 2 domain (SH2) binds: a. phosphotyrosine b. phosphorylated phosphinositol phospholipid c. cAMP d. proline-rich motif
phosphotyrosine
(Q017) After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode? a. ER membrane proteins b. all of these answers are correct c. soluble secreted proteins d. plasma membrane proteins
plasma membrane proteins
RTKs can activate the enzyme phosphoinositide 3-kinase, which phosphorylates inositol phospholipids. These phospholipids then do what? a. serve as phosphate donors in phosphorylation reactions b. serve as a docking site that recruit specific intracellular signaling proteins to the plasma membrane c. activate G proteins d. activate ras
serve as a docking site that recruit specific intracellular signaling proteins to the plasma membrane
A key function of the endosome is: secretion of neurosecretory hormones oxidative breakdown of toxic materials sorting of endocytosed material synthesis of most lipids and membrane proteins
sorting of endocytosed material
Which membrane-enclosed organelles most likely evolved in a similar manner? a. mitochondria and the Golgi apparatus b. chloroplasts and peroxisomes c. mitochondria and the nucleus d. the nucleus and the ER
the nucleus and the ER
(Q006) Proteins that are fully translated in the cytosol do not end up in a. transport vesicles. b. the interior of the nucleus. c. the mitochondria. d. the cytosol.
transport vesicles.
