biochem exam 3
Predict which bond of a target protein would be cleaved by caspase 3 executioner enzyme. 3 2 1 4
4
Signal transduction is part of a cell's response to an external signal. Although signal transduction pathways can differ in their details, there are some common elements. Determine which of the statements below accurately describe signal transduction pathways. Select the three correct statements. Select 3 correct answer(s) Question options: A receptor may pass on a signal by interacting with another protein or by acting as an enzyme. A receptor changes conformation upon binding, transmitting a signal across the cell membrane. Signal transduction cascades directly transmit a single stimulus to a single target. Signal transduction cascades, often involving protein kinases, amplify a signal intracellularly. A second messenger carries a signal from a tissue or organ to a target cell. A single ligand binding event produces a single species of second messenger.
A receptor may pass on a signal by interacting with another protein or by acting as an enzyme. A receptor changes conformation upon binding, transmitting a signal across the cell membrane. Signal transduction cascades, often involving protein kinases, amplify a signal intracellularly.
Two domains on the adaptor protein GRB2 are shown. Identify the type of each domain and the protein substrate these two domains bind to in the EGFR signaling pathway. A. 1) SH3 domain, 2) SOS protein, 3) SH2 domain, 4) EGFR B. 1) SH3 domain, 2) Shc protein, 3) SH2 domain, 4) EGFR C. 1) SH2 domain, 2) SOS protein, 3) SH3 domain, 4) TNFR D. 1) SH3 domain, 2) IRS protein, 3) SH2 domain, 4) EGFR E. 1) SH2 domain, 2) SOS protein, 3) SH3 domain, 4) GPCR
A. 1) SH3 domain, 2) SOS protein, 3) SH2 domain, 4) EGFR
Before breakfast, (1) __________ hormone levels are elevated and rates of metabolic flux through the glycogen (2) _________ and (3) _________ pathways are high, while rates of metabolic flux through the glycogen (4) _______ and (5) __________ pathways are low. Soon after breakfast,(6) ______ hormone levels (7) ______ leading to reduced blood glucose levels after several hours. A. 1) glucagon, 2) degradation, 3) gluconeogenesis, 4) synthesis, 5) glycolysis, 6) insulin, 7) increase B. 1) insulin, 2) synthesis, 3) gluconeogenesis, 4) degradation, 5) glycolysis, 6) glucagon, 7) increase C. 1) glucagon, 2) degradation, 3) glycolysis, 4) synthesis, 5) gluconeogenesis, 6) insulin, 7) decrease D. 1) insulin, 2) synthesis, 3) glycolysis 4) degradation, 5) gluconeogenesis, 6) glucagon, 7) increase E. 1) glucagon, 2) synthesis, 3) gluconeogenesis, 4) degradation, 5) glycolysis, 6) insulin, 7) decrease
A. 1) glucagon, 2) degradation, 3) gluconeogenesis, 4) synthesis, 5) glycolysis, 6) insulin, 7) increase
What three properties of glucokinase contribute to its functional role as a glucose sensor? 1. Glucokinase is expressed in pancreas cells where it inhibits the release of glucagon. 2. Glucokinase has a high Km and therefore its activity is dependent on high [glucose]. 3. Glucokinase is not inhibited by glucose-6P (G6P) and is active even if G6P accumulates. 4. Glucokinase has a low Km and therefore its activity is dependent on high [glucose]. 5. Glucokinase is expressed in pancreas cells where it stimulates the release of insulin. 6. Glucokinase is activated by insulin and inhibited by glucagon when [glucose] is high Answer options: A. 2, 3, 5 B. 2, 5, 6 C. 3, 4, 6 D. 2, 4, 5 E. 1, 2, 3
A. 2, 3, 5
Match the A, B and C labels with the corresponding type of enzyme inhibition in the figure. A. A) Competitive, B) Mixed, C) Uncompetitive B. A) Noncompetitive, B) Mixed, C) Competitive C. A) Mixed, B) Competitive, C) Uncompetitive D. A) Competitive, B) Mixed, C) Shared E. A) Uncompetitive, B) Covalent, C) Competitive
A. A) Competitive, B) Mixed, C) Uncompetitive
Which of the following DNA sequences is MOST likely to be bound by a steroid receptor? A. AGGAGAACATCATGTTCT B. AGGAGATAGGAGAACT C. TTTGATCCAGTTTCCAGT D. CCCAAGTTCCCAAG
A. AGGAGAACATCATGTTCT
How is the ∆Gº' value for a chemical reaction determined using the value for Keq ? A. At equilibrium, Keq = [P]/[R] and ∆G = 0, therefore ∆Gº' = -RT•lnKeq B. At equilibrium, Keq = [R]/[P] and ∆G = 0, therefore ∆Gº' = -RT•lnKeq C. At equilibrium, Keq = [P]/[R] and ∆G = 0, therefore ∆Gº' = +RT•lnKeq D. At equilibrium, Keq = [P]/[R] and ∆G = 1, therefore ∆Gº' = (1)•RT•lnKeq
A. At equilibrium, Keq = [P]/[R] and ∆G = 0, therefore ∆Gº' = -RT•lnKeq
Dexamethasone (Dex) is a high affinity ligand for the glucocorticoid receptor (GR), which has been used as an anti-inflammatory drug to treat patients with COVID-19. What is the molecular explanation for why Dex is 50 times more potent in treating inflammation than the natural glucocorticoid cortisol? A. Dex binding to GR is 50 times more efficient at shifting GR to the active R state conformation. B. Dex binding to GR is 50 times less efficient at shifting GR to the inactive T state conformation. C. Cortisol binding to GR is 50 times less efficient at shifting GR to the active T state conformation. D. Dex binding to GR is 50 times more efficient at shifting GR to the active T state conformation. E. Cortisol binding to GR is 50 times more efficient at shifting GR to the active R state conformation
A. Dex binding to GR is 50 times more efficient at shifting GR to the active R state conformation.
What is the overall net reaction of the glycolytic pathway? A. Glucose + 2 NAD+ + 2 Pi + 2 ADP --> 2 Pyruvate + 2 NADH + 2 H+ + 2 H2 O + 2 ATP B. Glucose + 2 NAD+ + 4 Pi + 4 ADP --> 2 Pyruvate + 2 NADH + 2 H+ + 2 H2 O + 4 ATP C. Glucose + 2 NADH + 2 Pi + 2 ATP --> 2 Pyruvate + 2 NAD+ + 2 H+ + 2 H2 O + 2 ADP D. Glucose + 2 NAD+ + 2 Pi + 2 ADP --> Pyruvate + NADH + H+ + 2 H2 O + 2 ATP E. Glucose + 2 FAD + 2 Pi + 2 ADP --> 2 Pyruvate + 2 FADH2 + 2 H+ + 2 H2 O + 2 ATP
A. Glucose + 2 NAD+ + 2 Pi + 2 ADP --> 2 Pyruvate + 2 NADH + 2 H+ + 2 H2 O + 2 ATP
What is the function of growth factor receptor-bound 2 (GRB2) protein in RTK signaling? A. It is an adaptor protein that binds to phosphotyrosine residues in RTKs and also binds to GEF proteins. B. It is an adaptor protein that binds to phosphoserine residues in IRSs and to GEF proteins like PI-3K. C. It is a tyrosine kinase protein that phosphorylates arginine residues in PI-3Kand in phospholipase C. D. It is a survival protein that binds to cysteine proteases and inhibits their auto-cleavage by TRADD. E. It is an adaptor protein that binds to G proteins like Ras and Gsa and also to MAPK, Raf, and ERK.
A. It is an adaptor protein that binds to phosphotyrosine residues in RTKs and also binds to GEF proteins.
The Lineweaver-Burk plot shown below is for a(n) __________ inhibitor. A. competitive B. mixed C. noncompetitive D. uncompetitive
A. competitive
Match each second messenger with its most correct target protein, each answer is only used once. Record your answer in the order of a, b, c, d, and e, by choosing the numbers 1, 2, 3, 4, and 5. Second Messenger ______ a. Cyclic AMP ______b. Inositol triphosphate ______c. Diacylglycerol ______d. Cyclic GMP ______e. Calcium Target Protein 1. Calcium channel protein 2. Protein kinase G 3. Protein kinase A 4. Calmodulin 5. Protein kinase C Answer Options: A. 1, 3, 5, 4, 2 B. 3, 1, 5, 2, 4 C. 3, 2, 1, 4, 5 D. 5, 1, 4, 2, 3 E. 3, 4, 5, 2, 1
B. 3, 1, 5, 2, 4
Put the following 10 biochemical processes in the correct order for the insulin signaling pathway; beginning with insulin binding to the receptor and ending with stimulation of Akt kinase enzyme activity. ___Binding of phosphoinositide 3-kinase to a phosphotyrosine on IRS-1. ___Tyrosine phosphorylation of insulin receptor substrate-1. ___Phosphorylation of phosphatidylinositol-4,5-bisphosphate by PI-3K. ___Conformational change in the beta subunits of the insulin receptor. ___Phosphoinositide-dependent kinase-1 and Akt binding to PIP3. ___Tyrosine phosphorylation of the cytosolic domains of the insulin receptor. ___Akt activation and dissociation from phosphatidylinositol-3,4,5-trisphosphate ___Conformational change in the alpha subunit of the insulin receptor. ___Phosphoinositide-dependent kinase-1 phosphorylation of Akt on Ser and Thr residues. ___Binding of insulin receptor substrate-1 to phosphotyrosine on the insulin receptor. Answer options: A. 5, 6 ,7, 2 ,9, 3, 10, 1, 8, 4 B. 6, 5 ,7, 2 ,8, 3, 10, 1, 9, 4 C. 6, 4 ,7, 1 ,8, 3, 10, 2, 9, 5 D. 6, 5 ,8, 2 ,7, 3, 9, 1, 10, 4 E. 7, 5 ,6, 2 ,8, 4, 10, 1, 9, 3
B. 6, 5 ,7, 2 ,8, 3, 10, 1, 9, 4
Activity of phosphofructokinase-1 (PFK-1) is tightly-controlled by allosteric regulators. Identify the two positive and two negative allosteric regulators of PFK-1 activity from the list of biomolecules below. In addition, identify the two biomolecules in the list that do not function as allosteric regulators of PFK-1. Type of PFK-1 Regulation: A. Positive allosteric regulation B. Negative allosteric regulation C. Not an allosteric regulator Biomolecules: 1. fructose-1, 6-BP 2. citrate 3. ATP 4. ADP 5. glucose-6P 6. fructose-2,6-BP Answer options: A. A:4,5; B:2,3; C:1,6 B. A:4,6; B:2,3; C:1,5 C. A:3,6; B:2,4; C:1,5 D. A:4,6; B:1,3; C:2,5 E. A:3,5; B:1,4; C:2,6
B. A:4,6; B:2,3; C:1,5
Catabolic pathways are always paired with anabolic pathways. Why? A. Catabolic pathways build up new molecules and anabolic pathways break down molecules. B. Catabolic pathways break down molecules and anabolic pathways build up new molecules. C. The pathways are not active in the cell at the same time. D. The metabolites for the pathways only serve as substrates for different enzymes
B. Catabolic pathways break down molecules and anabolic pathways build up new molecules.
Which type of reversible enzyme inhibition is illustrated by the initial velocity vs. [S] plot shown here? A. Mixed inhibition B. Competitive inhibition C. Uncompetitive inhibition D. Noncompetitive inhibition
B. Competitive inhibition
What distinguishes competitive from uncompetitive modes of enzyme inhibition? A. Competitive inhibitors bind irreversibly to E; uncompetitive inhibitors bind reversibly to E and ES. B. Competitive inhibitors bind E in the active site; uncompetitive inhibitors bind ES outside of the active site. C. Competitive inhibitors bind to both ES and E forms; uncompetitive inhibitors bind only to the EP form. D. Competitive inhibitors bind outside the E active site; uncompetitive inhibitors bind to the E active site. E. Competitive inhibitors bind to the substrate (S); uncompetitive inhibitors bind to E, ES, and EP.
B. Competitive inhibitors bind E in the active site; uncompetitive inhibitors bind ES outside of the active site.
Explain why a strain of yeast with a defect in the enzyme alcohol dehydrogenase can grow well under aerobic conditions, but not under anaerobic conditions. A. The yeast strain needs to generate ethanol in order to stimulate the PFK-1 reaction when anaerobic. B. The yeast strain cannot oxidize NADH to generate NAD+ for the GAPDH reaction when anaerobic. C. The yeast strain uses CO2 to generate NAD+ when aerobic, but GAPDH needs NADH when anaerobic. D. The yeast strain grows well when aerobic because acetaldehyde is quickly converted to lactate. E. The yeast strain grows equally well under aerobic and anaerobic, but polyphenol is lethal to this strain.
B. The yeast strain cannot oxidize NADH to generate NAD+ for the GAPDH reaction when anaerobic.
What is the mechanism by which anti-apoptotic signaling blocks apoptotic signaling in the same cell? A. Activation of phosphorylation cascades that phosphorylate CASP8 to block its methylation activity. B. Transcriptional activation of genes encoding inhibitors of caspase enzyme activation. C. Inhibition of CASP3 activity by activation of CASP8 procatalytic activation. D. Transcriptional repression of CAPS8 and CASP3 gene expression to block enzyme synthesis
B. Transcriptional activation of genes encoding inhibitors of caspase enzyme activation.
Use the free energy values listed in the table on the crib sheet to answer these questions. a) Calculate the DGº' value for the combined reaction shown below. b) Calculate the DG value for this same combined reaction. c) Is the combined reaction favorable under steady-state conditions? 1 Glucose + 2 ATP --> 2 glyceraldehyde-3P + 2 ADP Answer options: A. a) +2.1 kJ/mol, b) +53.6 kJ/mol, c) no B. a) +2.1 kJ/mol, b) -53.6 kJ/mol, c) yes C. a) -53.6 kJ/mol, b) +2.1 kJ/mol, c) no D. a) +4.2 kJ/mol, b) -107.2 kJ/mol, c) yes E. a) -53.6 kJ/mol, b) -2.1 kJ/mol, c) yes
B. a) +2.1 kJ/mol, b) -53.6 kJ/mol, c) yes delta Gº' (kJ/mol) = (-16.7) +( +1.7) + (-14.2) + (+23.8) +(+7.5) kJ/mol = +2.1 kJ/mol delta G (kJ/mol) = (-33.9) +(-2.9) + (-18.8) + (-0.4) +(+2.4) kJ/mol = -53.6 kJ/mol YES, favorable
The alpha subunit of trimeric G proteins can function to _________________. A. regulate ion channels. B. activate adenylate cyclase. C. inhibit phosphodiesterase. D. inhibit phospholipase A.
B. activate adenylate cyclase.
Interaction of the glucocorticoid receptor with which protein prevents nuclear localization? A. NfkB transcription factor p50 B. heatshock protein 90 C. annexin 1 D. ubiquitin E. cyclooxygenase-2
B. heatshock protein 90
The function of the GTPase activity in the G-alpha subunit is to ______ A. produce GDP for activation of the GPCR signaling pathway B. inactivate the GPCR signaling pathway C. produce Pi for activation of the GPCR signaling pathway D. activate the GPCR signaling pathway
B. inactivate the GPCR signaling pathway
The function of the GTPase activity in the G-alpha subunit is to ______. A. produce GDP for activation of the GPCR signaling pathway. B. inactivate the GPCR signaling pathway. C. produce Pi for activation of the GPCR signaling pathway. D. activate the GPCR signaling pathway.
B. inactivate the GPCR signaling pathway.
After breakfast, _______ hormone levels are high and rates of metabolic fluxthrough _______ degradation and _______ are low. Before breakfast,_______ hormone levels are high and rates of metabolic flux through_______ and _______ synthesis are low. A. glucagon; glycogen; glycolysis; insulin; gluconeogenesis; glycogen B. insulin; glycogen; gluconeogenesis; glucagon; glycolysis; glycogen C. insulin; glycogen; glycolysis; glucagon; gluconeogenesis; glycogen D. glucagon; glycogen; gluconeogenesis; insulin; glycolysis; glycogen
B. insulin; glycogen; gluconeogenesis; glucagon; glycolysis; glycogen
Place the following steps in proper order: A. phosphorylation of RTK cytoplasmic tails B. activation of downstream signaling pathways C. ligand binding, receptor dimerization, and kinase activation D. protein binding to RTK phosphotyrosines and phosphorylation of target proteins Question options: B, C, A, D C, A, D, B A, B, C, D C, D, A, B C, B, A, D
C, A, D, B
Aspartate transcarbamoylase (ATCase) is (1) _________ regulated by(2) _________, which is a positive regulator and (3) _________, which is a negative regulator of enzyme activity. A. (1) catalytically, (2) ATP, (3) CTP B. (1) allosterically, (2) CTP, (3) ATP C. (1) allosterically, (2) ATP, (3) CTP D. (1) covalently, (2) ADP, (3) CDP
C. (1) allosterically, (2) ATP, (3) CTP
What is the actual change in free energy at 37ºC for the phosphoglycerate mutase reaction converting 3-PGA to 2-PGA in erythrocytes if after drinking a glass of orange juice the [3-PGA] = 8 mM and the [2-PGA] = 0.08 mM? The standard change in free energy for the reaction is +4.5 kJ/mol. A. -6.5 kJ/mol B. +16.3 kJ/mol C. -7.3 kJ/mol D. -16.3 kJ/mol E. +7.3 kJ/mol
C. -7.3 kJ/mol delta G = delta Gº' + RT ln [products] / [reactants] delta G = (+4.5 kJ/mol) + (8.3 x 10^-3 kJ/mol•K) • (310K) • (ln (8 x 10^-5 M)/(8 x 10^-3 M)) delta G = -7.3 kJ/mol
What are the three primary mechanisms by which nuclear receptors control physiological responses? A. 1) change in free energy, 2) steroid expression, 3) DNA accessibility B. 1) ligand bioavailability, 2) receptor dimerization, 3) DNA phosphorylation C. 1) ligand bioavailability, 2) receptor expression, 3) DNA accessibility D. 1) ligand degradation, 2) receptor phosphorylation, 3) DNA accessibility
C. 1) ligand bioavailability, 2) receptor expression, 3) DNA accessibility
Put the following nine signaling events in the correct order following epinephrine binding to b2 adrenergic receptors in liver cells, which increases blood glucose soon after you see a ghost on Halloween. Step 1 Epinephrine binds to the N-terminal domain of the receptor. __ GDP is exchanged for GTP in the G-alpha subunit. __ The G-alpha and G-beta/gamma subunits dissociate. __ PKA phosphorylates target proteins leading to glucose export __ The GDP-bound heterotrimeric G protein binds to the receptor. __ Cyclic AMP synthesis leads to 2nd messenger activation of PKA. __ The G-alpha subunit binds to activates adenylate cyclase. __ The PKA regulatory subunit dissociates from the catalytic subunit. __ A conformational change in the C-terminus of the receptor. Answer options: A. 1, 5, 4, 9, 3, 7, 2, 8, 6 B. 1, 4, 5, 3, 9, 7, 8, 6, 2 C. 1, 4, 5, 9, 3, 7, 6, 8, 2 D. 1, 4, 9, 5, 3, 6, 7, 8, 2 E. 1, 3, 5, 9, 4, 7, 6, 2, 8
C. 1, 4, 5, 9, 3, 7, 6, 8, 2
Which of the THREE statements explain why it makes sense that caspase enzymes likeCASP3 function as executioners in the cell death pathway? 1. Caspases have a dispensable cysteine residue in the active site that is often acetylated. 2. Caspases are catalytic enzymes and can do a lot of damage in a short period of time. 3. Caspases are able use H 2O as a substrate, which is totally unique to killer enzymes. 4. Caspases function as a pure homodimer, which provides a unique subunit organization. 5. Caspases have preferred cleavage sites and degrade key proteins to quickly kill cells. 6. Caspases need to be activated by cleavage and are stored in cells as inactive zymogens. Answer options: A. 2, 3, 4 B. 1, 2, 6 C. 2, 5, 6 D. 1, 3, 4 E. 2, 4, 5
C. 2, 5, 6
Put the following glycolytic reactions in the correct order. Only 8 of the 10 reactions in the glycolytic pathway are listed. Your answer should be the relative order of the 8 reactions listed here. ___Phosphorylation reaction converting a hexose monophosphate into a hexose bisphosphate. ___A substrate level phosphorylation reaction generating the ATP replacing the ATP investment in stage 1. ___Substrate level phosphorylation reaction generating a net yield in ATP for the glycolytic pathway. ___Phosphorylation reaction of a hexose sugar generating the compound C6 H13 O9 P. ___A redox reaction utilizing inorganic phosphate and the oxidized coenzyme NAD+ . ___An isomerization reaction converting an aldose sugar into a ketose sugar. ___Cleavage reaction converting a diphosphate sugar into two monophosphate metabolites. ___A dehydration reaction generating a product with DGº' of phosphate hydrolysis twice that of ATP. Answer options: A. 3, 7, 8, 1, 5, 2, 4, 6 B. 4, 6, 8, 1, 5, 2, 3, 7 C. 3, 6, 8, 1, 5, 2, 4, 7 D. 3, 6, 8, 1, 4, 2, 5, 7 E. 3, 6, 7, 1, 5, 2, 4, 8
C. 3, 6, 8, 1, 5, 2, 4, 7
Which of these are artificial sweeteners (Arts) and which are metabolized (Mtbs) by glycolysis? *image with question Answer options: A. Arts; 1, 4, Mtbs; 2, 3 B. Arts; 2, 3, Mtbs; 1, 4 C. Arts; 2, 4, Mtbs; 1, 3 D. Arts; 3, 4, Mtbs; 1, 2 E. Arts; 1, 3, Mtbs; 2, 4
C. Arts; 2, 4, Mtbs; 1, 3
The enzyme PDK1 and Akt are required for downstream signaling in the insulin receptorpathway. What is the upstream signaling event that is required for phosphorylation of Akt by PDK1? A. Conversion of phosphatidylinositol-3,4,5-trisphosphate to phosphatidylinositol-4,5-bisphosphate. B. Conversion of phosphatidylinositol-4,5-bisphosphate to inositol-1,4,5-trisphosphate and DAG. C. Conversion of phosphatidylinositol-4,5-bisphosphate to phosphatidylinositol-3,4,5-trisphosphate. D. Condensation of IP3 and PIP2 to form PIP3 and generate pleckstrin homology domain binding sites. E. Conversion of phosphatidylinositol-3,4,5-trisphosphate to phosphatidylinositol-1,2,3-trisphosphate
C. Conversion of phosphatidylinositol-4,5-bisphosphate to phosphatidylinositol-3,4,5-trisphosphate.
Regulation of metabolic flux is dependent on two primary factors, one of them is availability of substrates, what is the other primary factor? A. Value for the change in standard free energy under physiological conditions, it can be high or low. B. Enzyme localization as exemplified by tissue expression, subcellular location, and membrane insertion. C. Level of enzyme activity as exemplified by tissue localization, allosteric control, and protein synthesis. D. Degree of substrate reactivity exemplified by the level of phosphorylation and number of C=C bonds. E. If the valve is completely open then the flux is high, however if the valve is half-way closed, then 50%
C. Level of enzyme activity as exemplified by tissue localization, allosteric control, and protein synthesis.
The signaling pathways linking vision, smell, and taste to neuronal signaling have processes in common, but also have one distinct difference. Which statement below best describes that distinction? A. They each use a different type of receptor protein; GPCR, RTK and TNF classes of receptors. B. They each use GSa proteins as the upstream signal, but each GSa stimulates different target proteins. C. The second messenger in each of these signaling systems is distinct; GMP, cAMP, DAG/IP3. D. The hormone that stimulates each of these pathways is distinct; insulin, glucagon, epinephrine. E. There are no distinctions between these pathways in that all three pathways activate glucose export.
C. The second messenger in each of these signaling systems is distinct; GMP, cAMP, DAG/IP3.
What explains how two reactions in the glycolytic pathway (rxns 5 and 8),which have small positive change in actual free energy (∆G), still occur under physiological conditions. A. They are actually favorable reactions when considering that 37 ∘C is higher than 25 ∘C inside cells. B. They are not actually required for the glycolytic pathway because of side reactions that occur. C. They are coupled to three highly favorable glycolytic reactions, which result in high rates of metabolic flux. D. They are coupled to three highly favorable reactions, which all require the hydrolysis of ATP to from ADP+P
C. They are coupled to three highly favorable glycolytic reactions, which result in high rates of metabolic flux.
a) What is the genetic basis for fructose intolerance? b) Why would drinking a liter of Coca-Cola soda with 100 grams of high fructose corn syrup everyday cause liver damage in these individuals? A. a) Defect in the enzyme F-6P aldolase, b) Liver cells become deficient in GAP and DHAP and die. B. a) Defect in the enzyme hexokinase, b) Liver cells are killed by too much sugar, especially fructose. C. a) Defect in the enzyme F-1P aldolase, b) Liver cells become deficient in Pi and ATP and die. D. a) Defect in the enzyme F-1,6-BP aldolase, b) Liver cells become deficient in F-2,6-BP and die. E. a) Defect in the enzyme Fructokinase, b) Liver cells become deficient in NAD+ and ATP and die
C. a) Defect in the enzyme F-1P aldolase, b) Liver cells become deficient in Pi and ATP and die.
If a mutation occurred in SODD that prohibited its interaction with the DD of TNF receptor, the TNF receptor would A. no longer form a trimer. B. no longer be able to release TNF-α. C. bind TRADD, even in the absence of TNF-α. D. bind NFkB, even in the absence of TNF-α
C. bind TRADD, even in the absence of TNF-α.
We eat foods containing sucrose (table sugar), lactose (milk sugar), and cellobiose(disaccharide of cellulose in plants). How many net moles of ATP per mole disaccharide do humans generate from the disaccharides sucrose, lactose, and cellobiose using the glycolytic pathway? A. sucrose: 2 ATP; lactose: 4 ATP; cellobiose: 2 ATP B. sucrose: 6 ATP; lactose: 2 ATP; cellobiose: 0 ATP C. sucrose: 4 ATP; lactose: 4 ATP; cellobiose: 0 ATP D. sucrose: 4 ATP; lactose: 2 ATP; cellobiose: 2 ATP E. sucrose: 2 ATP; lactose: 2 ATP; cellobiose: 0 ATP
C. sucrose: 4 ATP; lactose: 4 ATP; cellobiose: 0 ATP
The following drawing is a schematic representation of a dimerized receptor tyrosine kinase. Which arrow is pointing to the location of the kinase function? A. region A B. region B C. region C D. region D
D. region D
Which one of the following molecules can function as a second messenger? cyclic UMP adenylate cyclase magnesium calcium G-alpha subunit
Calcium
Caspases (cysteine-aspartate proteases) function as "executioners" in the cell death pathway. Choose three reasons why it makes sense that they function in this role rather than some other biomolecule. Select 3 correct answer(s) Question options: Caspases have preferred substrate recognition sites for cleavage, and therefore can preferentially degrade other proteins Caspases have longer stability in the cell than most proteins, since they are readily refolded by chaperones. Caspases must be activated by proteolytic cleavage to convert the inactive zymogen to the active form-this provides a means to control caspase activity by initiating the cleavage reaction. Caspases are rapidly produced by the ribosome after the signal for cell death is received. Caspases are enzymes that function catalytically and therefore can do a lot of damage in a very short amount of time
Caspases have preferred substrate recognition sites for cleavage, and therefore can preferentially degrade other proteins Caspases must be activated by proteolytic cleavage to convert the inactive zymogen to the active form-this provides a means to control caspase activity by initiating the cleavage reaction. Caspases are enzymes that function catalytically and therefore can do a lot of damage in a very short amount of time
Why are catabolic pathways are always paired with anabolic pathways? Question options: Both require redox reactions to operate. Both require ATP to operate. Catabolic pathways synthesize molecules and anabolic pathways degrade molecules. Catabolic pathways degrade molecules and anabolic pathways synthesize molecules.
Catabolic pathways degrade molecules and anabolic pathways synthesize molecules.
The TNF signaling pathway stimulates both an apoptosis and a cell survival pathway in the same cell. What molecular mechanism determines whether the cell survives or dies? Choose ONE correct answer. Question options: Cell death or survival in a TNF receptor stimulated cell is determined by the number of times the TNF receptor is stimulated. The default state is cell survival, however, if the TNF receptor is stimulated multiple times, then the overall signal for cell death will predominate. Cell death or survival in a TNF receptor stimulated cell is determined by the signals received from neighboring cells. If the neighboring cell is secreting "survival" stimulants, then the TNF receptor stimulated cell will also survive. Cell death or survival in a TNF receptor stimulated cell is determined by the relative amounts of TRADD protein produced by TNF signaling. Cell death or survival in a TNF receptor stimulated cell is determined by the relative expression level of downstream signaling proteins in the proapoptotic and anti-apoptotic pathways.
Cell death or survival in a TNF receptor stimulated cell is determined by the relative expression level of downstream signaling proteins in the proapoptotic and anti-apoptotic pathways.
If the standard free energy change for the reaction converting A to B is unfavorable, how can this reaction proceed in the forward direction under cellular conditions? Select TWO correct answers. Select 2 correct answer(s) Question options: Decrease the cellular concentrations of A until the actual free energy change is now negative. Couple the reaction to an exergonic reaction such as ATP hydrolysis. Decrease the cellular concentration of B until the actual free energy change is now negative. The reaction cannot proceed in the forward direction under any circumstances since the standard free energy change is positive.
Couple the reaction to an exergonic reaction such as ATP hydrolysis. Decrease the cellular concentration of B until the actual free energy change is now negative.
Below is shown the structure of a homodimer of the GR DNA-binding domain. Four areas are highlighted. Which is most likely to interact with DNA? D B A C A and C
D
Aspartate transcarbamoylase (ATCase) is (1) __________ regulated by ATP, which is a(2)________ regulator, and by CTP which binds to the (3)_______ subunit of ATCase and shifts the conformational equilibrium to the (4) ______ T state. CTP regulation of ATCase is called (5)_________. A. 1) covalently 2) positive, 3) regulatory, 4) active, 5) feedback inhibition B. 1) allosterically, 2) negative, 3) regulatory, 4) inactive, 5) feedforward activation C. 1) irreversibly, 2) positive, 3) catalytic, 4) inactive, 5) feedback inhibition D. 1) allosterically, 2) positive, 3) regulatory, 4) inactive, 5) feedback inhibition E. 1) allosterically, 2) negative, 3) catalytic, 4) active, 5) feedforward inhibition
D. 1) allosterically, 2) positive, 3) regulatory, 4) inactive, 5) feedback inhibition
(1)_______ is a first messenger in the form of gas, and (2)________ is a metabolite of the amino acid tyrosine that activates glucose export from liver cells. The second messenger (3)______ is produced by guanylate cyclase, whereas (4)________ and (5)_______ are produced by phospholipase C. A. 1) ammonium oxide, 2) insulin, 3) cyclic AMP, 4) calcium, 5) inositol- 4,5-trisphosphate B. 1) nitric oxide, 2) epinephrine, 3) cyclic GMP, 4) diacylglycerol, 5) inositol-3,4,5-trisphosphate C. 1) oxygen, 2) epinephrine, 3) cyclic GMP, 4) 3-phosphoglycerate, 5) inositol-1,4,5-trisphosphate D. 1) nitric oxide, 2) epinephrine, 3) cyclic GMP, 4) diacylglycerol, 5) inositol-1,4,5-trisphosphate E. 1) nitric oxide, 2) glucagon, 3) cyclic AMP, 4) diacylglycerol, 5) inositol-3,4,5-trisphosphate
D. 1) nitric oxide, 2) epinephrine, 3) cyclic GMP, 4) diacylglycerol, 5) inositol-1,4,5-trisphosphate
Match the biochemical process in list A with the type of enzymatic regulation in list B with regard to the control of glutamine synthetase activity by the enzymesglutamine synthetase adenylyltransferase and control of glutamine synthetaseadenylyltransferase activity by uridylyltransferase. Write your answers in column A from a→e and record. Choices in column B can be used once, more than once, or none at all. Column A ______ a. binding of ATP ______b. adenylylation ______c. binding of glutamine ______d. uridylylation ______e. binding of Pi Column B 1. allosteric control 2. subunit association 3. proteolytic cleavage 4. covalent modification Answer options: A. 4, 4, 3, 4, 2 B. 2, 4, 3, 4, 1 C. 4, 4, 1, 4, 3 D. 1, 4, 1, 4, 1 E. 1, 2, 4, 3, 1
D. 1, 4, 1, 4, 1
What is the functional difference between a first messenger and a second messenger in cell signaling pathways? A. 1st messengers bind to upstream receptors; 2nd messengers bind to downstream receptors. B. 1st messengers bind to receptors; 2nd messengers are activated by downstream signaling events. C. 1st messengers bind to membranes; 2nd messengers are activated by upstream signaling events. D. 1st messengers bind to receptors; 2nd messengers are activated by upstream signaling events.
D. 1st messengers bind to receptors; 2nd messengers are activated by upstream signaling events.
If there were a technique that allowed one to isolate EGFR1 and EGFR2 at discrete steps along their activation pathway, which of the following would be isolated? A. A monomer of EGFR2 that contains phosphotyrosines. B. A dimer in which EGFR1 contains phosphotyrosines but EGFR2 does not. C. A monomer of EGFR1 that contains phosphotyrosines. D. A dimer in which EGFR2 contains phosphotyrosines but EGFR1 does not.
D. A dimer in which EGFR2 contains phosphotyrosines but EGFR1 does not.
Signaling activity of G proteins is controlled by GTPase activating proteins (GAPs) and Guanine exchange factors (GEFs). What are the mechanisms by which GAPs and GEFs control G proteins? A. GAPs stimulate G proteins by blocking GTP hydrolysis; GEFs inhibit G proteins by stimulating GTP-GDP exchange. B. GAPs inhibit G proteins by stimulating GDP-GTP exchange; GEFs activate G proteins by stimulating GTP hydrolysis. C. GEFs inhibit G proteins by stimulating GTP hydrolysis; GAPs activate G proteins by stimulating GDP-GTP exchange. D. GAPs inhibit G proteins by stimulating GTP hydrolysis; GEFs activate G proteins by stimulating GDP-GTP exchange.
D. GAPs inhibit G proteins by stimulating GTP hydrolysis; GEFs activate G proteins by stimulating GDP-GTP exchange.
How can defects in the epidermal growth factor receptor signaling pathway lead to cancer? A. Loss-of-function mutations in the GRB2 protein that prevent inhibition of the EGFR signaling pathway. B. Gain-of-function mutations in the GTPase region of the GSa protein that stimulates cAMP production. C. Loss-of-function mutations in the tyrosine kinase region of the EGFR protein leading to high Ras activity. D. Gain-of-function mutations in the GTPase region of Ras protein that prevents turning off of the pathway. E. Gain-of-function mutations in the Ras protein that results in increased stimulation by GAP proteins
D. Gain-of-function mutations in the GTPase region of Ras protein that prevents turning off of the pathway.
Which subunit is responsible for dissociation of the heterotrimeric G protein? Choose one: A. Gβγ B. Gγ C. Gβ D. Gα
D. Gα
Below is shown a short sequence of a protein. Which of the following protein subdomains would most likely bind to this sequence? Hint: you need to look carefully at the structure in the figure and determine what domain binds to this structure. A. SHP B. SH2a C. SH2 SH3
D. SH3
What two pathways require enzymatic modification of phosphatidylinositol-4,5-bisphosphate? A. The MAPK pathway that uses PIP3 to generate DAG and IPs; and PI-3K to activate PTEN signaling. B. The PI-3K pathway that uses PIP2 as a docking site for SH3 domains; and phospholipase C signaling. C. The phospholipase C pathway that uses PIP3 as a docking site for PH domains; and GPCR signaling. D. The PI-3K pathway that uses PIP3 as a docking site for PH domains; and phospholipase C signaling. E. The TNF pathway that uses PIP2 as a docking site for SH2 domains; and protein kinase C signaling.
D. The PI-3K pathway that uses PIP3 as a docking site for PH domains; and phospholipase C signaling.
What is the Warburg effect and why is it an advantage to cancer cells? A. The Warburg effect refers to high levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce pyruvate, which provides a growth advantage. B. The Warburg effect refers to low levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce glucose, which provides a growth advantage. C. The Warburg effect refers to high levels of glycolytic flux to compensate for tumor hyperoxia conditions and to produce lactate, which provides a growth advantage. D. The Warburg effect refers to high levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce lactate, which provides a growth advantage. E. The Warburg effect is related to the way that cancer cells avoid the immune system by producing enzymes that degrade antibodies and prevent an immune response.
D. The Warburg effect refers to high levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce lactate, which provides a growth advantage.
A mutation in an enzyme at residue 44 blocks its ability to be regulated by phosphorylation. Which mutation to the right may cause this loss of regulation? The overall structure is not altered by the mutation and multiple kinases can phosphorylate residue 44 A. Tyr-44-Thr B. Thr-44-Ser C. Ser-44-Tyr D. Tyr-44-Trp E. Ser-44-Thr
D. Tyr-44-Trp
Which of the following proteins is regulated by autocleavage to produce an activated enzyme? A. catalase B. chymotrypsin C. glycogen phosphorylase D. pepsinogen E. aspartate transcarbamoylase
D. pepsinogen
Under conditions of high (1)_______ and elevated levels of a-ketoglutarate, the (2) ______activity of uridylyltransferase is (3)_______, resulting in uridylylation of glutamine synthetase (4)________and activation of its (5)________ function, which (6)_______ and activates glutamine synthetase. A. 1) glutamine, 2) uridylylation, 3) stimulation, 4) adenylyltransferase, 5) uridylylating, 6) uridylates B. 1) ATP, 2) adenylylation, 3) stimulation, 4) uridylyltransferase, 5) deadenylylating, 6) deadenylates C. 1) Pi , 2) uridylylation, 3) inhibited, 4) adenylyltransferase, 5) deadenylylating, 6) uridylylates D. 1) glutamine, 2) uridylylation, 3) stimulation, 4) adenylyltransferase, 5) deadenylylating, 6) deadenylates E. 1) ATP, 2) uridylylation, 3) stimulation, 4) adenylyltransferase, 5) deadenylylating, 6) deadenylates
E. 1) ATP, 2) uridylylation, 3) stimulation, 4) adenylyltransferase, 5) deadenylylating, 6) deadenylates
Which of the THREE statements below explain why it makes sense that caspase enzymes like CASP3 function as executioners in the cell death pathway? 1. Caspases have preferred cleavage sites and degrade key proteins to quickly kill cells. 2. Caspases are catalytic enzymes and can do a lot of damage in a short period of time. 3. Caspases need to be activated by cleavage and are easily stored in cells as inactive zymogens. 4. Caspases function as a pure homodimer, which provides a unique subunit organization. 5. Caspases have a dispensable cysteine residue in the active site that is often acetylated. 6. Caspases are able use H2 O as a substrate, which is totally unique to killer enzymes. Answer options: A. 2, 3, 4 B. 1, 2, 6 C. 2, 5, 6 D. 1, 3, 4 E. 1, 2, 3
E. 1, 2, 3
Put the following steps in the correct order to describe the process of signal transduction. List the numbers from a--> f that represent the correct order. (a) ______ downstream signaling activation (b)______ second messenger synthesis (c)______ upstream signaling activation (d) _____ first messenger binding (e)______ target protein response (f)______ receptor protein activation A. 5, 3, 4, 1, 6, 2 B. 6, 4, 3, 1, 5, 2 C. 5, 4, 2, 1, 6, 3 D. 4, 5, 3, 1, 6, 2 E. 5, 4, 3, 1, 6, 2
E. 5, 4, 3, 1, 6, 2
Put the following ten signaling events in the correct order following glucagon binding toglucagon receptors in liver cells, which leads to increased blood glucose levels in between meals. ___ Cyclic AMP synthesis leads to 2 nd messenger activation of PKA. ___Glucagon binds to the N-terminal domain of the receptor ___The PKA regulatory subunit dissociates from the catalytic subunit. ___Receptor binding stimulates GDP exchange for GTP in Gs a subunit. ___PKA phosphorylates target proteins leading to liver glucose export. ___The GDP-bound heterotrimeric Gs abg protein binds to the receptor. ___A conformational change occurs in the C-terminus of the receptor. ___The Gs a subunit binds to activates the enzyme adenylate cyclase. ___ Blood glucose levels increase providing an energy source for the brain. ___The Gs a and G bg subunits dissociate and diffuse through the membrane. Answer options: A. 8, 1, 7, 4, 9, 3, 2, 5, 10, 6 B. 7, 1, 8, 3, 10, 4, 2, 6, 9, 5 C. 6, 1, 8, 4, 9, 3, 2, 5, 10, 7 D. 7, 2, 8, 3, 9, 4, 1, 6, 10, 5 E. 7, 1, 8, 4, 9, 3, 2, 6, 10, 5
E. 7, 1, 8, 4, 9, 3, 2, 6, 10, 5
Metabolic flux is regulated by both availability of substrates and level of enzyme activity. Match the mechanism by which enzyme activity is regulated (A, B, C) with a specific example of this type of regulation (1, 2, 3, 4, 5, 6). Each mechanism is associated with two specific examples. Mechanism of Regulation: A. Catalytic activity B. Compartmentation C. Enzyme levels Example of Regulation: 1. covalent modification 2. protein synthesis 3. tissue localization 4. subcellular localization 5. allosteric control 6. gene transcription Answer Options: A. A:1,4; B:3,5; C:2,6 B. A:1,5; B:3,6; C:2,4 C. A:1,2; B:5,4; C:2,6 D. A:2,5; B:3,4; C:1,6 E. A:1,5; B:3,4; C:2,6
E. A:1,5; B:3,4; C:2,6
What is the Warburg effect and why is it an advantage to cancer cells? A. The Warburg effect is related to the way that cancer cells activate the immune system using allosteric molecules similar to how quarterbacks direct wide receivers in football. B. The Warburg effect refers low levels of glycolytic flux to compensate for tumor hypoxia conditions and to produce lactate, which provides a growth advantage. C. The Warburg effect refers high levels of gluconeogenic flux to compensate for tumor hypoxic conditions and to produce GAPDH, which provides a growth advantage. D. The Warburg effect refers high levels of anabolic metabolism to compensate for tumor hyperoxia conditions and to produce lactate, which provides a growth advantage. E. The Warburg effect refers high levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce lactate, which provides a growth advantage.
E. The Warburg effect refers high levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce lactate, which provides a growth advantage.
Muscle relaxation in response to appropriate neuronal input, which is followed by nitric oxide signaling, would be further increased if a(n) __________ were provided to the patient in the form of a pill. A. inhibitor of protein kinase A B. stimulator of cGMP phosphodiesterase C. stimulator of guanylate cyclase D. inhibitor of acetylcholine esterase E. inhibitor of cGMP phosphodiesterase
E. inhibitor of cGMP phosphodiesterase
A child experienced muscle fatigue whenever she vigorously ran in the playground, but not if she walked to school. Her physician correctly diagnosed her muscle fatigue as a result of exercise-induced ATP depletion in muscle cells. What defective enzyme causes reduced ATP in her fatigued muscle cells? A. hexokinase B. pyruvate kinase C. phosphofructokinase-1 D. aldolase E. lactate dehydrogenase
E. lactate dehydrogenase
What are the three mechanisms by which nuclear receptors control physiological responses? A. ligand methylation, DNA accessibility, receptor phosphorylation B. ligand accessibility, RNA bioavailability, receptor expression C. ligand bioavailability, catalytic activity, hormone degradation D. enzyme activity, DNA accessibility, receptor expression E. ligand bioavailability, DNA accessibility, receptor expression
E. ligand bioavailability, DNA accessibility, receptor expression
Signaling activity of G proteins is controlled by GTPase activating proteins (GAPs) and Guanine exchange factors (GEFs). What are the mechanisms by which GAPs and GEFs control G proteins? GAPs inhibit G proteins by stimulating GDP-GTP exchange; GEFs activate G proteins by stimulating GTP hydrolysis. GAPs stimulate G proteins by blocking GTP hydrolysis; GEFs inhibit G proteins by stimulating GTP-GDP exchange. GEFs inhibit G proteins by stimulating GTP hydrolysis; GAPs activate G proteins by stimulating GDP-GTP exchange. GAPs inhibit G proteins by stimulating GTP hydrolysis; GEFs activate G proteins by stimulating GDP-GTP exchange.
GAPs inhibit G proteins by stimulating GTP hydrolysis; GEFs activate G proteins by stimulating GDP-GTP exchange.
If protein kinase A is activated in a liver cell in response to epinephrine binding to the 2-adrenergic receptor, which of the following will result? Glycogen synthesis will be turned on. Glycogen degradation will be turned on. Glucose synthesis will be turned off. GLUT1 expression will be upregulated
Glycogen degradation will be turned on.
A pH/enzyme activity curve is shown above. Which of the following pairs of amino acids would be likely candidates as catalytic groups? *graph is a normal bell curve with middle over pH 7 His and Lys Glu and Lys Asp and His His and Cys
His and Cys
Rhodopsin is a well-characterized G protein-coupled receptor that binds retinal. Absorption of light by the retinal molecule allows important neuronal signals to be sent to your brain that enable vision. If you look at a bright light and quickly close your eyes, the retinal molecules quickly turn off that visual signal to the brain. Which of the following do you think is the best explanation for such an observation? Choose one: Inhibition of the visual signal requires GTPase activating proteins (GAP) binding and GTP hydrolysis. The G proteins, once activated, are separated into α and βγ subunits and this terminates the signal. Guanine nucleotide exchange factors, or GEFs, are slow to respond in order to reactivate the G proteins. Termination of the visual signal is completely dependent on removal of rhodopsin from the plasma membrane.
Inhibition of the visual signal requires GTPase activating proteins (GAP) binding and GTP hydrolysis
What is the function of growth factor receptor-bound 2 (GRB2) protein in RTK signaling? Question options: It is a tyrosine kinase protein that phosphorylates arginine residues in PI-3K and in phospholipase C. It is an adaptor protein that binds to phosphoserine residues in IRSs and to GEF proteins like PI-3K. It is an adaptor protein that binds to phosphotyrosine residues in RTKs and also binds to GEF proteins. It is an adaptor protein that binds to G proteins like Ras and GSa and also to MAPK, Raf, and ERK.
It is an adaptor protein that binds to phosphotyrosine residues in RTKs and also binds to GEF proteins.
Which of the following is true of procaspase 8? Question options: It is a kinase. It can be activated by phophorylation. It is proteolytically inactive. It can cleave caspase 3.
It is proteolytically inactive.
Which of the following statements accurately describe receptor tyrosine kinases (RTKs)? Select the three true statements. Select 3 correct answer(s) Question options: The intracellular domain has phosphatase domains. Ligand binding is required for autophosphorylation (cross-phosphorylation). A ligand binds to the extracellular domain. The receptor contains seven alpha helices that span the membrane. RTKs are dimeric in the presence of ligand.
Ligand binding is required for autophosphorylation (cross-phosphorylation). A ligand binds to the extracellular domain. RTKs are dimeric in the presence of ligand.
An enzyme undergoes a mutation that causes it to lose the ability to be regulated via phosphorylation. Which of the following mutations may lead to this loss of regulation? Assume that the overall structure is not altered by the mutation and multiple kinases can phosphorylate the wild-type protein. Thr --> Ser Ser --> Phe Ser --> Tyr Tyr --> Ser
Ser --> Phe
When ATCase is in the __________ state it indicates that ____________ is bound, and that ATCase is ______________ regulated. R; ATP; down T; CTP; down T; ATP; up R; CTP; up
T; CTP; down
What is the function of the GTPase activity in G proteins? The GTPase synthesize cyclic GMP to regulate downstream signals. The GTPase stimulates GDP to GTP exchange to activate signaling. The GTPase cleaves GTP to generate GDP and inactivate signaling. The GTPase cleaves GTP to generate GDP and activate signaling.
The GTPase cleaves GTP to generate GDP and inactivate signaling.
Put the following steps of the G protein cycle into the correct order. ____Dissociation of G-alpha and G-beta/gamma from a GPCR ____Ligand stimulation of the GEF function of a GPCR ____Reassociation of the heterotrimeric G complex with a GPCR ____GAPs stimulate the GTPase activity of G-alpha
__2__Dissociation of G-alpha and G-beta/gamma from a GPCR __1__Ligand stimulation of the GEF function of a GPCR __4__Reassociation of the heterotrimeric G complex with a GPCR __3__GAPs stimulate the GTPase activity of G-alpha
The second messenger cyclic AMP (cAMP) is synthesized from ATP by the activity of the enzyme adenylate cyclase. Cyclic AMP, in turn, activates proteins kinase A (PKA), which is responsible for most of the effects of cAMP within the cell. Determine the correct steps in the activation of PKA, and then number them in the correct order (1-5), starting after the adenylyl cyclase reaction. ____Two cAMP molecules bind to each PKA regulatory subunit ____The regulatory subunits move out of the active sites of the catalytic subunits, and the R2C2 complex dissociates. ____Each regulatory subunit is activated as the two cAMP molecules are released. ____Cytosolic cAMP concentration increases. ____The free catalytic subunits interact with proteins to phosphorylate Ser or Thr residues.
__2__Two cAMP molecules bind to each PKA regulatory subunit __3__The regulatory subunits move out of the active sites of the catalytic subunits, and the R2C2 complex dissociates. __5__Each regulatory subunit is activated as the two cAMP molecules are released. __1__Cytosolic cAMP concentration increases. __4__The free catalytic subunits interact with proteins to phosphorylate Ser or Thr residues.
The phosphoinositide-3 kinase (PI-3K) pathway is activated by insulin signaling in liver cells. Number the following statements 1-10 to order the sequence of events that lead to glucose uptake and glycogen synthesis in response to insulin signaling. The abbreviations for each signaling component of the pathway are defined in Section 8.3 of the textbook. _____Akt is phosphorylated and activated by the PDK1 serine/threonine kinase activity. _____PI-3K binds to phosphotyrosines on IRS proteins via SH2 domains _____IRS proteins bind to phosphotyrosines in the insulin receptor via PTB domains. ____Akt dissociates from PIP3 and phosphorylates downstream target proteins. ____PI-3K phosphorylates PIP2 to generate PIP3. ____Insulin binds to the insulin receptor and activates its intrinsic kinase activity. ____Increased rates of glucose uptake and glycogen synthesis lower blood glucose. ____Insulin receptor phosphorylates IRS proteins on tyrosine residues. ____PDK1 and Akt bind to PIP3 in the plasma membrane via PH domains. ____Insulin receptor autophosphorylates tyrosine residues in the cytoplasmic tail.
__8__Akt is phosphorylated and activated by the PDK1 serine/threonine kinase activity. __5__PI-3K binds to phosphotyrosines on IRS proteins via SH2 domains __3__IRS proteins bind to phosphotyrosines in the insulin receptor via PTB domains. __9__Akt dissociates from PIP3 and phosphorylates downstream target proteins. __6__PI-3K phosphorylates PIP2 to generate PIP3. __1__Insulin binds to the insulin receptor and activates its intrinsic kinase activity. __10__Increased rates of glucose uptake and glycogen synthesis lower blood glucose. __4__Insulin receptor phosphorylates IRS proteins on tyrosine residues. __7__PDK1 and Akt bind to PIP3 in the plasma membrane via PH domains. __2__Insulin receptor autophosphorylates tyrosine residues in the cytoplasmic tail.
A ligand binds to a transmembrane protein, which causes a conformational change in the protein that is detected by an intracellular protein. The intracellular protein is an enzyme that adds phosphate groups to target proteins. The phosphorylated proteins cause a physiological change within the cell. This process is an example of __________________. homeostasis. a metabolic pathway. an allosteric inhibition pathway. a signal transduction pathway.
a signal transduction pathway.
Procathepsin B is a lysosomal protease that is first translated as a proenzyme. On autocleavage it is fully activated. Procathepsin B is ________________. Question options: a zymogen. an allosteric enzyme. in the T state after autocleavage. inactive at low pH.
a zymogen.
If a mutation occurred in SODD that prohibited its interaction with the DD of TNF receptor, the TNF receptor would___________________. Question options: no longer form a trimer. bind TRADD, even in the absence of TNF-α. bind NFκB, even in the absence of TNF-α. no longer be able to release TNF-α. bind CASP 8 directly.
bind TRADD, even in the absence of TNF-α.
Which one of the following molecules can function as a second messenger? A. calcium B. cyclic UMP C. magnesium D. adenylate cyclase E. G-alpha subunit
calcium
The common structural pattern that is a distinguishing characteristic specific to all G-protein-coupled receptors is that they __________________. contain seven transmembrane helices. are transmembrane proteins. are only active when pairs of receptors dimerize. have a kinase domain on the intracellular side of the plasma membrane.
contain seven transmembrane helices
Which of the following choices below includes only first messenger signaling molecules? Ca2+, testosterone, protein kinase A cortisol, insulin, prostaglandins cytochrome c, insulin, estrogen receptor nitric oxide, estradiol, heme insulin, glucagon, glucose
cortisol, insulin, prostaglandins
Caspase 3 is responsible for_______________. Question options: activating caspase 8. dephosphorylating FasL. phosphorylating Fas. degrading key regulatory molecules.
degrading key regulatory molecules.
For some diseases like cancer, therapeutic interventions targeting small G protein signaling pathways could be beneficial, especially those interventions that inhibit Ras signaling since, in many cancers, Ras is constitutively active, meaning it is always on. Which of the following might be the best approach to inhibiting growth and division of cancer cells expressing overactive Ras? Choose one: increasing MAP kinase activity inhibiting Raf activity increasing GRB2 activity inhibiting receptor tyrosine kinases
inhibiting Raf activity
Which protein in the insulin receptor signaling pathway is capable of autophosphorylation? Question options: insulin receptor (IR) insulin receptor substrate (IRS) phosphatase and tensin homolog (PTEN) phosphatidylinositide 3-kinase (PI-3K)
insulin receptor (IR)
Which of the following are characteristics of allosteric enzymes like ATCase? Choose the THREE that apply. Allosteric enzymes: interconvert between a more active form and less active form. may have binding sites for regulatory molecules that are separate from active sites. tend to have a sigmoidal (S-shaped) curve of V0 vs. [S]. are generally small, single-subunit proteins. conform to Michaelis-Menten kinetics
interconvert between a more active form and less active form. may have binding sites for regulatory molecules that are separate from active sites. tend to have a sigmoidal (S-shaped) curve of V0 vs. [S].
Acetylcholinesterase is an important enzyme in the nervous system. Acetylcholinesterase activity is blocked by the nerve agent sarin gas, which forms a covalent bond with a Ser in the active site of the enzyme. Sarin gas is a(n) irreversible inhibitor. competitive inhibitor. allosteric effector. allosteric activator.
irreversible inhibitor.
Below is the molecular structure of a single bovine -arrestin subunit. Two locations are indicated. What is most likely to interact with the protein at these locations? GTP-bound Galpha phosphorylated GPCR protein kinase A beta ARK dephosphorylated GPCR
phosphorylated GPCR
If GRB2 were truncated so that the N-terminal domain was missing, the truncated protein would be unable to bind the_________________. Question options: proline-rich sequence of the SOS protein. phosphorylated Tyr of the SOS protein. phosphorylated Tyr of the RTK substrate. protein-rich sequence of the RTK substrate.
proline-rich sequence of the SOS protein.
The figure below shows a membrane-associated multi-enzyme complex. Reaction intermediates in this enzyme complex are used effectively because they__________. diffuse through the membrane to increase concentration gradient. combined to decrease the value of the mass action ratio Q. quickly channel from one enzyme to the next in coupled reactions. result in coupled reactions that have a positive delta Gº' value.
quickly channel from one enzyme to the next in coupled reactions.
A mutation causes a cell to divide uncontrollably. Analysis of the cell shows that both copies of the gene must have the mutation. From this information, it can be determined that the mutation is ______________. Question options: in a tumor suppressor gene. recessive. dominant. in a gene coding a kinase. a missense mutation.
recessive.
Binding of first messengers to G protein-coupled receptors results in ___________. stimulation of GTPase activity in the GPCR cytoplasmic tail. dimerization of GPCRs to form an active receptor complex. activation of tyrosine kinase activity in the GPCR cytoplasmic tail recruitment of heterotrimeric G proteins to the GPCR cytoplasmic tail.
recruitment of heterotrimeric G proteins to the GPCR cytoplasmic tail.
For the following reaction A→ B, if at equilibrium delta Gº'> 0, what can be said about the directionality of the reaction? Question options: strongly favored in both directions Not enough information is given. strongly favored in the reverse direction strongly favored in the forward direction
strongly favored in the reverse direction
