BIOC 384 Exam 3 All Questions

List three ways in which flux is controlled through glycolysis. regulation of glucokinase, regulation of fructokinase, and number of intermediates regulation of glucokinase, regulation of PFK-1, and concentration of glucose regulation of aldolase, regulation of PFK-1, and supply and demand of intermediates regulation of glucokinase, regulation of PFK-1, and supply and demand of intermediates

regulation of glucokinase, regulation of PFK-1, and supply and demand of intermediates

If blood glucose levels are elevated, the net effect of activating glucokinase in pancreatic beta cells is _____________. stimulating the production of hexokinase in liver cells. inhibiting glycolysis in liver cells. stimulating the release of insulin from pancreatic cells. inhibiting the production of 2,3-BPG in red blood cells.

stimulating the release of insulin from pancreatic cells.

When the regulatory subunit of PKA is bound to the catalytic subunit of PKA_____________. the catalytic subunit is inactive. the catalytic subunit is active. it forms a heterotrimeric complex. the pseudo substrate is phosphorylated. it cannot bind to ATP.

the catalytic subunit is inactive.

2-phosphoglycerate(2PG) is converted to phosphoenolpyruvate (PEP) by the enzyme enolase. The standard free energy change (delta Go') for this reaction is +1.7 kJ/mol. If the cellular concentrations are 2PG = 0.5 mM and PEP = 0.1 mM, what is the actual free energy change (delta G) at 37 C for the reaction 2PG ↔ PEP? +4146.4 kJ/mol -2.4 kJ/mol +2.4 kJ/mol 5.8 kJ/mol -4146.4 kJ/mol -5.8 kJ/mol

-2.4 kJ/mol

Auto-brewery syndrome in the human intestine mimics the process of home brew fermentation to produce beer. Put the following biochemical steps in order that are required to make a bottle of home brew beer. __Incubate live yeast under optimal aerobic conditions for 5 days. __Decant mixture into air tight container and add a small amount of pure cane sugar. __Disrupt the seed cell wall to release catabolic enzymes and incubate with water to produce glucose. __Allow carbonation to occur in the airtight container for 2 weeks. __Germinate grain to activate enzymes that will be needed to convert starch to glucose. __Incubate live yeast under optimal anaerobic conditions for 4 weeks. __Boil the grain mixture in the presence of plant parts to release flavor molecules. __Remove liquid from airtight container and expose to gustatory GPCRs to activate neurons.

1.Germinate grain to activate enzymes that will be needed to convert starch to glucose. 2.Disrupt the seed cell wall to release catabolic enzymes and incubate with water to produce glucose. 3.Boil the grain mixture in the presence of plant parts to release flavor molecules. 4.Incubate live yeast under optimal aerobic conditions for 5 days. 5.Incubate live yeast under optimal anaerobic conditions for 4 weeks. 6.Decant mixture into air tight container and add a small amount of pure cane sugar. 7.Allow carbonation to occur in the airtight container for 2 weeks. 8.Remove liquid from airtight container and expose to gustatory GPCRs to activate neurons.

Predict how oxygen saturation of hemoglobin would be affected in an individual with a defective hexokinase. 2,3-BPG levels would be reduced and oxygen binding decreased. 2,3-BPG levels would be reduced and oxygen binding increased. 2,3-BPG levels would be elevated and oxygen binding decreased. 2,3-BPG levels would be elevated and oxygen binding increased.

2,3-BPG levels would be reduced and oxygen binding increased.

Which statement explains why glucose phosphorylation could not occur without ATP investment? A. Without ATP investment, one or both of the substrates would need to exceed the solvent capacity of the cell for glucose phosphorylation to occur. B. Without ATP investment it would be impossible to regulate the entry of glucose into glycolysis. C. Without ATP investment, glucose would not become "trapped" in the cell and could easily be transported out as blood glucose levels decrease. This transport would reduce the amount of glucose available for some organs. D. Without ATP investment in stage I of glycolysis, the concentration of ATP would become too high and would inhibit phosphofructokinase, leading to inhibition of the entire glycolytic pathway.

A. Without ATP investment, one or both of the substrates would need to exceed the solvent capacity of the cell for glucose phosphorylation to occur. Under standard conditions, the reaction has a large, positive ΔG˚. Without ATP, this reaction would require a phosphate or glucose concentration that would exceed the solvent capacity of the cell in order for the reaction to become spontaneous.

The reaction catalyzed by phosphofructokinase-1 can be activated and inhibited by a number of allosteric factors. Sort the allosteric effectors listed below to indicate if they activate or inhibit this reaction. ATP citrate fructose-2,6-bisphosphate ADP AMP

Active: fructose-2,6-bisphosphate ADP AMP Inhibit: ATP citrate

Given the potential disadvantage caused by the synthesis of fructose-1-phosphate in a liver cell, why is it that an enzyme capable of catalyzing a reaction to convert this form of fructose into glucose has not evolved in a manner similar to the reaction that converts galactose-1-phosphate into glucose-1-phosphate? A. Glucose and galactose can be interconverted because they are epimers; it is not possible to convert a phosphorylated aldose to a ketose. B. C1 on fructose-1-phosphate cannot participate in an isomerization reaction because it is phosphorylated. C. UDP-glucose and UDP-galactose are both required for the conversion of galactose-1-phosphate to glucose-1-phosphate. No UDP-fructose exists, so this same type of reaction is not possible. D. The metabolic intermediates produced from the pathway that allows the entry of fructose-1-phosphate into glycolysis are very important for the cell, and there is no evolutionary pressure to remove this pathway.

B. C1 on fructose-1-phosphate cannot participate in an isomerization reaction because it is phosphorylated. Fructose-6-phosphate can be isomerized to glucose-6-phosphate in a reversible reaction catalyzed by the enzyme phosphoglucoisomerase. However, the isomerization of fructose-1-phosphate to glucose-1-phosphate could not be accomplished through the same mechanism. The presence of the phosphate group on C1 of fructose presents a bit of a challenge when it comes to isomerizing that ketose to an aldose, as this is the carbon needed to participate in the reaction. The reaction mechanism would require first hydrolyzing the phosphate, catalyzing the isomerization reaction, and then replacing the phosphate. This type of combined mechanism is not found in isomerases.

How can defects in EGF signaling lead to cancer? A. Loss-of-function mutation to GRB2, shutting down the protein entirely so that it cannot stimulate further downstream effects. B. Gain-of-function mutations to the GTPase region of Ras cause continuous stimulation of the MAPK signaling pathway in the absence of growth factors. C. Gain-of-function mutations to epidermal growth factors, making them unable to bind to the EGFR. D. Loss-of-function mutations to Ras that cause overstimulation of the IRS pathway and are insensitive to GAP regulation.

B. Gain-of-function mutations to the GTPase region of Ras cause continuous stimulation of the MAPK signaling pathway in the absence of growth factors.

Which two enzymes catalyze the two substrate level phosphorylation reactions in glycolysis? A. Hexokinase and phosphofructokinase-1 B. Pyruvate kinase and phosphoglycerate kinase C. Glyceraldehyde-3-phosphate dehydrogenase and pyruvate kinase D. Phosphoglycerate kinase and phosphofructokinase-1 E. Pyruvate kinase and glucokinase

B. Pyruvate kinase and phosphoglycerate kinase

The concentration of allosteric effectors in a cell is constantly changing with metabolic flux. Consider a skeletal muscle cell where [ATP] > [ADP]. Which of the following scenarios will result in the greatest increase in phosphofructokinase-1 activity? A. The glucose concentration inside the cell decreases as muscle activity increases. B. The glucose concentration inside the cell increases as muscle activity also increases. C. The glucose concentration inside the cell decreases along with muscle activity. D. The glucose concentration inside the cell increases as muscle activity decreases.

B. The glucose concentration inside the cell increases as muscle activity also increases. The largest increase in enzyme activity will occur when the concentration of the allosteric inhibitor is decreased while the concentration of the strongest allosteric activator is increased. An increase in muscle activity will deplete ATP, shifting the [ATP]/[ADP] ratio in favor of ADP. In addition to the decrease in ATP available to bind to the allosteric site of phosphofructokinase-1, the increased ADP will compete with available ATP for binding. An increase in glucose concentration will lead to a corresponding increase in fructose and in synthesis of the allosteric activator fructose-2,6-bisphosphate.

Glyceraldehyde-3-phosphate dehydrogenase catalyzes the phosphorylation of glyceraldehyde-3-phosphate, but unlike other glycolytic reactions, it does not require energy investment from ATP. This reaction occurs in two stages: oxidation/reduction and phosphorylation. Why is the oxidation/reduction reaction necessary to make phosphorylation favorable? A. The oxidation/reduction reaction is necessary to produce NADH, which is required for ATP synthesis. B. The oxidation/reduction reaction is necessary to form an intermediate with a large free energy of hydrolysis. C. The oxidation/reduction reaction is necessary to oxidize phosphate, allowing addition to the substrate. D. The oxidation/reduction reaction is for the substrate to bind to the enzyme.

B. The oxidation/reduction reaction is necessary to form an intermediate with a large free energy of hydrolysis. The oxidation/reduction step is necessary to form an acyl thioester, which has a large free energy of hydrolysis.

A patient's red blood cells have an abnormally high level of deoxyhemoglobin (T state) compared to oxyhemoglobin (R state), however flux through the glycolytic pathway was normal. It was found that the decreased oxygen transport resulted from a defect in the pathway shown to the right. What is the most likely defect? A. increased production of 3-PGA B. defect in 2,3-BPG phosphatase C. defect in phosphoglycerate kinase D. defect in bisphosphoglycerate kinase E. decreased production of 2,3-BPG

B. defect in 2,3-BPG phosphatase

The majority of sucralose ingested is not hydrolyzed in the human digestive tract, so it produces no glycemic response. A small percentage can be hydrolyzed to produce equimolar amounts of 1,6-dichloro-1,6-dideoxyfructose and 4-chloro-4-deoxygalactose. Would either of these hydrolysis products cause a false positive result with Benedict's test and the glucose oxidase-peroxidase system? Select all of the true statements below. Choose one or more: A.4-chloro-4-deoxygalactose would not cause a positive result with either test. B.1,6-dichloro-1,6-dideoxyfructose would not cause a positive result with either test. C.1,6-dichloro-1,6-dideoxyfructose would act as a substrate in the glucose oxidase-peroxidase reaction. D.4-chloro-4-deoxygalactose would give a positive result with Benedict's test. E.1,6-dichloro-1,6-dideoxyfructose would give a positive result with Benedict's test. F.4-chloro-4-deoxygalactose would act as a substrate in the glucose oxidase-peroxidase reaction.

B.1,6-dichloro-1,6-dideoxyfructose would not cause a positive result with either test. D.4-chloro-4-deoxygalactose would give a positive result with Benedict's test. Benedict's test will show a positive result in the presence of a reducing sugar, so this reaction could be initiated by the reducing sugar 4-chloro-4-deoxygalactose but not by the nonreducing sugar 1,6-dichloro-1,6-dideoxyfructose. The glucose oxidase-peroxidase reaction is enzyme-catalyzed, so neither hydrolysis product would give a positive result.

Place the following steps describing receptor tyrosine kinase (RTK) signaling 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 B, C, A, D C, B, A, D C, A, D, B C, D, A, B

C, A, D, B

The DG for the glycolytic pathway is -85 kJ/mol, whereas the DGº' for the glycolytic pathway is -35.5 kJ/mol. What accounts for the more favorable DG as compared to DGº' for the glycolytic pathway? A. Cellular metabolite concentrations account for the more favorable DGº' as compared to DG. B. Enzyme shift from T state to R state accounts for the more favorable DG as compared to DGº'. C. Cellular metabolite concentrations account for the more favorable DG as compared to DGº'. D. Enzyme turnover number and Km account for the more favorable DG as compared to DGº'. E. It is because enzymes alter the change in free energy, but not the equilibrium constant.

C. Cellular metabolite concentrations account for the more favorable DG as compared to DGº'.

Which of the following is true regarding the Benedict's test? A. Copper is used as a reducing agent to detect oxidizing sugars in solution. B. Zinc is used as an oxidizing agent to detect reducing sugars in solution. C. Copper is used as an oxidizing agent to detect reducing sugars in solution. D. Benedict's test is a reliable way to determine blood pressure.

C. Copper is used as an oxidizing agent to detect reducing sugars in solution.

Which of the following statements best describes the effect of ADP on the activity of PFK-1? A. High concentrations of ADP lead to increased formation of fructose-2,6-bisphosphate and enhanced activity of PFK-1. B. High concentrations of ADP block the inhibitory effect of ATP by competing for the same allosteric site on PFK-1. C. High concentrations of ADP enhance the activation of PFK-1 by fructose-2,6-bisphosphate by stabilizing the allosteric site. D. High concentrations of ADP block the synthesis of ATP, which reduces inhibition of PFK-1.

C. High concentrations of ADP enhance the activation of PFK-1 by fructose-2,6-bisphosphate by stabilizing the allosteric site.

Autocleavage of ____ generates ____, which _____procaspase 3 to generate _____, also known as the _____caspase A. CASP3; CASP8; cleaves; procaspase 8; stimulator B. Procaspase 8; CASP3; inhibits; CASP8; inhibitor C. Procaspase 8; CASP8; cleaves; CASP3; executioner D. CASP8; procaspase 8; activates; CASP3; executioner

C. Procaspase 8; CASP8; cleaves; CASP3; executioner

The reaction catalyzed by lactate dehydrogenase has a standard free energy change of 3.8 kJ/mol. What would be the minimum value of the [NAD+]/[NADH] ratio necessary for pyruvate reduction to be spontaneous under cellular conditions, assuming the [pyruvate]/[lactate] value is 1.1? A. 0.100 B. 0.200 C. 0.300 D. 0.250

D. 0.250

What are the three direct metabolic fates of pyruvate? A. 1) conversion to lactate; 2) conversion to phosphoenolpyruvate; 3) conversion to acetaldehyde. B. 1) import into the nucleus; 2) conversion to lactate; 3) conversion to acetaldehyde. C. 1) conversion to ethanol; 2) conversion to lactate; 3) import into the thylakoid lumen; D. 1) import into the mitochondria; 2) conversion to lactate; 3) conversion acetaldehyde. E. 1) conversion to acetaldehyde; 2) conversion to lactate; 3) conversion to ethanol.

D. 1) import into the mitochondria; 2) conversion to lactate; 3) conversion acetaldehyde.

Which of the following can enter glycolysis without additional reactions? A. Both products from lactose after lactate treatment B. Both products from sucrose after sucrase treatment C. Glycerol D. Both products from maltose after maltase treatment

D. Both products from maltose after maltase treatment Cleavage of the disaccharide maltose produces 2 molecules of glucose, which can both enter glycolysis. Sucrose is composed of glucose and fructose, which requires additional reactions to enter glycolysis. Lactose is similar, composed of glucose and galactose, which must undergo additional reactions to enter glycolysis. Glycerol requires additional reactions to enter late in the glycolytic cycle.

Predict the consequences of a genetic mutation that renders hexokinase to be defective. A. Increased amounts of pyruvate B. Increase in metabolic flux C. Increased activity of PFK-1 D. Decreased amounts ofglucose-6-Phosphate

D. Decreased amounts ofglucose-6-Phosphate

Which of the following activates a zymogen? A. Chymotrypsinogen B. Trypsinogen C. Pepsinogen D. Enterokinase

D. Enterokinase

What potential disadvantage does the alternate pathway of fructose catabolism in the liver introduce as compared to glucose catabolism? A. Fructose catabolism produces fewer net ATP molecules than glucose catabolism. B. Fructose catabolism requires the synthesis of additional enzymes that are not required for glucose catabolism C. Fructose catabolism produces fewer NADH molecules than glucose catabolism D. Fructose catabolism does not have as many regulatory steps as glucose catabolism.

D. Fructose catabolism does not have as many regulatory steps as glucose catabolism. The entry of fructose into glycolysis in the liver bypasses the phosphofructokinase-1 reaction, which is the major regulatory step of glycolysis.

In an individual with lactate dehydrogenase deficiency, would this [NAD+]/[NADH] ratio be sufficient to lead to a significant, lasting effect on glycolytic flux? A. Yes. Glycolytic flux is very sensitive to the [NAD+]/[NADH] ratio, and any movement away from the steady-state value would cause a significant disruption to glycolytic flux. B. No. The [NAD+]/[NADH] ratio has very little effect on glycolytic flux. The lactate dehydrogenase reaction is more important for preventing the buildup of pyruvate under anaerobic conditions, which can lead to inhibition of the pyruvate kinase reaction. As long as the mitochondrial oxidation reactions are able to reduce the concentration of pyruvate, the NADH concentration is not very important. C. Yes. NAD+ is required for the glyceraldehyde-3-phosphate dehydrogenase reaction, which is already unfavorable under standard conditions. Further reducing the concentration of NAD+ would make this reaction even more unfavorable under cellular conditions, and this reaction would therefore not be able to proceed in the forward direction. Glycolytic flux would be significantly affected as a result. D. No. As long as the individual was not attempting high-intensity anaerobic exercise, the mitochondrial shuttle system would quickly restore the steady-state ratio of [NAD+]/[NADH] with minimal effects on glycolytic flux.

D. No. As long as the individual was not attempting high-intensity anaerobic exercise, the mitochondrial shuttle system would quickly restore the steady-state ratio of [NAD+]/[NADH] with minimal effects on glycolytic flux. While the lactate dehydrogenase reaction is important for oxidizing NADH to maintain glycolytic flux, it is only essential under anaerobic conditions. An individual with a lactate dehydrogenase deficiency would not experience a serious disruption in glycolytic flux from a temporary disruption in the steady-state ratio of [NADH]/[NAD+] as long as the mitochondrial shuttle system and electron transport chain remain fully functional.

Phosphoenolpyruvate (PEP) is converted to pyruvate by the enzyme pyruvate kinase. The standard free energy change (D Go') is -31.4 kJ/mol. After eating a candy bar, Billy's cellular concentrations are pyruvate = 0.04 mM and PEP = 12mM. What is the DG of this reaction at 37 C? PEP --> Pyruvate A. -16.7 kJ/mol B. +6.3 kJ/mol C. -46.1 kJ/mol D. -33.3 kJ/mol E. -2.4 kJ/mol

DG= -31.4 kJ/mole + RT • ln (4 x 10-5M)/(12 x 10-3M) DG= [-31.4 kJ/mole] + [(8.3 x 10-3 kJ/mol•K) x (310 K) x (-5.7)] DG= -31.4 kJ/mole + -14.6 kJ/mol C. -46.1 kJ/mol

What effect do elevated levels of ATP have on glycolysis? Increase the affinity of PFK-1 for fructose-6-P and increase the rate of the pathway. Decrease the affinity of PFK-1 for fructose-6-P and slow rate of the pathway. Increase the concentration of PFK-1 in the R-state. Increase the concentration of glucose entering glycolysis.

Decrease the affinity of PFK-1 for fructose-6-P and slow rate of the pathway.

Which of the following statements best describes the effect of ADP on PFK-1 activity? A. ADP enhances the activation of PFK-1 by stabilizing fructose-2,6 bisphosphate binding. B. ADP blocks the synthesis of ATP and reduces the amount of ATP binding to the allosteric site. C. ADP stimulates the synthesis of fructose-2,6 bisphosphate, which allosterically activatesPFK-1. D. ADP is not phosphorylated to generate ATP by substrate level phosphorylation so less inhibition. E. ADP blocks the inhibitor effect of ATP by competing for binding to the same PFK-1allosteric site.

E. ADP blocks the inhibitor effect of ATP by competing for binding to the same PFK-1allosteric site.

Which protein is part of the TNF receptor-activated programmed cell death signaling pathway? TRAF2 FADD IKK NFkB

FADD

Glucose and fructose are both C6H12O6. What is the structural difference between them? Glucose is a five-membered ring and fructose is a six-membered ring. Fructose is a five-membered ring and glucose is a six-membered ring. Glucose is a linear molecule and fructose is a ring. Glucose is found in the boat conformation and fructose is a chair conformation.

Fructose is a five-membered ring and glucose is a six-membered ring.

G protein-coupled receptor

GDP-GTP exchange and dissociation of the heterotrimeric G protein.

Based on the structures of D-glucose and D-galactose, which one of the following statements is true? Glucose and galactose are epimers of each other. Glucose and galactose are tetroses. Glucose and galactose are ketoses. Glucose and galactose are anomers of each other.

Glucose and galactose are epimers of each other.

Which of the following statements is true of procaspase 8? It is cleaved by TRADD and binds to p65. It is activated by auto-cleavage. It is phosphorylated and activated by IKK. It cleaves and activates procaspase 3.

It is activated by auto-cleavage.

How does phosphoglycerate kinase make glycolysis energy neutral at this step? It uses ATP to produce 3-phosphoglycerate. It results in a reaction is endergonic. It results in a reaction at equilibrium. It produces 2 ATP along with 3-phosphoglycerate. It results in a reaction at equilibrium.

It produces 2 ATP along with 3-phosphoglycerate.

Choose the statement below that best describes what the actual change in free energy (deltaG) tells you about an enzymatic reaction that cannot be determined by the standard free energy (deltaGº') change. The actual change in free energy = 0, so it does not tell you anything. The spontaneity of the reaction in the presence of an inhibitor. The direction of the reaction at 1M substrate concentration at pH7. The temperature of the reaction at 1 atmosphere pressure. The direction of the reaction at equilibrium. The direction of the reaction under steady state conditions.

The direction of the reaction under steady state conditions.

What advantage is there to phosphoglycerate kinase having an open and closed configuration? It allows water to be trapped in the active site along with the substrate. The induced-fit mechanism maximizes accessibility of active site without sacrificing hydrophobic environment. It forces covalent binding of the substrate to the enzyme active site. Changing of the configuration of the enzyme makes the reaction exergonic.

The induced-fit mechanism maximizes accessibility of active site without sacrificing hydrophobic environment.

What is the mechanism by which anti-apoptotic signaling blocks apoptotic signaling in the same cell?

Transcriptional activation of genes encoding inhibitors of caspase enzyme activation.

Put the following glycolytic reactions in the correct order. Only 8 of the 10 reactions in the glycolytic pathway are listed, so the answer should be the relative order of the 8 reactions listed. ____Substrate level phosphorylation reaction generating a net yield in ATP for the glycolytic pathway. ____Phosphorylation reaction converting a hexose monophosphate into a hexose bisphosphate. ____An isomerization reaction converting an aldose sugar into a ketose sugar. ____A redox reaction utilizing inorganic phosphate and a coenzyme. ____A substrate level phosphorylation reaction generating the ATP needed to replace the ATP investment in stage 1 .____A dehydration reaction generating a high energy phosphorylated compound. ____Cleavage reaction converting a diphosphate sugar into two monophosphate metabolites. ____Phosphorylation reaction generating a hexose sugar.

__8__Substrate level phosphorylation reaction generating a net yield in ATP for the glycolytic pathway. __3__Phosphorylation reaction converting a hexose monophosphate into a hexose bisphosphate. __2__An isomerization reaction converting an aldose sugar into a ketose sugar. __5__A redox reaction utilizing inorganic phosphate and a coenzyme. __6__A substrate level phosphorylation reaction generating the ATP needed to replace the ATP investment in stage 1 .__7__A dehydration reaction generating a high energy phosphorylated compound. __4__Cleavage reaction converting a diphosphate sugar into two monophosphate metabolites. __1__Phosphorylation reaction generating a hexose sugar.

If Kerry's parents were both heterozygous for mutations in the lactate dehydrogenase gene, which is located on chromosome 11, what is the probability that her little brother is a) homozygous for the disease, b) heterozygous for the disease, c) homozygous normal without mutations? a) 25%; b) 50%; c) 25% a) 0%; b) 50%; c) 50% a) 25%; b) 25%; c) 50% a) 50%; b) 0%; c) 50% a) 50%; b) 25%; c) 25% a) 33%; b) 33%; c) 33%

a) 25%; b) 50%; c) 25%

a) Why does 18F-fluorodeoxyglucose accumulate in cells rather than being metabolized to pyruvate --> CO2 + H2O? b) Why is the brain and bladder the most intensely labeled with 18F-fluorodeoxyglucose as visualized by the PET scan shown below of an adult male without any cancer? a) Because after 18F-fluorodeoxyglucose is phosphorylated by hexokinase and is not metabolized or dephosphorylated. b) The brain converts the 18F-fluorodeoxyglucose to lactate using the Warburg effect and the bladder excretes the extra 18F-fluorodeoxyglucose. a) Because after 18F-fluorodeoxyglucose is phosphorylated by hexokinase and is metabolized to produce 18F-DHAP. b) The brain uses glucose as an energy source and the bladder excretes the extra 18F-fluorodeoxyglucose. a) Because after 18F-fluorodeoxyglucose is phosphorylated by GAPDH and is not metabolized or dephosphorylated. b) The brain uses glucose as an energy source and the bladder incorporates the 18F-fluorodeoxyglucose into urea. a) Because after 18F-fluorodeoxyglucose is phosphorylated by hexokinase and is not metabolized or dephosphorylated. b) The brain uses glucose as an energy source and the bladder excretes the extra 18F-fluorodeoxyglucose. a) Because after 18F-fluorodeoxyglucose is converted to pyruvate, which is not metabolized or dephosphorylated. b) The brain uses glucose as an energy source and the bladder excretes the extra 18F-fluorodeoxyglucose.

a) Because after 18F-fluorodeoxyglucose is phosphorylated by hexokinase and is not metabolized or dephosphorylated. b) The brain uses glucose as an energy source and the bladder excretes the extra 18F-fluorodeoxyglucose.

How is the delta G prime value for a chemical reaction determined using the value for Keq? a. At equilibrium, Keq=[P]/[R] and delta G = 0, therefore delta G prime = -RT*lnKeq b. At equilibrium, Keq=[R]/[P] and delta G = 0, therefore delta G prime = -RT*lnKeq c. At equilibrium, Keq=[P]/[R] and delta G = 0, therefore delta G prime = +RT*lnKeq d. At equilibrium, Keq=[P]/[R] and delta G = 1, therefore delta G prime = -RT*lnKeq

a. At equilibrium, Keq=[P]/[R] and delta G = 0, therefore delta G prime = -RT*lnKeq

The GS-alpha subunit of trimeric G proteins can function to inhibit phosphodiesterase. regulate ion channels. activate adenylate cyclase. inhibit phospholipase A.

activate adenylate cyclase.

The alpha subunit of trimeric G proteins can function to _________________. inhibit phospholipase A. activate adenylate cyclase. regulate ion channels. inhibit phosphodiesterase.

activate adenylate cyclase.

Tumor necrosis factor receptor

assembly of adaptor complexes through TNF receptor associated death domain proteins.

Why is glucokinase considered a glucose sensor? a. Because is has a low Km for glucose, which means its activity is dependent on high [glucose] b. Because is has a high Km for glucose, which means its activity is dependent on high [glucose] c. Because is has a low Km for glucose, which means its activity is dependent on low [glucose] b. Because it is expressed in pancreas cells and not liver cells

b. Because is has a high Km for glucose, which means its activity is dependent on high [glucose]

How are phosphoryl groups transferred in order to form ATP in the glycolysispathway? a. Oxidative phosphorylation b. Substrate-level phosphorylation c. Photophosphorylation d. Hyperphosphorylation

b. Substrate-level phosphorylation

The phosphoglycerate kinase reaction converts 1,3-BPG + ADP -> 3-phosphoglycerate + ATP. Where did the phosphate come from in 1,3 BPG that is used to generate ATP from ADP? inorganic phosphate used in the phosphofructokinase reaction b. ATP used in the hexokinase reaction c. Inorganic phosphate used in the glyceraldehyde-3P dehydrogenase reaction. d. ATP used in the phosphofructokinase reaction.

c. Inorganic phosphate used in the glyceraldehyde-3P dehydrogenase reaction.

Phosphofructokinase-1 is a crucial enzyme for determining whether or not a cell will progress through the glycolysis pathway. Its conformation and activity are controlled by several allosteric effectors; Which molecule is a positive effector forPFK-1? a. ATP b. Citrate c. Ca2+ d. AMP

d. AMP

What would be the effect in muscle cells of a deficiency in lactate dehydrogenase? buildup of CO2 deficiency of pyruvate buildup of glucose buildup of O2 deficiency of ATP

deficiency of ATP

An infant who has galactosemia is unable to convert______________. glucose-6-P to fructose-6-P glucose-1-P to galactose-1-P. galactose-1-P to glucose-6-P. galactose-1-P to glucose-1-P. glucose-6-P to galactose-1-P.

galactose-1-P to glucose-1-P.

Which reaction in glycolysis is a redox reaction? glucose glucose-6-P fructose-6-P fructose-1,6-BP glyceraldehyde-3-P 1,3-bisphosphoglycerate 2-phosphoglycerate phosphoenolpyruvate

glyceraldehyde-3-P 1,3-bisphosphoglycerate

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. The regulatory subunits move out of the active sites of the catalytic subunits, and the R2C2 complex dissociates. Two cAMP molecules bind to each PKA regulatory subunit. Cytosolic cAMP concentration increases. The free catalytic subunits interact with proteins to phosphorylate Ser or Thr residues. Each regulatory subunit is activated as the two cAMP molecules are released.

(1)Cytosolic cAMP concentration increases. (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. (4)The free catalytic subunits interact with proteins to phosphorylate Ser or Thr residues. (5)Each regulatory subunit is activated as the two cAMP molecules are released.

(a) Why is it critical for maintaining flux through the metabolic pathway that NADH be oxidized to NAD+, and (b) how is that done under anaerobic conditions in human cells? (a) NADH is required for the glyceraldehyde-3P dehydrogenase reaction; (b) by converting pyruvate to lactate. (a) NAD+ is required for the glyceraldehyde-3P dehydrogenase reaction; (b) by converting pyruvate to lactate. (a) NADH is required for the phosphofructokinase-1 reaction; (b) by converting pyruvate to lactate. (a) NAD+ is required for the glyceraldehyde-3P dehydrogenase reaction; (b) by converting pyruvate to ethanol. (a) NAD+ is required for the glyceraldehyde-3P dehydrogenase reaction; (b) by converting pyruvate to acetate.

(a) NAD+ is required for the glyceraldehyde-3P dehydrogenase reaction; (b) by converting pyruvate to lactate.

What are the three primary mechanisms by which nuclear receptors control physiological responses?

1. ligand bioavailability 2.receptor expressions 3. DNA accessibility

What is the functional difference between a 1st messenger and 2nd messenger in cell signaling pathways? 1st messengers bind to upstream receptors, 2nd messengers bind to downstream receptors 1st messengers bind to receptors, 2nd messengers are activated by downstream signaling events 1st messengers bind to membranes; 2nd messengers are activated by upstream signaling events' 1st messengers bind to receptors; 2nd messengers are activated by up stream signaling events

1st messengers bind to receptors; 2nd messengers are activated by up stream signaling events

Predict how oxygen transport is affected in individuals with a hexokinase deficiency as a result of decreased flux through the glycolytic pathway. 2,3-BPG levels are reduced leading to higher oxygen affinity and reduced oxygen transport to the tissues. 2,3-BPG levels are reduced leading to lower oxygen affinity and reduced oxygen transport to the tissues. 2,3-BPG levels are reduced leading to higher oxygen affinity and increased oxygen transport to the tissues. 2,3-BPG levels are increased leading to higher oxygen affinity and increased oxygen transport to the tissues.

2,3-BPG levels are reduced leading to higher oxygen affinity and reduced oxygen transport to the tissues.

What prevents hydrated Na+ and K+ ions from passing through the nicotinic acetylcholine receptor channel in the absence of acetylcholine? The diameter of the hydrated Na+ and K+ ions is too large to fit through the inner and outer chambers and they never reach the inner chamber. The nicotinic acetylcholine receptor is a G protein-coupled receptor that blocks Na+ and K+ channel by association with a heterotrimeric G protein. A ring of positively-charged amino acids in the upper and lower outer chambers prevents the hydrated ions from entering the channel. A ring of nonpolar amino acids in the interior chamber prevents the hydrated ions from moving through the constricted channel.

A ring of nonpolar amino acids in the interior chamber prevents the hydrated ions from moving through the constricted channel.

Which two properties of glucokinase explain why it is an ideal glucose sensor capable of stimulating insulin release from the pancreas? Glucokinase is allosterically activated by glucose in pancreatic beta cells. Glucokinase has a low Km relative to hexokinase and shows a linear rate increase from 0.5-2.0 mM glucose Glucokinase is only found in brain and heart cells, the two tissues that are the most dependent on glucose as an energy source. Glucokinase is activated by glucagon, which is the "I am hungry" hormone leading to insulin release. Glucokinase has a high Km and shows a linear rate increases from 5-10mM glucose. Glucokinase is allosterically inhibited by fructose-6-phosphate.

Glucokinase is allosterically activated by glucose in pancreatic beta cells. Glucokinase has a high Km and shows a linear rate increases from 5-10mM glucose.

Which one of the following processes occurs after activation of the PI-3K pathway by insulin signaling? Rates of glucose synthesis (gluconeogenesis) increase. GTP binds to the Ras protein to promote glucose export. Rates of glycogen synthesis decrease to increase blood glucose. Glucose uptake rates increase and lower blood glucose levels.

Glucose uptake rates increase and lower blood glucose levels

Module 7

Start

Module 8

Start

Module 9

Start

When ATCase is in the __________ state it indicates that ____________ is bound, and that ATCase is ______________ regulated. T; CTP; down T; ATP; up R; ATP; down R; CTP; up

T; CTP; down

What is the function of the GTPase activity in G proteins? The GTPase stimulates GDP to GTP exchange to activate signaling. The GTPase cleaves GTP to generate GDP and activate signaling. The GTPase synthesize cyclic GMP to regulate downstream signals. The GTPase cleaves GTP to generate GDP and inactivate signaling.

The GTPase cleaves GTP to generate GDP and inactivate signaling.

What is the Warburg effect and why is it an advantage to cancer cells? The Warburg effect refers high levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce lactate, which provides a growth advantage. The Warburg effect is related to the way that cancer cells avoid the immune system using decoy molecules similar to how military maneuvers were used in World War II. The Warburg effect refers high levels of glycolytic flux to compensate for tumor hyperoxia conditions and to produce lactate, which provides a growth advantage. The Warburg effect refers high levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce pyruvate, which provides a growth advantage. The Warburg effect refers low levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce glucose, which provides a growth advantage.

The Warburg effect refers high levels of glycolytic flux to compensate for tumor hypoxic conditions and to produce lactate, which provides a growth advantage.

Catabolic products of some pathways can be used as the substrates for anabolic pathways. During times of starvation or fasting, the liver uses many noncarbohydrate precursors to synthesize glucose. However, the catabolic products ______ of cannot be used to synthesize glucose. a. Monosaccharides b. Fatty acids c. Amino acids d. Nucleotides

b. Fatty acids Fatty acids are oxidized to produce acetyl CoA; no direct pathway exists to convert acetyl CoA to pyruvate or other intermediate metabolites in the glucose synthesis pathway.

Nuclear receptor

binding to specific DNA sequences and transcriptional regulation of downstream target genes.

The activity of protein kinase A (PKA) is regulated by cAMP. Which statement correctly describes the role of cAMP in this activation? PKA needs cAMP to act as a source of energy for the catalytic reaction. cAMP binds to the catalytic subunit of PKA, promoting association of the pseudosubstrate and activating it. cAMP binds to the active site of PKA, promoting its association with its substrates. cAMP binds to the regulatory subunit of PKA, promoting its dissociation from the catalytic subunit and activating it.

cAMP binds to the regulatory subunit of PKA, promoting its dissociation from the catalytic subunit and activating it. Activation of PKA and subsequent phosphorylation of downstream substrates is sensitive to cAMP levels.

Which of the following choices below includes only first messenger signaling molecules? insulin, glucagon, glucose cortisol, insulin, prostaglandins Ca2+, testosterone, protein kinase A nitric oxide, estradiol, heme cytochrome c, insulin, estrogen receptor

cortisol, insulin, prostaglandins

TNF signaling has two paths, both branching from a common protein, 1) FADD /2)TRADD. After this branching point, the 3)proliferative / 4) apoptotic pathway involves autocleavage of procaspase 8 into caspase 8, which then cleaves5) procaspase 3 / 6) procaspase 6 to continue signaling. The other branch activates7) NIK / 8) Ras, which activates IKK to activate 9) NFκB / 10) βARK in order to express genes that inhibit the caspases in the other branch. a) 2, 3, 6, 7, 9 b) 1, 3, 5, 8, 10 c) 1, 4, 6, 8, 10 d) 2, 4, 5, 7, 9

d) 2, 4, 5, 7, 9

Enzyme inhibitors have incredible potential for improving human health. Researchers have become increasingly interested in therapeutic inhibition of main protease (Mpro), a critical enzyme for the assembly of the SARS-CoV-2 pandemic virus, as a means of reducing the severity and transmission of COVID-19. Which of the following describes the best-case scenario for inhibitor development? high Kd, competitive inhibitor low Kd, competitive inhibitor low Kd, uncompetitve inhibitor high Kd, noncompetitive inhibitor

low Kd, competitive inhibitor Not only will the enzyme have high affinity for the inhibitor, but also it will block the active site, and the inhibitor could be competed away if necessary.

Nicotinic acetylcholine receptor

opening of the inner chamber to facilitate passive ion transport.

The catalytic activity and/or conformational stability of this protein is likely dependent upon (protonation) of peripheral amino acid side chains. These side chains are expected to have a (low pKa) value.

pepsin is secreted into the very acidic nature of the stomach. The catalytic acitivty and/or conformational stability of this protein is likely dependent upon protonation of peripheral amino acid side chains. these peripheral amino acid side chains are expected to have a low pKa value.

Which two of the following compounds are used to produce ATP by substrate-level phosphorylation in glycolysis? (check all that apply) 3-phosphoglycerate phosphoenolpyruvate 1,3-bisphosphoglycerate dihydroxyacetone phosphate 2-phosphoglycerate fructose-1,6-BP glucose-6P

phosphoenolpyruvate 1,3-bisphosphoglycerate

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? phosphorylated GPCR GTP-bound ARK dephosphorylated GPCR protein kinase A

phosphorylated GPCR

Binding of first messengers to G protein-coupled receptors results in ___________. recruitment of heterotrimeric G proteins to the GPCR cytoplasmic tail. dimerization of GPCRs to form an active receptor complex. activation of tyrosine kinase activity in the GPCR cytoplasmic tail stimulation of GTPase activity in the GPCR cytoplasmic tail.

recruitment of heterotrimeric G proteins to the GPCR cytoplasmic tail.

Cyclic GMP is the __________ during vasodilation. paracrine signal second messenger phosphodiesterase first messenger activator of nitric oxide synthetase

second messenger

Muscle relaxation in response to neuronal stimulation and nitric oxide signaling would be reduced if a(n) ______________was present. inhibitor of protein kinase A stimulator of cGMP phosphodiesterase stimulator of guanylate cyclase inhibitor of acetylcholine esterase

stimulator of cGMP phosphodiesterase

In the reaction A→ B, what can be said about the directionality of the reaction if when starting with equal concentrations of A and B at time zero (T0), you find that at equilibrium 30 minutes (T30) later, that [B] >> [A]? not enough information is given. strongly favored in both directions strongly favored in the reverse direction strongly favored in the forward direction

strongly favored in the forward direction

When protein kinase A (PKA) is inactive, which of the following is true? the regulatory subunit has cyclic GMP bound in place of cyclic AMP ATP is bound to the regulatory subunit to inhibit subunit dissociation the intrinsic pseudo substrate peptide is bound to the active site cAMP is bound to the catalytic site to inhibit the regulatory subunit

the intrinsic pseudo substrate peptide is bound to the active site

aspartate transcarboxylase (ATCase) is (1)_______ regulated by (2)________, which is a positive regulator and (3)_______, which is a negative regulator of enzyme activity. 1 catalytically, 2 ATP, 3 CTP 1 allosterically 2CTP 3 ATP 1 allosterically 2 ATP 3 CTP 1 covalently 2 ATP 3 CTP

1 allosterically 2 ATP 3 CTP

The β2-adrenergic receptor is best characterized as which of the following? :mostly α helices none of the above mostly β sheets mostly β turns

:mostly α helices

Which metabolic pathway is an example of a catabolic pathway in animals? A. Pentose phosphate pathway B. Gluconeogenesis C. Fatty acid synthesis D. Glycogen degradation

D. Glycogen degradation Catabolic pathways degrade macromolecules for the purpose of energy capture. Glycogen is the storage form of glucose in animals, so glycogen degradation releases glucose to enter glycolysis. Anabolic pathways use energy to build up biomolecules. Examples include the pentose phosphate pathway, gluconeogenesis, and fatty acid synthesis.

The GRB2 protein plays a critical role in connecting the upstream EGF receptor signaling pathway to the downstream MEK pathway. What is that role? GRB2 is a tyrosine kinase that phosphorylates EGFR through a SH2 domain that activates the MEK pathway. GRB2 is an adaptor protein that binds to SOS protein through two SH2 domains and to Ras protein through a SH4 domain. GRB2 is an adaptor protein that binds to EGFR through a SH2 domain and to SOS protein through two SH3 domains. GRB2 is an adaptor protein that binds to EGFR through a SH2 domain and SOS protein through a PIP2 domain.

GRB2 is an adaptor protein that binds to EGFR through a SH2 domain and to SOS protein through two SH3 domains.

Long polypeptides, when folded into tertiary structures, can bring two amino acids within the polypeptide close together even though they are far apart in sequence. In the Gqα protein, the amino terminus and carboxyl terminus are found in close proximity. What would you say is an accurate description of this part of the protein? Gqα begins and ends with α helices that come in close proximity when folded. Gqα begins and ends with β strands that come in close proximity when folded. Gqα has an α helix at one end and a β strand at the other that come in close proximity when folded. The Gqα polypeptide has little secondary structure at its ends that instead can be described as loose coils.

Gqα has an α helix at one end and a β strand at the other that come in close proximity when folded.

How will Taylor avoid auto-brewery syndrome given that he will likely still have yeast in his microbiome owing to the anti-inflammatory drugs? He needs to stop eating all carbohydrates and only consume pure protein in the form of granola bars. He needs to eat more white rice and less salmon to avoid fermentation of omega-3 fatty acids. He needs to avoid high carbohydrate snacks like potato chips and donuts on an empty stomach. He needs to drink mezcal every morning which has enough alcohol to kill yeast and prevent auto-brewery syndrome. He needs to drink more unfiltered home brew beer and less kombucha to kill off the yeast in his intestine.

He needs to avoid high carbohydrate snacks like potato chips and donuts on an empty stomach.

Cultures of two different human cell types are exposed to the same steroid signaling molecule. Analysis of gene expression shows that only one of the cell types activated gene expression characteristic of the steroid signaling pathway. Which of the following is the most likely explanation for this difference? The steroid ligand can only cross the plasma membrane in one cell type. Only one cell type phosphorylates the steroid ligand to activate it. Only one of the cell types expresses the cognate steroid receptor. Only one cell type contains the DNA sequences that the steroid receptor binds to.

Only one of the cell types expresses the cognate steroid receptor.

A new protein is discovered that contains a pleckstrin homology domain. Which of the following is likely to bind to the protein? Ca2+ IP3 PIP3 PI-3K

PIP3

Procathepsin B is a lysosomal protease that is first translated as a proenzyme. On autocleavage it is fully activated. Procathepsin B is ________________. in the T state after autocleavage. inactive at low pH. an allosteric enzyme. a zymogen.

a zymogen.

The (1) Gsα/ (2) Gqα GPCR is stimulated when a ligand binds to(3) α1 or β2/ (4) glucagon or β2 receptors. This activate sadenylate cyclase, which converts (5) ATP / (6) PIP2 to the (7)first/ (8) second messenger cAMP, which activates (9) PKA/ (10)PKC for net glucose transport. A. 1, 4, 5, 8, 9 B. 1, 3, 5, 8, 9 C. 2, 3, 5, 8, 10 D. 1, 4, 5, 8, 10

A. 1, 4, 5, 8, 9

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-3K and 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.

Which of the following processes are points of regulation for controlling enzyme-mediated biochemical reactions. There are five correct answers, choose the letter with the correct answers listed. a. Proteolytic Processing b. Guanine Methylation c. Protein Targeting d. Incorporation of D Amino Acids e. Carboxyl Termini Dehydration f. RNA Processing g. Protein Degradation h. Dihydrolipidation of Arginine i. Disulfide Bond Acetylation j. Serine Phosphorylation A. j, f, a, g, c B. h, c, f, i, e C. a, c, d, f, h D. i, g, f, d, a E. b, i, h, c, a

A. j, f, a, g, c a. Proteolytic Processing c. Protein Targeting f. RNA Processing g. Protein Degradation j. Serine Phosphorylation

Put the following steps in the correct order describing inhibition of glutamine synthetase by a metabolite allosteric effector. A. Adenylation of glutamine synthetase. B. Glutamine binding to uridylyltransferase C. Deuridylation of glutamine synthetase adenylyltransferase B, C, A B, A, C C, B, A A, B, C

B, C, A B. Glutamine binding to uridylyltransferase C. Deuridylation of glutamine synthetase adenylyltransferase A. Adenylation of glutamine synthetase.

Match each second messenger with its most correct target protein, each answer is only used once Second Messenger a. Cyclic AMP b. Inositol triphosphate c. Diacylglycerol d. Cyclic GMP e. Calcium Target protein_____ 1. Calcium channel protein 2. Protein kinase 3. Protein kinase 4. Calmodulin 5. Protein kinase C 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

Which of the following is an example of feedback inhibition? A. Pepsinogen is cleaved to generate pepsin, an important enzyme in digestion. B. ATCase is in its R state when ATP is abundant, and in its T state when CTP is abundant. C. Glycogen phosphorylase is active when phosphorylated. D. ATCase is in its R state when CTP is abundant, and in its T state when ATP is abundant.

B. ATCase is in its R state when ATP is abundant, and in its T state when CTP is abundant.

You are hiking the finger rock trail in the Catalina mountains and come across a rattlesnake crossing the trail, which activates a physiological stress response. Choose the answer below that correctly identifies the (a) hormone and (b)receptor in a shared signaling pathway in liver cells that is activated by a physiological stress response, and (c) the target enzyme that is activated in the downstream pathway identified by parts a + b. All three answers must be correct. A. a) glucagon; b) a1 adrenergic receptor; c) adenylate cyclase B. a) epinephrine; b) b2 adrenergic receptor; c) adenylate cyclase C. a) epinephrine; b) b2 adrenergic receptor; c) phospholipase c D. a) glucagon; b) glucagon receptor; c) phospholipase c E. a) epinephrine; b) a1 adrenergic receptor; c) adenylate cyclase

B. a) epinephrine; b) b2 adrenergic receptor; c) adenylate cyclase

Which of the following statements is true concerning the role of cGMP in vasodilation? A. Sildenafil prolongs NO-mediated vasodilation by stimulating production of cGMP. B. cGMP is a secondary messenger that acts on protein kinase G. C. Increased cGMP leads to increased NO, which serves as a secondary messenger for vasodilation. D. Vasodilation is increased by increased activity of cGMP phosphodiesterase.

B. cGMP is a secondary messenger that acts on protein kinase G. cGMP is a secondary messenger for vasodilation. Increased NO leads to increased cGMP, which activates protein kinase G. Sildenafil, or Viagra, prolongs vasodilation by inhibiting cGMP phosphodiesterase. cGMP phosphodiesterase degrades cGMP and decreases vasodilation. By inhibiting this enzyme, the concentration cGMP remains higher and vasodilation is prolonged.

Which of the following correctly describes the biochemistry of the amino acids at the termini of pepsin? A. three polar amino acids at the N-terminus and one charged amino acid at the C-terminus B. two nonpolar amino acids at the N-terminus and one polar amino acid at the C-terminus C. three charged amino acids at the N-terminus and two polar amino acids at the C-terminus D. two charged amino acids at the N-terminus and two nonpolar amino acids at the C-terminus

B. two nonpolar amino acids at the N-terminus and one polar amino acid at the C-terminus regarding the biochemistry of the amino acids at the termini of pepsin, there are two nonpolar amino acids at the N-terminus and a polar amino acid at the C-terminus.

When (1)glutamine synthetase/(2)glycogen synthase is adenylated by glutamine synthetase adenylyl transferase, the enzyme is in the (3)T/(4)R state. This results in(5)increasing/(6)decreasing metabolic flux. The adenylation mechanism depends on whether or not glutamine synthetase adenylyl transferase is(7)uridylated/(8)phosphorylated on a specific(9)serine/(10)tyrosine residue. A.1,3,5,7,10 B.1,3,6,7,10 C.1,3,6,7,9 D.1,4,5,7,10

B.1,3,6,7,10

Why are Ras mutations so prevalent in certain types of cancers? Because a recessive mutation in Ras requires two mutations to cause a gain of function oncogene activation. Because a tumor suppressor mutations in Ras require only one mutation to be a gain of function oncogene activation. Because dominant mutations block signaling pathways that are required for cell growth, and thereby lead to a loss of function oncogene activation. Because a dominant mutation in Ras requires only one mutation to be a gain of function oncogene activation.

Because a dominant mutation in Ras requires only one mutation to be a gain of function oncogene activation.

Why is fructose toxic to liver cells, but not muscle cells, in individuals with a defect in the enzyme aldolase B? Because liver cells, but not muscle cells, use up ATP converting fructose to fructose-6P, which cannot be further metabolized. Because liver cells lack the enzyme hexokinase, but not muscle cells, and depend on aldolase B to convert glucose to glucose-6P in the glycolytic pathway. Because liver cells, but not muscle cells, use up ATP converting fructose to fructose-1P, which cannot be further metabolized. Because liver cells, but not muscle cells, use hexokinase to convert glucose to glucose-6P, which cannot be further metabolized.

Because liver cells, but not muscle cells, use up ATP converting fructose to fructose-1P, which cannot be further metabolized.

Put the following ten 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. A. 1, 5, 4, 9, 3, 7, 2, 8, 6, 10 B. 1, 4, 5, 3, 9, 7, 8, 6, 2, 10 C. 1, 4, 5, 9, 3, 7, 6, 8, 2, 10 D. 1, 4, 9, 5, 3, 6, 7, 8, 2, 10 E. 1, 3, 5, 9, 4, 7, 6, 2, 8, 10

C. 1, 4, 5, 9, 3, 7, 6, 8, 2, 10 _4_ GDP is exchanged for GTP in the G-alpha subunit. _5_ The G-alpha and G-beta/gamma subunits dissociate. _9_ PKA phosphorylates target proteins leading to glucose export. _3_ The GDP-bound heterotrimeric G protein binds to the receptor. _7_ Cyclic AMP synthesis leads to 2nd messenger activation of PKA. _6_ The G-alpha subunit binds to activates adenylate cyclase. _8_ The PKA regulatory subunit dissociates from the catalytic subunit. _2_ A conformational change in the C-terminus of the receptor.

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 H2O 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. A. 2, 3, 4 B. 1, 2, 6 C. 2, 5, 6 D. 1, 3, 4 E. 2, 4, 5

C. 2, 5, 6 2. Caspases are catalytic enzymes and can do a lot of damage in a short period of time. 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.

For TNF receptors, which of the following inhibits receptor signaling? A. Bound TNF-αα B. Bound TRADD proteins C. Bound SODD proteins D. Death domains

C. Bound SODD proteins In its inactive form, TNF receptors are not bound to a ligand, and SODD proteins are bound to the death domains. This inhibits receptor signaling. Binding of TNF-αα causes a conformational change that leads to SODD dissociation and TRADD binding. TRADD binds downstream signaling proteins and thus allows for receptor signaling.

Interaction of glucocorticoid receptors with which of the following prevents binding to glucocorticoid response elements (GREs)? A. p50 B. p60 C. Hsp90 D. Annexin I gene

C. Hsp90 Prior to binding glucocorticoids, the receptor forms an inactive complex with the chaperonin Hsp90. Upon ligand binding, the GR is released from Hsp90 and is able to bind to GREs located on the annexin I gene. The increased expression from annexin I, in addition to suppression of the cyclooxygenase-2 gene by sequestering p65, leads to reduced inflammation.

What is the target of ββ-adrenergic receptor kinase? A. Gαα B. Gβγβγ C. The cytoplasmic tail of the G protein-coupled receptor D. ββ-arrestin

C. The cytoplasmic tail of the G protein-coupled receptor ββ-adrenergic receptor kinase targets the cytoplasmic tail of the GPCR. This phosphorylated GPCR is the binding site for ββ-arrestin, which tags the GPCR for degradation in lysosomes or recycling.

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 G Sa proteins as the upstream signal, but each G Sa stimulates different target proteins. C. The second messenger in each of these signaling systems is distinct; GMP, cAMP, DAG/IP 3. 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/IP 3.

An inhibitor binds to the enzyme-substrate complex and has the following Lineweaver-Burkplot. How would you expect the Vmax and Km to change? A. Vmax and Km increased B. Vmax unchanged, Km decreased C. Vmax and Km decreased D. Vmax decreased, Km unchanged

C. Vmax and Km decreased

Put the following signal transduction pathway steps in the correct order: upstream signaling protein second messenger receptor protein first messenger target proteins downstream signaling protein D, C, A, B, F, E C, D, A, B, F, E D, C, B, A, F, E D, E, C, A, B, F

D, C, A, B, F, E first messenger receptor protein upstream signaling protein second messenger downstream signaling protein target proteins

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 enzymes glutamine synthetase adenylyl transferase and control of glutamine synthetase adenylyl transferase activity by uridylyl transferase. Column A a. binding of ATP b. adenylation c. binding of glutamine d. uridylation e. binding of Pi Column B 1. allosteric control 2. subunit association 3. proteolytic cleavage 4. covalent modification 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

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 inhibit by stimulating GDP-GTP exchange; GEFs activate by stimulating GTP hydrolysis. B. GAPs stimulate by blocking GTP hydrolysis; GEFs inhibit by stimulating GTP-GDP exchange. C. GEFs inhibit by stimulating GTP hydrolysis; GAPs activate by stimulating GDP-GTP exchange. D. GAPs inhibit by stimulating GTP hydrolysis; GEFs activate by stimulating GDP-GTP exchange. E. GAPs stimulate by inhibiting GDP-GTP exchange; GEFs activate by stimulating GDP phosphorylation.

D. GAPs inhibit by stimulating GTP hydrolysis; GEFs activate by stimulating GDP-GTP exchange.

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.

Put the following steps in the correct order to describe the process of signal transduction. (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. e -> a -> b -> c -> f -> d B. d -> f -> c -> b -> e -> a C. d -> f -> b -> c -> a -> e D. f -> d -> c -> b -> a -> e E. d -> f -> c -> b -> a -> e

E. d -> f -> c -> b -> a -> e

The allosteric activator ____________ stimulates activity of the enzyme __________ and is not a reactant in the glycolytic pathway, whereas the metabolite ___________ stimulates activity of the enzyme __________ using a feed forward mechanism to increase glycolytic flux. F-6-P; PFK-1; F-1,6-BP; Pyruvate Kinase F-2,6-BP; PFK-1; F-6-P; Pyruvate Kinase F-2,6-BP; PFK-1; F-1,6-BP; Pyruvate Kinase F-2,6-BP; Pyruvate Kinase; F-1,6-BP; PFK-1 F-1,6-BP; PFK-1; F-2,6-BP; Pyruvate Kinase F-2,6-BP; Glucokinase; F-1,6-BP; Pyruvate Carboxylase

F-2,6-BP; PFK-1; F-1,6-BP; Pyruvate Kinase

Glucose and fructose are both C6H12O6. What is the structural difference between them? Glucose is found in the boat conformation and fructose is a chair conformation. Glucose is a five-membered ring and fructose is a six-membered ring. Fructose is a five-membered ring and glucose is a six-membered ring. Glucose is a linear molecule and fructose is a ring.

Fructose is a five-membered ring and glucose is a six-membered ring

What is the function of the lactate dehydrogenase reaction in muscle cells during intense exercise? It regenerates NAD+ for the GAPDH reaction to maintain glycolytic flux and produce ATP for muscle contraction. It regenerates NAD+ for the PFK-1 reaction to maintain glycolytic flux and produce ATP for muscle contraction. It produces lactate to provide a carbon source for ATP production that is needed for muscle contraction. It regenerates NADH for the GAPDH reaction to maintain glycolytic flux and produce ATP for muscle contraction. It converts pyruvate to lactate in order to prevent alcoholic fermentation under anaerobic conditions in muscle cells.

It regenerates NAD+ for the GAPDH reaction to maintain glycolytic flux and produce ATP for muscle contraction.

How can an unfavorable reaction (∆G°' > 0) still occur in a metabolic pathway? Link it to a favorable reaction. Link it to another unfavorable reaction. They cannot be used in metabolic pathway reactions. Increase the temperature of the reaction.

Link it to a favorable reaction.

Which of the following correctly describes how phosphorylation of PIP2 to generate PIP3 propagates the insulin receptor signal? PIP3 binds to IRS-2, activating PI-3K. PIP3 is chemically inert, and must be dephosphorylated to PIP2 for downstream signaling to continue. PIP3 recruits Akt, a PH domain-containing protein, and PDK1 to the plasma membrane. PIP3 is degraded into IP3 and diacylglycerol.

PIP3 recruits Akt, a PH domain-containing protein, and PDK1 to the plasma membrane. Membrane-bound PIP3 recruits the Akt pleckstrin homology domain to the plasma membrane, resulting in upregulation of GLUT4 glucose transporters and removal of glucose from the bloodstream.

The sugar compound phosphatidylinositol-3,4,5-triphosphate (______) is produced by _________ in the insulin pathway, whereas inositol-1,4,5-trisphosphate (______) is a second messenger produced by ________ in the epinephrine pathway.2singlechoice poll question, The sugar compound phosphatidylinositol-3,4,5-triphosphate (______) is produced by _________ in the insulin pathway, whereas inositol-1,4,5-trisphosphate (______) is a second messenger produced by ________ in the epinephrine pathway. PIP2; SHC; PIP3; IRS-1PIP3; PLC; IP3; PI-3KIP3; PI-3K; PIP3; PLC PIP3; PI-3K; IP3; PLC

PIP3; PI-3K; IP3; PLC

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. Ser -> Phe Tyr -> Ser Ser -> Tyr Thr -> Ser

Ser -> Phe

What advantage is there to phosphoglycerate kinase having an open and closed protein configuration? It allows water to be trapped in the active site along with the substrate. It forces covalent binding of the substrate to the enzyme active site. Changing of the configuration of the enzyme makes the reaction exergonic. The induced-fit mechanism maximizes accessibility of active site without sacrificing hydrophobic environment.

The induced-fit mechanism maximizes accessibility of active site without sacrificing hydrophobic environment.

What characteristic is true for both RTKs and GPCRs? When activated, the receptor has enzymatic activity. The receptor transmits ions. The receptor undergoes a conformational change on activation. The receptor binds to intracellular proteins only when activated.

The receptor undergoes a conformational change on activation.

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. Tyr --> Phe Thr --> Ser Ser --> Tyr Ser --> Thr

Tyr --> Phe

Put the following eight signaling events in the correct order describing how glucagon binding to glucagon receptors in liver cells increases blood glucose levels in between meals. __Glucagon binds to the N-terminal domain of the receptor. __GDP is exchanged for GTP in the G-alpha subunit. __PKA phosphorylates downstream proteins that control glucose export.. __The C-terminal domain undergoes a conformational change. __Production of cyclic AMP leads to activation of PKA. __The G-alpha and G-beta/gamma subunits dissociate. __The GDP-bound heterotrimeric G protein binds to the receptor. __The G-alpha subunit binds to activates adenylate cyclase.

_1__Glucagon binds to the N-terminal domain of the receptor. __2__The C-terminal domain undergoes a conformational change. __3__The GDP-bound heterotrimeric G protein binds to the receptor. __4__GDP is exchanged for GTP in the G-alpha subunit. __5__The G-alpha and G-beta/gamma subunits dissociate. __6__The G-alpha subunit binds to activates adenylate cyclase. __7__Production of cyclic AMP leads to activation of PKA __8__PKA phosphorylates downstream proteins that control glucose export..

Put the following steps of the G protein cycle into the correct order. Dissociation of G-alpha and G-beta/gamma from a GPCR Reassociation of the heterotrimeric G complex with a GPCR GAPs stimulate the GTPase activity of G-alpha Ligand stimulation of the GEF function of a GPCR

__1__Ligand stimulation of the GEF function of a GPCR __2__Dissociation of G-alpha and G-beta/gamma from a GPCR __3__GAPs stimulate the GTPase activity of G-alpha __4__Reassociation of the heterotrimeric G complex with a GPCR

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 __________________. a metabolic pathway. an allosteric inhibition pathway. a signal transduction pathway. homeostasis.

a signal transduction pathway.

Based on the Butowt, R. and von Bartheld, C.S. (2020) paper: a) what might explain why ~60% of COVID-19 patients do not experience anosmia even though they experience other symptoms of SARS-CoV-2 infection? b) what might explain why ~10% of COVID-19 patients with anosmia do not regain their sense of smell even after 3 months? a) The olfactory support cells were not infected and/or killed by the virus. b) The stem cells needed to replenish olfactory support cells were killed. a) The olfactory support cells were infected by COVID-19 but not by SARS-CoV-2. b) The stem cells needed to replenish olfactory support cells were killed. a) The olfactory support cells were not infected and/or killed by the virus. b) The olfactory receptor neurons contain antibodies that are secreted and kill the virus. a) The olfactory receptor neurons do not contain olfactory receptors. b) The stem cells need to replenish olfactory support cells were killed.

a) The olfactory support cells were not infected and/or killed by the virus. b) The stem cells needed to replenish olfactory support cells were killed.

Which human disease states are treated by glucocorticoids based on the anti-inflammatory response of cells to glucocorticoid treatment? Choose the three most common (use a Google search). insomnia gout obesity arthritis prostate cancer asthma dermatitis stress ophidiophobia

arthritis asthma dermatitis

Receptor tyrosine kinase

autophosphorylation of the cytoplasmic tail and binding of adaptor proteins to Tyr-P.

Metabolism is best defined as a collection of enzymes that convert metabolites into pathways. biochemical reactions that convert mechanical work into energy. biochemical reactions that convert chemical energy into work. cellular processes that activate cell division.

biochemical reactions that convert chemical energy into work.

Which of the following is true about insulin binding on receptor tyrosine kinase? a) Insulin binding stimulates dephosphorylation of the β subunits of the receptor b) The binding of insulin to the receptor facilitates binding of a subsequent insulin, similar to oxygen on hemoglobin c) Typically only one insulin can bind to the receptor due to negative cooperativity d) Insulin activates a single signaling pathway within liver cells

c) Typically only one insulin can bind to the receptor due to negative cooperativity

Caffeine is a phosphodiesterase inhibitor. Based on your understanding of cAMP flux in the cell, which of the following might you see as a result of excessive caffeine intake by an undergraduate biochemistry student cramming for exams?AMP levels will increase. Adenylate cyclase activity will increase. Protein kinase A activity will decrease. cAMP levels will increase.

cAMP levels will increase. A phosphodiesterase inhibitor will prevent degradation of cAMP to AMP.

Which one of the following molecules can function as a second messenger? G-alpha subunit magnesium calcium adenylate cyclase cyclic UMP

calcium

In which of the following glycolytic pathway reactions is ATP phosphoryl transfer energy required to drive the reaction in the forward direction? 1,3-Bisphosphoglycerate → 3-phosphoglycerate glucose-6-phosphate → fructose-6-phosphate glucose → glucose-6-phosphate 2-Phosphoglycerate → 3-phosphoglycerate

glucose → glucose-6-phosphate

Which binding site most likely represents the area of greatest structural change in response to ligand binding? SOS binding DNA binding heterotrimeric G protein binding cAMP binding

heterotrimeric G protein binding

After breakfast, ______ hormone levels are high and rates of metabolic flux through ____ degradation and _____ are low. Before breakfast ______ hormone levels are high and rates of metabolic flux through _____ and ____ synthesis are low>

insulin glycogen gluconeogenesis glucagon glycolysis glycogen

When blood glucose levels are high in humans, the hormone ___________ stimulates metabolic flux through the __________ pathway and inhibits flux through the __________ pathway. The net effect of this hormone signaling is to increase ___________ of glucose. glucagon, gluconeogenesis, glycolysis, efflux glucagon, gluconeogenesis, glycolysis, influx insulin, gluconeogenesis, glycolysis, influx insulin, glycolysis, gluconeogenesis, influx glucagon, glycolysis, gluconeogenesis, efflux

insulin, glycolysis, gluconeogenesis, influx

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) allosteric effector. irreversible inhibitor. competitive inhibitor. allosteric activator.

irreversible inhibitor.

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. reversible inhibitor. allosteric effector.

irreversible inhibitor. "forms a covalent bond with a Ser"

Flux is defined as the rate at which __________is/are interconverted. cells metabolites minerals energy

metabolites

Which of the following are characteristics of allosteric enzymes like ATCase? Choose the THREE that apply. Allosteric enzymes: tend to have a sigmoidal (S-shaped) curve of V0 vs. [S]. may have binding sites for regulatory molecules that are separate from active sites. interconvert between a more active form and less active form. are generally small, single-subunit proteins. conform to Michaelis-Menten kinetics

tend to have a sigmoidal (S-shaped) curve of V0 vs. [S]. may have binding sites for regulatory molecules that are separate from active sites. interconvert between a more active form and less active form.

An inhibitor that binds only to the ES complex and not free enzyme is known as a(n) ___________ inhibitor. competitive uncompetitive irreversible mixed

uncompetitive