Biochem Exam 4 HW Questions

An enzyme at a concentration of 0.1uM has an initial velocity of 10uM/s at 5uM substrate concentration; at this enzyme concentration, the enzyme has a Vmax value of 30uM/s. What is the Km value for this enzyme in uM?

10

Which steps in glycolysis are likely to be highly regulated? (select all that apply) a. 10 b.3 c. 6 d. 4 e. 5 f. 1 g. 2 h. 9 i. 8 j. 7

a. 10 b.3 f. 1

Below is the data obtained in lab from measuring initial velocities of a reaction: [reactant] Vi 2mM 1mM/s 4mM 2mM/s 6mM 3mM/s 8mM 4mM/s What type of reaction is this? a. 1st order b. the order cannot be determined c. saturation kinetics d. zero order

a. 1st order

Which option below accurately reflects net yields for glycolysis in humans, starting with 1 molecule of glucose? a. 2 ATP, 2 NADH, 2 pyruvate b.2 ATP, 4 NADH, 2 CO2 c. 4 ATP, 2 NADH, 2 pyruvate d. 4 ATP, 4 NADH, 2 pyruvate

a. 2 ATP, 2 NADH, 2 pyruvate

Which of the following is correct for a competitive inhibitor a. A Lineweaver-Burke plot will show that the Km is higher b. If you increase the inhibitor concentration, the Km will not change c. It lowers the Vmax

a. A Lineweaver-Burke plot will show that the Km is higher

Glycolysis is a. A catabolic pathway converting glucose to pyruvate that results in net ATP production b. A catabolic pathway converting glucose to pyruvate that results in net ATP consumption c. An anabolic pathway converting glucose to pyruvate that results in net ATP production d. An anabolic pathway converting glucose to pyruvate that results in net ATP consumption

a. A catabolic pathway converting glucose to pyruvate that results in net ATP production

Glycolysis requires a. An investment of 2 ATP molecules, as well as incorporation of 2 Pi molecules, and usage of 2 NAD+ per glucose b. An investment of 1 ATP molecule and 1 ADP, and usage of 1 NADP+ per glucose c. Consumption of 2 NADH molecules and incorporation of 2 Pi molecules d. An investment of 2 ADP per glucose

a. An investment of 2 ATP molecules, as well as incorporation of 2 Pi molecules, and usage of 2 NAD+ per glucose

Which of the following is correct regarding uncompetitive inhibition: a. As the amount of uncompetitive inhibitor increases, the Km decreases b. As the amount of uncompetitive inhibitor increases, the Vmax increases c. The Vmax remains unchanged at all inhibitor concentrations d. The Km remains unchanged at all inhibitor concentrations

a. As the amount of uncompetitive inhibitor increases, the Km decreases

The catabolism of fatty acids is known as beta-oxidation and produces large amounts of ATP because fatty acids are so reduced. The synthesis of fatty acids involves enzymes known as synthases. What can be said about the catabolism and anabolism of fatty acids? a. Both pathways must be exergonic; beta oxidation produces ATP while fatty acid synthesis consumes ATP b. The energy used to synthesize fatty acids is derived from the ATP generated by their oxidation c. Beta oxidation is exergonic while fatty acid biosynthesis is endergonic d. The synthesis of fatty acids must be the reverse of beta-oxidation (or, beta-oxidation 'running in reverse')

a. Both pathways must be exergonic; beta oxidation produces ATP while fatty acid synthesis consumes ATP

Which of the following could be typical catabolic end products? (select all that apply) a. CO2 b. nucleotides c. ATP d. polypeptides e. TAGs f. urea, (NH2)2 -C=O

a. CO2 c. ATP f. urea, (NH2)2 -C=O

Which statement below best describes what glycolysis accomplishes? a. Oxidation of glucose to pyruvate with generation of some ATP and NADH; it does not require O2 and does not produce CO2 b. Oxidation of glucose to lactate with the generation of ATP in the mitchondria c. Breakdown of glucose to pyruvate with net generation of 2 ATP; it requires O2 and occurs in the cytosol d. Oxidation of glucose to CO2 with generation of ATP and NADH in the presence oxygen in the mitochondria

a. Oxidation of glucose to pyruvate with generation of some ATP and NADH; it does not require O2 and does not produce CO2

Individuals with a mutation in glyceraldehyde kinase (also called "triose kinase" or "TK) will generate oxidative damage in their livers. This is a very rare mutation, however, and it is not fatal. Consider what may metabolically happen in a person with this TK mutation that renders the enzyme inactive. The mutation is called TK*. ("tee-kay-star")You have a patient who has the TK* mutaiton AND they metabolize fructose at the same rate as a person without the mutation.Which of the following would be expected to occur in this patient's liver? a. Oxidative liver damage can be avoided by limiting fructose consumption for a person with TK*. b. Fructose cannot be converted into Fructose-1-phosphate in liver with a person with TK*. c. All 6 carbons from fructose can still be converted to pyruvate with the same net ATP yield as the conversion of glucose to pyruvate in a person with TK*. d. Fructose in liver with a TK* person will be regulated by PFK. Fructose in liver for a person with a normal wild-type TK will by-pass PFK. e. Fructose will not be converted into glycerol in a person with TK* f. If all fructose in liver is converted to pyruvate in this patient, then none of the fructose is converted into DHAP. g. A person with TK* will spend more ATP to convert fructose into GAP than someone without the mutation. Thus the ATP yield in glycolysis from fructose will be lower for a person with TK*. h. A person with TK* can generate glyceraldehyde and DHAP from fructose

a. Oxidative liver damage can be avoided by limiting fructose consumption for a person with TK*. c. All 6 carbons from fructose can still be converted to pyruvate with the same net ATP yield as the conversion of glucose to pyruvate in a person with TK*. h. A person with TK* can generate glyceraldehyde and DHAP from fructose

Which enzymatic steps in glycolysis are irreversible and/or the main targets of glycolytic regulation? a. PFK b. aldolase c. enolase d. hexokinase e. pyruvate kinase f. glyceraldehyde-3-phosphate dehydrogenase

a. PFK d. hexokinase e. pyruvate kinase

ATP is a product of the last step of the glycolysis pathway. Phosphofructokinase (PFK) is an enzyme near the beginning of the glycolysis pathway. It is a kinase that converts fructose-6-phosphate and ATP to fructose-1,6 bisphosphate and ADP. The fact that the velocity of PFK decreases with increasing ATP concentration suggests which of the following: a. PFK is an allosteric enzyme that is activated by ADP; it has quaternary structure b. PFK is an allosteric enzyme that is inhibited by ATP; it has quaternary structure c. PFK is an allosteric enzyme that is inhibited by ATP; it is a monomer d. PFK is inhibited by glucose and activated by cAMP

a. PFK is an allosteric enzyme that is activated by ADP; it has quaternary structure

Which statement is correct concerning reactions that are near-equilibrium vs. far-from-equilibrium as found in glycolysis? a. PGM and PGI catalyze near equilibrium reactions while hexokinase is a far from equilibrium reaction b. All glycolytic reactions are near equilibrium reactions because gluconeogenesis is the reverse of glycolysis c. Hexokinase is a near-equilibrium reaction while TIM is a far from equilibrium reaction d. PK and PFK are catalyze near equilibrium reactions while hexokinase is a far from equilibrium reaction e. All glycolytic reactions are far from equilibrium because the pathway of glycolysis has a large and negative change in Gibbs Free Energy.

a. PGM and PGI catalyze near equilibrium reactions while hexokinase is a far from equilibrium reaction

Which of the following is correct regarding the fermentation of pyruvate in humans? a. Pyruvate is reduced to lactate in one enzymatic step along with the generation of NAD+ for glycolysis b. Pyruvate is reduced to lactic acid and this results in a lower pH c. Pyruvate is oxidized to lactic acid and generates one molecule of NADH for glycolysis d. Pyruvate is converted to lactic acid and generates one molecule of NAD+ to allow glycolysis to continue

a. Pyruvate is reduced to lactate in one enzymatic step along with the generation of NAD+ for glycolysis

Which statement below is most correct a. The Km will change for a competitive inhibitor b. The Km will change for a noncompetitive inhibitor c. Km will not change for a competitive inhibitor d. Km will not change for an uncompetitive inhibitor

a. The Km will change for a competitive inhibitor

One reason why ATP hydrolysis has a large, negative Gibbs Free Energy in the cell is because: a. The concentration of ATP is typically greater than that of ADP b. The net charge on ATP is amplified by Mg2+ through charge-charge repulsion c. ATP is resonance stabilized, while ADP contains more bridging oxygens d. ATP is more soluble than the products of its hydrolysis

a. The concentration of ATP is typically greater than that of ADP

An enzyme obeys Michaelis-Menten kinetics, what must be true of the enzymatic reaction? a. The conversion of product to substrate can be considered negligible and the concentration of the [ES] complex does not change over the course of the reaction b. The rate limiting step of the reaction may be either substrate binding or product release and the initial velocity increases linearly at low substrate concentrations c. The reaction follows first order kinetics at high substrate concentration and the reaction follows zero order kinetics at low substrate concentrations d. The rate limiting step is substrate binding and most of the enzyme is present as free enzyme at high substrate concentrations

a. The conversion of product to substrate can be considered negligible and the concentration of the [ES] complex does not change over the course of the reaction

On a Michaelis-Menten plot measuring Vi vs. [S] for an enzyme, what is correct regarding the reaction when the [S] is very high and the plot is approaching its horizontal asymptote? a. The enzyme is becoming saturated b. The enzyme is at equilibrium c. The enzyme is far from Vmax d. The enzyme has a low kcat value

a. The enzyme is becoming saturated

The first enzyme in the glycolysis pathway is hexokinase; while pyruvate kinase (PK) is the last. Based on the data handed out, which statement below best describes the actual change in Gibbs Free Energy for the glycolysis pathway in heart muscle cells? a. The pathway is exergonic with a change of about -80kJ/mol b. Glycolysis does not generate net energy, so the change in Gibbs Free Energy is 0.0kJ/mole c. The pathway is endergonic with a change of about +55 kJ/mol d. The pathway is endergonic with a change of about +80kJ/mol e. The pathway is exergonic with a change of about -55kJ/mol f. The pathway is exergonic with a change of about -25kJ/mol g. The pathway is endergonic with a change of about +25kJ/mol

a. The pathway is exergonic with a change of about -80kJ/mol

Glycolysis results in the conversion of glucose into pyruvate. Gluconeogenesis results in the conversion of pyruvate into glucose. If the cell doesn't regulate its business well, the reactions catalyzed by which of the following enzymes are most likely to be in a substrate cycle: a. The reactions catalyzed by the enzymes Hexokinase, PFK, and PK b. The reactions catalyzed by TIM and PGM c. The reactions catalyzed by the enzymes Aldolase and TIM d. The reactions catalyzed by PGI, TIM, and PGM (the isomerases)

a. The reactions catalyzed by the enzymes Hexokinase, PFK, and PK

Which of the following correctly describes the Gibbs Free Energy change for the entire glycolytic pathway? a. The standard Gibbs Free Energy change is negative; if glycolysis is active, then the actual change in Gibbs Free Energy is negative, too. b. The standard Gibbs Free Energy change is positive; if glycolysis is active, then the actual change in Gibbs Free Energy is negative, too. c. The standard Gibbs Free Energy change is negative; if glycolysis is active, then the actual change in Gibbs Free Energy is positive

a. The standard Gibbs Free Energy change is negative; if glycolysis is active, then the actual change in Gibbs Free Energy is negative, too.

What can be said of the entry of mannose and galactose into glycolysis metabolism? a. They are six-carbon sugars, so they enter through hexokinase and before PFK. They result in the same net ATP yield in glycolysis as glucose. b. They enter as fructose and as GAP. They produce the same amount of ATP in glycolysis as glucose c. They enter through hexokinase and produce less ATP than glucose in glycolysis because they must be isomerized upon entry and isomerization requires a greater ATP input d. They enter glycolysis after PFK, and result in less ATP yield than glucose in glycolysis

a. They are six-carbon sugars, so they enter through hexokinase and before PFK. They result in the same net ATP yield in glycolysis as glucose.

You are studying a hydrolase that degrades an antibiotic. For your assays, you add purified enzyme in a buffer to various concentrations of substrate (antibiotic) and measure the initial velocity in a spectrophotometer. For your first set of assays, the enzyme concentration is 2µM. You aren't detecting enough product in your assays, so you double the total enzyme concentration in your assays to 4µM. Which of the following describes what will happen: a. Vmax will double, but kcat remains unchanged b. Both Vmax and kcat will double c. kcat will decrease by half d. kcat will double, but Vmax remains unchanged

a. Vmax will double, but kcat remains unchanged

Which of the following conditions, events, or changes would be most likely to change the kcat for an enzyme? (select all that apply) a. a mutation in the active site of an enzyme b. a change in pH c. a change in substrate concentration d. addition of a competitive inhibitor e. a change in enzyme concentration f. a change in temperature

a. a mutation in the active site of an enzyme b. a change in pH f. a change in temperature

Can you draw or ID the characteristic bond or atoms for the following high energy compounds? Can you name a compound that belongs to each of the types of high energy compound classes below? a. acyl phosphates b. thioesters c. inorganic diphosphate, PPi, the honorary high energy compound which has a phosphoanhydride d. phosphorylated amines e. enol phosphates f. phosphoanhydrides

a. acyl phosphates

Besides two molecules of pyruvate, what are the net products of glycolysis per molecule of glucose? a. none of the options are correct b. 2 ATP and 2 NADH c. 4 ATP and 2 NADH d. 4 ATP and 4 NADH e. 2 ATP and 4 NADH

b. 2 ATP and 2 NADH

You are studying an oxidoreductase that activates a pro-drug. You vary substrate concentration from 0 to 10µM. You obtain a Lineweaver-Burke plot for this enzyme. The equation for the fitted line on the plot is: y = 8x + 4. What is the Km for this enzyme? a. -0.5uM b. 2uM c. -2uM d. 0.5uM

b. 2uM

When galactose enters glycolysis, what must galactose be converted to first? a. A UDP-galactose by phosphorylation at the C6 position by a kinase b. A UDP-glucose by transfer of a UMP to a galactose-1-phosphate c. A UDP-fructose through isomerization by an epimerase acting on a galactose-1-phosphate d. A glucose-1-phosphate generated by the action of a phosphorylase

b. A UDP-glucose by transfer of a UMP to a galactose-1-phosphate

Glycolysis produces: a. A net of two ATP molecules per glucose and some CO2 b. A net of two ATP molecules per glucose as well as some NADH c. A net consumption of 2 ATP molecules per glucose and 2 molecules of NADPH d. A net of zero ATP molecules and 2 NADPH molecules per glucose

b. A net of two ATP molecules per glucose as well as some NADH

What is produced upon the anaerobic fermentation of pyruvate? a. acetylCoA and NADPH b. A reduced end product, like ethanol or lactate, and NAD+ c. oxygen, ATP, and a lower pH d. An oxidized end product, CO2, and NADH

b. A reduced end product, like ethanol or lactate, and NAD+

Which of the following are NET products of glycolysis from 1 molecule of glucose? (glycolysis is defined as glucose --> --> --> pyruvate) check all that apply a. O2 b. ATP c. Acetyl-CoA d. Pi e. ADP f. pyruvate g. CO2 h. NADH

b. ATP f. pyruvate h. NADH

A noncompetitive inhibitor will: a. Bind to the ES complex (bound enzyme) and lower the Vmax b. Bind to either free enzyme (unbound) or the ES complex (bound enzyme) and lower the Vmax c. Bind to the free enzyme (unbound) only and increase the Km d. Increase the Km and lower the Vmax

b. Bind to either free enzyme (unbound) or the ES complex (bound enzyme) and lower the Vmax

Enzymes with simple Michaelis-Menten kinetics have _________ shaped plots of substrate concentration versus initial velocity, while allosterically controlled enzymes tend to have _________ shaped plots. a. Linear, Hyperbolic b. Hyperbolic, Sigmoidal c. Symmetric, Asymmetric d. Sigmoidal, Hyperbolic

b. Hyperbolic, Sigmoidal

Proteases are hydrolase enzymes that use water to break apart peptide bonds. Shown below is an entity from a hydrolase. Which statement about the entity is most correct? a. It is a transition state because oxygen, a very electronegative atom, cannot hold on to a negative charge b. It is a transition state because oxygen does not form three bonds c. It is an intermediate because no rules or bonding or valency are violated d. It is an intermediate because this compound could be synthesized by a chemist

b. It is a transition state because oxygen does not form three bonds

Which of the following is correct concerning the enzyme phosphofructokinase-1: a. It generates ATP by substrate-level phosphorylation and is allosterically inhibited by high levels of ATP b. It is allosterically inhibited by ATP and citrate, and allosterically activated by AMP and fructose 2,6-bisphosphate c. It is the product of feedback inhibition by pyruvate and it is allosterically activated by glucose d. It is allosterically inhibited by its product, glucose 6-phosphate Clear my choice

b. It is allosterically inhibited by ATP and citrate, and allosterically activated by AMP and fructose 2,6-bisphosphate

Which of the following correctly describes the entry of mannose into glycolysis? a. It enters as glyceraldehyde-3-phosphate and by-passes the PFK step; it produces the same amount of ATP as glucose b. It is phosphorylated by hexokinase and results in the same ATP yield as glucose c. It enters as a UDP-mannose and it requires an additional high-energy phosphate investment compared to glucose d. It is isomerized to a glucose and is phosphorylated by hexokinase to enter as a glucose-1-phosphate; it has the same ATP yield as glucose

b. It is phosphorylated by hexokinase and results in the same ATP yield as glucose

What does the pentose phosphate pathway accomplish for the cell? a. It produces NAD+, which is needed to keep glycolysis going under anaerobic conditions b. It produces NADPH, which is needed for many anabolic reactions c. It produces NADPH, which is needed for many catabolic reactions d. It produces 7 carbon sugars needed for nucleic acids

b. It produces NADPH, which is needed for many anabolic reactions

Which statement best describes what a kinase, phosphorylase, and phosphatase accomplish in the cell? a. Kinases are regualated by phosphatases; phosphatases are regulated by kinases; phosphorylases are regulated by phosphates b. Kinases will phosphorylate substrates with ATP; phosphatases will remove phosphates from substrates; phosphorylases will use Pi to place a phosphate on substrates c. Kinases will phosphorylate substrates and have hydrolase activity; phosphatases generate phosphate: phosphorylases will remove phosphates d. Kinases activate enzymes; phosphatases deactivate enzymes; phosphorylases regulate phosphate

b. Kinases will phosphorylate substrates with ATP; phosphatases will remove phosphates from substrates; phosphorylases will use Pi to place a phosphate on substrates

You determine the initial velocity for an enzyme at 5µM is 10µM/min at a substrate concentration of 2µM. You determine that the maximum velocity at 5 µM of enzyme is 20µM/min. What is the Km and kcat? a. Km is 10µM and kcat is 4/min b. Km is 2µM and kcat is 4/min c. Km is 5µM and kcat is 100/min d. Km is 2µM and kcat is 0.25/min

b. Km is 2µM and kcat is 4/min

What does fermentation generate that is so critical for the metabolic needs of the organisms undergoing this process? a. Ethanol b. NAD+ c. Pyruvate d. CO2 e. ATP (directly)

b. NAD+

Which statement below best describes why glycolysis and gluconeogensis are not perfect "reversals" of each other? a. Glycolysis starts and ends with glucose and pyruvate. Gluconeogenesis does not start and end with glucose and pyruvate. The beginning and end points are different. b. Some steps in glycolysis have a large and negative dG value. Gluconeogenesis must use a different chemical approach to bypass such reactions. c. Glycolysis is -dG. Gluconeogenesis is +dG.

b. Some steps in glycolysis have a large and negative dG value. Gluconeogenesis must use a different chemical approach to bypass such reactions.

Which of the following accurately describes what happens to a carbohydrate in glycolysis a. glycolysis ends with the production of pyruvate, a hexose sugar that is an anomer of fructose b. The ATP investment is made by phosphorylating hexose sugars prior to aldolase cleavage c. the triose sugars in the latter stage of glycolysis are phosphorylated by ligases d. the phosphorylated hexose sugars that occur at the beginning of glycolysis are 'high-energy' compounds that are not re-arranged

b. The ATP investment is made by phosphorylating hexose sugars prior to aldolase cleavage

What is a biological significance of metabolic reactions that are, essentially, irreversible in the cell: a. They are evolutionary mistakes b. The are often points of regulation in pathways and frequently have large, negative values for Gibbs Free Energy c. They allow the cell to run pathways in reverse d. They are always anabolic reactions

b. The are often points of regulation in pathways and frequently have large, negative values for Gibbs Free Energy

Which of the follow correctly describes the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase? a. the dehydrogenase performs substrate-level phosphorylation b. The dehydrogenase is an oxidoreductase c. NADH is produced d. the dehydrogenase produces a 'high-energy' compound e. inorganic phosphate (Pi) is incorporated into the substrate

b. The dehydrogenase is an oxidoreductase c. NADH is produced d. the dehydrogenase produces a 'high-energy' compound e. inorganic phosphate (Pi) is incorporated into the substrate

Consider a plot of initial velocity vs. [S] for an enzyme obeying Michaelis-Menten kinetics. These plots form the rectangular hyperbola that we saw many times. Which of the following statements is most likely correct? a. At low substrate concentration, the enzyme exhibits zero order kinetics. At high substrate concentration it exhibits first order kinetics b. The enzyme shows first order kinetics at low substrate concentration and zero order kinetics at high substrate concentration c. The plot shows when equilibrium is reached at a high substrate concentration d. The horizontal asymptope depicts the Km value for the enzyme

b. The enzyme shows first order kinetics at low substrate concentration and zero order kinetics at high substrate concentration

Which of the following best describes allosteric enzymes: a. Allosteric enzymes do not exhibit cooperativity and will covalently bind their activators in the active site b. The enzyme typically has quaternary structure and an inhibitor often does not chemically resemble the substrate c. Allosteric enzymes exhibit cooperative and typically lack quaternary structure d. Allosteric enzymes contain multiple active sites in each subunit and will act on multiple substrates

b. The enzyme typically has quaternary structure and an inhibitor often does not chemically resemble the substrate

A unimolecular isomerization reaction has a Keq value of 3. Which of the following is correct for the addition of an enzyme to accelerate this reaction in a cell? a. The actual Gibbs Free Energy (∆G) will be negative at equilibrium b. The product will be more abundant than substrate at equilibrium c. The concentration of product and substrate will be equal at equilibrium d. The substrate will be more abundant at equilibrium

b. The product will be more abundant than substrate at equilibrium

Consider the enzymatic conversion of Substrate (S) into product (P). Based on the reaction coordinate shown below for the enzyme catalyzed reaction, what can be concluded about the chemical reaction? a. The reaction is exergonic where [P] > [S] at equilibrium b. The reaction is endergonic where [S] > [P] at equilibrium c. The reaction is endergonic where [P] > [S] at equilibrium d. The reaction is exergonic where [S] > [P] at equilibrium

b. The reaction is endergonic where [S] > [P] at equilibrium

The first step in glycolysis is catalyzed by the enzyme hexokinase. The reaction is ATP + Glucose <----> Glucose-6-P + ADP The reaction and some parameters are shown in the image below. To which class of enzymes does this reaction belong? a. Isomerase b. Transferase c. Ligase d. Oxidoreductase e. Lyase f. Hydrolase

b. Transferase

What type of inhibitor is displayed on the Lineweaver-Burk plot below? a. Competitive b. Uncompetitive c. Noncompetitive

b. Uncompetitive

Consider the following progress curves for two different unimolecular isomerization reactions. The reactions are: Reaction #1 A <----> B and Reaction #2 X <----> Y Based on the progress curves, what can be said of the reactions? (Study the axes and their units.) (multiple answers may be selected, or 1 answer may be selected) a. Both reactions have a negative ΔGº'. b. Under the given set of conditions, reaction 1 reaches equilibrium faster than reaction 2. c. Both reactions will have the same value for ΔG under the given set of conditions. d. Reaction 2 has a larger Keq than reaction 1

b. Under the given set of conditions, reaction 1 reaches equilibrium faster than reaction 2. d. Reaction 2 has a larger Keq than reaction 1

In an enzyme reaction involving one enzyme and one substrate, the rate of the reaction depends on a. the enzyme concentration at first and the substrate concentration later on. b. both substrate and enzyme concentrations. c. substrate concentration. d. enzyme concentration.

b. both substrate and enzyme concentrations.

The glycolytic pathway oxidizes glucose to two molecules of pyruvate and also produces a net of two molecules of ATP. ATP allosterically inhibits the enzyme, PFK-1, that catalyzes the third step of glycolysis. This is an example of ________. a. feed-forward activation b. feedback inhibition c. competitive inhibition d. negative cooperativity

b. feedback inhibition

Which statement below best describes the entry of fructose into glycolysis in liver? a. fructose enters as a fructose-1-phosphate after being phosphorylated by hexokinase b. fructose enters as GAP, and does not pass through PFK c. fructose enters as a glucose-1-phosphate after being phosphorylated by FBPase d. fructose enters as a fructose-6-phosphate after being phosphorylated by PKA

b. fructose enters as GAP, and does not pass through PFK

What is the difference in fructose catabolism in liver and muscle? a. fructose is isomerized to glucose in muscle and enters as a GAP; fructose is converted to UDP-fructose in liver and enters at hexokinase b. fructose enters at hexokinase in muscle as a fructoase-6-phosphate; fructose enters as a GAP in liver after a fructokinase and aldolase reaction c. fructose is phosphorylated to fructose-1-phosphate by hexokinase in muscle; it enters as GAP after being phosphorylated by PFK in liver d. fructose is phosphrylated by hexokinase in both liver and muscle; in both liver and muscle it enters as GAP, bypassing the PFK enzyme

b. fructose enters at hexokinase in muscle as a fructoase-6-phosphate; fructose enters as a GAP in liver after a fructokinase and aldolase reaction

It might be difficult to determine either Km or Vmax from a graph of velocity vs. substrate concentration and so researchers may use a Lineweaver-Burke plot. Why can Michaelis-Menten plots sometimes be problematic? a. the graph is sigmoidal. b. in some cases, too much substrate is required to determine them c. enzymes switch between first order and zero order kinetics d. the points on the graph are often not spread out on the hyperbola.

b. in some cases, too much substrate is required to determine them

Which of the following correctly describes the reaction catalyzed by GAP dehydrogenase in glycolysis, which is a very critical reaction? a. it is a near equilibrium isomerase that generates the NADH needed for fermentation b. it generates a high energy product, produces NADH, and requires Pi as a substrate c. it reduces NAD+, generates ATP by substrate-level phosphorylation, and is near equilibrium d. it consumes ATP, produces a high energy product, and oxidizes NADH Clear my choice

b. it generates a high energy product, produces NADH, and requires Pi as a substrate

Which statement below best describes the term "substrate-level phosphorylation"? a. making ATP through the proton gradient generated at the electron transport chain b. making ATP in an enzymatic reaction from a high energy substrate molecule c. an unusual, difficult, and dangerous dance move that can only be attempted by the most spry and unassuming dance phenome physicists... like Dr. Rodriguez d. a kinase uses and ATP to transfer a phosphate from ATP onto a second substrate molecule

b. making ATP in an enzymatic reaction from a high energy substrate molecule

In the presence of a competitive inhibitor, an enzyme will: a. now have a lower Vmax and have a higher Km for its native substrate b. now have a higher Km for its native substrate c. now have a lower Vmax and a lower Km for its native substrate d. now have a lower Vmax

b. now have a higher Km for its native substrate

Which statement best describes the difference between a phosphatase and a kinase: a. a phosphatase is essentially a kinase that is running in reverse, because the reverse reaction is more thermodynamically favorable b. phosphatases catalyze the removal of a phosphate group while kinases may utilize ATP to phosphorylate a substrate c. a phosphatase synthesizes ATP from ADP + Pi, while a kinase hydrolyzes ATP to ADP + Pi d. phosphatases are required for generating "high energy" compounds as products while kinases hydrolyze ATP to ADP

b. phosphatases catalyze the removal of a phosphate group while kinases may utilize ATP to phosphorylate a substrate

The steady state assumption in enzyme kinetics: a. insures that the product of an enzymatic reaction will always be formed b. states that the formation of ES is equal to its breakdown c. explains why enzymes are effective catalysts d. is based upon the fact that the maximum velocity of an enzyme is very high e. none of the above

b. states that the formation of ES is equal to its breakdown

Consider a 4 step pathway: A --> B --> C --> D --> E If the actual Gibbs Free Energy change in an 'average' cell for each reaction, in isolation, is: -3kJ/mole, -18 kJ/mole, 0.1 kJ/mole, and 12 kJ/mole, which step is likely to be the most regulated? a. step 1 b. step 2 c. step 3 d. step 4 e. none of the steps f. all of the steps

b. step 2

An enzyme at 0.1µM concentration in the presence of saturating substrate conditions is found to have a Vmax of 10µM/min. The enzyme satisfies Michaelis-Menten conditions. What is the kcat for this enzyme? a. 1/min b. 0.1/min c. 100/min d. 10/min

c. 100/min

An enzyme at 2µM concentration in the presence of saturating substrate conditions is found to have a Vmax of 5µM/min. The enzyme satisfies Michaelis-Menten conditions. What is the kcat for this enzyme? a. 0.4/min b. 5/min c. 2.5/min d. 10/min

c. 2.5/min

An enzymatic reaction satisfying Michaelis-Menten conditions has a Vmax of 20 μM/min. At a substrate concentration of 5 μM, the initial velocity is 2 μM/min. What is the Km for the reaction? a. 100 μM b. 4 μM c. 45 μM d. 10 μM

c. 45 μM

Which of the following is correct regarding glucose in solution? a. It is mainly found in a pyranose form b. It is predominantly in the beta-conformation c. All answer options are correct d. It is cyclized

c. All answer options are correct

Why do metabolic pathways typically consist of multiple intermediates and involve multiple enzymes: a. Multiple steps in a pathway allows for distinct points of regulation - such as feedback regulation or control points at mostly irreversible steps. b. Because enzymes typically only catalyze simple chemical reactions with small chemical changes from substrate to product. In an entire pathway like glycolysis, the first intermediate usually gets greatly changed by the end. This is too much to ask of any one enzyme. c. All options are valid d. If a pathway is conducted in one step, it may release (or require) entirely too much energy in one large and uncontrolled step.

c. All options are valid

Which of the following is correct regarding glycolysis? a. Glycolysis is only used by aerobic organisms b. Only eukaryotes use glycolysis c. All organisms use a glycolytic pathway and it occurs in the cytosol

c. All organisms use a glycolytic pathway and it occurs in the cytosol

Which are generally true concerning anabolic and catabolic pathways? Select all that apply. a. Anabolic pathways are -dG. Catabolic pathways are +dG. b. Anabolic pathways are always "spiral." Catabolic pathways are always "linear." c. Anabolic pathways will often use NADPH if an electron input is needed. Catabolic pathways will often generate NADH. d. Anabolic pathways often consume ATP. Catabolic pathways often generate ATP.

c. Anabolic pathways will often use NADPH if an electron input is needed. Catabolic pathways will often generate NADH. d. Anabolic pathways often consume ATP. Catabolic pathways often generate ATP.

Which of the following best describes the relationship between anabolism and catabolism? a. Catabolic reactions operate in pathways that have a negative change in Gibbs Free Energy; anabolic reactions in pathways that have a positive change in Gibbs Free Energy b. Catabolic reactions are regulated and far-from equilibrium while anabolic reactions are near-equilibrium reactions c. Catabolic reactions supply the chemical energy needed for anabolic reactions d. Anabolic reactions supply the Gibbs Free Energy needed for far-from equilibrium reactions

c. Catabolic reactions supply the chemical energy needed for anabolic reactions

What type of inhibition is depicted below? a. Anticompetitive b. Uncompetitive c. Competitive d. Noncompetitive (mixed)

c. Competitive

Shown below is a transition state and a drug. The image was taking from a peer-reviewed article recently published. The drug is immucillin. The transition state is for a purine nucleoside phosphorylase. Which statement below is correct regarding this figure? a. Entity B on the right is the transition state, Entity A on the left is the drug b. Entity A on the left is an intermediate, Entity B on the right is the drug c. Entity A on the left is the transition state, Entity B on the right is the drug d. Entity A on the left is a substrate, Entity B on the right is a product

c. Entity A on the left is the transition state, Entity B on the right is the drug

Which step in an enzyme-catalyzed reaction was assumed to be negligible by Michaelis and Menton? a. Conversion of ES to E + S. b. Formation of ES from E + S. c. Formation of ES from E + P. d. Formation of E + P from ES.

c. Formation of ES from E + P.

When PKA phosphorylates PFK-2 in liver, what is going to occur in liver? Select all possible answers a. Fructose-6-phosphate will be converted to Fructose-1,6-bP b. Fructose-1,6-bP will be converted to Fructose-2,6-bP c. Fructose-2,6-bP will be converted to F-6-P d. gluconeogenesis will occur

c. Fructose-2,6-bP will be converted to F-6-P d. gluconeogenesis will occur

Study the reactions of glycolysis. Which equation best summarizes the glycolysis pathway: a. Glucose + Pi + NAD+ à pyruvate + NADH + H2O + H+ b. Glucose + 2Pi + 2NADH + H+ à 2 pyruvate + 2NAD+ c. Glucose + 2ADP + 2Pi + 2NAD+ à 2 pyruvate + 2ATP + 2NADH + 2H2O + H+ d. Glucose + 2ATP + NAD+ à pyruvate + 2ADP + NADH + 2H2O + 2Pi + H+ e. Glucose + 2ADP + 2H2O à 2 pyruvate + 2ATP + CO2 + 2H+

c. Glucose + 2ADP + 2Pi + 2NAD+ à 2 pyruvate + 2ATP + 2NADH + 2H2O + H+

What statement below best describes why hemoglobin is an allosteric protein: a. Hemoglobin has quaternary structure; all proteins with quaternary structure are allosteric... they just have to be. It doesn't feel right for proteins with multiple subunits to lack allostery. Right? b. Hemoglobin only has one binding site and this is at the heme cofactor c. Hemoglobin has non-heme binding sites for small molecules other than oxygen.

c. Hemoglobin has non-heme binding sites for small molecules other than oxygen.

Creatine is a popular sports supplement. Its effectiveness is still being investigated. Cells typically contain a limited supply ATP that can sometimes be depleted quickly. Consider the production of phosphocreatine below: The ΔG°' value for this reaction is close to +10.0 kJ/mole, and its ΔG value in the cell is close to 0.0kJ/mole. Based on this information, what could you say about phosphocreatine? a. It is not a high energy compound, but allows the cell to build up its storage of ATP b. Phosphocreatine can serve to generate ATP in the cell when ATP concentrations are very high (10^6 more ATP than phosphocreatine for example). c. It is a high energy compound that might be able to serve as energy currency if the cell is depleted of ATP d. It a high energy compound with a +ΔG°' value when it undergoes hydrolysis of its phosphate group

c. It is a high energy compound that might be able to serve as energy currency if the cell is depleted of ATP

Which statement below is an accurate description of anabolism? a. It is the breakdown of larger biomolecules into smaller precursors with an input of chemical energy b. It is the biosynthesis of larger biomolecules from smaller precursors and it releases chemical energy c. It is the biosynthesis of larger biomolecules from smaller precursors with an input of chemical energy d. We learned how it can be a richly rewarding personal experience for people who want to achieve unnatural proportions, make new friends, and establish new communal living accommodations in a state facility.

c. It is the biosynthesis of larger biomolecules from smaller precursors with an input of chemical energy

What is significant regarding the enzymatic step converting fructose 6-phosphate to fructose 1,6-bisphophate in glycolysis? a. It is an oxidation-reduction reaction that regenerates NAD+ b. It generates the first high-energy intermediate and produces ATP c. It is the rate-limiting step and the most important control step in glycolysis d. It is the first example substrate-level phosphorylation in the catabolism of glucose e. none of the options are correct

c. It is the rate-limiting step and the most important control step in glycolysis

What is significant regarding the step converting fructose 6-phosphate to fructose 1,6-bisphophate in glycolysis: a. It generates the first high-energy intermediate and produces ATP by substrate level phosphorylation b. It utilizes inorganic phosphate and releases CO2 c. It is the rate-limiting step that is far from equilibrium and highly regulated d. It is an oxidation-reduction reaction that regenerates needed NAD+

c. It is the rate-limiting step that is far from equilibrium and highly regulated

Phosphofructokinase (PFK) catalyzes the conversion of Fructose-6-phosphate to Fructose-1,6-bisphosphate. Identify the concentrations of ATP and ADP that will result in maximal activity of PFK. a. Low ATP, Low ADP b. High ATP, High, ADP c. Low ATP, High ADP d. High ATP, Low ADP

c. Low ATP, High ADP

An uncompetitive inhibitor will do which of the following a. Raise the Vmax and lower the Km b. Sit out of the game and remain on the bench c. Lower the Vmax and lower the Km d. Raise the Km

c. Lower the Vmax and lower the Km

Which of the following is produced when humans ferment pyruvate into lactate? (select all that apply) a. lactic acid b. CO2 c. NAD+ d. ATP e. lactate f. O2 g. ethanol

c. NAD+ e. lactate

Glycolysis catabolizes glucose into pyruvate and produces net ATP. Yet, glycolysis has a negative ∆G°' value of -45kJ/mole. What statement below best describes how this is possible? a. The cell keeps the concentrations of reactants and products in a ratio such that ∆G°' is negative. b. Because 1 molecule of glucose is converted into 2 molecules of pyruvate, the entropy of the cell increases, making ∆G favorable. c. Because CO2 is released in glycolysis, the entropy of the cell increases and this is thermodynamically favorable. d. Glycolysis produces some high energy intermediate compounds that have a greater (more negative and favorable ∆G°') phosphoryl transfer potential than ATP.

d. Glycolysis produces some high energy intermediate compounds that have a greater (more negative and favorable ∆G°') phosphoryl transfer potential than ATP.

Consider the rate constants for an enzyme catalyzed reaction: E + S <--> ES --> E + P Which enzyme will have greater affinity for its substrate: Enzyme A, for which k1 >> k-1 and k2 Enzyme B, for which k-1 >> k1 and k2 Enzyme C, for which k2 >> k1 and k-1 a. it cannot be determined b. enzyme C c. enzyme A d. enzyme B

c. enzyme A

Which option below best describes the inputs (substrates and reactants) for glycolysis? a. glucose, NAD+, Pi, CO2 b. glucose, NAD+, O2, Pi c. glucose, NAD+, Pi d. glucose, NADH, O2

c. glucose, NAD+, Pi

Consider this isomerase reaction that is the second step in glycolysis: glucose-6-phosphate → fructose-6-phosphate The concentration of glucose-6-phosphate is usually about 5 times higher than the concentration of fructose-6-phosphate and ΔG is a small, but negative value in the cell. When the reaction reaches equilibrium, there is about 1.7 more fructose-6-P than glucose-6-P Imagine that conditions surge so that glucose-6-phosphate is now 500 times higher than fructose-6-phosphate. What will happen to ΔG? a. The surge in G6P brings the reaction immediately to equilibrium, where ΔG is now zero. b. The sign for ΔG will be reversed because the reaction is now reversed after the surge c. ΔG for the forward reaction (G6P → F6P) will become both larger and more negative upon the surge. This will drive the forward reaction. d. Nothing will happen to ΔG. It never changes as the concentration changes.

c. ΔG for the forward reaction (G6P → F6P) will become both larger and more negative upon the surge. This will drive the forward reaction.

Identify the saccharide shown below: **can't see image lol** a. β-D-mannose b. α-D-glucose c. β-D-glucose d. β-D-galactose

c. β-D-glucose

Which type of plot would result in a straight line for an enzyme obeying Michaelis-Menten kinetics? a. vi vs. [S] b. 1/vi vs. [S] c. kcat vs. Km d. 1/vi vs. 1/[S]

d. 1/vi vs. 1/[S]

An enzymatic reaction satisfying Michaelis-Menten conditions has a Vmax of 10 mM/min. At a substrate concentration of 2 mM, the initial velocity is 1 mM/min. What is the KM for the reaction? a. 10 uM b. 8 uM c. 5 uM d. 18 uM

d. 18 uM

Which statement below best summarizes glycolysis with respect to reactions near and far from equilibrium and regulation? a. 3 reactions are near equilibrium and highly regulated; the remaining 7 reactions are far from equilibrium and not regulated b. all reactions in glycolysis are from from equilibrium and 3 reactions are highly regulated c. all reactions in glycolysis are near-equilibrium and 3 reactions are highly regulated d. 3 reactions are far from equilibrium and highly regulated; the remaining 7 reactions are near-equilibrium and not regulated

d. 3 reactions are far from equilibrium and highly regulated; the remaining 7 reactions are near-equilibrium and not regulated

You are studying a hydrolase that that degrades an antibiotic. For your assays, you add purified enzyme in a buffer to various concentrations of substrate (antibiotic) and measure the initial velocity in a spectrophotometer. For your first set of assays, the enzyme concentration is 2µM. At 2µM of total enzyme concentration, the Vmax for this enzyme is 6µM/sec. What is the kcat? a. 0.33/sec b. 12uM/sec c. 3uM/sec d. 3/sec e. 0.33uM/sec f. 12/sec

d. 3/sec

Which of the following statements is correct regarding the conversion of NAD+ to NADH in glycolysis? a. NADH gets reduced to NAD+ by GAP dehydrogenase in glycolysis b. NAD+ is the soluble electron carrier form that contains two electrons and takes those two electrons to the electron transport chain c. NAD+ carries a net positive charge, while NADH is a neutral molecule; NAD+ is the high energy molecule used for substrate-level phosphorylation glycolysis d. A dehydrogenase uses H:‾ to reduce NAD+ to NADH

d. A dehydrogenase uses H:‾ to reduce NAD+ to NADH

Hexokinase catalyzes the first step in glycolysis, which is: Glucose + ATP <----> Glucose-6-P + ADP The complete 3-step mechanism of hexokinase is shown below. What type of catalysis is being shown in the mechanism? a. Transition state catalysis b. Diffusion controlled catalysis c. Covalent catlaysis d. Acid-base catalysis

d. Acid-base catalysis

In glycolysis, the production of fructose 1,6-bisphosphate (FBP) occurs early in the pathway. Pyruvate kinase, catalyzes the last step in glycolysis. When FBP activates pyruvate kinase, this is an example of: a. Allosteric feeback inhibition b. Product inhibition c. Substrate activation d. Allosteric feed-forward activation

d. Allosteric feed-forward activation

What reason best accounts for the advantage gained by the series of isomerizations and aldolase cleavage that occurs after the ATP investment phase a. The isomerizations and aldolase cleavage are the result of substrate-level phosphorylation, so they are just necessary products of the energy return stage b. The isomerizations are the most regulated steps of glycolysis as they are the farthest from equilibrium and very irreversible c. The six-carbon hexose must be converted to a three-carbon sugar because phosphorylation of a 3-carbon compound is thermodynamically forbidden d. Fructose 1,6 bisphosphate, a hexose, is not a high energy compound and must be cleaved and re-arranged to produce high energy compounds for substrate-level phosphorylation

d. Fructose 1,6 bisphosphate, a hexose, is not a high energy compound and must be cleaved and re-arranged to produce high energy compounds for substrate-level phosphorylation

Which of the following is correct regarding pyruvate kinase regulation? a. Fructose-1,6-bisphosphate will inhibit it, while ADP can activate it b. ATP will activate it while ADP will inhibit it c. Fructose-2,6-bisphosphate will feed forward activate it, while ATP can inhibit it d. Fructose-1,6-bisphosphate will feed forward activate it, while ATP can inhibit it

d. Fructose-1,6-bisphosphate will feed forward activate it, while ATP can inhibit it

Which glycolytic enzyme below typically catalyzes a near-equilibrium step in the cell under usual (steady-state) conditions? a. hexokinase b. PFK c. pyruvate kinase d. GAP Dehydrogenase

d. GAP Dehydrogenase

Which statement below is correct regarding the entry of fructose into glycolysis? a. In muscle, it enters through hexokinase and results in a higher ATP yield in glycolysis than glucose. In liver it enters at the PFK steps and is highly regulated b. In liver and muscle, fructose will enter as fructose-2,6-bisphosphate. c. In muscle and liver, it enters as GAP and thus is not highly regulated when it enters glycolysis as it skips the major regulatory step in both liver and muscle. d. In muscle, it enters through hexokinase. In liver, it enters as GAP.

d. In muscle, it enters through hexokinase. In liver, it enters as GAP

Which of the options below depict two examples of product inhibition in glycolysis: a. The inhibition of enolase by H20 and the inhibition of phosphoglycerate kinase by ATP b. The inhibition of triose phosphate isomerase by glyceraldehyde 3-phosphate and dihydroxyacetone phosphate c. The inhibition of glyceraldehyde 3-phosphate dehydrogenase by NADH and the inhibition of glucose 6-phosphate isomerase by ATP d. The inhibition of pyruvate kinase by ATP and the inhibition of hexokinase by glucose 6-phosphate

d. The inhibition of pyruvate kinase by ATP and the inhibition of hexokinase by glucose 6-phosphate

Which statement below best explains one of the biochemical reasons why excess lactate formation in diabetics can be problematic? Use your biochemical and chemical reasoning skills. Marshall all the power of the nerd gods at your disposal! a. The lactate is converted into ethanol by a decarboxylation reaction. This causes excess CO2 production and lowering blood pH by forming carbonic acid. b. The lactate will be fermented to acetate and then converted to acetyl-CoA, which is biosynthesized into fatty acids and converted to glucose via gluconeogenesis c. The lactate that has been generated serves to directly lower the pH of the blood, causing acidosis. d. The lactate is transported to the liver via the Cori cycle, where it is converted to glucose and the glucose is exported, further increasing blood glucose.

d. The lactate is transported to the liver via the Cori cycle, where it is converted to glucose and the glucose is exported, further increasing blood glucose.

Under what conditions would you expect to encounter fermentation: a. There is an ample supply of glucose and ATP b. An anaerobic organism is currently using plentiful nitrate (NO3-) as a terminal electron acceptor c. In an aerobic organism there is plenty of oxygen and ample NAD+ d. There is no terminal electron acceptor present, like oxygen, and further oxidation of pyruvate cannot proceed

d. There is no terminal electron acceptor present, like oxygen, and further oxidation of pyruvate cannot proceed

Which of the following is correct for an enzyme obeying Michaelis-Menten kinetics: a. One way to increase the turnover number of an enzyme is to increase the concentration of the enzyme b. Under substrate conditions where an enzyme is operating at Vmax, you can further increase/change Vmax by increasing the substrate concentration c. The initial velocity can best be experimentally determined by using an enzyme and substrate concentration that are equal. d. Under substrate conditions where an enzyme is operating at Vmax, you can further increase/change Vmax by increasing the enzyme concentration

d. Under substrate conditions where an enzyme is operating at Vmax, you can further increase/change Vmax by increasing the enzyme concentration

Which of the following is correct for an enzyme obeying Michaelis-Menten kinetics: a. Under substrate conditions where an enzyme is operating at Vmax, you can further increase/change Vmax by increasing the substrate concentration b. One way to increase the turnover number of an enzyme is to increase the concentration of the enzyme c. The initial velocity can best be experimentally determined by using an enzyme and substrate concentration that are equal. d. Under substrate conditions where an enzyme is operating at Vmax, you can further increase/change Vmax by increasing the enzyme concentration

d. Under substrate conditions where an enzyme is operating at Vmax, you can further increase/change Vmax by increasing the enzyme concentration

The generation of lactate is: a. a process that is used to directly generate ATP from pyruvate by using lactate dehydrogenase b. necessary for entry of pyruvate into the TCA cycle, which allows for the generation of ATP in the absence of oxygen c. a process that is necessary for the removal of CO2 waste product under anaerobic conditions d. a process that reduces pyruvate and generates NAD+, while the lactate can enter the liver to under gluconeogenesis

d. a process that reduces pyruvate and generates NAD+, while the lactate can enter the liver to under gluconeogenesis

To burn TAGs for energy, the TAGs are first broken down into fatty acids, the fatty acids are then carried in to the mitochondrial matrix where they are broken down into multiple acetyl-CoA molecules. Acetyl-CoA is a two-carbon compound. The conversion of fatty acids into Acetyl-CoA is an example of: a. inhibition b. anabolism c. steady-state kinetics d. catabolism

d. catabolism

Think of the equation we have used to calculate Vmax. Which of the following changes would be most likely or could possibly change the Vmax value for an enzyme? a. changing the concentration of substrate b. changing the Km value for an enzyme by mutating the active site so that the affinity of the enzyme for substrate decreases c. adding a competitive inhibitor to compete with substrate for the active site of the enzyme d. changing the concentration of enzyme

d. changing the concentration of enzyme

Most drugs are transition-state analogs that inhibit enzymes. As such, they bind tightly to the active site of the target enzyme and inhibit the enzymatic reaction. If a transition-state analog is found to ONLY bind to free enzyme (E), and is unable to bind to the ES complex, what type of inhibitor will this drug be? a. noncompetitive b. uncompetitive c. transitional d. competitive

d. competitive

What are the two possible strategies for which a reaction could have the dG value for the reaction shift from + to - a. increase the ATP concentration and increase the amount of NADH b. increase the concentration of enzyme and decrease the concentration of water c. decrease the concentration of products and increase the concentration of ATP d. couple the reaction to ATP hydrolysis or increase reactant concentration

d. couple the reaction to ATP hydrolysis or increase reactant concentration

In a catabolic pathway, major nutrients are _________ broken down resulting in the synthesis of __________ . a. exergonically; ADP b. endergonically; ATP c. endergonically; ADP d. exergonically; ATP e. endergonically; NADP+

d. exergonically; ATP

Which of the following best describes how fructose enters glycolysis? a. fructose enters as PEP in liver and GAP or DHAP in liver b. fructose enters as GAP and DHAP in muscle c. fructose enters as glucose in muscle and enters as fructose-6-P in liver d. fructose enters as GAP in liver

d. fructose enters as GAP in liver

Acyl phosphates such as 1,3-bisphosphoglycerate have a ______ phosphoryl group transfer potential compared to ATP, which can be recognized by the _______ ΔG°' values for hydrolysis when compared to ATP hydrolysis. a. lower; more positive b. lower; more negative c. greater; more positive d. greater; more negative

d. greater; more negative

The net pathway of glycolysis: a. is at equilibrium with a large and negative actual Gibbs Free Energy (ΔG) value b. has a net consumption of energy due to substrate level phosphorylation c. has a large and positive actual Gibbs Free Energy (ΔG) value and is reversible d. has a large and negative actual Gibbs Free Energy (ΔG) value and is irreversible

d. has a large and negative actual Gibbs Free Energy (ΔG) value and is irreversible

In a first-order unimolecular chemical reaction, the rate of the reaction will: a. be greater for larger Keq values, and less for smaller Keq values b. be determined by the overall Gibbs Free Energy value of reactants and products c. remain the same for all concentrations of reactant tested d. increase linearly as the concentration of reactant increases

d. increase linearly as the concentration of reactant increases

Glyceraldehyde 3-phosphate dehydrogenase a. is an isomerase catalyzing a near-equilibrium reaction that converts glyceraldehyde 3-phosphate into 1,3-bisphophoglycerate b. catalyze an irreversible reaction that produces ATP from phosphoenolpyruvate and generates NAD+ c. is an oxidoreductase that oxidizes ATP to Pi and generates glyceraldehyde 3-phosphate d. is an oxidoreductase that incorporates inorganic phosphate into glyceraldehyde 3-phosphate and reduces NAD+ to NADH

d. is an oxidoreductase that incorporates inorganic phosphate into glyceraldehyde 3-phosphate and reduces NAD+ to NADH

Glycerol is a 3-carbon molecule with 3 hydroxyl groups. In liver, the generation of glycerol for TAG biosynthesis can be... a. made from fructose once it is converted to GAP and oxidized by a dehydrogenase b. made from fatty acids by the action of an oxidoreductase that uses inorganic phosphate c. made from DHAP by the action of triose phosphate isomerase in a diffusion-controlled reaction that reduces ketones to alcohols d. made from fructose after the aldose reaction and reduction of glyceraldehyde to glycerol by a dehydrogenase

d. made from fructose after the aldose reaction and reduction of glyceraldehyde to glycerol by a dehydrogenase

Which of the scenarios below is able to decrease flux in a pathway: i. Increased production (translation) of the enzyme for a rate-determining step ii. Production of a final product, which serves as an allosteric feedback inhibitor of a near-equilibrium reaction iii. Introduction of an allosteric activator that regulates a far-from equilibrium reaction a. options i, ii, and iii b. options i and ii c. option i only d. option ii only e. options i and iii f. option iii only

d. option ii only

Consider a 4 step pathway: A --> B --> C --> D --> E The actual Gibbs Free Energy change in an 'average' cell for each reaction, in isolation, is: -2kJ/mole for step 1, -18 kJ/mole for step 2, 0.1 kJ/mole for step 3, and 12 kJ/mole for step 4. Which step is likely the committed step? a. all of the above steps b. step 3 c. step 4 d. step 2

d. step 2

Once PPi and UDP-glucose are formed, an enzyme called pyrophosphorylase immediately catalyzes the conversion of PPi into Pi + Pi. What accounts for the thermodynamic driving force of this reaction in the cell? a. the dephosphorylation of Glucose-1-phosphate b. the formation of UDP-glucose, a high-energy molecule c. the transfer of a phosphate group from Glucose-1-phosphate to UMP d. the conversion of PPi to 2Pi by pyrophosphorylase

d. the conversion of PPi to 2Pi by pyrophosphorylase

The initial velocity of an enzyme reaction (v0) describes: a. the concentration of both enzyme and substrate at the start of the reaction. b. the concentration of substrate at maximal velocity c. the concentration of the enzyme at maximal velocity d. the rate of the reaction when the substrate and enzyme are first mixed

d. the rate of the reaction when the substrate and enzyme are first mixed

Which of the following are high energy molecules generated in glycolysis? Select all that apply a. glucose-6-phosphate b. 2BP c. pyruvate d. GAP e. 1,3-bPG f. NADH g. PEP

e. 1,3-bPG g. PEP

Consider the reaction for ATP hydrolysis: ATP + H2O <----> ADP + Pi + H+ ΔGº' = -31 kJ/mole Which of the following strategies could a cell REALISTICALLY or reasonably do to make the hydrolysis of ATP even more thermodynamically favorable? There are some things that a cell cannot reasonably change without harming the cell. Select all that apply a. Decrease the concentration of ATP b. Increase the concentration of Pi c. Decrease the concentration of H+ d. Increase the concentration of H2O e. Decrease the concentration of Pi f. Increase the concentration of ADP g. Decrease the concentration of H2O h. Increase the concentration of H+ i. Decrease the concentration of ADP j. Increase the concentration of ATP

e. Decrease the concentration of Pi i. Decrease the concentration of ADP j. Increase the concentration of ATP

Which of the following statements BEST describes the Michaelis-Menton constant Km? a. It is a measure of enzyme efficiency. b. It has units of concentration. c. It is numerically equal to the affinity between the enzyme and its substrate. d. It is a measure of the rate of a catalytic process. e. It is numerically equal to the substrate concentration required to reach half maximal velocity for an enzyme-catalyzed reaction

e. It is numerically equal to the substrate concentration required to reach half maximal velocity for an enzyme-catalyzed reaction

Under aerobic conditions, pyruvate is typically oxidized to ________. While in anaerobic conditions, pyruvate can be reduced to _________. a. none of the options are correct b. acetaldehyde; NADH c. acetaldehyde; glyceraldehyde-3-phosphate d. NAD+ ; acetyl CoA e. acetyl CoA; lactate

e. acetyl CoA; lactate

PFK is the major regulatory step in glycolysis. Which of the following compounds serve to ACTIVATE PFK? (select all that apply) a. Glucose b. Fructose-6-phosphate c. Citrate d. Glucose-6-phosphate e. Pi f. AMP g. NAD+ h.Fructose-2,6-bisphosphate i. Pyruvate j. NADH k. PEP l. ATP m. ADP

f. AMP h. Fructose-2,6-bisphosphate m. ADP

Name one enyzme in glycolysis that is likely to be highly regulated (use the enzyme names listed in table 15-1)

hexokinase

Generally speaking, mutations in glycolytic enzymes that render the enzyme inactive are usually lethal... to the extent that the embryo wouldn't even develop. But, there is one mutant that abolishes activity in a glycolytic enzyme and it is not lethal. Which enzyme is it? Here is are the outputs or inputs per 1 molecule of glucose for a person with that mutation: ATP: net yield of 0 per glucose NADH: net yield of 1 per glucose Pyruvate: net yield of 1 per glucose Pi: net consumption of 1 per glucose NAD+: net consumption of 1 per glucose

triose phosphate isomerase

Consider the standard Gibbs Free Energy for the reactions of glycolysis, which converts Glucose into Pyruvate. The change in energy is depicted in the figure below. Each enzymatic step is numbered in the diagram with the orange font. The enzyme that converts glucose into G-6-P is, accordingly, step #1; and G6P to F6P is step #2. The enzyme that converts PEP into Pyruvate is, accordingly, step #10 Gluconeogenesis is the conversion of pyruvate into glucose, especially in liver, so this newly made glucose can be shipped out of liver and to the brain when the body is out of glucose. Most steps in glycolysis and gluconeogensis are shared, but not all. Using what you know about pathways, equilibrium, and thermodynamics, which enzymatic steps are thus likely to be SHARED AND COMMON between glycolysis and gluconeogenesis. Select all that apply. 1. #1 2. #2 3. #3 4. #4 5. #5 6. #6 7. #7 8. #8 9. #9 10. #10

2. #2 4. #4 5. #5 6. #6 7. #7 8. #8 9. #9

Which of the following 4 reactions below are thermodynamically permitted in the forward direction as drawn when all reactants and products for the reaction are at equal concentrations? 1) ATP + creatine --> creatine-P + ADP 2) ATP + glycerol ---> glycerol-3-P + ADP 3) ATP + pyruvate ---> phosphenolpyruvate + ADP 4) ATP + glucose ---> glucose-6-P + ADP Use the table below to guide your analysis. Selection all rxns that could go forward as written. 1. ATP + creatine --> creatine-P + ADP 2. ATP + glycerol ---> glycerol-3-P + ADP 3. ATP + pyruvate ---> phosphenolpyruvate + ADP 4. ATP + glucose ---> glucose-6-P + ADP 5. none of the reactions could go forward as written at equimolar concentrations

2. ATP + glycerol ---> glycerol-3-P + ADP 4. ATP + glucose ---> glucose-6-P + ADP

A Linweaver-Burke plot for an enzyme yields and equation of: Y= 5X + 2 All tested substrate concentrations were in mM. What is the Km for this enzyme?

2.5

The kcat for an enzyme is 2/s. The enzyme concentration is 10nM. What is the Vmax in units of nM/s?

20

At a substrate concentration of 3mM, an enzyme has an initial velocity of 1mM/s. The Vmax for this enzyme is 10mM/s. What is the Km of this enzyme in units of mM?

27

An enzyme at a concentration of 0.1uM has an initial velocity of 10uM/s at 5uM substrate concentration; at this enzyme concentration, the enzyme has a Vmax value of 30uM/s. What is the kcat of this enzyme (in units of "per second")?

300

At an enzyme concentration of 0.001uM, the Vmax for enzymatic reaction is 3uM/s. What is the kcat for this enzyme?

3000

kcat, Km, and Vmax are all constants for an enzyme True False

False

An enzyme catalyzed reaction can be thought of as a mixture of first order and zero-order reactions. At low substrate concentrations the reaction is zero-order. At high substrate concentrations the reaction is first-order. True False

False

Consider an enzymatic reaction consisting of three chemical steps, whereby the 3rd and final step results in product formation. There is no relation between the speed of an individual step and that step's activation energy. True False

False

Enzymes change the Keq value for a chemical reaction True False

False

Enzymes change ΔG for a chemical reaction True False

False

NADPH is required for glycolysis True False

False

Reactions in glycolysis are also part of the electron transport chain (ETC) True False

False

The initial velocity in a progress curve can be measured or taken at any time point in the course of a reaction. Whether 1 minute into the reaction or 10 minutes into the reaction. It doesn't matter. True False

False

Transition states are unstable species that obey the proper rules of bonding and valency. True False

False

A first-order chemical reaction will increase linearly in initial velocity as the concentration of reactant (or substrate) increases True False

True

During a resting phase, lactate produced in muscle can ultimately be stored as glycogen with a net investement of ATP. The ATP investment can be recovered should the glycogen be fully broken down into glucose-1-P that enters glycolysis and the Krebs Cycle True False

True

During a resting phase, lactate produced in muscle can ultimately be stored as glycogen with a net investement of ATP. The ATP investment can be recovered should the glycogen be fully broken down into glucose-1-P that enters glycolysis and the Krebs Cycle. True False

True

Enzymes cause a chemical reaction to reach equilibrium sooner than an un-catalyzed reaction. True False

True

Enzymes lower the activation energy of a chemical reaction. True False

True

Glycolysis does not require oxygen True False

True

Most reactions in glycolysis are near-equilibrium reactions at physiological conditions. A few glycolysis reactions are far-from equilibrium and these constitute the more regulated reactions. True False

True

The far from equilibrium reactions in a pathway are often the most highly regulated steps in a pathway True False

True

Which statement below best describes the connection between catabolism and anabolism: a. Catabolism produces a combination of small molecule precursors, chemical energy, and reducing equivalents (electrons) that can then be used in anabolic pathways to construct cellular components. b. Anabolism produces a combination of precursors, chemical energy, and reducing equivalents (electrons) that can then be used in catabolic pathways to construct cellular components. c. Catabolism and anabolism provides energy in the form of ATP. Anabolism provides small molecule precursors for biosynthesis while catabolism synthesizes biomolecules. d. There is no chemical or energetic relation between catabolism and metabolism.

a. Catabolism produces a combination of small molecule precursors, chemical energy, and reducing equivalents (electrons) that can then be used in anabolic pathways to construct cellular components.

What can be said of the production of ATP from FADH2 and NADH in the electron transport chain? a. FADH2 results in less net ATP being synthesized because it results in fewer protons being pumped out of the matrix b. NADH participates in 2 electron transfer reactions, while FADH2 participates in 1 electron transfer reactions c. NADH is a produced at Complex II in the electron transport chain as a result of succinate dehydrogenase being a member of Complex II d. FADH2 transfers electrons from cytochrome c to ubiquinone, whereas NADH transfers electrons from ubiquinone to cytochrome c

a. FADH2 results in less net ATP being synthesized because it results in fewer protons being pumped out of the matrix

PFK-2 (aka "PFK-2/FBPase-2 bifunctional") in liver is in an unphosphorylated state. What can be said of PFK-2 and the state of the cell? a. Glycolysis is favored and F-2,6-bP is being synthesized as the allosteric activator of PFK and allosteric inhibitor of FBPase b. Gluconeogenesis is favored and F-2,6-bP is being synthesized as the allosteric activator of PFK and allosteric inhibitor of FBPase c. Gluconeogenesis is favored and F-2,6-bP is being degraded into F-6-P through the phosphatase activity of PFK-2.

a. Glycolysis is favored and F-2,6-bP is being synthesized as the allosteric activator of PFK and allosteric inhibitor of FBPase

A competitive inhibitor will change which parameter: a. Increases Km b. Lowers Km c. Increases kcat d. lowers kcat

a. Increases Km

An enzyme has a Km value of 2mM for its substrate. At a concentration of 1mM, what will be true of the enzyme? a. Increasing substrate concentration will increase the velocity b. Linear progress curves could not be generated at 1mM substrate concentration for this enzyme c. The enzyme is saturated with substrate

a. Increasing substrate concentration will increase the velocity

Which of the following are fates of pyruvate? (select all that apply) a. It could be converted to alanine for amino acid production b. It could be converted to acetyl-CoA to enter the TCA cycle c. It could be converted to OAA to enter the TCA cycle, be used for amino acid production, or be used for gluconeogenesis d. It can be converted directly to citrate for glycolysis regulation e. It could be converted to lactate or ethanol in fermentation

a. It could be converted to alanine for amino acid production b. It could be converted to acetyl-CoA to enter the TCA cycle c. It could be converted to OAA to enter the TCA cycle, be used for amino acid production, or be used for gluconeogenesis e. It could be converted to lactate or ethanol in fermentation

Which statement below is correct regarding mannose catabolism in glycolysis? a. It has the same glycolytic ATP yield as glucose b. It produces less net ATP than glucose c. It produces CO2 in glycolysis d. It produces less NADH than glucose e. It has the same NADH yield as glucose f. It results in ATP production by substrate-level phosphorylation

a. It has the same glycolytic ATP yield as glucose e. It has the same NADH yield as glucose f. It results in ATP production by substrate-level phosphorylation

Which of the following explains how enzymes are categorized into 6 different classes: a. It is based upon the types of chemical reactions the enzymes catalyze b. It is based upon the size of the enzymes in terms of primary sequence length c. It is based upon the solubility and cellular location of each enzyme d. It is based upon an index of the enzymes' properties of hydrophobicity, pI, and net charge

a. It is based upon the types of chemical reactions the enzymes catalyze

What role does NADPH typically play in the cell? a. It provides electrons to biosynthetic reactions b. It supplies electrons to the electron transport chain (ETC) c. It provides electrons for catabolic pathways d. It removes electrons from reduced metabolic fuels

a. It provides electrons to biosynthetic reactions

What are some of the potential reasons for the large, negative Gibbs Free Energy value for ATP hydrolysis: a. It relieves the highly localized negative charge of ATP and AMP is more soluble than ATP b. It prevents the auto-hydrolysis of ATP with a nucleophilic Mg2+ ion c. It converts ATP from a charged molecule to a neutral molecule d. Negative charge is favorably transferred to bridging oxygens of the phosphoanhydride bond

a. It relieves the highly localized negative charge of ATP and AMP is more soluble than ATP

Consider a unimolecular isomerization reaction in the cell, such as the conversion of IPP to DMAPP. The structures of IPP and DMAPP are shown below: The reaction, in the direction of IPP --> DMAPP, has a ΔGº' of + 4.7 kJ/mole However, DMAPP is needed to make cholesterol and other isoprenoids, so the cell must be able to generate DMAPP from IPP. What strategy or strategies can the cell use to propel this reaction in the forward direction to produce DMAPP? Select all that apply a. Keep the concentration of DMAPP "low" b. Keep the concentration of IPP "high" c. Keep the concentration of IPP "low" d. Keep the concentration of DMAPP "high" e. Couple the reaction to a thermodynamically favorable reaction, such as ATP hydrolysis

a. Keep the concentration of DMAPP "low" b. Keep the concentration of IPP "high"

Which statement is FALSE about most metabolic pathways? a. Most pathways are reversible under physiological conditions. b. The rates of pathway reactions vary to respond to changing conditions. c. Pathways serve to increase the efficiency of energy transfers. d. The enzymes that catalyze reactions in metabolic pathways generally catalyze only a single step.

a. Most pathways are reversible under physiological conditions.

What type of inhibition is indicated by the data graphed below? **graph with same -1/[S] but changing value for 1/Vo** a. Noncompetitive. b. Competitive. c. Irreversible. d. Uncompetitive.

a. Noncompetitive.

You have a good understanding of the physiological logic that gives rise to the biochemistry in the cell. Using your understanding of biochemistry and physiology, you know something about how AMP can affect key enzymes in pathways. With respect to the regulation of glycolysis and gluconeogenesis, AMP serves to: a. allosterically inhibit FBPase and inhibit gluconeogenesis; allosterically activate PFK and stimulate glycolysis b. allosterically activate FBPase and activate gluconeogenesis; allosterically inhibit PFK and inhibit glycolysis c. allosterically inhibit pyruvate kinase to inhibit glycolysis, and allosterically inhibit PEPCK to stimulate gluconeogenesis d. allosterically activate FBPase-2/PFK-2 to phosphorylate fructose-6-phosphate, which then results in stimulating gluconeogenesis

a. allosterically inhibit FBPase and inhibit gluconeogenesis; allosterically activate PFK and stimulate glycolysis

When pyruvate is fermented to ethanol in microbes, the pyruvate will... a. become reduced and will release one carbon as a CO2 b. be converted first to lactate and then to ethanol with a decarboxylase c. undergo two reduction reactions to generate two NAD+ molecules and one CO2 d. undergo an oxidation reaction to generate the NADH that glycolysis needs

a. become reduced and will release one carbon as a CO2

The conversion of triacylglycerides into fatty acids for the purpose of energy generation is an example of which of the following? a. catabolism b. anabolism c. anaerobism d. chemoautotrophy e. glycolysis

a. catabolism

In a catabolic pathway, a reaction is highly regulated and is the rate-determining step of the pathway. This reaction is most likely... a. far-from equilibrium and irreversible with a large and negative ∆G value. b. a shared reaction between the catabolic pathway and an anabolic pathway. c. near-equilibrium and the committed step in the pathway. d. far-from equilibrium and generates ATP.

a. far-from equilibrium and irreversible with a large and negative ∆G value.

Which conditions below would be most likely to achieve maximum velocity for an enzyme? a. high substrate concentration b. a high kcat value c. high enzyme concentration d. low substrate concentration

a. high substrate concentration

A substrate cycle (ie, futile cycle) in a metabolic pathway ________. a. is a good point for regulation of the pathway b. is a point that starts a cascade effect c. includes only diffusion-controlled reactions d. allows for substrates to be passed to alternative pathways

a. is a good point for regulation of the pathway

In glycolysis, phosphofructokinase-1: a. is the rate limiting step as well as the most regulated; it is allosterically inhibited by ATP and citrate b. it is allosterically activated by NADH and represents the critical control point of glycolysis c. catalyzes a near-equilibrium reaction using a high phosphoryl transfer potential substrate to make ATP d. will produce fructose 1,6-bisphosphate; while it is activated by AMP to produce fructose 1-phosphate in gluconeogenesis because it is bifunctional

a. is the rate limiting step as well as the most regulated; it is allosterically inhibited by ATP and citrate

A noncompetitive inhibitor will: a. lower Vmax b. increase Vmax c. increase Km d. lower Km

a. lower Vmax

The reason to rewrite the Michaelis-Menten equation (such as the Lineweaver-Burk plot) is to a. more easily calculate Vmax and Km. b. form enzyme kinetic data as a hyperbolic curve. c. visualize reactions better. d. more easily calculate catalytic proficiency

a. more easily calculate Vmax and Km.

Which option below best describes products of glycolysis a. pyruvate, ATP, NADH, H2O b. pyruvate, CO2, ATP, NADH c. pyruvate, ADP, NADH, O2 d. pyruvate, ATP, NAD+, Pi

a. pyruvate, ATP, NADH, H2O

The first step in glycolysis is catalyzed by the enzyme hexokinase. The reaction is: Glucose + ATP <----> Glucose-6-P + ADP An image of the reaction along with some reaction parameters is shown below. If I were to mix glucose, ATP, glucose-6-P, and ADP in a test tube without any enzyme at 15ºC such that ΔG = -5kJ/mole, which parameter would change by the addition of hexokinase? a. the amount of time it takes for the reaction to reach Keq values b. the temperature of the reaction would change from being 15ºC c. AMP would be generated instead of ADP d. glucose-1-phosphate would be made instead of glucose-6-phosphate e. none of these answer options would change or are correct f. the value of ΔGº' g. the value of Q h. the value of Keq i. the value of ΔG

a. the amount of time it takes for the reaction to reach Keq values

What does a "low" Km value indicate? a. the enzyme has high affinity for its substrate b. the enzyme cannot become saturated c. the enzyme converts few molecules of substrate into product per second d. the reaction is not product favored

a. the enzyme has high affinity for its substrate

In glycolysis a. there are several reactions that are far from equilibrium and irreversible b. there are no reactions that are far from equilibrium, with all steps being easily reversible. c. there is just one reaction that is far from equilibrium and it is reversible d. no reactions are near equilibrium, all steps are far from equilibrium and irreversible

a. there are several reactions that are far from equilibrium and irreversible

The non-enzymatic hydrolysis of sucrose into glucose and fructose in water (shown below) is an example of a pseudo first-order reaction because: sucrose + H2O -> glucose + fructose a. water is of such high concentration as to be considered constant. b. water is present at concentrations proportional to the sucrose. c. no enzymes are involved. d. water has no role in the reaction.

a. water is of such high concentration as to be considered constant.

Which of the following compounds are both found in glycolysis AND are considered "high energy"? (select all that apply) a. glucose-6-phosphate b. 1,3-BPG c. NADH d. acetyl-CoA e. pyruvate f. PEP

b. 1,3-BPG f. PEP

For one molecule of glucose, the number of ATP directly produced by glycolysis is: a. 16 b. 2 c. 32 d. 42

b. 2

Which of the following statements best describes near-equilibrium reactions in metabolic pathways: a. Near-equilibrium reactions have a ∆G value that is of a large and negative value under typical physiological conditions and often represent the committed step in pathways b. Near-equilibrium reactions have a ∆G value near 0.0 kJ/mole and do not change direction with small changes in substrate or product concentrations c. Near-equilibrium reactions have a ∆G value near 0.0 kJ/mole under typical physiological conditions and are often shared between catabolic and anabolic pathways d. Near-equilibrium reactions have a ∆G value near 0.0 kJ/mole under typical physiological conditions and are usually the rate-limiting steps and highly regulated

c. Near-equilibrium reactions have a ∆G value near 0.0 kJ/mole under typical physiological conditions and are often shared between catabolic and anabolic pathways

Which intermediates in glycolysis directly allow for substrate-level phosphorylation by a single enzymatic reaction? (select all that apply) a. glucose-6-phosphate b. NADH c. PEP d. 1,3-BPG e. fructose-1,6-bisphosphate

c. PEP d. 1,3-BPG

Which step in glycolysis is the major regulatory step? a. GAP dehydrogenase b. hexokinase c. PFK d. pyruvate kinase

c. PFK

In gluconeogenesis, what statement below best describes the role of phosphatases? a. Phosphatases are necessary to carry out substrate-level phosphorylation in gluconeogenesis. b. Phosphatases are necessary to convert pyruvate, which lacks a phosphate group, into PEP, which contains a phosphate group. c. Phosphatases carry out two of the irreversible steps. They function to catalyze the steps by-passing the PFK and hexokinase reactions of glycolysis. d. A phosphatase degrades fructose-2,6-bisphosphate into fructose-6-phosphate. This activity serves to inhibit gluconeogenesis and activate glycolysis. Clear my choice

c. Phosphatases carry out two of the irreversible steps. They function to catalyze the steps by-passing the PFK and hexokinase reactions of glycolysis.

Below is the data obtained in lab from measuring initial velocities of a non-enzymatic reaction: [reactant] Vi 2mM 1mM/s 4mM 2mM/s 6mM 3mM/s 8mM 4mM/s How was the data for the Vi values obtained? a. The Vi was plotted vs. [reactant]. The enzyme will show zero or first order kinetics. b. The amount of reactant formed was monitored over time. The equilibrium concentration of the [reactant] determines the Vi. c. Progress curves were measured at each [reactant] concentration. The slope of the beginning of a progress curve provides the Vi. d. The data were plotted for [reactant] vs. Vi. The Vi was obtained from the slope of this plot.

c. Progress curves were measured at each [reactant] concentration. The slope of the beginning of a progress curve provides the Vi.

If the substrate concentration for an enzymatic reaction is 1000X greater than the Km value, which of the following would be correct? a. The substrate cannot be hidden from the witch-fairies of the woodlands; they will steal the substrate at night and embalm it in ambrosia. b. The enzyme is most likely operating under first-order kinetics. c. The enzyme is most likely operating under zero-order kinetics. d. Changing the substrate concentration by 10% will very likely change the initial velocity by 10%

c. The enzyme is most likely operating under zero-order kinetics.

Many enzymes that obey Michaelis-Menten kinetics have evolved such that their Km is close in value to the concentration of the substrate the enzyme typically encounters in the cell. This allows for which of the following: a. The enzyme to operate at ½ Vmax at very high substrate concentrations. b. The enzyme to use the substrate and product as allosteric activators and feedback inhibitors. c. The enzyme's initial velocity to respond to small changes in concentration. d. The enzyme to always operate at Vmax in the cell.

c. The enzyme's initial velocity to respond to small changes in concentration.

What are some of the roles dehydrogenases play in the TCA cycle at various reactions? a. They are oxidoreductases that may generate NAD+ or FAD; some result in carboxylations. b. Dehydrogenases generate water and CO2 in the TCA cycle c. They are oxidoreductases that may generate NADH or FADH2; some result in decarboxylations. d. They are oxidoreductases that may generate NADH or FADH2; they produce ATP by substrate-level phosphorylation

c. They are oxidoreductases that may generate NADH or FADH2; some result in decarboxylations.

Which statement is FALSE about catabolic pathways? a. They generate lower mass molecules from larger ones. b. They have a net release of energy. c. They have a net consumption of ATP. d. They include the citric acid cycle.

c. They have a net consumption of ATP.

Which statement best explains why metabolic pathways are carried out in discrete steps by multiple enzymes: a. Enzymes have different solubilities and some need to be in different compartments b. It prevents futile cycles of simultaneous catabolism and anabolism c. This allows for points of regulation with various enzymes and controls Gibbs free energy consumption or generation d. A metabolic pathway operates at equilibrium, with ∆G = 0 kcal/mole

c. This allows for points of regulation with various enzymes and controls Gibbs free energy consumption or generation

What impact on Vmax will doubling [E] have? a. Vmax will turn from the light and to the shadow realm, where it will be cursed to wander its own Elysian fields until redemption day. b. Vmax will remain unchanged. It is a constant. c. Vmax will double d. Vmax will decrease by 1/2

c. Vmax will double

The metabolic production of lactate is: a. a process that is necessary for the removal of CO2 waste product under anaerobic conditions b. a process that is used to directly generate ATP from pyruvate by using lactate dehydrogenase c. a process that reduces pyruvate and generates NAD+, while the lactate can enter the liver to under gluconeogenesis d. necessary for entry of pyruvate into the TCA cycle, which allows for the generation of ATP in the absence of oxygen

c. a process that reduces pyruvate and generates NAD+, while the lactate can enter the liver to under gluconeogenesis

Phosphorylation can be used to either inactivate or activate enzymes. This is a key element in the regulation of glucose metabolism. Phosphorylation of glycogen phosphorylase ________ it; phosphorylation of glycogen synthase ________ it. a. inactivates; inactivates b. inactivates; activates c. activates; inactivates d. activates; activates

c. activates; inactivates

Which of the following are properly described allosteric regulators of PFK in glycolysis? a. ATP is an activator and NAD+ is an activator b. AMP is an inhibitor and ATP is an inhibitor c. citrate is an inhibitor and fructose-2,6-bP is an activator d. Fructose-2,6-bP is an inhibitor and Fructose-1,6-bP is an activator

c. citrate is an inhibitor and fructose-2,6-bP is an activator

In the cell, glyceraldehyde 3-phosphate dehydrogenase and phosphoglycerate kinase physically interact. Which explanation below helps to explain this evolved ability: a. It allows for reciprocal allosteric regulation of each enzyme by ATP and prevents a substrate cycle b. It is a means of allosteric regulation to control flux through glycolysis because this reaction would otherwise be the slowest step. c. The NADH that is generated by the dehydrogenase is immediately used to reduce 1,3-bisphosphoglycerate. d. It allows channeling of 1,3-bisphosphoglycerate. This is a means to thermodynamically drive the reaction of the dehydrogenase, which has a positive standard Gibbs free energy

d. It allows channeling of 1,3-bisphosphoglycerate. This is a means to thermodynamically drive the reaction of the dehydrogenase, which has a positive standard Gibbs free energy

An inhibitor binds to a site other than the active site of the enzyme. Which statement below correlates with this observation? a. The inhibition must be irreversible. b. It must be a competitive inhibitor. c. It could be irreversible, competitive, noncompetitive or uncompetitive. The data do not relate to the type of inhibition. d. It could be noncompetitive or uncompetitive inhibition.

d. It could be noncompetitive or uncompetitive inhibition.

Why is phosphorylation such a common means of regulation in the cell? a. Phosphorylation requires a small molecule and does not spend any energy b. The cell is very high in phosphate and the cell can make gradients c. Phosphorylation has a favorable Gibbs Free Energy change and is a non-covalent interaction d. It is forms a stable covalent linkage and makes a significant chemical change on a protein

d. It is forms a stable covalent linkage and makes a significant chemical change on a protein

In reality, most inhibitors are "mixed" This means they are not 100% competitive or 100% uncompetitive, etc. Rather, they are bit of a blend of each. But, usually an inhibitor has a dominant mode of inhibition. Thus, it is "mostly a competitive" or "mostly noncompetitive", etc. Below are actual experimental results of the inhibition of phthalic acid on tyrosinase. To what enzymatic species does phthalic acid most prefer binding to? a. It mostly binds to the ES complex. It may or may not bind in the active site b. Phthalic acid is not an inhibitor, based on this data. It is an allosteric activator c. It has an equal preference for the ES complex or free enzyme, E. Phthalic acid is an allosteric inhibitor. d. It mostly binds to free enzyme and likely in the active site

d. It mostly binds to free enzyme and likely in the active site

Lactate is generated in exercising muscle under anaerobic conditions by reducing pyruvate. Which statement below best describes why transporting lactate generated in muscle to the liver is advantageous? a. Lactate can be oxidized to glucose in liver and this generates net ATP through reduction. b. In muscles, lactate is an acid that generates a low pH and must be removed to restore pH balance. c. Products of fermentation, such as lactate, are useless waste compounds and the liver is responsible for removing oxidized waste products from the blood. d. Lactate is not a fully oxidized product of glucose; ATP can still be obtained through further oxidation if lactate can enter glycolysis or the TCA cycle. e. Lactate is a feedback inhibitor of glycolysis and muscle needs glycolysis to be functioning.

d. Lactate is not a fully oxidized product of glucose; ATP can still be obtained through further oxidation if lactate can enter glycolysis or the TCA cycle.

Which of the following elements is required for the enzymatic reaction that produces phosphoenolpyruvate? a. Potassium b. Manganese c. Calcium d. Magnesium

d. Magnesium

Which of the following are produced in glycolysis? (select all that apply) a. CO2 b. O2 c. NADPH d. NADH e. ATP f. pyruvate g. Pi

d. NADH e. ATP f. pyruvate

Which statement below best describes the difference between NADH and NADPH? a. NADH is generated in the oxidative phase of the pentose-phosphate-pathway; NADPH is generated in the carboxylative phase of the pentose-phosphate-pathway b. NADH is produced mostly in the pentose-phosphate-pathway; NADPH is made by plants for biosynthetic reactions c. NADH is a soluble electron carrier to shuttle electrons to the ETC; NADPH is an insoluble electron carrier found in cell membranes d. NADH is often generated from catabolic reactions to shuttle electrons to the ETC; NADPH often supplies electrons for biosynthetic reactions

d. NADH is often generated from catabolic reactions to shuttle electrons to the ETC; NADPH often supplies electrons for biosynthetic reactions

What does the pentose phosphate produce that the cell needs? a. NADPH and CO2 b. ATP, NADPH, NADH, and glycerol c. NADP+ and ribose d. NADPH and 5 carbon sugars for nucleic acids

d. NADPH and 5 carbon sugars for nucleic acids

Which enzyme is the major regulatory step of glycolysis? a. pyruvate kinase b. hexokinase c. TIM d. PFK e. GAP dehydrogenase

d. PFK

Hexokinase is the first step in glycolysis, it catalyzes the reaction shown below: **hexokinase** Water is a nucleophile which can break down (hydrolyze) ATP into ADP. How might the enzyme hexokinase prevent a water molecule from being a nucleophile that disrupts the reaction? a. By stabilizing all transition states b. Perhaps through covalent catalysis c. Perhaps through a diffusion controlled reaction d. Perhaps through an induced-fit mechanism e. Perhaps by generating an entropy trap with a reaction intermediate

d. Perhaps through an induced-fit mechanism

Study the image outlining the mechanism of pyruvate decarboxylase and select the statement correctly analyzing the reaction. a. The TPP cofactor serves as an acid to donate a proton to a nucleophilic pyruvate b. Pyruvate carboxylase is acting as a hydrolase in the forward direction and a lyase in the reverse direction c. This reaction proceeds by formation of an oxonium ion intermediate which releases CO2 d. The TPP cofactor serves as a nucleophile and acetaldehyde is a product

d. The TPP cofactor serves as a nucleophile and acetaldehyde is a product

Which of the following is correct concerning competitive inhibition: a. The Vmax and the Km will both increase b. The Km remains unchanged with the Vmax increases c. The Vmax and the Km will both decrease d. The Vmax will remaining unchanged while the Km will increase

d. The Vmax will remaining unchanged while the Km will increase