Deck 9: Glycolysis: a Paradigm of Metabolic Regulation

Question 1

Which of the following metabolic pathways is only found in plants?

A) glycolysis
B) citrate cycle
C) photosynthesis
D) urea cycle

Answer 1

photosynthesis

Question 2

What is the main difference between energy conversion pathways and metabolite synthesis pathways?

A) Energy conversion pathways produce ATP.
B) Energy conversion pathways deplete ATP.
C) Metabolite synthesis pathway uses ATP to break down metabolites.
D) Metabolite synthesis pathway uses ATP to break down pyruvate.

Answer 2

Energy conversion pathways produce ATP.

Question 3

Glucose and fructose are both C₆H_{1 2}O₆. What is the structural difference between them?

A) Glucose is a five-membered ring and fructose is a six-membered ring.
B) Fructose is a five-membered ring and glucose is a six-membered ring.
C) Glucose is a linear molecule and fructose is a ring.
D) Glucose is found in the boat conformation and fructose is a chair conformation.

Answer 3

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

Question 4

For the following reaction A $\rightarrow$ B, if at equilibrium $\Delta$ DG $\degree$ ^' > 0, what can be said about the directionality of the reaction?

A) strongly favored in the forward direction
B) strongly favored in the reverse direction
C) strongly favored in both directions
D) Not enough information is given.

Question 5

Calculate the net $\Delta$ G $\degree$ ^' for the following series of reactions:

A) 14 kJ/mol
B) -6 kJ/mol
C) 6 kJ/mol
D) 0 kJ/mol

Question 6

Which of the following is an energy conversion pathway?

A) urea cycle
B) citrate cycle
C) nitrogen fixation and assimilation
D) fatty acid degradation and synthesis

Question 7

A chiral center is an atom with

A) two different functional groups and a strong dipole.
B) four different functional groups and which lacks a plane of symmetry.
C) all the same functional groups and a plane of symmetry.
D) the ability to hydrogen bond.

Question 8

Metabolism is best defined as a collection of

A) biochemical reactions that convert chemical energy into work.
B) biochemical reactions that convert mechanical energy into work.
C) enzymes that convert glucose into carbon dioxide.
D) enzymes that convert amino acids into proteins.

Question 9

Which of the following pathways are found in both plants and animals?

A) photosynthesis and carbon fixation
B) urea cycle
C) nitrogen fixation
D) citrate cycle

Question 10

Flux is defined as the rate at which is/are interconverted.

A) enzymes
B) metabolites
C) sugars
D) energy

Question 11

Compare the structure of an aldose to a ketose.

A) Ketose has a carbon backbone with an aldehyde group at the end of the molecule, whereas aldose has a ketone group at the end of the molecule.
B) Ketose has a carbon backbone with a ketone group at the end of the molecule, whereas aldose has an aldehyde group at the end of the molecule.
C) Both have a carbon backbone where ketose has a ketone group at the end of the molecule, and aldose also has an aldehyde group at the end of the molecule.
D) Both have a carbon backbone where ketose has a ketone group on the second carbon in the molecule, and aldose also has an aldehyde group at the end of the molecule.

Question 12

Catabolic pathways are always paired with anabolic pathways. Why?

A) Catabolic pathways build up new molecules and anabolic break down molecules.
B) Catabolic pathways break down molecules and anabolic build up new molecules.
C) Both require ATP to operate.
D) Both require redox reactions to operate.

Question 13

How can an unfavorable reaction ( $\Delta$ G $\degree$ ^' > 0) still occur in a metabolic pathway?

A) Link it to another unfavorable reaction.
B) Link it to a favorable reaction.
C) They cannot be used in metabolic pathway reactions.
D) Increase the temperature of the reaction.

Question 14

Which of the following is the correct formula for glucose?

A)C₁₂H₂₂O₁₁
B) C₆H ₁₂O₆
C) C₆H₆O₆
D) C₁₄N₂H ₁₈O₅

Question 15

A shared intermediate can be defined as a molecule that is

A) a reactant in a pathway.
B) the final product of a pathway.
C) the final product of a pathway and the reactant of the next pathway.
D) favorable to produce.

Question 16

What may be the root cause of the slowing of the flux of metabolites through the glycolysis and gluconeogenesis pathways in your body?

A) elevated levels of amino acids in the body
B) elevated levels of glycogen in the body
C) lowered levels of protein synthesis
D) lowered levels of enzyme activity

Question 17

In the following series of reactions, what is the shared intermediate?

A) glucose-6-P
B) fructose-6-P
C) ATP
D) fructose-1,6-P

Question 18

Review the figure below. Shared intermediates are used so effectively in coupled reactions because they

A) allow products to diffuse through membrane to increase concentration gradient.
B) increase the value of $\Delta$ G $\degree$ ^' .
C) decrease the value of Q.
D) limit product diffusion and allow intermediates to channel from one enzyme to the next.

Question 19

In the reaction A $\rightarrow$ B, if at equilibrium [B] >> [A], what can be said about the directionality of the reaction?

A) strongly favored in the forward direction
B) strongly favored in the reverse direction
C) strongly favored in both directions
D) Not enough information is given.

Question 20

Is the net reaction favorable for the following series of coupled reactions?

A) Yes, $\Delta$ G $\degree$ ^' < 0
B) No, $\Delta$ G $\degree$ ^' < 0
C) Yes, $\Delta$ G $\degree$ ^' > 0
D) No, $\Delta$ G $\degree$ ^' > 0

Question 21

Sucrose is a nonreducing sugar. Why?

A) Sucrose does not contain an aldehyde functional group.
B) Sucrose does not react with heat.
C) Sucrose is a pyranose that cannot be reacted with copper.
D) Sucrose is a disaccharide that cannot be converted to an open chain.

Question 22

Explain the difference between a Fisher projection and a Haworth projection.

A) Fischer projections illustrate the cyclic form, whereas Haworth projections represent the linear form.
B) The Haworth projection illustrates the six-membered rings, whereas the Fischer projection represents the five-membered rings.
C) Haworth projections illustrate the cyclic form, whereas Fischer projections represent the linear form.
D) Fischer projections show the boat conformation, whereas Haworth projections show the chair conformation.

Question 23

In the following figure, what is the linkage between the two monosaccharide units and is this a reducing sugar?

A) " $\alpha$ 1 $\rightarrow$$\beta$ 2, nonreducing"
B) " $\alpha$ 1 $\rightarrow$$\alpha$ 1, nonreducing"
C) " $\alpha$ 1 $\rightarrow$$\beta$ 2, reducing"
D) " $\alpha$ 1 $\rightarrow$$\alpha$ 2, reducing"

Question 24

In which of the following metabolic conversions is ATP "consumed" during glycolysis?

A) 1,3-Bisphosphoglycerate $\rightarrow$ 3-phosphoglycerate
B) glucose $\rightarrow$ glucose-6-phosphate
C) 2-Phosphoglycerate $\rightarrow$ 3-phosphoglycerate
D) glucose-6-phosphate $\rightarrow$ fructose-6-phosphate

Question 25

Which of following is an anomeric pair?

A) "D-glucose and D-fructose"
B) "D-glucose and L-fructose"
C) "D-glucose and L-glucose"
D) " $\alpha$ -D-glucose and $\beta$ -D-glucose"

Question 26

During the cyclization of D-glucose, where is a new chiral center formed?

A) C-1
B) C-3
C) C-4
D) C-5

Question 27

Which of the following is NOT a reason why glycolysis is considered one of the core metabolic pathways in nature?

A) Glycolytic enzymes are hugely conserved among all living organisms.
B) It is a primary pathway for ATP generation under anaerobic conditions.
C) Metabolites of glycolysis are precursors for a large number of interdependent pathways.
D) It is a primary pathway for nitrogen generation.

Question 28

Define ketose.

A) Only ketose molecules have CH₂OH.
B) Ketose molecules have ketone functional groups.
C) Ketose molecules have aldehyde functional groups.
D) Ketose molecules are all five-membered rings.

Question 29

The glycolytic pathway is responsible for passing molecules to which other pathways?

A) citrate cycle and nitrogen fixation
B) photosynthesis and oxidative phosphorylation
C) citrate cycle and oxidative phosphorylation
D) urea cycle and fatty acid synthesis

Question 30

What does glycolysis accomplish for the cell?

A) It generates ADP for the cell to be used in other cycles.
B) It generates ATP and pyruvate for the cell to be used in other cycles.
C) It generates glucose to be used for storage.
D) It generates CO₂ that is exhaled.

Question 31

What is the relationship between the molecules in the figure below?

A) They are isomers.
B) They are anomers.
C) They are epimers.
D) They are identical.

Question 32

The test using copper to determine blood glucose levels is called a test.

A) glycolysis
B) phosphorylation
C) Benedict's
D) McKee's

Question 33

Which of the following best defines substrate-level phosphorylation?

A) direct transfer of a P_i to an ADP
B) direct transfer of a P_i to an ATP
C) indirect transfer of a P_i to an ATP
D) indirect transfer of a P_i to glucose

Question 34

Define aldose.

A) Only aldose molecules have CH₂OH.
B) Aldose molecules have ketone functional groups.
C) Aldose molecules have aldehyde functional groups.
D) Aldose molecules are all five-membered rings.

Question 35

Which of the following compounds contains a "high-energy" bond and is used to produce ATP by substrate-level phosphorylation in glycolysis?

A) glucose
B) fructose-1,6-BP
C) 3-phosphoglycerate
D) 1,3-bisphosphoglycerate

Question 36

Anomers differ from each other by changes at the carbon.

A) chiral
B) C-2
C) C-3
D) C-1

Question 37

Which of the following is the correct net reaction for glycolysis?

A) glucose + 2 ATP $\rightarrow$ 2 lactate + 2 ADP + 2 P_i
B) glucose + 2 ADP + 2 P_i + 2 NAD⁺ $\rightarrow$ 2 pyruvate + 2 ATP + 2 NADH + 4 H⁺
C) glucose + 2 ADP + 2 P_i $\rightarrow$ 2 CH₃CH₂OH + 2 CO₂ + 2 ATP
D) glucose + 2 ADP + 2 P_i + 2 NAD⁺ $\rightarrow$ 2 pyruvate + 2 ATP + 2 NADH + 2 H⁺ + 2H₂O

Question 38

A carbohydrate that reacts with oxidizing agents such as Cu+2 is called a(n) sugar.

A) oxidizing
B) reducing
C) rentose
D) aldose

Question 39

Distinguish between D and L isomers.

A) D is right handed and L is left handed.
B) D is left handed and L is right handed.
C) D and L only differ in the position of one chiral center.
D) D is the boat conformation and L is the chair conformation.

Question 40

Name the following disaccharide using descriptive nomenclature.

A) Glc( $\alpha$ 1 $\rightarrow$$\beta$ 2)Fru
B) Glc( $\alpha$ 1 $\rightarrow$$\alpha$ 2)Glc
C) Gal( $\beta$ 1 $\rightarrow$ 4)Glc
D) Glc( $\alpha$ 1 $\rightarrow$$\alpha$ 4)Glc

Question 41

Where in the body is glucokinase found?

A) small intestine
B) liver
C) heart
D) thyroid

Question 42

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change ( $\Delta$ G ^' $\degree$ ) of 23.8 kJ/mol. Under what conditions (encountered in erythrocytes) will the free-energy change ( $\Delta$ G) be negative, enabling the reaction to proceed to products?

A) The free-energy change will be negative if the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate.
B) The reaction will not go to the right spontaneously under any conditions because the $\Delta$ G ^' $\degree$ is positive.
C) Under standard conditions, enough energy is released to drive the reaction to the right.
D) The free-energy change will be negative when there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.

Question 43

How does phosphoglycerate kinase make glycolysis energy neutral at this step?

A) It uses ATP to produce 3-phosphoglycerate.
B) It produces 2 ATP along with 3-phosphoglycerate.
C) It results in a reaction at equilibrium.
D) It results in a reaction is endergonic.

Question 44

In the presence of high concentrations of ADP and F6P, how does the equilibrium shift between the T state and R state of PFK-1? High concentrations of ADP and F6P

A) shift equilibrium to the R state.
B) shift equilibrium to the T state.
C) do not bind to PFK.
D) dancel each other out and have no effect.

Question 45

The first reaction in glycolysis that produces a high-energy compound is catalyzed by

A) aldolase.
B) triose phosphate isomerase.
C) enolase.
D) phosphofructokinase-1.

Question 46

In the presence of lactase, lactose is cleaved into the monosaccharides glucose and

A) glucose.
B) fructose.
C) galactose.
D) maltose.

Question 47

If blood glucose levels are elevated, what does glucokinase do in response?

A) inhibits glycolysis
B) stimulates the production of more hexokinase
C) stimulates the release of insulin
D) inhibits production of 2,3-BPG

Question 48

If you are unable to digest milk products, what is the metabolic root of that issue?

A) maltase
B) lactase
C) sucrose
D) glucose oxidase

Question 49

Which of the following metabolic conversions is considered to be the major control point of glycolysis?

A) fructose-1,6-bisphosphate $\rightarrow$ dihydroxyacetone phosphate + glyceraldehyde-3-phosphate
B) 1,3-Bisphosphoglycerate + ADP $\rightarrow$ 3-Phosphoglycerate + ATP
C) 2-phosphoglyerate $\rightarrow$ phosphoenolpyruvate
D) fructose-6-phosphate $\rightarrow$ fructose-1,6-bisphosphate

Question 50

Which coenzyme is required to convert glyceraldehyde-3-P into 1,3-bisphosphosphoglycerate?

A) FAD⁺
B) NAD⁺
C) ATP
D) P_i

Question 51

If a person has a deficiency in fructose-1-P, what effects does that have on the body?

A) Fructose-6-P concentrations increase.
B) Fructose-6-P is depleted.
C) ATP concentrations increase.
D) Glucose-6-P concentrations increase.

Question 52

What advantage is there to phosphoglycerate kinase having an open and closed configuration?

A) It allows water to be trapped in the active site along with the substrate.
B) It forces covalent binding of the substrate to the enzyme active site.
C) The induced-fit mechanism maximizes accessibility of active site without sacrificing hydrophobic environment.
D) Changing of the configuration of the enzyme makes the reaction exergonic.

Question 53

To produce 4 ATP requires 122 kJ/mol. Which reactions in the glycolytic pathway produce enough energy to be able to overcome this deficit?

A) hexokinase, phosphofructokinase-1, and pyruvate kina
B) hexokinase, phosphofructokinase-1, and pyruvate kinase
C) phosphofructokinase-1, aldolase, and pyruvate kinase
D) hexokinase, enolase, and pyruvate kinase

Question 54

The enzyme phosphoglycerate mutase operates at $\Delta$ G ≈ 0 kJ/mol. That indicates that the reversibility of that reaction

A) is spontaneous.
B) occurs rapidly.
C) occurs at equilibrium.
D) is nonspontaneous.

Question 55

What effect do elevated levels of ATP have on glycolysis?

A) decrease the affinity of PFK-1 for fructose-6-P and slow rate of the pathway
B) increase the affinity of PFK-1 for fructose-6-P and increase the rate of the pathway
C) increase the concentration of PFK-1 in the R-state
D) increase the concentration of glucose entering glycolysis

Question 56

Fructose-1,6-bisphosphate is cleaved by aldolase. What is required for the reaction to proceed?

A) production of endergonic intermediate
B) substrate phosphorylation
C) cleaving of high-energy phosphate bond
D) formation of Schiff base intermediate

Question 57

Predict how oxygen saturation would be affected if an individual has defective hexokinase enzymes.

A) 2,3-BPG levels are elevated and oxygen binding decreases.
B) 2,3-BPG levels are reduced and oxygen binding increases.
C) 2,3-BPG levels are elevated and oxygen binding increases.
D) 2,3-BPG levels are reduced and oxygen binding decreases.

Question 58

Hexokinase has a Km of 0.1 mM for glucose, whereas glucokinase has a Km of 10 mM for glucose. What does that mean for their relative affinities for glucose?

A) Glucokinase has a higher affinity.
B) Hexokinase has a higher affinity.
C) Km does not measure affinity.
D) They are different enzymes and affinity cannot be compared between enzymes.

Question 59

The rate limiting step can be defined as a level of enzyme activity that can be regulated to be __________ even when substrate levels are _.

A) high; high
B) low; high
C) high; low
D) low; low

Question 60

Using the table below, explain why glycolysis is an overall favorable reaction pathway.

A) Overall the pathway is $\Delta$ G > 0.
B) Overall the pathway is $\Delta$ G = 0.
C) Overall the pathway is $\Delta$ G < 0.
D) Overall the pathway is $\Delta$ G < 1.

Question 61

During glycolysis, the steps between glucose and formation of glyceraldehyde-3-phosphate

A) consume 2 ATP and 2 NADH.
B) consume 2 ATP.
C) produce 2 ADP and 2 NADH.
D) produce 2 ATP and 2 NADH.

Question 62

Which reaction in glycolysis is a redox reaction?

A) glyceraldehyde-3-P $\rightarrow$ 1,3-bisphosphoglycerate
B) glucose $\rightarrow$ glucose-6-P
C) 2-phosphoglycerate $\rightarrow$ phosphoenolpyruvate
D) fructose-6-P $\rightarrow$ fructose-1,6-BP

Question 63

List three ways in which flux is controlled through glycolysis.

A) regulation of aldolase, PFK-1, and supply and demand of intermediates
B) regulation of glucokinase, fructokinase, and number of intermediates
C) regulation of glucokinase, PFK-1, and concentration of glucose
D) regulation of glucokinase, PFK-1, and supply and demand of intermediates

Question 64

Fructose 1,6-bisphosphate is converted to two products with a standard free energy of 23.8 kJ/mol. Under what condition(s) will this reaction become spontaneous?

A) spontaneous under any conditions
B) spontaneous under all conditions
C) when there is a high concentration of products relative to the concentration of fructose 1,6-bisphosphate
D) when there is a low concentration of products relative to the concentration of fructose 1,6-bisphosphate

Question 65

What would the effect be of a lack of lactate dehydrogenase?

A) buildup of glucose
B) buildup of CO₂
C) deficiency of ATP
D) deficiency of pyruvate

Question 66

The NADH that is produced by glycolysis under anaerobic conditions is regenerated to NAD⁺ by the conversion of

A) acetaldehyde $\rightarrow$ ethanol.
B) lactate $\rightarrow$ pyruvate.
C) phosphoenolpyruvate $\rightarrow$ pyruvate.
D) pyruvate $\rightarrow$ lactate.

Question 67

Using glucose metabolism, justify the following statement: Metabolic pathways are highly interdependent and are exquisitely controlled by enzyme activity levels and substrate bioavailability.

Question 68

An infant who obtains nourishment from milk and who has galactosemia is unable to convert

A) galactose-1-P to glucose-6-P.
B) glucose-6-P to galactose-1-P.
C) galactose-1-P to glucose-1-P.
D) glucose-1-P to galactose-1-P.

Question 69

Given figures A and B below, label the chiral center on each and state if the molecule is a D or L enantiomer.

Question 70

Illustrate both the Fisher and Haworth projections for glucose and fructose

Question 71

Galactosemia is deficiency in which enzyme?

A) galactokinase
B) galactose-1-P uridyltransferase
C) UDP-galactose 4-epimerase
D) phosphoglucomutase

Question 72

List the major metabolic pathways in animals and classify each as either an energy conversion pathway or a synthesis/degradation pathway

Question 73

List the major metabolic pathways in plants and classify each as either an energy conversion pathway or a synthesis/degradation pathway.

Question 74

What is the potential metabolic fate of pyruvate under aerobic conditions?

A) produce lactate
B) produce ethanol
C) produce carbon dioxide and water
D) produce glucose

Question 75

Which of these cofactors participates directly in MOST of the redox reactions in the fermentation of glucose to lactate?

A) ADP
B) ATP
C) NAD⁺/NADH
D) FAD/FADH₂

Question 76

What is the potential metabolic fate of pyruvate during strenuous exercise?

A) produce lactate
B) produce ethanol
C) produce carbon dioxide and water
D) produce glucose

Question 77

Glucokinase is a molecular sensor for which molecule?

A) glucose
B) lactose
C) galactose
D) maltose

Question 78

Which enzyme is the main regulator of glycolysis?

A) hexokinase
B) PFK-1
C) pyruvate kinase
D) aldolase

Question 79

What is the fate of pyruvate in the presence of yeast, Saccharomyces cerevisiae?

A) converts to CO₂ and ethanol
B) converts to H₂O and CO₂
C) converts to lactate and ethanol
D) converts to lactate and glucose

Question 80

When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which one of the following statements is MOST correct, when applied to the reaction below (R = 8.315 J/mol·K and T = 298 K)?
Glucose 6-phosphate $\harr$ fructose 6-phosphate

A) " $\Delta$ G ^' $\degree$ is +1.7 kJ/mol."
B) " $\Delta$ G ^' $\degree$ is -1.7 kJ/mol."
C) " $\Delta$ G ^' $\degree$ is zero."
D) "It is not possible to calculate $\Delta$ G ^' $\degree$ "