Deck 17: Glycolysis

Question 1

Which of the following is a characteristic of the coupling between glycolysis and the citric acid cycle?

A)Citrate inhibits glucokinase to regulate glycolysis.
B)Glycolysis feeds acetyl-CoA,via pyruvate,to the citric acid cycle.
C)Oxaloacetate builds up when the citric acid cycle reaches saturation.
D)Glycolysis directs electrons into the electron transport chain for the purpose of ATP production.

Answer 1

B

Question 2

Which of the following is a step in the phosphoglucoisomerase-catalyzed reaction on glucose-6-phosphate?

A)C-4 proton is removed
B)creation of a carbonyl group at C-1
C)opening of the pyranose ring
D)removal of a furanose ring

Answer 2

C

Question 3

Which of the following concerning the isomerase reaction of glucose-6-phosphate to fructose-6-phosphate is correct?

A)Zn²⁺ is required for activity.
B)It is a ketose-to-aldose isomerization.
C)Transferring the carbonyl from C-1 to C-2 creates a new primary alcohol group at C-1.
D)The reaction is irreversible with a large negative DG.

Answer 3

C

Question 4

Which of the following is NOT an important reason to phosphorylate glucose in the first step of glycolysis?

A)The large positive free energy is important in getting the pathway started.
B)Glucose-6-phosphate has a negative charge,preventing transport out of the cell.
C)The concentration of free glucose in the cell is lowered,favouring influx of glucose.
D)Regulatory control can be imposed only at a reaction,not at equilibrium.

Question 5

Which enzyme is NOT involved in the first 5 steps of glycolysis?

A)phosphofructokinase-1 (PFK-1)
B)phosphoglycerate kinase
C)fructose bisphosphate aldolase
D)triose phosphate isomerase (TPI)

Question 6

Which of the following is a characteristic of type I diabetes mellitus?

A)glucokinase induction
B)low levels of glucokinase
C)excess insulin production
D)over production of liver glycogen

Question 7

Which of the following products is formed when a-D-glucose reacts with ATP?

A)α-D-glucose-1-phosphate
B)α-D-fructose-1-phosphate
C)α-D-glucose-6-phosphate
D)α-D-fructose-6-phosphate

Question 8

Which of the following enzymes catalyzes this reaction?
ADP + ADP ↔ ATP + AMP

A)adenylate cyclase
B)protein kinase C
C)adenylate kinase
D)guanylate cyclase

Question 9

Which of the following is a characteristic of fructose bisphosphate aldolase in animal tissues?

A)It is a Class II aldolase.
B)It belongs to the transferase class of enzymes.
C)The reaction is reversible in erythrocytes (DG is very small).
D)The products are an aldopentose phosphate and a ketotriose phosphate.

Question 10

Which of the following characterizes the conversion of glucose to lactate?

A)aerobic pathway with no net oxidation
B)"primed" by ATP phosphorylation
C)located in the mitochondria
D)net production of 4 ATP per glucose

Question 11

Which of the following is NOT an allosteric regulator of phosphofructokinase-1?

A)glucose-6-phosphate
B)ATP
C)AMP
D)?-D-fructose-2,6-bisphosphate

Question 12

Which of the following is a characteristic of phosphofructokinase-1 (PFK-1)?

A)ATP increases the affinity of the enzyme for fructose-6-phosphate.
B)It is the most important regulatory site in glycolysis.
C)PFK-1 activity is a function of the lipid content of the cell.
D)ATP decreases the Km of PFK-1 for fructose-6-phosphate.

Question 13

Glucokinase has a Km value of 10.0 mM,whereas hexokinase has a Km value of 0.1 mM.Which of the following is this consistent with?

A)Glucokinase acts on glucose only at high glucose concentrations.
B)Glucokinase acts on glucose at low concentrations.
C)Hexokinase acts on glucose only at high levels of glucose.
D)Hexokinase acts at about half-maximal velocity at glucose concentrations of 4-5 mM.

Question 14

Which of the following enzymes catalyzes the step that commits glucose to glycolysis?

A)phosphofructokinase-1 (PFK-1)
B)hexokinase
C)phosphoglucoisomerase
D)glucokinase

Question 15

How is phosphofructokinase-1 regulated?

A)Low ATP stimulates the enzyme,but fructose-2,6-bisphosphate inhibits.
B)High ATP stimulates the enzyme,and fructose-2,6-bisphosphate activates.
C)High ATP stimulates the enzyme,but fructose-2,6-bisphosphate inhibits.
D)Low ATP stimulates the enzyme,and fructose-2,6-bisphosphate activates.

Question 16

Which of the following is a characteristic of dihydroxyacetone phosphate?

A)It is an enantiomer of glyceraldehyde-3-phosphate.
B)It is derived from C4-C6 of fructose-1,6-bisphosphate.
C)It is isomerized to glyceraldehyde-3-phosphate by triose phosphate isomerase (TPI).
D)It is the least abundant component of the TPI reaction at equilibrium.

Question 17

Which of the following characteristics applies to Class I aldolases?

A)an enediol intermediate
B)a requirement for biotin
C)a Schiff base intermediate
D)coenzyme requirement for thiamine pyrophosphate (TPP)

Question 18

Which of the following actions of phosphoglucoisomerase occurs when is secreted by T-cells?

A)It phosphorylates galactose.
B)It isomerizes galactose-6-phosphate to glucose-6-phosphate.
C)It promotes the survival of certain spinal neurons and sensory nerves.
D)It glycosylates sphingolipids surrounding nerves.

Question 19

Which of the following subclass of enzymes do hexokinase and glucokinase belong to?

A)transferase
B)oxidoreductase
C)hydrolase
D)lyase

Question 20

Which of the following is NOT a characteristic of the phosphofructokinase-1 catalyzed reaction?

A)endergonic
B)"priming reaction"
C)"valve" controlling the rate of glycolysis
D)commits the cell to metabolize glucose

Question 21

Which of the following molecules has the most highly exergonic hydrolysis,considering that only the highest energy bond is hydrolyzed?

A)phosphoenolpyruvate
B)fructose-6-phosphate
C)1,3-bisphosphoglycerate
D)fructose-1,6-bisphosphate

Question 22

PEP and 2-PG have similar amounts of potential metabolic energy with respect to decomposition to Pᵢ,CO₂,and H₂O.Which of the following statements applies to enolase-catalyzed decomposition of PEP and 2-PG?

A)The enolase reaction creates a much more unstable reactive intermediate.
B)The enolase reaction rearranges 2-PG into a form from which more potential energy can be released by hydrolysis.
C)The enolase reaction rearranges 2-PG to a form with greater binding potential to the enzyme.
D)The enolase reaction changes the DG of the reaction to increase the potential energy.

Question 23

Which of the following stable tautomers of pyruvate is formed during the conversion of PEP to pyruvate?

A)enol
B)keto
C)imine
D)aldol

Question 24

Which of the following reactions does a mutase catalyze?

A)2-phosphoglycerate Û phosphoenolpyruvate + H₂O
B)pyruvate + NADH + H⁺ Û lactate + NAD⁺
C)3-phosphoglycerate Û 2-phosphoglycerate
D)dihydroxyacetone phosphate Û glyceraldehyde-3-phosphate

Question 25

Which of the following processes do mutases catalyze?

A)movement of a functional group within a substrate molecule
B)phosphorylation from ATP
C)hydrolysis of a phosphate ester
D)addition of water across a double bond

Question 26

Which of the following class of enzymes does glyceraldehyde-3-phosphate dehydrogenase belong to?

A)oxidoreductases
B)isomerases
C)transferases
D)hydrolases

Question 27

Which of the following substrate carbons is attacked by a cysteine -SH group during the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase,resulting in the formation of a hemithioacetal?

A)alpha
B)acidic
C)amino
D)carbonyl

Question 28

Which of the following for 2,3-bisphosphoglycerate (2,3-BPG)is correct?

A)Erythrocytes typically have low levels of 2,3-BPG.
B)1,3-BPG is synthesized from 2,3-BPG.
C)2,3-BPG is involved in unloading oxygen from hemoglobin.
D)A kinase converts 2,3-BPG to 3-phosphoglycerate.

Question 29

Which of the following enzymes has a mechanism very similar in function to triose phosphate isomerase?

A)hexokinase
B)phosphoglucoisomerase
C)phosphofructokinase
D)fructose-1,6-bisphosphate aldolase

Question 30

Which of the following enzymes catalyzes the reaction 1,3-bisphosphoglycerate ? 2,3-bisphosphoglycerate?

-Which of the following enzymes catalyzes the reaction 1,3-bisphosphoglycerate ? 2,3-bisphosphoglycerate?

A)bisphosphoglycerate phosphatase
B)bisphosphoglycerate mutase
C)2,3-bisphosphoglycerate synthetase
D)1,3-bisphosphoglycerate hydrolase

Question 31

Which of the of the following covalent modifications does cAMP-dependent protein kinase carry out on pyruvate kinase?

A)carboxylation
B)phosphorolysis
C)phosphorylation
D)decarboxylation

Question 32

Which of the following is the first intermediate of glycolysis with free energy of hydrolysis more negative than that of ATP?

A)glucose-6-phosphate
B)fructose-1,6-bisphosphate
C)dihydroxyacetone phosphate
D)1,3-bisphosphoglycerate

Question 33

What is the net ATP yield per glucose molecule at the end of the glycolytic pathway?

A)1
B)2
C)3
D)4

Question 34

Which of the following enzymes,when genetically defective,can result in the most common form of hemolytic anemia?

A)pyruvate kinase
B)hexokinase
C)PFK-1
D)phosphoglycerate mutase

Question 35

Which of the following enzymes catalyzes substrate-level phosphorylation during glycolysis?

A)phosphoglycerate kinase
B)hexokinase
C)phosphofructokinase
D)glucokinase

Question 36

Addition of water across a double bond,or removal of water to form a double bond,is catalyzed by a subclass of the lyase class of enzymes.Which of the following enzymes would be a lyase?

A)glyceraldehyde-3-phosphate dehydrogenase
B)triose phosphate isomerase (TPI)
C)phosphoglycerate mutase
D)enolase

Question 37

Which of the following are the 3 main products of glycolysis?

A)ATP;pyruvate;NAD⁺
B)NAD⁺;ADP;FAD
C)ATP;NAD⁺;ADP
D)ATP;pyruvate;NADH

Question 38

Which of the following enzymes catalyzes a reversible reaction that is an equilibrium-controlled step of glycolysis?

A)pyruvate kinase
B)aldolase
C)phosphofructokinase-1
D)glucokinase

Question 39

Which of the following is an allosteric effector of pyruvate kinase?

A)acetyl-CoA
B)pyruvate
C)citrate
D)PFK-1

Question 40

Which of the following enzymes of glycolysis is NOT allosterically regulated?

A)phosphofructokinase-1
B)glyceraldehyde-3-phosphate dehydrogenase
C)hexokinase
D)pyruvate kinase

Question 41

Which of the following two enzymes catalyze the two oxidation-reduction reactions in the fermentation of alcohol from glucose?

A)glyceraldehyde-3-phosphate dehydrogenase and alcohol dehydrogenase
B)alcohol dehydrogenase and pyruvate decarboxylase
C)lactate dehydrogenase and pyruvate decarboxylase
D)glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase

Question 42

Under anaerobic conditions,skeletal muscle generates lactate from pyruvate.Why does it do this?

A)to lower the pH
B)to promote release of oxygen from hemoglobin
C)to generate additional ATP
D)to regenerate NAD⁺ for further glycolysis

Question 43

Which of the following enzymes converts UDP-galactose to UDP-glucose?

A)galactokinase
B)galactose-uridylyl transferase
C)UDP-glucose-4-epimerase
D)UDP-galactose-2-epimerase

Question 44

How is lactose metabolized in lactase-deficient animals?

A)by intestinal enzymes
B)by intestinal bacteria
C)by intestinal viruses
D)by intestinal a-amylase

Question 45

Which of the following enzymes is defective in the rare hereditary galactosemia?

A)galactokinase
B)galactose-1-phosphate uridylyl transferase
C)phosphoglucomutase
D)UDP-glucose pyrophosphorylase

Question 46

What happens to lactate after it is produced by anaerobic muscle tissue?

A)It is stored in muscle until oxygen is available.
B)It is carried by the blood to the liver for gluconeogenesis back to glycogen.
C)It is further oxidized to acetate in muscle.
D)It is transferred to erythrocytes to release oxygen from hemoglobin.

Question 47

Seven of the 10 reactions of glycolysis are reversible (DG near zero)and can be used in reverse of glycolysis for gluconeogenesis.Which enzymes catalyze the three irreversible reactions?

A)triose phosphate isomerase,phosphoglycerate mutase,pyruvate kinase
B)enolase,phosphoglycerate kinase,phosphofructokinase-1
C)phosphoglycerate mutase,phosphoglucoisomerase,glyceraldehyde-3-phosphate dehydrogenase
D)hexokinase,phosphofructokinase-1,pyruvate kinase

Question 48

Which of the following enzymes is NOT used when fructose is metabolized to pyruvate in the liver?

A)triose phosphate isomerase
B)glyceraldehyde-3-phosphate dehydrogenase
C)glucokinase
D)phosphofructokinase-1

Question 49

Which of the following two proteins form the dimeric complex lactose synthase?

A)lactase and ?-galactosidase
B)galactosyl transferase and lactase
C)a-lactalbumin and galactosyl transferase
D)galactosyl transferase and ?-galactosidase

Question 50

Which of the following enzymes may cause galactosemia to disappear in adults due to its metabolism of galactose-1-phosphate?

A)protein kinase A
B)UDP-glucose-4-epimerase
C)phosphoglucomutase
D)UDP-glucose pyrophosphorylase

Question 51

Which of the following explains why fructose in the diet or fructose from sucrose in the diet can be a source of calories for fat synthesis in the liver?

A)Glycerol (the "backbone" of triacylglycerols)comes specifically from fructose.
B)Fructose enters glycolysis after the primary regulation point,PFK-1.
C)Fructose provides a net of 4 ATP from glycolysis.
D)Fructose enters the branch of glycolysis that forms fat.

Question 52

If glucose were labelled with ¹⁴C at carbon #6,which carbon of pyruvate would have the ¹⁴C?

A)carboxyl carbon
B)ketone carbon
C)methyl carbon
D)The 14C would be lost as CO₂.

Question 53

Which of the following statements regarding sugar metabolism is correct?

A)Lactase,a b-galactosidase-type enzyme,cleaves the a(1,4)glycosidic bond observed in lactose.
B)In the liver,fructose is converted to fructose-1-P,then to DHAP and glyceraldehyde,thus skipping normal glycolytic regulation.
C)In the muscle,fructose is converted into fructose-1-P by hexokinase.
D)Galactose enters glycolysis as galactose-6-P.

Question 54

What is the net yield of the oxidation of 1 mole of glucose by anaerobic glycolysis?

A)2 moles of pyruvate and 2 moles of ATP
B)2 moles of lactate,2 moles of NADH,and 2 moles of ATP
C)2 moles of pyruvate,2 moles of NADH,and 4 moles of ATP
D)2 moles of lactate and 2 moles of ATP

Question 55

Which of the following enzymes in the liver is used to phosphorylate fructose to fructose-1-phosphate?

A)glucokinase
B)phosphofructokinase-1
C)hexokinase
D)fructokinase

Question 56

Where does glycerol generated by hydrolysis of triacylglycerols enter glycolysis?

A)at the glyceraldehyde-3-phosphate stage
B)at the 3-phosphoglycerate stage
C)at the 2-phosphoglycerate stage
D)at the dihydroxyacetone phosphate stage