MCQ: Glycolysis, Gluconeogenesis, Pentose Phosphate Pathways

Question 1

Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. Glycolysis is an example of:
A) aerobicmetabolism.
B) anabolic metabolism.
C) a net reductive process.
D) fermentation.
E) oxidative phosphorylation.

Answer 1

D) fermentation.

Question 2

During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most important reaction involved in the reoxidation of NADH is:
A) dihydroxyacetone phosphate → glycerol 3-phosphate B) glucose 6-phosphate → fructose 6-phosphate
C) isocitrate → α-ketoglutarate
D) oxaloacetate → malate
E) pyruvate → lactate

Answer 2

E) pyruvate → lactate

Question 3

The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of:
A) 1molofNAD+and2molofATP. B) 1molofNADHand1molofATP.
C) 2molofNAD+and4molofATP. D) 2molofNADHand2molofATP. E) 2molofNADHand4molofATP.

Answer 3

E) 2molofNADHand4molofATP.

Question 4

Which of the following statements is not true concerning glycolysis in anaerobic muscle?
A) Fructose1,6-bisphosphataseisoneoftheenzymesofthepathway.
B) It is an endergonic process.
C) It results in net synthesis of ATP.
D) ItresultsinsynthesisofNADH.
E) Its rate is slowed by a high [ATP]/[ADP] ratio.

Answer 4

It is an endergonic process.

Question 5

When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts anaerobically because:
A) glycolysisdoesnotoccurtosignificantextentunderaerobicconditions.
B) muscle is metabolically less active under aerobic than anaerobic conditions.
C) the lactic acid generated is rapidly incorporated into lipids under aerobic conditions.
D) underaerobicconditionsinmuscle,themajorenergy-yieldingpathwayisthepentosephosphate
pathway, which does not produce lactate.
E) under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidized by
the citric acid cycle rather than reduced to lactate.

Answer 5

under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidized by
the citric acid cycle rather than reduced to lactate.

Question 6

Glycolysis in the erythrocyte produces pyruvate that is further metabolized to:
A) CO2.
B) ethanol.
C) glucose.
D) hemoglobin. E) lactate.

Answer 6

E) lactate.

Question 7

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 nearly correct, when applied to the reaction below (R = 8.315 J/mol·K and T = 298 K)?
Glucose 6-phosphate ↔ fructose 6-phosphate
A) ∆G’° is +1.7 kJ/mol.
B) ∆G’°is–1.7kJ/mol.
C) ∆G’°isincalculablylargeandnegative.
D) ∆G’° is incalculably large and positive.
E) ∆G’° is zero.

Answer 7

A) ∆G’° is +1.7 kJ/mol.

Question 8

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change (∆G’°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free- energy change (∆G) be negative, enabling the reaction to proceed to the right?
A) Iftheconcentrationsofthetwoproductsarehighrelativetothatoffructose1,6-bisphosphate.
B) The reaction will not go to the right spontaneously under any conditions because the ∆G’° is
positive.
C) Under standard conditions, enough energy is released to drive the reaction to the right.
D) Whenthereisahighconcentrationoffructose1,6-bisphosphaterelativetotheconcentrationof
products.
E) When there is a high concentration of products relative to the concentration of fructose 1,6-
bisphosphate.

Answer 8

Whenthereisahighconcentrationoffructose1,6-bisphosphaterelativetotheconcentrationof
products.

Question 9

Which of these cofactors participates directly in most of the oxidation-reduction reactions in the fermentation of glucose to lactate?
A) ADP
B) ATP
C) FAD/FADH2
D) Glyceraldehyde3-phosphate E) NAD+/NADH

Answer 9

E) NAD+/NADH

Question 10

In comparison with the resting state, actively contracting human muscle tissue has a:
A) higherconcentrationofATP.
B) higher rate of lactate formation.
C) lower consumption of glucose.
D) lowerrateofconsumptionofoxygen
E) lower ratio of NADH to NAD+.

Answer 10

B) higher rate of lactate formation.

Question 11

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except:
A) ATP synthesis.
B) catalysis by phosphoglycerate kinase.
C) oxidation of NADH to NAD+.
D) theformationof1,3-bisphosphoglycerate.
E) utilization of Pi.

Answer 11

C) oxidation of NADH to NAD+.

Question 12

The first reaction in glycolysis that results in the formation of an energy-rich compound (i.e., a compound whose hydrolysis has a highly negative ∆G’°) is catalyzed by:
A) glyceraldehyde3-phosphatedehydrogenase.
B) hexokinase.
C) phosphofructokinase-1.
D) phosphoglyceratekinase.
E) triose phosphate isomerase.

Answer 12

A) glyceraldehyde3-phosphatedehydrogenase.

Question 13

Which of the following is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?
A) ATP
B) Cu2+ 
C) heme
D) NAD+ 
E) NADP+

Answer 13

D) NAD+

Question 14

Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride?
A) 2-phosphoglycerate B) Glucose
C) Glyoxylate
D) Phosphoenolpyruvate E) Pyruvate

Answer 14

A) 2-phosphoglycerate

Question 15

Glycogen is converted to monosaccharide units by:
A) glucokinase.
B) glucose-6-phosphatase
C) glycogen phosphorylase.
D) glycogen synthase.
E) glycogenase.

Answer 15

C) glycogen phosphorylase.

Question 16

Which of the following statements is incorrect?
A) Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle.
B) In anaerobic muscle, pyruvate is converted to lactate.
C) In yeast growing anaerobically, pyruvate is converted to ethanol.
D) Reduction of pyruvate to lactate regenerates a cofactor essential for glycolysis.
E) Under anaerobic conditions pyruvate does not form because glycolysis does not occur.

Answer 16

Under anaerobic conditions pyruvate does not form because glycolysis does not occur.

Question 17

The ultimate electron acceptor in the fermentation of glucose to ethanol is:
A) acetaldehyde. B) acetate.
C) ethanol.
D) NAD+.
E) pyruvate.

Answer 17

A) acetaldehyde.

Question 18

In the alcoholic fermentation of glucose by yeast, thiamine pyrophosphate is a coenzyme required by:
A) aldolase.
B) hexokinase.
C) lactate dehydrogenase.
D) pyruvate decarboxylase.
E) transaldolase.

Answer 18

D) pyruvate decarboxylase.D) pyruvate decarboxylase.

Question 19

Which of the following compounds cannot serve as the starting material for the synthesis of glucose via gluconeogenesis?
A) acetate
B) glycerol
C) lactate
D) oxaloacetate E) α-ketoglutarate

Answer 19

A) acetate

Question 20

An enzyme used in both glycolysis and gluconeogenesis is:
A) 3-phosphoglyceratekinase.
B) glucose 6-phosphatase.
C) hexokinase.
D) phosphofructokinase-1.
E) pyruvate kinase.

Answer 20

A) 3-phosphoglyceratekinase.

Question 21

Which one of the following statements about gluconeogenesis is false?
A) Forstartingmaterials,itcanusecarbonskeletonsderivedfromcertainaminoacids.
B) It consists entirely of the reactions of glycolysis, operating in the reverse direction.
C) It employs the enzyme glucose 6-phosphatase.
D) Itisoneofthewaysthatmammalsmaintainnormalbloodglucoselevelsbetweenmeals.
E) It requires metabolic energy (ATP or GTP).

Answer 21

It consists entirely of the reactions of glycolysis, operating in the reverse direction.

Question 22

All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis) are also involved in the reversal of this flow (gluconeogenesis) except:
A) 3-phosphoglyceratekinase. B) aldolase.
C) enolase.
D) phosphofructokinase-1.
E) phosphoglucoisomerase.

Answer 22

D) phosphofructokinase-1.

Question 23

In humans, gluconeogenesis:
A) canresultintheconversionofproteinintobloodglucose.
B) helps to reduce blood glucose after a carbohydrate-rich meal.
C) is activated by the hormone insulin
D) isessentialintheconversionoffattyacidstoglucose.
E) requires the enzyme hexokinase.

Answer 23

canresultintheconversionofproteinintobloodglucose.

Question 24

Which of the following substrates cannot contribute to net gluconeogenesis in mammalian liver?
A) alanine
B) glutamate
C) palmitate
D) pyruvate
E) α-ketoglutarate

Answer 24

C) palmitate

Question 25

Which of the following statements about the pentose phosphate pathway is correct?
A) Itgenerates36molofATPpermoleofglucoseconsumed.
B) It generates 6 moles of CO2 for each mole of glucose consumed
C) It is a reductive pathway; it consumes NADH.
D) Itispresentinplants,butnotinanimals.
E) It provides precursors for the synthesis of nucleotides.

Answer 25

E) It provides precursors for the synthesis of nucleotides.

Question 26

The main function of the pentose phosphate pathway is to:
A) givethecellanalternativepathwayshouldglycolysisfail.
B) provide a mechanism for the utilization of the carbon skeletons of excess amino acids.
C) supply energy.
D) supplyNADH.
E) supply pentoses and NADPH.

Answer 26

) supply pentoses and NADPH.

Question 27

The metabolic function of the pentose phosphate pathway is:
A) actasasourceofADPbiosynthesis.
B) generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.
C) participate in oxidation-reduction reactions during the formation of H2O.
D) provideintermediatesforthecitricacidcycle.
E) synthesize phosphorus pentoxide.

Answer 27

generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.

Question 28

Which of the following statements about the pentose phosphate pathway is incorrect?
A) It generates CO2 from C-1 of glucose.
B) It involves the conversion of an aldohexose to an aldopentose.
C) It is prominant in lactating mammary gland.
D) ItisprincipallydirectedtowardthegenerationofNADPH.
E) It requires the participation of molecular oxygen.

Answer 28

It requires the participation of molecular oxygen.

Question 29

Which of the following enzymes acts in the pentose phosphate pathway?
A) 6-phosphogluconatedehydrogenase
B) Aldolase
C) Glycogen phosphorylase
D) Phosphofructokinase-1
E) Pyruvate kinase

Answer 29

6-phosphogluconatedehydrogenase