Chapter 14

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) aerobic metabolism.
B) anabolic metabolism.
C) a net reductive process.
D) fermentation.
E) oxidative phosphorylation.

Answer 1

D) fermentation.

Question 2

The anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied by a
net gain of:

A) 1 mol of ATP.
B) 1 mol of NADH.
C) 2 mol of ATP.
D) 2 mol of NADH.
E) none of the above.

Answer 2

C) 2 mol of ATP.

Question 3

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 3

E) pyruvate → lactate

Question 4

If glucose labeled with 14C in C-1 were fed to yeast carrying out the ethanol fermentation, where
would the 14C label be in the products?

A) In C-1 of ethanol and CO2
B) In C-1 of ethanol only
C) In C-2 (methyl group) of ethanol only
D) In C-2 of ethanol and CO2
E) In CO2 only

Answer 4

C) In C-2 (methyl group) of ethanol only

Question 5

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) 1 mol of NAD+ and 2 mol of ATP.
B) 1 mol of NADH and 1 mol of ATP.
C) 2 mol of NAD+ and 4 mol of ATP.
D) 2 mol of NADH and 2 mol of ATP.
E) 2 mol of NADH and 4 mol of ATP.

Answer 5

E) 2 mol of NADH and 4 mol of ATP.

Question 6

In an anaerobic muscle preparation, lactate formed from glucose labeled in C-3 and C-4 would be
labeled in:

A) all three carbon atoms.
B) only the carbon atom carrying the OH.
C) only the carboxyl carbon atom.
D) only the methyl carbon atom.
E) the methyl and carboxyl carbon atoms

Answer 6

C) only the carboxyl carbon atom.

Question 7

Which of the following statements is not true concerning glycolysis in anaerobic muscle?

A) Fructose 1,6-bisphosphatase is one of the enzymes of the pathway.
B) It is an endergonic process.
C) It results in net synthesis of ATP.
D) It results in synthesis of NADH.
E) Its rate is slowed by a high [ATP]/[ADP] ratio.

Answer 7

B) It is an endergonic process.

Question 8

When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts
anaerobically because:

A) glycolysis does not occur to significant extent under aerobic conditions.
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) under aerobic conditions in muscle, the major energy-yielding pathway is the pentose phosphate
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 8

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

Question 9

Glycolysis in the erythrocyte produces pyruvate that is further metabolized to:

A) CO2.
B) ethanol.
C) glucose.
D) hemoglobin.
E) lactate.

Answer 9

E) lactate.

Question 10

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 –1.7 kJ/mol.
C) ∆G’° is incalculably large and negative.
D) ∆G’° is incalculably large and positive.
E) ∆G’° is zero.

Answer 10

A) ∆G’° is +1.7 kJ/mol.

Question 11

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 freeenergy change (∆G) be negative, enabling the reaction to proceed to the right?

A) 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 ∆G’° is
positive.
C) Under standard conditions, enough energy is released to drive the reaction to the right.
D) When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of
products.
E) When there is a high concentration of products relative to the concentration of fructose 1,6-
bisphosphate.

Answer 11

D) When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of
products.

Question 12

Glucose labeled with 14C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:

A) C and D.
B) all three carbons.
C) its carbonyl carbon.
D) its carboxyl carbon.
E) its methyl carbon.

Answer 12

E) its methyl carbon.

Question 13

If glucose labeled with 14C at C-1 (the aldehyde carbon) were metabolized in the liver, the first
radioactive pyruvate formed would be labeled in:

A) all three carbons.
B) both A and C.
C) its carbonyl carbon.
D) its carboxyl carbon.
E) its methyl carbon.

Answer 13

E) its methyl carbon.

Question 14

In an anaerobic muscle preparation, lactate formed from glucose labeled in C-2 would be labeled in:

A) all three carbon atoms.
B) only the carbon atom carrying the OH.
C) only the carboxyl carbon atom.
D) only the methyl carbon atom.
E) the methyl and carboxyl carbon atoms.

Answer 14

B) only the carbon atom carrying the OH.

Question 15

If glucose labeled with 14C in C-3 is metabolized to lactate via fermentation, the lactate will contain
14C in:

A) all three carbon atoms.
B) only the carbon atom carrying the OH.
C) only the carboxyl carbon atom.
D) only the methyl carbon atom.
E) the methyl and carboxyl carbon atoms

Answer 15

C) only the carboxyl carbon atom.

Question 16

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) Glyceraldehyde 3-phosphate
E) NAD+/NADH

Answer 16

E) NAD+/NADH

Question 17

In comparison with the resting state, actively contracting human muscle tissue has a:

A) higher concentration of ATP.
B) higher rate of lactate formation.
C) lower consumption of glucose.
D) lower rate of consumption of oxygen
E) lower ratio of NADH to NAD+
.

Answer 17

B) higher rate of lactate formation.

Question 18

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) the formation of 1,3-bisphosphoglycerate.
E) utilization of Pi.

Answer 18

C) oxidation of NADH to NAD+

Question 19

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) glyceraldehyde 3-phosphate dehydrogenase.
B) hexokinase.
C) phosphofructokinase-1.
D) phosphoglycerate kinase.
E) triose phosphate isomerase.

Answer 19

A) glyceraldehyde 3-phosphate dehydrogenase.

Question 20

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 20

D) NAD+

Question 21

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 21

A) 2-phosphoglycerate

Question 22

Glycogen is converted to monosaccharide units by:

A) glucokinase.
B) glucose-6-phosphatase
C) glycogen phosphorylase.
D) glycogen synthase.
E) glycogenase.

Answer 22

C) glycogen phosphorylase.

Question 23

Galactosemia is a genetic error of metabolism associated with:

A) deficiency of galactokinase.
B) deficiency of UDP-glucose.
C) deficiency of UDP-glucose: galactose 1-phosphate uridylyltransferase.
D) excessive ingestion of galactose.
E) inability to digest lactose.

Answer 23

C) deficiency of UDP-glucose: galactose 1-phosphate uridylyltransferase.

Question 24

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 24

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

Question 25

The ultimate electron acceptor in the fermentation of glucose to ethanol is:

A) acetaldehyde.
B) acetate.
C) ethanol.
D) NAD+
E) pyruvate.

Answer 25

A) acetaldehyde.

Question 26

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 26

D) pyruvate decarboxylase.

Question 27

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 27

A) acetate

Question 28

An enzyme used in both glycolysis and gluconeogenesis is:

A) 3-phosphoglycerate kinase.
B) glucose 6-phosphatase.
C) hexokinase.
D) phosphofructokinase-1.
E) pyruvate kinase.

Answer 28

A) 3-phosphoglycerate kinase.

Question 29

Which one of the following statements about gluconeogenesis is false?

A) For starting materials, it can use carbon skeletons derived from certain amino acids.
B) It consists entirely of the reactions of glycolysis, operating in the reverse direction.
C) It employs the enzyme glucose 6-phosphatase.
D) It is one of the ways that mammals maintain normal blood glucose levels between meals.
E) It requires metabolic energy (ATP or GTP).

Answer 29

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

Question 30

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-phosphoglycerate kinase.
B) aldolase.
C) enolase.
D) phosphofructokinase-1.
E) phosphoglucoisomerase.

Answer 30

D) phosphofructokinase-1.

Question 31

In humans, gluconeogenesis:

A) can result in the conversion of protein into blood glucose.
B) helps to reduce blood glucose after a carbohydrate-rich meal.
C) is activated by the hormone insulin
D) is essential in the conversion of fatty acids to glucose.
E) requires the enzyme hexokinase.

Answer 31

A) can result in the conversion of protein into blood glucose.

Question 32

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 32

C) palmitate

Question 33

Which of the following statements about the pentose phosphate pathway is correct?

A) It generates 36 mol of ATP per mole of glucose consumed.
B) It generates 6 moles of CO2 for each mole of glucose consumed
C) It is a reductive pathway; it consumes NADH.
D) It is present in plants, but not in animals.
E) It provides precursors for the synthesis of nucleotides.

Answer 33

E) It provides precursors for the synthesis of nucleotides.

Question 34

The main function of the pentose phosphate pathway is to:

A) give the cell an alternative pathway should glycolysis fail.
B) provide a mechanism for the utilization of the carbon skeletons of excess amino acids.
C) supply energy.
D) supply NADH.
E) supply pentoses and NADPH.

Answer 34

E) supply pentoses and NADPH.

Question 35

The metabolic function of the pentose phosphate pathway is:

A) act as a source of ADP biosynthesis.
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) provide intermediates for the citric acid cycle.
E) synthesize phosphorus pentoxide

Answer 35

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

Question 36

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) It is principally directed toward the generation of NADPH.
E) It requires the participation of molecular oxygen.

Answer 36

E) It requires the participation of molecular oxygen.

Question 37

Glucose breakdown in certain mammalian and bacterial cells can occur by mechanisms other than
classic glycolysis. In most of these, glucose 6-phosphate is oxidized to 6-phosphogluconate, which is
then further metabolized by:

A) an aldolase-type split to form glyceric acid and glyceraldehyde 3-phosphate.
B) an aldolase-type split to form glycolic acid and erythrose 4-phosphate.
C) conversion to 1,6-bisphosphogluconate.
D) decarboxylation to produce keto- and aldopentoses
E) oxidation to a six-carbon dicarboxylic acid.

Answer 37

D) decarboxylation to produce keto- and aldopentoses

Question 38

Which of the following enzymes acts in the pentose phosphate pathway?

A) 6-phosphogluconate dehydrogenase
B) Aldolase
C) Glycogen phosphorylase
D) Phosphofructokinase-1
E) Pyruvate kinase

Answer 38

A) 6-phosphogluconate dehydrogenase

Question 39

The oxidation of 3 mol of glucose by the pentose phosphate pathway may result in the production of:

A) 2 mol of pentose, 4 mol of NADPH, and 8 mol of CO2.
B) 3 mol of pentose, 4 mol of NADPH, and 3 mol of CO2.
C) 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2.
D) 4 mol of pentose, 3 mol of NADPH, and 3 mol of CO2.
E) 4 mol of pentose, 6 mol of NADPH, and 6 mol of CO2.

Answer 39

C) 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2.

Question 40

Glucose, labeled with 14C in different carbon atoms, is added to a crude extract of a tissue rich in the
enzymes of the pentose phosphate pathway. The most rapid production of 14CO2 will occur when the
glucose is labeled in:

A) C-1.
B) C-3.
C) C-4.
D) C-5.
E) C-6.

Answer 40

A) C-1.

Question 41

In a tissue that metabolizes glucose via the pentose phosphate pathway, C-1 of glucose would be
expected to end up principally in:

A) carbon dioxide.
B) glycogen.
C) phosphoglycerate.
D) pyruvate.
E) ribulose 5-phosphate.

Answer 41

A) carbon dioxide.