Deck 14: Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Question 1

Which item is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

A) ATP
B) Cu²⁺
C) heme
D) NAD⁺
E) NADP⁺

Answer 1

D

Question 2

Which reaction in glycolysis utilizes a covalent enzyme intermediate?

A) phosphofructokinase-1
B) hexokinase
C) phosphohexose isomerase
D) aldolase
E) triose phosphate isomerase

Answer 2

D

Question 3

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

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

Answer 3

E

Question 4

If glucose labeled with ¹⁴C at C-2 were metabolized in the liver, the first radioactive pyruvate formed would be labeled in:

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

Question 5

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 statement is MOST nearly correct, when applied to the reaction below (R = 8.315 J/mol · K and T = 298 K)? glucose 6-phosphate $\leftrightarrow$ fructose 6-phosphate

A) $\Delta$ G'° is +1.7 kJ/mol.
B) $\Delta$ G'° is -1.7 kJ/mol.
C) $\Delta$ G'° is incalculably large and negative.
D) $\Delta$ G'° is incalculably large and positive.
E) $\Delta$ G'° is zero.

Question 6

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change ( $\Delta$ G'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change ( $\Delta$ 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 $\Delta$ 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.

Question 7

Which reaction in glycolysis requires ATP as a substrate?

A) hexokinase
B) glyceraldehyde-3-phosphate dehydrogenase
C) pyruvate kinase
D) aldolase
E) phosphoglycerate kinase

Question 8

The compound [¹⁸F]2-fluoro-2-deoxyglucose is a(n):

A) intermediate in glycolysis
B) positive regulator of glycolysis
C) potent anti-cancer agent
D) antibiotic
E) imaging agent used to detect tumors

Question 9

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.

Question 10

Which reaction in glycolysis utilizes a covalent enzyme intermediate?

A) phosphofructokinase-1
B) glyceraldehyde-3-phosphate dehydrogenase
C) phosphohexose isomerase
D) enolase
E) triose phosphate isomerase

Question 11

The first reaction in glycolysis that results in the formation of an energy-rich compound is catalyzed by:

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

Question 12

Glycogen is converted to monosaccharide units by:

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

Question 13

Which reaction in glycolysis is a ketose to aldose isomerization?

A) hexokinase
B) phosphoglycerate mutase
C) enolase
D) aldolase
E) triose phosphate isomerase

Question 14

Which reaction in glycolysis produces ATP as a product?

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

Question 15

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate do NOT involve:

A) ATP synthesis.
B) catalysis by phosphoglycerate kinase.
C) oxidation of NADH to NAD⁺.
D) the formation of 1,3-bisphosphoglycerate.
E) utilization of P_i.

Question 16

In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?

A) serine
B) threonine
C) tyrosine
D) histidine
E) arginine

Question 17

Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which compound would you expect to increase in concentration following the addition of fluoride?

A) 2-phosphoglycerate
B) glucose
C) glyoxylate
D) phosphoenolpyruvate
E) pyruvate

Question 18

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.

Question 19

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.

Question 20

Which reaction in glycolysis is an aldose to ketose isomerization?

A) enolase
B) phosphoglycerate mutase
C) phosphohexose isomerase
D) aldolase
E) glyceraldehyde-3-phosphate dehydrogenase

Question 21

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⁺.

Question 22

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

Question 23

Which cofactor 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

Question 24

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

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

Question 25

Which compound CANNOT serve as the starting material for the synthesis of glucose via gluconeogenesis?

A) acetate
B) glycerol
C) lactate
D) oxaloacetate
E) $\alpha$ -ketoglutarate

Question 26

Which substrate CANNOT contribute to net gluconeogenesis in mammalian liver?

A) alanine
B) glutamate
C) palmitate
D) pyruvate
E) $\alpha$ -ketoglutarate

Question 27

Which statement 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).

Question 28

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 answers is correct.

Question 29

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.

Question 30

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.

Question 31

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.

Question 32

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 $\rightarrow$ glycerol 3-phosphate.
B) glucose 6-phosphate $\rightarrow$ fructose 6-phosphate.
C) isocitrate $\rightarrow$ $\alpha$ -ketoglutarate.
D) oxaloacetate $\rightarrow$ malate.
E) pyruvate $\rightarrow$ lactate.

Question 33

Which statement 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.

Question 34

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.

Question 35

Which statement 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.

Question 36

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.

Question 37

Which enzyme that is involved in the flow of carbon from glucose to lactate (glycolysis) is NOT also involved in the reversal of this flow (gluconeogenesis)?

A) 3-phosphoglycerate kinase
B) aldolase
C) enolase
D) phosphofructokinase-1
E) phosphoglucoisomerase

Question 38

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.

Question 39

The metabolic function of the pentose phosphate pathway is to:

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.

Question 40

Which statement 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.

Question 41

What is the general name for an enzyme that catalyzes an intramolecular phosphoryl shift?

A) phosphatase
B) mutase
C) kinase
D) phosphoylase
E) phosphate translocase

Question 42

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.

Question 43

Which statement regarding glycolysis is TRUE?

A) Both substrate-level phosphorylation reactions in glycolysis are irreversible.
B) The oxidation reaction in glycolysis produces two high-energy molecules.
C) There are four isomerization reactions in glycolysis.
D) One inorganic phosphate is consumed as a substrate for each glucose molecule metabolized via glycolysis.
E) All of the statements are true.

Question 44

Which process does NOT occur in the steps of glycolysis between glyceraldehyde-3-phosphate and phosphoenolpyruvate?

A) ATP synthesis.
B) an isomerization.
C) a hydration reaction.
D) phosphoryl transfer.
E) oxidation.

Question 45

Which enzyme acts in the pentose phosphate pathway?

A) 6-phosphogluconate dehydrogenase
B) aldolase
C) glycogen phosphorylase
D) phosphofructokinase-1
E) pyruvate kinase

Question 46

Which enzyme catalyzes an energy-capture reaction in glycolysis?

A) hexokinase.
B) pyruvate kinase
C) glyceraldehyde-3-phosphate dehydrogenase
D) pyruvate kinase and glyceraldehyde-3-phosphate dehydrogenase
E) hexokinase, pyruvate kinase, and glyceraldehyde-3-phosphapate dehydrogenase

Question 47

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.

Question 48

Which reaction does NOT convert gluconeogenic precursors to the next step in gluconeogenesis?

A) Glycerol is converted to dihydroxyacetone phosphate using the enzymes glycerol kinase and glycerol-3-phosphate dehydrogenase.
B) Lactate is converted to alanine using lactate dehydrogenase.
C) Alanine is converted to pyruvate using alanine aminotransferase.
D) Glutamate is converted to $\alpha$ -ketoglutarate using either glutamate dehydrogenase or an aminotransferase.
E) Pyruvate is carboxylated using bicarbonate and pyruvate carboxylase.

Question 49

Which statement 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.

Question 50

Which statement is TRUE for glycolysis?

A) Pyruvate kinase phosphorylates pyruvate during glycolysis.
B) Hexokinase catalyzes an unregulated step in glycolysis.
C) A dehydration reaction generates a high-energy molecule.
D) Hexokinase catalyzes an unregulated step in glycolysis, and a dehydration reaction generates a high-energy molecule .
E) None of the statements is true.

Question 51

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.

Question 52

Which compound(s) is/are a high-energy intermediate(s) in glycolysis?

A) fructose 1,6-bisphosphate
B) NADH
C) 1,3-bisphosphoglycerate and phosphoenol pyruvate
D) fructose 1,6-bisphosphate, 1,3-bisphosphoglycerate, and phosphoenol pyruvate
E) NADH, 1,3-bisphosphoglycerate, and phosphoenol pyruvate

Question 53

Which compound(s) is/are a high-energy product(s) of glycolysis?

A) fructose 1,6-bisphosphate
B) ATP and NADH
C) 1,3-bisphosphoglycerate and phosphoenol pyruvate
D) fructose 1,6-bisphosphate, 1,3-bisphosphoglycerate, and phosphoenol pyruvate
E) ATP, NADH, 1,3-bisphosphoglycerate, and phosphoenol pyruvate

Question 54

In some tissues, an increase in insulin will substantially increase the glucose transporters in the cell membrane and the transport of glucose into cells. Which tissues react in this manner?

A) red blood cells and the brain
B) the brain and the liver
C) the liver and muscle
D) muscle and adipose tissue
E) adipose tissue and red blood cells

Question 55

Which statement is FALSE concerning glycolysis?

A) It is activated by high [AMP].
B) It results in a net synthesis of ATP.
C) It results in the synthesis of NAD⁺.
D) Its rate is slowed by a high [NADH]/ [NAD⁺] ratio.
E) None of the 11 intermediates in the glycolytic pathway are phosphorylated.

Question 56

Which amount of ATP and NADH identifies net production when 1 mol of DHAP is converted to 1 mol of pyruvate?

A) 2 mol of ATP and 2 mol of NADH
B) 2 mol of ATP and 1 mol of NADH
C) 2 mol ATP and 0 mol of NADH
D) 1 mol ATP and 2 mol of NADH
E) 1 mol ATP and 0 mol of NADH

Question 57

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.

Question 58

The enzyme 2,3-BPG mutase produces 1,3-BPG in red blood cells through an isomerization (rearrangement) reaction. What amino acid(s) would you predict to be important in substrate binding?

A) Asp
B) Glu
C) Lys
D) Leu
E) both Asp and Glu

Question 59

Which statement is TRUE regarding the glycolytic pathway?

A) It includes reactions catalyzed by three isomerase enzymes.
B) It includes five phosphate transfer reactions.
C) It includes three enzymes that are regulated by product inhibition.
D) All of the statements are true.
E) None of the statements is true.

Question 60

Why is an anaerobic fate of pyruvate necessary in skeletal muscle?

A) It is required to maintain the reducing environment of the cytosol.
B) It allows for the re-oxidation of NADH to NAD⁺, as NAD⁺ is in limited supply during anaerobic conditions.
C) It decreases the pH of the skeletal muscle cell, thereby increasing release of oxygen from myoglobin.
D) All of the answers are correct.
E) None of the answers is correct.

Question 61

What is the net yield of ATP produced by the anaerobic fermentation of one molecule of galactose to two molecules of lactate in myocytes

A) 2
B) 3
C) 4
D) 6
E) None of the answers is correct.

Question 62

In glycolysis there are two reactions that require one ATP each and two reactions that produce one ATP each. This being the case, how can fermentation of glucose to lactate lead to the net production of two ATP molecules per glucose?

Question 63

There are a variety of fairly common human genetic diseases in which enzymes required for the breakdown of fructose, lactose, or sucrose are defective. However, there are very few cases of people having a genetic disease in which one of the enzymes of glycolysis is severely affected. Why do you suppose such mutations are seen so rarely?

Question 64

In humans, the Cori cycle shifts part of the metabolic burden of active muscle to the liver. Which two metabolic pathways are involved in this cycle?

A) glycolysis and gluconeogenesis
B) pentose phosphate pathway and gluconeogenesis
C) glycolysis and the pentose phosphate pathway
D) gluconeogenesis and the Calvin cycle
E) None of the answers is correct.

Question 65

Briefly describe the possible metabolic fates of pyruvate produced by glycolysis in humans, and explain the circumstances that favor each.

Question 66

Show how NADH is recycled to NAD⁺ under aerobic conditions and under anaerobic conditions. Why is it important to recycle NADH produced during glycolysis to NAD⁺?

Question 67

Which process is NOT involved in the steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate?

A) a substrate-level phosphorylation reaction
B) catalysis by an isomerase enzyme
C) reduction of NAD⁺ to NADH
D) the formation of a mixed anhydride intermediate.
E) the indirect coupling of reactions catalyzed by a kinase and a dehydrogenase enzyme

Question 68

Which process is NOT considered a general function of the pentose phosphate pathway?

A) the production of NADPH for reductive biosynthesis in adipose cells
B) the production of NADPH to help prevent oxidative stress in erythrocytes
C) the production of pentoses necessary for nucleotide synthesis
D) the production of erythrose 4-phosphate for synthesis of aromatic amino acids
E) the transfer of electrons to NADP⁺ for eventual entry into the electron transport chain

Question 69

Which amount of ATP and NADH identifies net production when 3 mol of ribulose 5-phosphate are converted to pyruvate?

A) 4 mol of ATP and 2 mol of NADH
B) 5 mol of ATP and 3 mol of NADH
C) 8 mol of ATP and 5 mol of NADH
D) 10 mol of ATP and 5 mol of NADH
E) 10 mol of ATP and 6 mol of NADH

Question 70

Which compound links glycolysis and nucleotide synthesis?

A) acetyl-CoA
B) oxaloacetate
C) citrate
D) glucose 6-phosphate
E) glucose 3-phosphate

Question 71

Define "fermentation" and explain, by describing relevant reactions, how it differs from glycolysis. Your explanation should include a discussion of the role of NADH in the reaction(s).

Question 72

Which carbon atom in one of the glycolytic intermediates shown below would have to be radiolabeled with ¹⁴C in order to ensure all the radioactivity would be release as ¹⁴CO₂ during alcoholic fermentation?

A) C6 of glucose 6-phosphate.
B) C3 of fructose 1,6-bisphosphate.
C) C1 of pyruvate.
D) C2 of glyceraldehyde 3-phosphate.
E) C5 of fructose 6-phosphate.

Question 73

The pentose phosphate pathway is multifunctional with metabolic flexibility. Which statement is FALSE with respect to this pathway?

A) All the enzymes in this pathway are located in the cytosol.
B) All intermediates in this pathway are phosphorylated.
C) The activities of transaldolases and transketolases link this pathway to gluconeogenesis.
D) It generates NADH for reductive biosynthesis.
E) In erythrocytes, this pathway is required to maintain glutathione in a reduced state.

Question 74

Two reactions, extra to the ten reactions of glycolysis, are involved in ethanol fermentation by yeast under anaerobic conditions. What is the purpose served by these two reactions in the metabolism of yeast cells?

A) They are required to re-oxidize limited amounts of NADH.
B) They are required to ensure a net oxidation of glucose.
C) They are required to sustain glycolysis, ensuring ATP production.
D) They are required to both ensure a net oxidation of glucose and sustain glycolysis, ensuring ATP production
E) They are required to both re-oxidize limited amounts of NADH and sustain glycolysis, ensuring ATP production

Question 75

What is the energetic cost of running the Cori cycle per glucose molecule?

A) 2 NTP
B) 3 NTP
C) 4 NTP
D) 5 NTP
E) 6 NTP

Question 76

If glucose, radioactively labeled in the C-2 position with ¹⁴C, is used as a substrate in a yeast extract maintained under strictly anaerobic conditions, what is the location of ¹⁴C in the product ethanol?

A) ¹⁴CH₃-CH₂-OH
B) CH₃-¹⁴CH₂-OH
C) CH₃-CHOH-¹⁴COO^-
D) It is released as ¹⁴CO₂ by pyruvate decarboxylase and never becomes part of ethanol.
E) It is released as ¹⁴CO₂ by alcohol dehydrogenase and never becomes part of ethanol.

Question 77

Which statement describes the activity of hexokinase I CORRECTLY?

A) It catalyzes the conversion of glucose-6-phosphate into fructose 1,6-bisphosphate.
B) It requires Mn²⁺ for maximal activity.
C) It uses inorganic phosphate to form glucose-6-phosphate.
D) It is relatively nonspecific in its choice of monosaccharides.
E) This enzyme is classified as a ligase enzyme, as it couples the phosphorylation of glucose to the cleavage of ATP.

Question 78

Which statement does NOT describe a general function of the pentose phosphate pathway?

A) The pentose phosphate pathway is used to produce NADPH for reductive biosynthesis in adipocytes.
B) The pentose phosphate pathway is used to facilitate the elimination of dangerous peroxides in erythrocytes.
C) The pentose phosphate pathway allows for the entry of dietary pentose intermediates into the glycolytic pathway.
D) The pentose phosphate pathway allows for the conversion of hexoses into pentoses that may be used as precursors in the synthesis of nucleosides.
E) The pentose phosphate pathway produces reduced molecules whose electrons may be shuttled to the mitochondria for oxidative phosphorylation.

Question 79

_____ is a product of pyruvate in erythrocytes.

A) CO₂ + H₂O
B) Ethanol + CO₂
C) Glucose
D) Erythrose-4-phosphate
E) Lactate

Question 80

What is the net yield of ATP produced by the anaerobic fermentation of one molecule of sucrose in myocytes?

A) 2
B) 3
C) 4
D) 6
E) 8