Deck 13: Glucose Metabolism

Question 1

In eukaryotes, glycolysis typically occurs in the _____, gluconeogenesis typically occurs in the _____.

A) mitochondria; cytosol
B) Golgi apparatus; mitochondria
C) endoplasmic reticulum; mitochondria
D) cytosol; cytosol
E) lysosome; cytosol

Answer 1

cytosol; cytosol

Question 2

The coenzyme _____ is the oxidizing agent in glycolysis.

A) ADP
B) thiamine pyrophosphate
C) NAD⁺
D) FAD
E) biotin

Answer 2

NAD⁺

Question 3

Which of the following represents the net products of glycolysis from one molecule of glucose?

A) 2 pyruvate, 2 NADH, 2 ATP
B) 2 pyruvate, 2 NADH, 4 ATP
C) 3 pyruvate, 2 NADH, 4 ATP
D) 6 CO₂, 30 ATP
E) 6 CO₂, 32 ATP

Answer 3

2 pyruvate, 2 NADH, 2 ATP

Question 4

In glycolysis, the net gain of ATP during the energy investment phase is _____ while the net gain of ATP during the energy payoff phase is _____.

A) -4; 6
B) -2; 4
C) -2; 2
D) -1; 3
E) 0; 2

Question 5

With a $\Delta$ G of -16.7 kJ/mol, the reaction catalyzed by hexokinase is considered to be _____.

A) at equilibrium
B) substrate and product concentration dependent
C) freely reversible
D) metabolically irreversible
E) none of the above

Question 6

Phosphoglucose isomerase has a $\Delta$ G of 2.2 kJ/mol but a $\Delta$ G of -1.4 kJ/mol. Based upon this difference, which of the following is true?

A) within a cell, concentrations are non-standard
B) within a cell, the concentration of glucose-6-phosphate is higher than fructose-6-phosphate
C) within a cell, concentrations of products are often lowered by their rapid use in other reactions
D) within a cell, the reaction catalyzed by phosphoglucose isomerase would be considered freely reversible
E) all of the above

Question 7

In bacterial cells, _____ is an activator of phosphofructokinase while _____ is an inhibitor.

A) glucose-6-phosphate; ATP
B) ADP; phosphoenolpyruvate
C) fructose-2,6-bisphosphate; fructose-6-phosphate
D) AMP; glyceraldehyde-3-phosphate
E) citrate; ADP

Question 8

The enzyme responsible for the synthesis of fructose-2,6-bisphosphate is _____.

A) phosphofructokinase-2
B) hexosephosphatekinase-2
C) aldolase-2
D) phosphofructose isomerase-2
E) none of the above

Question 9

Glyceraldehyde-3-phosphate dehydrogenase oxidizes _____.

A) an alcohol to a ketone
B) a carboxylic acid to CO₂
C) an alcohol to an aldehyde
D) an aldehyde to a carboxylic acid
E) an aldehyde to an alcohol

Question 10

What residue of phosphoglycerate mutase undergoes covalent catalysis during the reaction?

A) Asp
B) His
C) Ser
D) Tyr
E) Cys

Question 11

What is the greatest driving force for the reaction catalyzed by pyruvate kinase?

A) hydrolysis of phosphate from phosphoenolpyruvate
B) transfer of phosphate from phosphoenolpyruvate to ADP
C) release of ATP from active site
D) tautomerization of enolpyruvate to pyruvate
E) release of pyruvate from the active site

Question 12

Fill in the missing reagents in the following reaction.

A) reactant: NAD⁺ + H⁺; product: NADH
B) reactant: NADH + H⁺; product: NAD⁺
C) reactant: ATP; product: ADP + P_i
D) reactant: NADH + H⁺; product: CO₂
E) none of the above

Question 13

What coenzyme is required for the conversion of pyruvate to oxaloacetate?

A) NADH
B) pyridoxal phosphate
C) biotin
D) thiamine
E) FADH₂

Question 14

Which of the following correctly describes the mechanism of pyruvate carboxylase?

A) ATP and bicarbonate react, carboxyphosphate formed, carboxyl group transferred to biotin, deprotonated pyruvate attacks carboxyl group
B) ATP and bicarbonate react, carboxyl group transferred to biotin carboxyphosphate formed, deprotonated pyruvate attacks carboxyl group
C) ATP and bicarbonate react, carboxyphosphate formed, deprotonated pyruvate attacks carboxyl group, carboxyl group transferred to biotin
D) carboxyphosphate formed, ATP and bicarbonate react, carboxyl group transferred to biotin, deprotonated pyruvate attacks carboxyl group
E) carboxyphosphate formed, deprotonated pyruvate attacks carboxyl group, ATP and bicarbonate react, carboxyl group transferred to biotin

Question 15

Which of the following forms a substrate cycle with hexokinase?

A) phosphoglucose isomerase
B) glucose-6-phosphatase
C) phosphofructokinase
D) phosphoglycerate kinase
E) fructose bisphosphatase

Question 16

What would occur if both phosphofructokinase and fructose bisphosphatase were active simultaneously?

A) a futile cycle
B) a substrate cycle
C) an inhibitor cycle
D) the alanine cycle
E) the Cori cycle

Question 17

Fructose-2,6-bisphosphate is an activator of _____ and an inhibitor of _____.

A) phosphofructokinase; hexokinase
B) fructose bisphosphatase; phosphofructokinase
C) phosphofructokinase; fructose bisphosphatase
D) glucose-6-phosphatase; pyruvate kinase
E) pyruvate kinase; phosphoenolpyruvate carboxykinase

Question 18

Muscle cells are not able to supply glucose for other tissues because they do not contain which of the following enzymes?

A) debranching enzyme
B) pyruvate carboxylase
C) glycogen phosphorylase
D) fructose bisphosphatase
E) glucose-6-phosphatase

Question 19

Which of the following correctly relates the order of intermediates during the synthesis of glycogen?

A) glucose $\rarr$ glucose-1-phosphate $\rarr$ glucose-6-phosphate $\rarr$ UDP-glucose $\rarr$ glycogen
B) glucose $\rarr$ glucose-6-phosphate $\rarr$ glucose-1-phosphate $\rarr$ UDP-glucose $\rarr$ glycogen
C) glucose $\rarr$ glucose-6-phosphate $\rarr$ UDP-glucose $\rarr$ glucose-1-phosphate $\rarr$ glycogen
D) glucose $\rarr$ UDP-glucose $\rarr$ glucose-1-phosphate $\rarr$ glucose-6-phosphate $\rarr$ glycogen
E) glucose $\rarr$ UDP-glucose $\rarr$ glucose-6-phosphate $\rarr$ glucose-1-phosphate $\rarr$ glycogen

Question 20

In the muscle, when a residue of glucose is cleaved from glycogen and converted to pyruvate via glycolysis, what is the net ATP production?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 21

In the event that NADPH is needed but ribose is not, which of the following is an end product of the pentose phosphate pathway?

A) ribulose-5-phosphate
B) dihydroxyacetone phosphate
C) fructose-1,6-bisphosphate
D) 1,3-bisphosphoglycerate
E) glyceraldehyde-3-phosphate

Question 22

A deficiency of pyruvate kinase in red blood cells increases the production of 2,3-bisphosphoglycerate, further reducing the delivery of oxygen by red blood cells.

Question 23

Fructose intolerance results from a deficiency of fructose-1-phosphate aldolase, resulting in cell death of liver tissue.

Question 24

During infancy, an inability to convert ___ into glucose can be deadly since ___ is the major carbohydrate source.

Question 25

A deficiency of glucose-6-phosphate dehydrogenase decreases the production of ___ in red blood cells thus resulting in ___ of oxidative damage

Question 26

The most common type of glycogen storage disease is ___ which is caused by a defect in ___.

Question 27

Which of the following best explains the energetically favorable formation of UDP-glucose in the liver and muscle?

A) $\Delta$ G°' for the reaction glucose-1-phosphate + UTP $\rarr$ UDP-glucose + PP_i is very negative.
B) $\Delta$ G°' for the reaction glucose-1-phosphate + UTP $\rarr$ UDP-glucose + PP_i is very positive.
C) $\Delta$ phosphoglucoisomerase°' for the reaction PP_i $\rarr$ 2P_i is very negative.
D) $\Delta$ G°' for the reaction PP_i $\rarr$ 2P_i is very positive.
E) $\Delta$ G°' for the overall reaction is very positive.

Question 28

Which of the following best describes the function of the glycogen debranching enzyme in glycogenolysis?

A) It cleaves $\alpha$ (1 $\rarr$ 6) branch points releasing glucose-6-phosphate.
B) It cleaves $\alpha$ (1 $\rarr$ 6) branch points releasing glucose-1-phosphate.
C) It cleaves $\alpha$ (1 $\rarr$ 6) branch points releasing glucose.
D) It transfers an $\alpha$ (1 $\rarr$ 4) linked trisaccharide unit to the nonreducing end of an alternate branch, then cleaves the $\alpha$ (1 $\rarr$ 6) branch point, releasing glucose-1-phosphate.
E) It transfers an $\alpha$ (1 $\rarr$ 4) linked trisaccharide to the nonreducing end of an alternate branch, then cleaves the $\alpha$ (1 $\rarr$ 6) branch point, releasing glucose.

Question 29

Which is the net equation for aerobic glycolysis?

A) Glucose + 2 ATP $\rarr$ 2 lactate + 2 ADP + 2 P_i
B) Glucose + 2 ADP + 2 P_i + 2 NAD⁺ $\rarr$ 2 pyruvate + 2 ATP + 2 NADH + + 2 H₂O 4 H⁺
C) Glucose + 2 ADP + 2 P_i $\rarr$ 2 lactate + 4 ATP + 4 H⁺
D) Glucose + 2 ATP + 2 NAD⁺ $\rarr$ 2 pyruvate + 4 ATP + 4 NADH + 4 H⁺
E) Glucose + 2 ADP + 2 P_i + 2 NAD⁺ $\rarr$ 2 lactate + 4 ATP + 2 NADH + 4 H⁺

Question 30

Which of the following statements about glycogen is true?
I. Glycogen is a polymer of glucose in $\alpha$ (1 $\rarr$ 6) linkages with $\alpha$ (1 $\rarr$ 4) linked branches every 8-14 residues.
II. UDP-glucose is produced from glycogen by the action of the enzyme phosphorylase.
III. In glycogen breakdown, glucose residues are sequentially removed from the nonreducing ends.
IV. The breakdown of glycogen in skeletal muscle ultimately supplies glucose-6-phosphate, which can enter glycolysis to generate ATP.

A) I, II, III, IV
B) I, II
C) II, III, IV
D) III, IV
E) III only

Question 31

Which of the following compounds is used to produce ATP by substrate-level phosphorylation in glycolysis?

A)

B)

C)

D)

E)