Deck 15: Glycogen Metabolism and Gluconeogenesis

Question 1

Matching
Choose the correct answer from the list. Not all the answers will be used.
Carboxylation of pyruvate in humans requires ______ as an essential dietary nutrient.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Answer 1

biotin

Question 2

Which of the following serves as the free energy source for the metabolic conversion of oxaloacetate to phosphoenolpyruvate, which is catalyzed by PEP carboxykinase?

A)hydrolysis of PP_i
B)hydrolysis of ATP
C)hydrolysis of GTP
D)hydrolysis of an internal phosphoanhydride bond
E)hydrolysis of a thioester intermediate

Answer 2

hydrolysis of GTP

Question 3

Matching
Choose the correct answer from the list. Not all the answers will be used.
Glucose can be synthesized from noncarbohydrate precursors by______.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Answer 3

gluconeogenesis

Question 4

What is the net energetic cost of converting two pyruvate to one glucose by gluconeogenesis in ATP equivalents?

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

Question 5

Matching
Choose the correct answer from the list. Not all the answers will be used.
Both glycogen synthesis and glycogen breakdown share the metabolite ______.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Question 6

Matching
Choose the correct answer from the list. Not all the answers will be used.
Low blood glucose (< 5mM)levels result in the release of ______.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Question 7

Matching
Choose the correct answer from the list. Not all the answers will be used.
An enzyme present in the endoplasmic reticulum of liver cells is ______.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Question 8

The biotin prosthetic group of pyruvate carboxylase is covalently attached to a ______ residue of the enzyme?

A)valine
B)serine
C)lysine
D)arginine
E)the biotin is attached non-covalently

Question 9

Matching
Choose the correct answer from the list. Not all the answers will be used.
The first step in the breakdown of glycogen is catalyzed by ______.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Question 10

Matching
Choose the correct answer from the list. Not all the answers will be used.
The breakdown of glycogen is referred to as ______.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Question 11

Matching
Choose the correct answer from the list. Not all the answers will be used.
______ activates glycogen breakdown.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Question 12

Which of the following enzymes catalyzes the conversion of glucose-1-phosphate to glucose-6-phosphate?

A)glucose-1-isomerase
B)glucokinase
C)glucose-1-phosphatase
D)phosphoglucomutase
E)glycogen phosphorylase

Question 13

In glycogen synthesis, the intermediate between glucose-1-phosphate and glycogen is

A)UDP-glucose .
B)UDP-glycogen.
C)glucose-1,6-bisphosphate.
D)glucose-6-phosphate.
E)glucose.

Question 14

Which of the following enzymes directly converts phosphorylase b into the more active form, phosphorylase a?

A)cAMP-dependent protein kinase
B)phosphorylase kinase
C)protein kinase A
D)adenylate cyclase
E)phosphoprotein phosphatase-1

Question 15

Muscle cells are not able to supply glucose for other tissues because

A)they lack the GLUT2 transporter.
B)they lack pyruvate carboxylase.
C)they lack glucose-6-phosphatase.
D)they lack the malate-aspartate shuttle.
E)they lack glycogen phosphorylase.

Question 16

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 17

Individuals with McArdle's disease lack the ____ in the ____,

A)debranching enzyme; liver
B)phosphoglucomutase; liver
C)glycogen phosphorylase; muscle
D)phosphoglucomutase; muscle
E)glycogen phosphorylase; liver

Question 18

Which of the following aides in formation of a primer for glycogen synthesis ?

A)glycogen synthase
B)UDP-glucose pyrophosphatate
C)glycogenin
D)UDP-glycogen
E)amylo-(1,4 $\rarr$ 1,6)-transglycosylase

Question 19

Matching
Choose the correct answer from the list. Not all the answers will be used.
The membrane-bound polyisoprenol involved in the synthesis of N-linked glycoproteins is called ______.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Question 20

Matching
Choose the correct answer from the list. Not all the answers will be used.
______ cells lack receptors for the hormone glucagon.

A)phosphorylase α
B)gluconeogenesis
C)glucagon
D)glucose-6-phosphatase
E)cAMP
F)biotin
G)insulin
H)glycogenolysis
I)liver
J)glucose-1-phosphate
K)dolichol
L)muscle

Question 21

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 22

Which of the following is correct concerning the metabolic reaction shown below? Pyruvate + CO₂ + ATP SYMBOL 174 \f "Symbol" oxaloacetate + ADP + P_i
I.This metabolic reaction is catalyzed by pyruvate carboxykinase.
II.The enzyme that catalyzes this reaction is activated by high concentrations of acetyl-CoA .
III.The enzyme that catalyzes this reaction is covalently bonded to the coenzyme pyridoxal-5ꞌ-phosphate.
IV.The enzyme that catalyzes this reaction is located in the endoplasmic reticulum of the cell .

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

Question 23

The synthesis of N-linked oligosaccharides occur in the _____ while O-linked oligosaccharides are synthesized in the ______.

A)Golgi apparatus; endoplasmic reticulum
B)cytosol; Golgi apparatus
C)mitochondrial matrix; endoplasmic reticulum
D)endoplasmic reticulum; Golgi apparatus
E)Golgi apparatus; mitochondrial matrix

Question 24

Which of the following best describes the role of fructose-2,6-bisphosphate (FBP)in liver cells?

A)It is an intermediate in glycolysis.
B)It is an intermediate in gluconeogenesis.
C)It is an intermediate in both glycolysis and gluconeogenesis.
D)FBP is a potent allosteric activator of phosphofructokinase and an inhibitor of fructose bisphosphatase.
E)FBP is a potent allosteric activator of fructose bisphosphatase and an inhibitor of phosphofructokinase.

Question 25

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)( $\Delta$ G°' 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 26

Increased levels of epinephrine in the blood will
I.activate adenylate cyclase in liver and muscle cells.
II.stimulate glycogen synthesis.
III.inhibit glycolysis in the muscle cell.
IV.stimulate gluconeogenesis in the muscle cell.

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

Question 27

What is the net ATP yield for a muscle cell that stores one dietary glucose molecule as glycogen and then releases it and sends it through glycolysis?

A)0
B)1
C)2
D)3
E)4

Question 28

If cAMP levels are high
I.Glycogenolysis will occur in muscle cells but not liver cells.
II.Glucose released from muscle glycogen will enter glycolysis.
III.Glucose released from liver glycogen will exit liver cells via the GLUT4 transporter.
IV.Glucose will enter liver cells resulting in glycogen synthesis.

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

Question 29

Hexokinase does not catalyze the final step in gluconeogenesis as written below because glucose-6-phosphate + ADP $\rarr$ glucose + ATP

A)the phosphate bond in glucose-6-phosphate does not have a high enough free energy to form ATP.
B)ATP inhibits hexokinase and blocks the reaction from occurring as written.
C)hexokinase is only reversible when high levels of ATP are present.
D)hexokinase does not bind glucose-6-phosphate.
E)none of the above

Question 30

Which statement is true regarding the activation of pyruvate carboxylase by acetyl-CoA?

A)Feedback activation enhances flux through glycolysis.
B)Feedforward activation enhances the entry of pyruvate through the TCA cycle as Acetyl-CoA.
C)Ensures that gluconeogenesis occurs rather than pyruvate conversion to acetyl-CoA.
D)Ensures that ATP is not wasted in the production of oxaloacetate.
E)Feedback inhibition ensures that excess glucose-6-phosphate is not produced.

Question 31

The diagram represents a "substrate cycle" in glucose metabolism.Which of the following statements about the cycle is true?

A)Reactions I & II are catalyzed by the same enzyme and help establish equilibrium between the two metabolites.
B)Reaction II produces ATP by substrate-level phosphorylation.
C)Reaction II is catalyzed by an allosteric enzyme that is inhibited by fructose-2-6-bisphosphate.
D)Reaction I is involved in the biosynthesis of glucose.
E)Reaction II occurs under low-energy conditions when the cell needs ATP.

Question 32

Levels of glucose-6-phosphate (G6P)are affected by which of the following?
I.glycogen breakdown
II.activity of the pentose phosphate pathway
III.galactose preparation for entry into glycolysis

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

Question 33

Which of the following metabolic conversions involved in glucose synthesis requires the direct expenditure of ATP?
I.3-Phosphoglycerate $\rarr$ 1,3-bisphosphoglycerate
II.Glyceraldehyde-3-phosphate + dihydroxyacetone phosphate $\rarr$ fructose-1,6-bisphosphate
III.Fructose-1,6-bisphosphate $\rarr$ fructose-6-phosphate
IV.1,3-Bisphosphoglycerate $\rarr$ glyceraldehyde-3-phosphate

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

Question 34

What molecules correspond to correspond to X and Y in the following gluconeogenic reaction? Fructose-1,6-bisphosphotase + X $\rarr$ Fructose-6-phosphate + Y

A)X = NADH + H⁺ , Y = NAD⁺
B)X = ATP ,Y = ADP + P_i
C)X = NAD⁺ , Y = NADH + H⁺
D)X = GTP ,Y = GTP + Pi
E)X = H₂O , Y = Pi

Question 35

The breakdown of glycogen produces G1P.Which of the following is FALSE regarding G1P?

A)It is involved in the utilization of fructose by glycolysis in the liver.
B)It is involved in the utilization of fructose by glycolysis in the muscle.
C)It is involved in utilization of galactose by glycolysis.
D)It is converted to G6P by phosphoglucoisomerase (PGI).
E)It is produced as an intermediate in the central glycolytic sequence.

Question 36

Avidin, a protein intact in raw egg whites, prevents the absorption of biotin in the intestine resulting in biotin deficiency.Which of the following is affected in individuals who consume large amounts of raw egg?

A)Oxaloacetate $\rarr$ phosphoenolpyruvate
B)1,3-Bisphosphoglycerate $\rarr$ glyceraldehyde-3-phosphate
C)Fructose-1,6-bisphosphate $\rarr$ fructose-6-phosphate
D)Pyruvate $\rarr$ oxaloacetate
E)Phosphoenolpyruvate $\rarr$ 2-phosphoglycerate

Question 37

Which of the following is true regarding the reaction shown below? pyruvate + HCO₃⁻ + ATP $\rarr$ oxaloacetate + ADP + P_i
I.It requires the direct transport of oxaloacetate across the membrane.
II.It utilizes the malate-aspartate shuttle in some species.
III.It is essential for gluconeogenesis.
IV.Its reactants require the function of enzymes which are only found in the cytosol.

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

Question 38

Which of the following metabolic conversions does not occur in gluconeogenesis?

A)oxaloacetate $\rarr$ phosphoenolpyruvate
B)fructose-1,6-bisphosphate $\rarr$ fructose-6-phosphate
C)GTP $\rarr$ CO₂ + GDP
D)NADH + H⁺ $\rarr$ NAD⁺
E)1,3-bisphosphoglycerate $\rarr$ 3-phosphoglycerate

Question 39

Which statement is TRUE concerning the metabolic reaction shown below?

A)The enzyme that catalyzes this reaction is called a mutase.
B)The enzyme that catalyzes this reaction is called a kinase.
C)This reaction requires the free energy of ATP hydrolysis.
D)This reaction requires multiple steps catalyzed by a phosphorylase and a mutase.
E)The oxidation level of glucose-1-phosphate is higher than that of glucose-6-phosphate.

Question 40

Which enzyme has an intermediate of the form presented below?

A)phosphofructokinase
B)glycogen phosphorylase
C)phosphohexose isomerase
D)phosphoglucomutase
E)none of the above

Question 41

Which of the following describes a sequence which will ultimately activate glycogen breakdown in a muscle?

A)epinephrine binds β receptors. $\rarr$ cAMP $\rarr$ PKA $\rarr$ phosphorylase kinase $\rarr$ glycogen phosphorylase
B)epinephrine bind α receptors $\rarr$ Ca²⁺ increase $\rarr$ phosphorylase kinase $\rarr$ glycogen phosphorylase
C)glucagon $\rarr$ glucagon receptors $\rarr$ cAMP $\rarr$ PKA $\rarr$ phosphorylase kinase $\rarr$ glycogen phosphorylase
D)PP1 binding to unphosphorylated Gm $\rarr$ dephosphorylates glycogen phosphorylase and phosphorylase kinase
E)All of these will activate glycogen breakdown in a muscle.

Question 42

Which of the following overall sequences is correct with regard to gluconeogenesis?

A)Oxaloacetate $\rarr$ PEP $\rarr$ G6P $\rarr$ Glucose
B)Pyruvate $\rarr$ FBP $\rarr$ PEP $\rarr$ Glucose
C)Lactate $\rarr$ PEP $\rarr$ Pyruvate $\rarr$ G6P
D)Oxaloacetate $\rarr$ F6P $\rarr$ FBP $\rarr$ Glucose
E)F6P $\rarr$ FBP $\rarr$ Glucose $\rarr$ G6P

Question 43

Which enzyme below is NOT required for the synthesis of branched glycogen?

A)glycogen phosphorylase
B)glycogen synthase
C)branching enzyme
D)phosphoglucomutase
E)All are required for synthesis of glycogen.

Question 44

Phosphoprotein phosphatase -1 (PP1)

A)catalyzes the phosphorylation of phosphorylase kinase.
B)increases glycogen breakdown when active.
C)catalyzes the dephosphorylation of phosphorylase kinase.
D)catalyzes the dephosphorylation of glycogen phosphorylase.
E)Both C and Dare correct.

Question 45

The glycogen debranching enzyme is required for

A)the transfer of 3-glucose units from one branch to another.
B)the transfer of phosphate from one position to another.
C)cleaving $\alpha$ (1 $\rarr$ 6)sugar linkages
D)A and C
E)A, B and C

Question 46

Patient "G" has a glycogen storage disease which results in decreased muscle glycogen levels.Muscle biopsies indicate poor glycogen structure in the muscle.Which of the following enzymes might be related to the cause?

A)muscle debranching enzyme
B)muscle glycogen phosphorylase
C)liver debranching enzyme
D)muscle glycogen synthase
E)liver glycogen synthase

Question 47

The Cori cycle is effective because

A)it allows the use of the lactate generated during anaerobic glycolysis to produce pyruvate.
B)it uses less ATP than gluconeogenesis.
C)it uses the compound DHAP and G3P generated during glycolysis to transport reducing equivalents.
D)A and B
E)A and C

Question 48

A deficiency in the enzyme PEPCK (PEP carboxykinase)would

A)block function of the malate/aspartate shuttle.
B)block transfer of reducing equivalents across the membrane in the heart and liver.
C)inhibit formation of ATP via oxidative phosphorylation.
D)inhibit formation of NADH.
E)decrease flux through gluconeogenesis.

Question 49

A deficiency in muscle glycogen phosphorylase would result in

A)normal muscle glycogen structure.
B)abnormal muscle glycogen structure.
C)elevated muscle glycogen levels
D)A and C
E)B and C

Question 50

Which of the following will NOT activate glycogen phosphorylase in the liver?

A)epinephrine
B)glucagon
C)eating a high carbohydrate meal
D)cAMP
E)All of the above will activate glycogen phosphorylase.