ABI 103 Chapter 16: Glycogen Metabolism and Gluconeogenesis

The breakdown of glycogen is referred to as ______.

glycogenolysis

Glucose can be synthesized from noncarbohydrate precursors by______.

gluconeogenesis

Carboxylation of pyruvate in humans requires ______ as an essential dietary nutrient.

biotin

______ activates glycogen breakdown.

cAMP

An enzyme present in the endoplasmic reticulum of liver cells is ______.

glucose-6-phosphatase

______ cells lack receptors for the hormone glucagon.

Muscle

Low blood glucose (< 5mM) levels result in the release of ______.

glucagon

The first step in the breakdown of glycogen is catalyzed by ______.

phosphorylase a

Both glycogen synthesis and glycogen breakdown share the metabolite ______.

glucose-1-phosphate

The membrane-bound polyisoprenol involved in the synthesis of N-linked glycoproteins is called ______.

dolichol

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

D) phosphoglucomutase

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

E) glycogen phosphorylase; liver

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.

A) UDP-glucose .

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?1,6)-transglycosylase

C) glycogenin

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

B) phosphorylase kinase

The biotin residue of prosthetic group of pyruvate carboxylase is covalently attached to a ______ the enzyme?
A) valine
B) serine
C) lysine
D) arginine
E) the biotin is attached non-covalently

C) lysine

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 PPi
B) hydrolysis of A TP
C) hydrolysis of GTP
D) hydrolysis of an inter

C) hydrolysis of GTP

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

D) 6

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

C) they lack glucose-6-phosphatase.

Which of the following statements about glycogen is true?
I. Glycogen is a polymer of glucose in ?(1?6) linkages with ?(1?4) linked branches every 8-14 residues.
II. UDP-glucose is produced from glycogen by the action of the enzyme phosphorylase.
III. In

D) III, IV

Which of the following metabolic conversions does not occur in gluconeogenesis?
A) oxaloacetate ? phosphoenolpyruvate
B) fructose-1,6-bisphosphate ? fructose-6-phosphate
C) GTP ? CO2 + GDP
D) NADH + H+ ? NAD+
E) 1,3-bisphosphoglycerate ? 3-phosphoglycerat

E) 1,3-bisphosphoglycerate ? 3-phosphoglycerate

Which of the following is correct concerning the metabolic reaction shown below? Pyruvate + CO2 + ATP ? oxaloacetate + ADP + Pi
I. This metabolic reaction is catalyzed by pyruvate carboxykinase.
II. The enzyme that catalyzes this reaction is activated by

C) II only

What molecules correspond to correspond to X and Y in the following gluconeogenic reaction?
Fructose-1,6-bisphosphotase + X ? Fructose-6-phosphate + Y
A) X = NADH + H+ Y = NAD+
B) X=ATP+ Y = ADP + Pi
C) X = NAD Y = NADH + H
D) X=GTP Y = GTP + Pi
E) X=H2O

E) X=H2O Y = Pi

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

A) I only

The diagram represents a "substrate cycle" in glucose metabolism. Which of the following statements about the cycle is true?
Fructose-6-Phosphate--> I--> Fructose-1,6-bisphosphate-->II-->Fructose-6-Phosphate (circle)
A) Reactions I & II are catalyzed by t

C) Reaction II is catalyzed by an allosteric enzyme that is inhibited by fructose-2-
6-bisphosphate.

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

A) I only

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 ? phosphoenolpyruvate
B)

D) Pyruvate ? oxaloacetate

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

C) Ensures that gluconeogenesis occurs rather than pyruvate conversion to
acetyl-CoA.

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

C) 2

Which of the following best describes the function of the glycogen debranching enzyme in glycogenolysis?
A) It cleaves ?(1?6) branch points releasing glucose-6-phosphate.
B) It cleaves ?(1?6) branch points releasing glucose-1-phosphate.
C) It cleaves ?(1?

E) It transfers an ?(1?4) linked trisaccharide to the nonreducing end of an
alternate branch, then cleaves the ?(1?6) branch point releasing glucose.

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. Gluco

D) II only

Which of the following best explains the energetically favorable formation of UDP-glucose in the liver and muscle?
A) ?G� for the reaction glucose-1-phosphate + UTP ? UDP-glucose + PPi is very negative.
B) ?G� for the reaction glucose-1-phosphate + UTP ?

C) ?G� for the reaction PPi ? 2Pi is very negative.

Hexokinase does not catalyze the final step in gluconeogenesis as written below because glucose-6-phosphate + ADP ? 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

A) the phosphate bond in glucose-6-phosphate does not have a high enough free energy to form ATP.

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

D) FBP is a potent allosteric activator of phosphofructokinase and an inhibitor of
fructose bisphosphatase.

Which of the following is true regarding the reaction shown below? pyruvate + HCO3? + ATP ? oxaloacetate + ADP + Pi
I. It requires the direct transport of oxaloacetate across the membrane. II. It utilizes the malate-aspartate shuttle in some species.
III.

B) II, III

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) endoplasmi

D) endoplasmic reticulum; Golgi apparatus

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

B) I, II, III

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 invo

D) It is converted to G6P by phosphoglucoisomerase (PGI).

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 ?(1 6) sugar linkages
D) A and C
E) A, B and C

D) A and C

Which of the following describes a sequence which will ultimately activate glycogen breakdown in a muscle?
A) epinephrine binds ? receptors. cAMP PKA phosphorylase kinase glycogen phosphorylase
B) epinephrine bind ? receptors Ca2+ increase phosphorylase k

A) epinephrine binds ? receptors. cAMP PKA phosphorylase kinase glycogen phosphorylase

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 phosphory

E) Both C and Dare correct.

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.

C) eating a high carbohydrate meal

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) mus

D) muscle glycogen synthase

Which of the following overall sequences is correct with regard to gluconeogenesis?
A) Oxaloacetate --> PEP --> G6P --> Glucose
B) Pyruvate --> FBP --> PEP --> Glucose
C) Lactate --> PEP --> Pyruvate --> G6P
D) Oxaloacetate --> F6P --> FBP --> Glucose
E)

A) Oxaloacetate --> PEP --> G6P --> Glucose

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.

A) glycogen phosphorylase

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

D) A and C

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
redu

A) it allows the use of the lactate generated during anaerobic glycolysis to produce pyruvate.

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.

E) decrease flux through gluconeogenesis.