Where are the two major sites for glycogen storage in humans?
Liver and muscle
Adipose tissue and kidney
Liver and kidney
Muscle and kidney
Liver and brain
Liver and muscle
In humans, which one of the following statements about gluconeogenesis is TRUE?
Is essential in the conversion of fatty acids to glucose
Requires the enzyme hexokinase
Helps to reduce blood glucose after a carbohydrate-rich meal
Can result in the conversi
Can result in the conversion of protein into glucose
Which of the following statements is TRUE regarding glycogen synthase?
It uses glucose-1-phosphate as a substrate.
It catalyzes formation of glycosidic bonds.
It is activated by protein kinases.
It is activated by Ca2+ ions.
It catalyzes formation of glycosidic bonds.
What is the net energy gain when 1 molecule of glucose from glycogen stores is converted to lactate?
2 ATP
3 ATP
2 NADH + 2 ATP
2 NADH + 3 ATP
2 NADH + 4 ATP
3 ATP
Which of the following statements about glycogen is FALSE?
Glycogen signals the fasting state and is released into the bloodstream when blood sugar levels are low.
UDP-glucose is an "activated" compound that can donate a glucose molecule to a growing glyc
Glycogen signals the fasting state and is released into the bloodstream when blood sugar levels are low.
Why is an anaerobic fate of pyruvate necessary?
To allow for the re-oxidation of NADH to NAD+, which is in limited supply.
To allow for the complete catabolism of glucose to CO2 and H2O.
To allow lactate to be converted back to pyruvate which will then pr
To allow for the re-oxidation of NADH to NAD+, which is in limited supply.
Which of the following is FALSE regarding glycogen?
Glucose is stored as a polymer to reduce its chemical reactivity.
The main chain of the glycogen polymer predominately contains glucose residues linked via 1-6 glycosidic bonds.
The first step in glycoge
The main chain of the glycogen polymer predominately contains glucose residues linked via 1-6 glycosidic bonds
Which of the following steps is/are not involved in the synthesis of glycogen?
The formation of UDP-glucose from glucose-1-phosphate and UTP.
The conversion of glucose-1-phosphate to glucose-6-phosphate.
The synthesis of glucose-1-phosphate from glucose a
B and C.
Which of the following statements is TRUE regarding glycogen synthase?
Glycogen synthase catalyzes the formation of glycosidic bonds.
Glycogen synthase is activated by calcium ions.
Glycogen is both a substrate and product of the reaction catalyzed by gly
A and C
Under anaerobic conditions in the muscle what is the net yield of ATP from glycolysis when glycogen is used as a starting material?
5 ATP
2 ATP
3 ATP
4 ATP
3 ATP
What is the NET number of phosphoanhydride bonds broken in the addition of one molecule of glucose to a pre-existing glycogen molecule?
2
4
3
0
1
2
There is an immediate energetic advantage to muscle in using its own glycogen stores in glycolysis rather than glucose from the bloodstream. Which statement accurately explains why this is so?
Glucose transport into muscle cells is an active transport pro
Glycogen is broken down by phosphorolysis and this reduces the number of ATP molecules that must be invested in the hexoses stage of glycolysis.
What is the purpose of glycogen in muscle?
To serve as a source of glucose-6-phosphate which is subsequently dephosphorylated by glucose-6-phosphatase and transported out of the cell.
To activate kinases and regulate glucose metabolism.
To serve as a sour
To serve as a source of fuel for ATP synthesis within that tissue.
Which one of the following enzymes is the rate-limiting enzyme in glycogen breakdown?
Glycogen synthase
Glycogen phosphorylase
Glucose-6-phosphatase
Hexokinase
Glycogen phosphorylase
Which of the following is TRUE of glycogen phosphorylase?
It uses UDP-glucose as a substrate.
It catalyzes formation of glycosidic bonds.
It is the rate-limiting enzyme in glycogen synthesis.
It is activated by Ca2+ ions
It is activated by Ca2+ ions
The breakdown of glycogen is referred to as ______.
glycogenolysis
cAMP
pancreas
glucose-6-phosphatase
dolichol
biotin
glucagon
liver
insulin
glucose-1-phosphate
phosphorylase a
gluconeogenesis
glycogenolysis
The first step in the breakdown of glycogen is catalyzed by ______.
glucagon
glucose-6-phosphatase
cAMP
liver
biotin
glycogenolysis
pancreas
glucose-1-phosphate
insulin
dolichol
phosphorylase a
gluconeogenesis
phosphorylase a
Both glycogen synthesis and glycogen breakdown share the metabolite ______.
cAMP
pancreas
gluconeogenesis
glucagon
biotin
glucose-1-phosphate
liver
dolichol
phosphorylase a
glucose-6-phosphatase
insulin
glycogenolysis
glucose-1-phosphate
Which of the following enzymes catalyzes the conversion of glucose-1-phosphate to glucose-6-phosphate?
glucose phosphatase
hexokinase
glucokinase
phosphoglucomutase
glycogen phosphorylase
phosphoglucomutase
Which of the following enzymes is defective/missing in individuals who have McArdle's disease?
phosphoglucomutase
glycogen phosphorylase
glucose-6-phosphatase
debranching enzyme
pyruvate carboxylase
glycogen phosphorylase
In glycogen synthesis, the intermediate between glucose-1-phosphate and glycogen is
glucose
UDP-glucose (or uridine diphosphate glucose)
glucose-6-phosphate
glucose-1,6-bisphosphate
UDP-glucose (or uridine diphosphate glucose)
Which of the following enzymes converts phosphorylase b is to the more active phosphorylase a?
calmodulin
glycogenin
phosphoprotein phosphatase-1
cAMP-dependent protein kinase
phosphorylase kinase
phosphorylase kinase
Which of the following statements about glycogen is false?
Glycogen is a polymer of glucose in (14) linkages with (16) linked branches every 8-14 residues.
UDP-glucose is produced from glycogen by the action of the enzyme phosphorylase.
The breakdown of g
UDP-glucose is produced from glycogen by the action of the enzyme phosphorylase.
Which enzyme has an intermediate of the form presented?
Phosphohexose isomerase
Phosphoglucomutase
Phosphofructokinase
Glucose bisphosphatase
Glycogen phosphorylase
Phosphoglucomutase
A muscle cell takes a glucose molecule, stores it as part of a glycogen molecule and later releases it and sends it through glycolysis. What will be the net ATP yield?
1
2
3
4
more than 4
2
Which of the following best describes the function of the glycogen debranching enzyme in glycogenolysis?
It transfers an alpha(14) linked trisaccharide unit from a limit branch to the nonreducing end of another branch, and then cleaves the alpha(16) branc
It transfers an alpha(14) linked trisaccharide unit from a limit branch to the nonreducing end of another branch, and then cleaves the alpha(16) branch point releasing glucose.
Which of the following best explains why the formation of UDP-glucose from glucose-1-phosphate in the liver and muscle is energetically favorable?
?G�' for the reaction glucose-1-phosphate + UTP UDP-glucose + PPi is very positive.
?G�' for the reaction PP
?G�' for the reaction PPi 2Pi is very negative.
Why does glycogen breakdown produce about 10% glucose, rather than glucose-6-phosphate?
Glycogen debranching enzyme hydrolyzes, rather than phosphorylyzes glycogen randomly at a low frequency.
Glycogen debranching enzyme hydrolyzes, rather than phosphoryl
Glycogen debranching enzyme hydrolyzes, rather than phosphorylyzes the remaining branch residue, after the limit branch has been transferred.
Which of the following accurately describes the regulation of glycogen synthase?
The enzyme is activated by ADP and Pi.
The enzyme's activity varies with the concentration of G6P and with the fraction of enzyme that is dephosphorylated.
The phosphorylated
The enzyme's activity varies with the concentration of G6P and with the fraction of enzyme that is dephosphorylated.
Why is glycogen debranching enzyme necessary?
It allows regulation of the rate of glycogenolysis.
Because the substrate binding cleft of glycogen phosphorylase cannot accommodate chains of glycogen closer than 4-5 residues away from a branch.
Because glyc
Because the substrate binding cleft of glycogen phosphorylase cannot accommodate chains of glycogen closer than 4-5 residues away from a branch.
What are some of the considerations for the optimal degree of branching in glycogen?
More branches will decrease the number of free ends
More branches will decrease the osmotic pressure.
More branches will increase the number of free ends on the surface,
More branches will increase the number of free ends on the surface, but with too many branches the size of glycogen will be limited by the maximum density possible.
What are some of the considerations for the optimal chain length in glycogen?
Shorter chain lengths are better, so that the maximum number of ends is available to release glucose rapidly.
Optimal chain length is a compromise between number of available en
Optimal chain length is a compromise between number of available ends, and the need for debranching enzyme.
Which pair below correctly matches an enzyme with its allosteric activator?
glucose-6-phosphatase / ADP
hexokinase / glucose-1-phosphate
pyruvate kinase / ADP
phosphofructokinase-1 / fructose-1,6-bisphosphate
pyruvate kinase / ADP
Which one of the following processes most completely describes phosphorolysis reactions?
Hydrolyzing a polymer and adding a phosphate group.
Splitting a polymer and adding a phosphate group
Splitting a polymer.
Removing a phosphate group from a polymer.
Splitting a polymer and adding a phosphate group
How does insulin promote glycogen synthesis in the liver?
By causing the dephosphorylation of both glycogen phosphorylase and glycogen synthase.
By inhibiting glycogen synthase.
By binding to glycogen phosphorylase.
By activating glycogen phosphorylase
By causing the dephosphorylation of both glycogen phosphorylase and glycogen synthase.
Which pair below correctly matches an enzyme with its inhibitor?
Fructose-1,6-bisphosphatase / ATP
Hexokinase / glucose-6-phosphate
Pyruvate decarboxylase / acetyl-CoA
Hexokinase / glucose-6-phosphate
Which of the following is TRUE of glycogen metabolism?
The product of the glycogen phosphorylase reaction is glucose-6-phosphate.
Calcium ions activate a phosphatase that subsequently activates glycogen phosphorylase.
Immediately following a high carbohyd
Glucagon acts via kinases that subsequently activate glycogen phosphorylase
Which of the following statements regarding gluconeogenesis is TRUE?
It is likely to occur when cellular ATP levels are high.
Fructose-2,6-bisphosphate activates gluconeogenesis.
The conversion of phosphoenolpyruvate to 2-phosphoglycerate occurs in two st
It is likely to occur when cellular ATP levels are high.
Which of the following statements regarding gluconeogenesis is FALSE?
The bypass of the pyruvate kinase step of glycolysis requires two reactions, which occur in the mitochondrial matrix.
There are 7 shared reactions between glycolysis and gluconeogenesis
Gluconeogenesis consumes a net of 1 CO2 molecule.
Which of the following compounds is NOT a substrate for the synthesis of glucose via gluconeogenesis?
alanine
glycerol
oxaloacetate
lactate
leucine
leucine
Which of the following statements regarding glycolysis and gluconeogenesis is FALSE?
Glycolysis occurs in the cytosol, gluconeogenesis occurs in the cytosol and mitochondrial matrix.
Glycolysis is oxidative, gluconeogenesis is reductive.
Glycolysis is exe
Glycolysis is exergonic, gluconeogenesis is endergonic.
In humans, which one of the following statements regarding gluconeogenesis is TRUE?
Gluconeogenesis allows storage of glucose following a meal.
Gluconeogenesis is activated by glucagon.
Gluconeogenesis is an endergonic pathway.
Gluconeogenesis is activate
Gluconeogenesis is activated by glucagon.
Which of the following statements regarding gluconeogenesis is TRUE?
It primarily occurs in the liver
It is catalyzed by all the same enzymes as glycolysis
It leads to the synthesis of glucose in muscle tissue
A and C
It primarily occurs in the liver
The synthesis of phosphoenolpyruvate from pyruvate proceeds through two enzyme-catalyzed reactions. These reactions:
Lead to the net production of ATP
Are both irreversible because they are coupled to nucleotide hydrolysis
Occur in the mitochondrial matri
Occur in the mitochondrial matrix
In a cell undergoing gluconeogenesis, how many high energy intermediates are required to make one molecule of glucose if starting from oxaloacetate?
2 ATP, 2 GTP and 2 NADH
4 ATP, and 2 NADH
1 ATP, 1 GTP and 1 NADH
4 ATP and 2 GTP
2 ATP, 2 GTP and 2 NADH
In humans, which one of the following statements regarding gluconeogenesis is FALSE?
Gluconeogenesis requires the enzyme glucose-6-phosphatase.
Gluconeogenesis is activated when ADP levels are high.
Gluconeogenesis helps to maintain blood glucose levels b
Gluconeogenesis is activated when ADP levels are high.
Which of the glycolytic enzymes listed below also plays a role in gluconeogenesis?
pyruvate kinase
phosphofructokinase-1
hexokinase
glyceraldehyde-3-phosphate dehydrogenase
glyceraldehyde-3-phosphate dehydrogenase
Is fructose-1,6-bisphosphatase activated, inhibited, or unaffected in response to a glucagon signal?
Inhibited
Unaffected
Activated
Activated
The enzyme fructose-1,6-bisphosphatase is activated by which of the following?
ADP
Fructose-6-phosphate
Ca2+
None of the above
None of the above
Glycolysis and gluconeogenesis are reciprocally regulated at the steps that interconvert fructose-6-phosphate and fructose-1,6-bisphosphate. Which of the following statements about this regulation is TRUE?
Phosphofructokinase-2 (PFK-2) is activated by pro
Phosphofructokinase-2 (PFK-2) is activated by protein dephosphorylation.
In skeletal muscle, which statement is NOT accurate regarding the regulation of glycogen metabolism?
Calcium ions activate a kinase that subsequently activates glycogen phosphorylase.
Insulin causes the dephosphorylation of glycogen synthase, which result
Glucagon acts via kinases that subsequently activate glycogen phosphorylase
Glucose can be synthesized from noncarbohydrate precursors by______.
glucose-1-phosphate
glycogenolysis
dolichol
liver
pancreas
phosphorylase a
insulin
gluconeogenesis
glucagon
biotin
glucose-6-phosphatase
cAMP
gluconeogenesis
Carboxylation of pyruvate in humans requires ______ as an essential dietary nutrient.
dolichol
gluconeogenesis
glucagon
glucose-6-phosphatase
insulin
liver
glucose-1-phosphate
pancreas
cAMP
phosphorylase a
biotin
glycogenolysis
biotin
When blood sugar level is low ______ is released.
glucose-6-phosphatase
liver
glycogenolysis
insulin
phosphorylase a
gluconeogenesis
glucose-1-phosphate
glucagon
pancreas
dolichol
cAMP
biotin
glucagon
The membrane-bound polyisoprenol involved in the synthesis of N-linked glycoproteins is called ______.
phosphorylase a
glucose-1-phosphate
cAMP
liver
pancreas
dolichol
gluconeogenesis
glucagon
glucose-6-phosphatase
biotin
insulin
glycogenolysis
dolichol
Which of the following proteins forms the glycogen "primer"?
glycogenin
glycogen synthase
UDP-glucose pyrophosphorylase
glycogen phosphorylase
glycogenin
The biotin prosthetic group of pyruvate carboxylase is covalently attached to a ______ residue of the enzyme?
glutamate
arginine
lysine
serine
histidine
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?
hydrolysis of an internal phosphoanhydride
hydrolysis of ATP ADP + Pi
hydrolysis of ATP A
hydrolysis of GTP GDP + Pi
What is the net energetic cost of converting two pyruvate to one glucose by gluconeogenesis in ATP equivalents?
8
2
4
6
6
Which of the following metabolic conversions does not occur in gluconeogenesis?
1,3-bisphosphoglycerate 3-phosphoglycerate
oxaloacetate phosphoenolpyruvate
fructose-1,6-bisphosphate fructose-6-phosphate
NADH + H+ NAD+
glucose-6-phosphate glucose
1,3-bisphosphoglycerate 3-phosphoglycerate
What are the coenzyme forms that correspond to X and Y in the following gluconeogenic reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase?
X = NADH + H+, Y = NADP+
X = FAD, Y = FADH2
X = NADH + H+, Y = NAD+
X = NAD+, Y = NADH + H+
X = NADPH + H
X = NADH + H+, Y = NAD+
Biosynthesis requires the expenditure of free energy. Which of the following metabolic conversions involved in glucose synthesis requires the direct expenditure of ATP free energy (ATP is also a reactant)?
Glyceraldehyde-3-phosphate + dihydroxyacetone pho
3-Phosphoglycerate 1,3-bisphosphoglycerate
The diagram represents a "substrate cycle" or "futile cycle" in glucose metabolism. Which of the following statements about the cycle is correct?
Reaction I is catalyzed by an allosteric enzyme that is activated by fructose-2-6-bisphosphate.
Reaction II p
Reaction I is catalyzed by an allosteric enzyme that is activated by fructose-2-6-bisphosphate.
Increased levels of epinephrine in the blood will:
inhibit glycolysis in the muscle cell.
stimulate gluconeogenesis in the muscle cell.
activate adenylate cyclase in liver and muscle cells.
inhibit the formation of cAMP.
stimulate glycogen synthesis
activate adenylate cyclase in liver and muscle cells.
Avidin, a protein in egg whites, binds biotin very tightly and prevents its absorption in the intestine. Consumption of large amounts of raw eggs can result in a biotin deficiency. Which of the following metabolic conversions cannot occur without biotin?
Pyruvate oxaloacetate
If cAMP levels are high
It transfers an alpha(14) linked trisaccharide unit from a limit branch to the nonreducing end of another branch, and then cleaves the alpha(16) branch point releasing glucose-1-phosphate.
It transfers an alpha(14) linked trisaccha
It transfers an alpha(14) linked trisaccharide unit from a limit branch to the nonreducing end of another branch, and then cleaves the alpha(16) branch point releasing glucose
Why doesn't hexokinase catalyze the final step of gluconeogenesis as
glucose-6-phosphate + ADP glucose + ATP ?
?G�' for this reaction is very negative, and thus unfavorable
?G�' for this reaction is very positive, and thus unfavorable.
Since ATP inhibits
?G�' for this reaction is very negative, and thus unfavorable
Which of the following best describes the role of fructose-2,6-bisphosphate (F2,6P) in liver cells?
F2,6P is a potent allosteric activator of phosphofructokinase and an inhibitor of fructose bisphosphatase.
It is an intermediate in both glycolysis and glu
F2,6P is a potent allosteric activator of phosphofructokinase and an inhibitor of fructose bisphosphatase
In liver cells, if cAMP concentrations are high
PFK-2/FBPase-2 will function to generate more F-2,6-P, thereby enhancing glycolysis & depressing gluconeogenesis.
PFK-2/FBPase-2 will function to degrade F-2,6-P, thereby enhancing glycolysis & depressing gl
PFK-2/FBPase-2 will function to degrade F-2,6-P, thereby enhancing gluconeogenesis & depressing glycolysi
In which cellular location does the following reaction take place?
pyruvate + HCO3- + ATP oxaloacetate + ADP + Pi
mitochondrial matrix
It depends upon the specific cell type/species.
cytosol
endoplasmic reticulum
mitochondrial matrix
In which cellular location does the synthesis of N-linked oligosaccharides take place?
mitochondrial matrix
It depends upon the specific cell type/species.
cytosol
Golgi apparatus
Golgi apparatus