Chapter 22—Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate
Pathway
MULTIPLE CHOICE
1. Gluconeogenesis is the synthesis of:
a.
glucose from non-carbohydrate precursors.
b.
glycogen from glucose.
c.
pyruvate from glucose.
d.
fatty acids from glucose.
e.
glucose from fatty acids.
2. The pentose phosphate pathway is an important source of ____, and for ____, an essential precursor
for ATP, NAD+, FAD, CoA, DNA and RNA.
a.
ATP; NADH
b.
NADH; NADPH
c.
NADPH; ribose-5-phosphate
d.
ribose-5-phosphate; ATP
e.
all are true
3. All are substrates for gluconeogenesis EXCEPT:
a.
glycerol.
b.
lactate.
c.
acetate.
d.
pyruvate.
e.
most amino acids.
4. The major tissues carrying out gluconeogenesis are the ____ and ____.
a.
brain; muscles
b.
muscles; kidneys
c.
liver; kidneys
d.
liver; red blood cells
e.
red blood cells; brain
5. Glucose monitoring devices use the reaction, Glucose + O2 + H2O → gluconate + 2 ____, which is
catalyzed by the enzyme ____.
a.
H2O; glucose hydrolase
b.
H2O; glucose oxidase
c.
H2O2; peroxidase
d.
H2O2; glucose oxidase
e.
H2O; gluconate synthase
6. In the gluconeogenic pathway, the three regulated reactions of glycolysis catalyzed by ____, ____ and
____ are replaced by alternative reactions.
a.
glucokinase; PFK-1; pyruvate kinase
b.
phosphoglucoisomerase; PFK-1; pyruvate kinase
c.
PFK-1; triose phosphate isomerase; pyruvate kinase
d.
glucokinase; PFK-1; glyceraldehyde-3-phosphate dehydrogenase
e.
glucokinase; PFK-1; pyruvate carboxylase
7. Which of the following enzymes is found in gluconeogenesis but not glycolysis?
a.
phosphoglucoisomerase
b.
glucose-6-phosphatase
c.
pyruvate carboxylase
d.
fructose-1,6-bisphosphatase
e.
PEP carboxykinase
8. All are required for pyruvate carboxylase EXCEPT:
a.
biotin covalently linked to the enzyme.
b.
thiamin pyrophosphate (TPP).
c.
ATP.
d.
acetyl-CoA as an allosteric activator.
e.
tetrameric enzyme in the mitochondria.
9. In the pyruvate carboxylase catalyzed reaction, bicarbonate is “activated” by attachment to the ____ of
ATP to form ____.
a.
-phosphate; carbonyl ADP
b.
-phosphate; carbonyl AMP
c.
-phosphate; carbonylphosphate
d.
-phosphate; carbonylphosphate
e.
-phosphate; carbonyl AMP
10. The reaction sequence for the pyruvate carboxylase catalyzed reaction is:
A.
formation of N-carbonyl biotin
B.
attack of HCO3− on ATP
C.
liberation of Pi
D.
formation of carbonylphosphate
E.
C-3 carbanion of pyruvate attack on N-carbonyl biotin
a.
B, D, A, E, C
b.
B, D, A, C, E
c.
D, C, B, E, A
d.
D, B, C, A, E
e.
E, C, B, A, D
Garrett/Grisham 5e Test Bank 3
11. If levels of ____ and/or ____ are low, pyruvate is directed primarily into ____; but if they are high,
pyruvate is converted into ____ for gluconeogenesis.
a.
NADH; ATP; glycolysis; OAA
b.
ATP; NADPH; glycolysis; acetyl CoA
c.
ATP; acetyl CoA; TCA cycle; OAA
d.
NAD+; acetyl CoA; TCA cycle; acetyl CoA
e.
ATP; acetyl CoA; glycolysis; malate
12. All of the enzymes of gluconeogenesis may be found in the cytosol EXCEPT ____ which is only
found in the mitochondria.
a.
PEP carboxykinase
b.
pyruvate carboxylase
c.
fructose-1,6-bisphosphatase
d.
glucose-6-phosphatase
e.
all are only in cytosol
13. Pyruvate carboxylase consumes a(n) ____ to drive a carboxylation so that ____ could use the energy
from decarboxylation to facilitate formation of PEP.
a.
NADH; pyruvate dehydrogenase
b.
NADH; lactate dehydrogenase
c.
ATP; pyruvate kinase
d.
ATP; PEP carboxykinase
e.
GTP; nucleotide diphosphate kinase
14. The primary regulatory point of gluconeogenesis is ____.
a.
glucose-6-phosphatase
b.
fructose-1,6-bisphosphatase
c.
fructose-2,6-bisphosphatase
d.
pyruvate carboxylase
e.
PEP carboxykinase
15. Which of the following reactions represents the gluconeogenic alternative to the irreversible reaction
of PFK-1 in glycolysis?
a.
fructose-6-P + ADP → fructose + ATP
b.
fructose-6-P + H2O → fructose + Pi
c.
fructose-1,6-bisphosphate + ADP → fructose-6-P + ATP
d.
fructose-1,6-bisphosphate + H2O → fructose-6-P + Pi
e.
none of the above
16. The endoplasmic reticulum bound enzyme that hydrolyzes glucose-6-phosphate to glucose in liver is:
a.
glucokinase.
b.
glucose oxidase.
c.
hexokinase.
d.
phosphoglucomutase.
e.
glucose-6-phosphatase.
17. Glucose-6-phosphatase is located in the ____ and produces ____ in vesicles that diffuse to the ____
releasing their contents into the blood stream.
a.
mitochondria; lactate; cytosol
b.
cytosol; glucose; plasma membrane
c.
endoplasmic reticulum; glucose-6-phosphate; cytosol
d.
endoplasmic reticulum; glucose; plasma membrane
e.
cytosol; glucose-6-phosphate; endoplasmic reticulum
18. Gluconeogenesis is not simply reversal of glycolysis since 2 pyruvate → glucose requires the input of
____ equivalents of ATP and ____ equivalents of GTP.
a.
0; 6
b.
2; 4
c.
3; 3
d.
4; 2
e.
6; 0
19. In the Cori cycle, the liver ____ because it has a typically high ____.
a.
shares the load of exercising muscle; acetate level
b.
converts lactate to lactose; galactose
c.
shares the load of exercising muscle; NAD+/NADH ratio
d.
burns fat; ATP
e.
converts glucose to lactate; NAD+/NADH ratio
20. Which of the following is absolutely essential for the activation of pyruvate carboxylase?
a.
high concentrations of acetyl-CoA
b.
low levels of ATP
c.
high levels of oxaloacetate
d.
high levels of TCA cycle intermediates
e.
high levels of citrate
21. Cellular levels of fructose-2,6-bisphosphate (F-2,6-BP) are controlled by the tandem enzyme ____ and
____.
a.
fructokinase; F-2,6-BPase
b.
F-2,6-BPase; PFK-2
c.
PFK-2; PFK-1
d.
PFK-1; F-2,6-BPase
e.
PFK-2; fructokinase
22. ____ phosphorylates and thus ____ the enzyme PFK-2 which simultaneously ____ F-2,6-BPase.
a.
adenylate cyclase; activates; inhibits
b.
adenylate cyclase; inhibits; activates
c.
cAMP-dependent protein kinase; activates; inhibits
d.
cAMP-dependent protein kinase; inhibits; activates
e.
cAMP-dependent protein kinase; activates; activates
23. All are true for -amylase EXCEPT:
a.
catalyzes hydrolysis of (1→4) linkages in starch.
b.
is an important component of saliva and pancreatic juice.
c.
catalyzes hydrolysis of (1→6) linkages in amylopectin.
d.
catalyzes hydrolysis of (1→4) linkages in glycogen.
e.
activity is reduced in highly branched regions of polysaccharides and stops four residues
from any branch point.
24. Limit dextrins are degraded by the action of ____ which has two distinct enzymatic activities known
as ____ and ____.
a.
-amylase; –amylase; (1→6)glucosidase
b.
debranching enzyme; oligo(1,4→ 1,4)glucanotransferase; (1→6)glucosidase
c.
debranching enzyme; oligo(1,4→ 1,4)glucanotransferase; (1→6)glucosidase
d.
-amylase; oligo(1,4→ 1,6)glucanotransferase; (1→6)glucosidase
e.
-amylase; –amylase; oligo(1,4→ 1,4)glucanotransferase
25. The energy input for the synthesis of glycogen occurs during which of the following enzyme catalyzed
steps?
a.
phosphoglucomutase
b.
UDP-glucose pyrophosphorylase
c.
glycogen synthase
d.
amylo-(1,4→1,6)-transglycosylase
e.
none of the above require energy input
26. The initiation of glycogen synthesis occurs by transfer of glucose from UDP-glucose to the:
a.
4-position of free glucose.
b.
2-position of fructose.
c.
non-reducing end of maltose.
d.
serine-OH group of glycogen synthase.
e.
tyrosine-OH group of glycogenin.
Garrett/Grisham 5e Test Bank 6
27. All are characteristics of AGEs EXCEPT:
a.
AGEs mean advanced glycation end-products.
b.
Glycated hemoglobin in a patient is an indication of blood glucose levels over the past few
months.
c.
AGEs generated by elevated blood glucose contribute to circulation, joint and vision
problems of diabetics.
d.
AGEs form by enzyme catalyzed Schiff base formation between sugars and proteins.
e.
AGEs alter the function of the protein to which they are attached.
28. A blood test for “Glycated hemoglobin” can determine the:
a.
present blood glucose concentration.
b.
average glucose concentration in the blood over the past several months.
c.
level of AGEs in the blood stream.
d.
blood glucose concentration over this last month.
e.
none are true.
29. Glycogen synthesis and degradation must be carefully controlled at ____ and ____ to properly serve
the metabolic needs for the organism.
a.
glucokinase; hexokinase
b.
hexokinase; glycogen synthase
c.
glycogen synthase; glucokinase
d.
glycogen phosphorylase; glycogen synthase
e.
glycogen phosphorylase; hexokinase
30. Which of the following effectors is required for glycogen synthase activity when the enzyme is
phosphorylated?
a.
glucose-1-phosphate
b.
glucose-6-phosphate
c.
fructose-1,6-bisphosphate
d.
fructose-2,6-bisphosphate
e.
UDP-glucose
31. Insulin in the bloodstream is a response to increased blood glucose, and:
a.
stimulates gluconeogenesis.
b.
inhibits glycolysis.
c.
stimulates glycogen synthesis in muscle and liver.
d.
stimulates glycogen breakdown in liver.
e.
inhibits phosphoprotein phosphatase-1.
32. Physiological effects of insulin include all EXCEPT:
a.
stimulates glycogen synthesis
b.
induces synthesis of glucokinase, PFK-1 and pyruvate kinase
c.
stimulates active transport of glucose and amino acids into muscle and adipose tissues
d.
stimulates fructose-1,6-bisphosphatase
e.
inhibits glycogen phosphorylase
33. An individual with von Gierke’s disease lacks the enzyme ____ which is a liver enzyme used to
maintain ____. As a result, the patient is ____.
a.
glycogen synthase; liver glycogen; fat
b.
glycogen synthase; ATP levels; weak
c.
phosphoprotein phosphatase-1; blood glucose; hypoglycemic
d.
glucose-6-phosphatase; blood glucose; hypoglycemic
e.
glucose-6-phosphatase; muscle glycogen; weak
34. Among the many physiological changes elicited by epinephrine, the initiation of the adenylyl cyclase
cascade includes all EXCEPT:
a.
activation of glycogenolysis in liver.
b.
inhibition of glycogen synthase.
c.
stimulation of glycolysis by 2000 fold.
d.
activation of glycogenolysis in muscles.
e.
all are true
35. All are physiological changes initiated by glucagon EXCEPT:
a.
activation of glycogenolysis in liver.
b.
stimulation of liver gluconeogenesis.
c.
long-term maintenance of steady-state levels of glucose in the blood stream.
d.
activation of glycogenolysis in muscles.
e.
all are true.
36. Which of the following occurs as a result of cortisol release from the adrenal gland?
a.
activation of gluconeogenesis
b.
increased glycogen synthesis
c.
activation of the urea cycle
d.
increased degradation of muscle protein
e.
all of the above
37. Characteristics of glucose-6-phosphate dehydrogenase include all EXCEPT:
a.
located in the mitochondria.
b.
strongly inhibited by [NADPH].
c.
inhibited by fatty acid-CoA.
d.
uses NADP+ as a coenzyme.
e.
forms a cyclic ester (lactone) of 6-phosphogluconate.
38. The ratio of NADP+/NADPH in liver runs about 1/67 which means that:
a.
it is similar to the ratio of NAD+/NADH.
b.
glucose-6-phosphate dehydrogenase will be turned on most of the time.
c.
glucose-6-phosphate is rate limiting for pentose phosphate pathway.
d.
glucose-6-phosphate preferentially goes to the pentose phosphate pathway.
e.
glucose-6-phosphate dehydrogenase activity is dependent upon use of some of the
NADPH before activity increases.
39. The 6-phosphogluconate dehydrogenase reaction is an example of ____ and results in the production
of ____.
a.
substrate-level phosphorylation; ATP
b.
oxidative-decarboxylation; NADPH
c.
TPP-assisted decarboxylation; NADH
d.
phosphate addition; ADP
e.
none of the above
40. Phosphopentose isomerase is quite similar to the reaction and mechanism of the ____ catalyzed
reaction.
a.
UDP-glucose epimerase
b.
phosphoglycerate isomerase
c.
phosphopentose epimerase
d.
phosphoglucoisomerase
e.
all are similar
41. The polyol pathway is a suspected pathway for diabetic induced cataract formation and involves the
enzyme:
a.
aldose reductase.
b.
glucose-6-phosphate dehydrogenase.
c.
phosphopentose isomerase.
d.
phosphopentose epimerase.
e.
transaldolase.
42. A transaldolase is an enzyme that catalyzes:
a.
transfers of three-carbon units from a ketose to an aldose.
b.
isomerization of ketoses into aldoses such as the conversion of ribulose-5-phosphate to
ribose-5-phosphate.
c.
epimerization of ketoses such as the conversion of xylulose-5-phosphate into ribulose-5-
phosphate.
d.
TPP-dependent transfer of 2-carbon units to the recipient aldose.
e.
transfer of keto groups from C-2 to C-3 of a ketose.
43. Transketolase belongs to what class of enzymes?
a.
oxidoreductases
b.
isomerases
c.
hydrolases
d.
transferases
e.
ligases
44. Which of the following reactions is catalyzed by a transketolase in the pentose phosphate pathway?
I.
fructose-6-P + glyceraldehyde-3-P xylulose-5-P + erythrose-4-P
II.
erythrose-4-P + fructose-6-P sedoheptulose-7-P + glyceraldehyde-3-P
III.
sedoheptulose-7-P + glyceraldehyde-3-P ribose-5-P + xyulose-5-P
a.
I only
b.
II and III
c.
II only
d.
I and III
e.
I and II
45. The transaldolase catalyzed activity is similar to what glycolytic enzyme?
a.
phosphoglucomutase
b.
enolase
c.
glyceraldehyde-3-phosphate dehydrogenase
d.
PFK-1
e.
aldolase
46. The appropriate sequence for the transketolase catalyzed reaction would be:
A.
reactive enamine attack on the aldehyde group of an aldose
B.
-cleavage of Schiff base intermediate to release an aldose
C.
formation of Schiff base intermediate of a new ketose
D.
active site lysine forms Schiff base with keto-carbonyl group
E.
Schiff base hydrated to ketose and enzyme
a.
C, A, B, D, E
b.
D, B, A, C, E,
c.
D, A, B, E, C
d.
A, D, B, C, E
e.
E, D, C, B, A
Garrett/Grisham 5e Test Bank 10
47. When a cell with the pentose phosphate pathway has need for more pentose phosphates, but no
additional NADPH:
a.
glucose-6-phosphate dehydrogenase is activated.
b.
the oxidative and non-oxidative enzymes of the pentose phosphate pathway are active.
c.
the non-oxidative enzymes produce pentose phosphates from fructose-6-phosphate and
glyceraldehyde-3-phosphate.
d.
all enzymes of glycolysis and pentose phosphate pathway are active.
e.
none are true.
48. Which of the following can be used as a substrate for gluconeogenesis in the liver?
a.
alanine
b.
glutamic acid
c.
glycerol
d.
succinate
e.
all of the above
49. Which of the following results when glucagon binds to its receptor?
a.
glycolysis is activated
b.
protein synthesis is activated
c.
the citric acid cycle is inhibited
d.
glycogen synthesis is inhibited
e.
gluconeogenesis is inhibited
50. If NADPH is needed for biosynthetic reactions but ribose-5-P is not needed, which of the following
best represents the net reaction of the pentose phosphate pathway?
a.
4 Fruc-6-P + 2 glyceraldehyde-3-P → 6 ribose-5-P
b.
3 Gluc-6-P + 6 NADP+ → 6 NADPH + 3 CO2 + 2 Fruc-6-P + 1 glyceraldehyde-3-P
c.
Gluc-6-P + 2 NADP+ → 2 NADPH + CO2 + ribose-5-P
d.
both b and c will occur
e.
None of the above
51. What coenzyme is found in pyruvate carboxylase that aids in many carboxylation reactions?
a.
thiamine pyrophosphate
b.
biotin
c.
folic acid
d.
lipoic acid
e.
none of the above
52. Which of the following enzymes would be activated by phosphorylation as a result of glucagon
binding to its receptor on the cell membrane?
a.
pyruvate carboxylase
b.
glycogen synthase
c.
pyruvate kinase
d.
fructose-2,6-bisphosphatase
e.
none of the above
53. Which of the following pairs of enzymes would NOT be active in the liver at the same time?
a.
aldolase and triose phosphate isomerase
b.
fructose-1,6-bisphosphatase and phosphofructokinase-2
c.
pyruvate kinase and phosphofructokinase-1
d.
glycogen synthase and glucokinase
e.
none of the above
54. AMP is often used in the cytosol as an indicator of low cellular energy. Which of the following
enzymes would be inhibited by AMP?
a.
glucose-6-phosphate dehydrogenase
b.
phosphofructokinase-1
c.
glycogen synthase
d.
glyceraldehyde-3-phosphate dehydrogenase
e.
none of the above
55. If both NADPH and ribose-5-P are needed which of the following best represents the net reaction of
the pentose phosphate pathway?
a.
4 Fruc-6-P + 2 glyceraldehyde-3-P → 6 ribose-5-P
b.
3 Gluc-6-P + 6 NADP+ → 6 NADPH + 3 CO2 + 2 Fruc-6-P + 1 glyceraldehyde-3-P + 6
H+
c.
Gluc-6-P + 2 NADP+ + 2 H2O → 2 NADPH + CO2 + ribose-5-P + 2 H+
d.
Gluc-6-P + 12 NADP+ + 6 H2O → 1 2 NADPH + 6 CO2 + 12 H+ + Pi
e.
None of the above