Biochemistry Exam 2 ~ 2006/2005/2004

Front 1

Which of the following monosaccharides is not an aldose?
A. glyceraldehyde
B. ribose
C. erythrose
D. fructose
E. glucose

Back 1

D. fructose

Front 2

When two carbohydrates are epimers:
A. they differ only in the configuration around one carbon atom.
B. they differ in length by one carbon.
C. one is a pyranose, the other a furanose.
D. one is an aldose, the other a ketose.
E. they rotate plane-polarized light in the same direction.

Back 2

B. they differ in length by one carbon.

Front 3

Which of the following is an epimeric pair?
A. D-glucose and D-glucosamine
B. D-glucose and L-glucose
C. D-lactose and D-sucrose
D. L-mannose and L-fructose
E. D-glucose and D-mannose

Back 3

E. D-glucose and D-mannose

Front 4

Which of the following pairs is interconverted in the process of mutarotation?
A. D-glucose and L-glucose
B. D-glucose and D-galactose
C. Alpha-D-glucose and Beta-D-glucosamine
D. alpha-D-glucose and beta-D-glucose
E. D-glucose and D-fructose

Back 4

D. alpha-D-glucose and beta-D-glucose

Front 5

Which of the following is not a reducing sugar?
A. glucose
B. glyceraldehyde
C. sucrose
D. ribose
E. fructose

Back 5

C. sucrose

Front 6

In the structure below, how many of the monosaccharide units are furanose and pyranose structures? What is the linkage between the two monosaccharide units? Is this a reducing sugar?
A. Two pyranose, a beta linkage and a non-reducing sugar
B. One furanose and one pyranose, an alpha linkage and a
reducing sugar
C. Two pyranose, a beta linkage and a reducing sugar
D. Two furanose, a beta linkage and a non-reducing sugar
E. Two furanose, a beta linkage and a reducing sugar

Back 6

C. Two pyranose, a beta linkage and a reducing sugar

Front 7

Which of the following statements about starch and glycogen is false?
A. Both starch and glycogen are stored intracellularly as
insoluble granules.
B. Glycogen is more extensively branched than starch.
C. Both serve primarily as structural elements in cell walls.
D. Amylose is unbranched; amylopectin and glycogen contain
(1-6) branches.
E. Both are homopolymers of glucose.

Back 7

C. Both serve primarily as structural elements in cell walls.

Front 8

In the favored chair form of -D-glucopyranose, which of the following is true?
A. The hydroxyl group of carbon 6 is also close to the
pyranose oxygen.
B. All the hydroxyl groups are in the equatorial position
and all the hydrogens are in the axial position.
C. The anomeric hydrogen is always equatorial.
D. All the hydroxyl groups are in the axial position and all
the hydrogens are in the equatorial position.
E. None of the above is true.

Back 8

B. All the hydroxyl groups are in the equatorial position
and all the hydrogens are in the axial position.

Front 9

D-Glucose is called a reducing sugar because it undergoes an oxidation-reaction at the anomeric carbon. One of the
products of this reaction is:
A. muramic acid
B. D-glucuronate
C. D-ribose
D. D-galactose
E. D-gluconate

Back 9

E. D-gluconate

Front 10

When a mixture of glucose-6-phosphate and fructose-6-
phosphate is incubated with the enzyme phosphohexoseisomerase
(which catalyzes the interconversion of these two
compounds) until equilibrium is reached, the nal mixture
contains twice as much glucose-6-phosphate as fructose-6-phosphate. Which one of the following statements is
most nearly correct, when applied to this reaction below?
(R=8.315 J/K/mol; T = 298 K)
A. Delta G is incalculably large and positive.
B. Delta G = +1.72 kJ/mol.
C. Delta G is zero.
D. Delta G is incalculably large and negative.
E. Delta G = -1.72 kJ/mol.

Back 10

B. Delta G = +1.72 kJ/mol.

Front 11

The standard free-energy changes for the reactions below are
given BLAH What is the overall Delta G for the following reaction?
BLAH
A. +73.5 kJ/mol
B. -73.5 kJ/mol
C. +12.5 kJ/mol
D. -12.5 kJ/mol
E. Delta G cannot be calculated without Keq.

Back 11

D. -12.5 kJ/mol

Front 12

Which of the following compounds does not have a large negative
free energy of hydrolysis?
A. ADP
B. 3-phosphoglycerate
C. thioesters (e.g., acetyl-CoA)
D. 1,3-bisphosphoglycerate
E. phosphoenolpyruvate

Back 12

B. 3-phosphoglycerate

Front 13

The anaerobic conversion of 1 mol of glucose to 2 mol of
lactate by fermentation is accompanied by a net gain of:
A. 2 mol of ATP
B. 1 mol of NADH
C. 1 mol of ATP
D. 2 mol of NADH
E. None of the above

Back 13

A. 2 mol of ATP

Front 14

If glucose labeled with 14C in C-1 were fed to yeast carrying out ethanol fermentation, where would the 14C label be in the products?
A. In CO2 only
B. In C-2 of ethanol and CO2
C. in C-2 (methyl group) of ethanol only
D. In C-1 of ethanol only
E. in C-1 of ethanol and CO2.

Back 14

C. in C-2 (methyl group) of ethanol only

Front 15

The catalytic mechanism of phosphoglucoseisomerase involves which type of enzyme-linked (not covalent) intermediate?
A. tetrahedral intermediate
B. thiohemiacetal
C. trans-enediolate
D. cis-enediolate
E. Schi base

Back 15

D. cis-enediolate

Front 16

Which statement is true? The glyceraldehyde-3-P dehydrogenase
reaction
A. uses ATP as one of its substrates
B. is a highly exergonic reaction
C. is a highly regulated enzyme step in glycolysis
D. is inhibited by citrate
E. involves formation of a thiohemiacetal that is converted
to a thioester.

Back 16

E. involves formation of a thiohemiacetal that is converted

Front 17

The hydrolysis of phosphoenolpyruvate proceeds with a Delta G of about -62 kJ/mol. The greatest contributing factors to this reaction are the destabilization of the reactants by electrostatic
repulsion and stabilization of the product pyruvate
by:
A. polarization
B. electrostatic attraction
C. tautomerization
D. resonance
E. ionization

Back 17

C. tautomerization

Front 18

In liver, fructose metabolism is initiated with the formation
A. of fructose-6-P and then cleavage to glyceraldehyde-3-P
and dihydroxyacetone
B. of fructose-1-P and then formation of fructose-1,6-bis-P
C. of fructose-6-P and then conversion to glucose-6-P
which is metabolized
D. of fructose-6-P and then formation of fructose-1,6-bis-P.
E. of fructose-1-P and then cleavage to dihydroxyacetone-
P and glyceraldehyde

Back 18

E. of fructose-1-P and then cleavage to dihydroxyacetone-
P and glyceraldehyde

Front 19

Galactosemia is usually a genetic error of metabolism associated with:
A. excessive ingestion of glucose
B. inability to digest lactose
C. deficiency of galactokinase
D. deficiency of UDP-glucose:galactose-1-phosphate uridylyltransferase
E. deficiency of UDP-glucose

Back 19

D. deficiency of UDP-glucose:galactose-1-phosphate uridylyltransferase

Front 20

In the alcoholic fermentation of glucose by yeast, thiamine
pyrophosphate is a coenzyme required by
A. pyruvate decarboxylase
B. aldolase
C. lactate dehydrogenase
D. transaldolase
E. hexokinase

Back 20

A. pyruvate decarboxylase

Front 21

Which glycolytic enzyme has a phosphohistidine residue that
is important for its cataytic activity?
A. triose-P isomerase
B. phospho-hexoseisomerase
C. aldolase
D. phosphoglyceraldehyde dehydrogenase
E. phosphoglyceromutase

Back 21

E. phosphoglyceromutase

Front 22

In the list of enzymes below, three enzymes are essential and unique for gluconeogenesis. Starting with pyruvate as your
substrate, list those unique enzymes in the sequence of their conversion from pyruvate to glucose. Thus, the first unique
reaction of pyruvate in gluconeogenesis should be catalyzed by [enzyme #1], the next unique reaction needed for gluconeogenesis
should be catalyzed by [enzyme #2], and the
subsequent unique reaction catalyzed by a gluconeogenic enzyme should be listed for [enzyme #3].

A fructose-1,6-bisphosphatase
B phosphoglyceromutase
C phosphofructokinase 1
D glyceraldehyde-3-P dehydrogenase
E lactate dehydrogenase
F hexokinase
G PEP carboxykinase
H enolase
I phosphoglucoseisomerase
J pyruvate carboxylase
K None of the above

Enzyme #3
Enzyme #2
Enzyme #1

Back 22

Enzyme #3 - A. fructose-1,6-bisphosphatase
Enzyme #2 - G. PEP carboxykinase
Enzyme #1 - J. pyruvate carboxylase

Front 23

A metabolic pathway proceeds according ot the scheme R ->
S -> T -> U -> V -> W.
A regulatory enzyme X catalyzes the rst reaction in the
pathway. Which of the following is most likely correct for
this pathway?
A. Either metabolite U or V is likely to be a positive modulator,
increasing the activity of X.
B. The last product W is likely to be a positive modulator,
increasing the activity of X.
C. The last product W is likely to be a negative modulator
of X, leading to feedback inhibition.
D. The last reaction will be catalyzed by a second regulatory
enzyme.
E. The rst product S is probably the primary negative
modulator of X, leading to feedback inhibition.

Back 23

C. The last product W is likely to be a negative modulator of X, leading to feedback inhibition.

Front 24

Which of the following statements about enzymes is not true?
A. They affect the rate of the forward and backward rates
equally.
B. They may catalyze reactions by selectively binding to
the transition state.
C. They sometimes form covalent bonds with the substrate.
D. They alter the equilibrium constant for the reaction.

Back 24

D. They alter the equilibrium constant for the reaction.

Front 25

In a plot of 1/V against 1/[S] for an enzyme-catalyzed reaction, the presence of a competitive inhibitor will alter the
A. Vmax
B. intercept on the 1/V axis
C. pK of the plot
D. curvature of the plot
E. intercept on the 1/[S] axis

Back 25

E. intercept on the 1/[S] axis

Front 26

How many stereoisomers of the linear form of a ketoheptose
are possible (include both D and L forms)?
A. 32
B. 16
C. 4
D. 8

Back 26

D. 8

Front 27

You construct a Lineweaver-Burk plot (1/V0 vs. 1/[S]) for
an enzyme-catalyzed reaction. You use units of mol/L/min
for V0 and mM for [S]. In the absence of any inhibitors, the
plot gives a straight line with slope 3.0 and y-intercept 1.2.
In the presence of 5 M of a mixed inhibitor, a similar plot
gives a straight line with slope 4.5 and y-intercept 2.8. What
are Ki and Ki'?
A. Ki = 10.0 uM, Ki' = 7.2 uM
B. Ki = 10.0 uM, Ki' = 3.8 uM
C. Ki = 2.3 uM, Ki' = 9.5 uM
D. Ki = 1.8 uM, Ki' = 9.5 uM
E. Ki = 2.3 uM, Ki' = 3.8 uM
F. Ki = 1.8 uM, Ki' = 7.2 uM

Back 27

F. Ki = 1.8 uM, Ki' = 7.2 uM

Front 28

Duloxetine (Cymbalta), a recently introduced antidepressant,
is metabolized by the 1A2 and 2D6 isozymes of cytochrome
P450 to an inactive derivative that is rapidly excreted. Coadministration
of a drug that inhibits one or both of these
isozymes would pose a risk of
A. increasing plasma levels of duloxetine, raising the possibility
of toxicity
B. increasing the rate at which duloxetine is converted to
a toxic derivative
C. decreasing plasma levels of duloxetine, reducing its effectiveness
D. None of these possibilities would be a major concern.

Back 28

A. increasing plasma levels of duloxetine, raising the possibility of toxicity

Front 29

Consider the reduction of lipoic acid by NADH
Lipoic acid + NADH + H+ -> dihydrolipoic acid + NAD+
What is nDelta;G for the reaction as written?
A. +21.3 kJ/mol
B. -21.3 kJ/mol
C. -5.8 kJ/mol
D. +12.5 kJ/mol
E. -12.5 kJ/mol
F. +5.8 kJ/mol

Back 29

F. +5.8 kJ/mol

Front 30

In the RNase A reaction
A. a covalent bond is formed between the enzyme and substrate
B. a bound metal ion plays a key role in the reaction
C. the kinetics may be described by a "ping-pong" mechanism
D. histidine residues act as both general acid and general
base catalysts

Back 30

D. histidine residues act as both general acid and general
base catalysts

Front 31

Give the systematic name of the following disaccharide
A. Alpha-D-glucopyranosyl-(1->4)-beta-D-galactopyranose
B. Alpha-D-glucopyranosyl-(1->4)-beta-D-mannopyranose
C. beta-D-glucopyranosyl-(1->4)-beta-D-galactopyranose
D. beta-D-glucopyranosyl-(1->4)-beta-D-glucopyranose

Back 31

C. beta-D-glucopyranosyl-(1->4)-beta-D-galactopyranose

Front 32

In the binding equation sigma = [L]/([L] + Kd), the parameter sigma
represents
A. the degree of cooperativity of binding
B. the number of binding sites on each protein molecule
C. the fraction of binding sites occupied by ligand
D. the affinity of each site for ligand
E. None of the above

Back 32

C. the fraction of binding sites occupied by ligand

Front 33

Estimate Delta G' for the phosphorylation of glycerol by ATP to yield glcyerol-1-phophate and ADP.
A. -21.3 kJ/mol
B. -14.6 kJ/mol
C. +5.8 kJ/mol
D. +30.5 kJ/mol

Back 33

A. -21.3 kJ/mol

Front 34

The rate of a chemical reaction step is determined by
A. the value of the equilibrium constant
B. the detailed pathway from the transition state to the
products
C. the free energy dierence between reactants and the
transition state
D. the free energy dierence between reactants and the
products

Back 34

C. +5.8 kJ/mol

Front 35

For an enzyme-catalyzed reaction, initial velocity is plotted against substrate concentration. The limiting slope of the plot as [S] -> 0 is
A. Vmax
B. kcat
C. Km
D. Vmax/Km
E. k-1/k1

Back 35

D. Vmax/Km

Front 36

In writing a balanced redox reaction for the conversion of one mole of isocitrate to one mole of succinate plus two moles of carbon dioxide
A. one molecule of NAD+ is converted to NADH
B. two molecules of NAD+ are converted to NADH
C. two molecules of NADH are converted to NAD+
D. three molecules of NADH are converted to NAD+
E. one molecule of NADH is converted to NAD+
F. no interconversion of NADH and NAD+ is necessary
G. three molecules of NAD+ are converted to NADH

Back 36

E. one molecule of NADH is converted to NAD+

Front 37

For an enzyme-catalyzed reaction, Vmax = 5.0 mmol/L/min and Km=10 mM. At what substrate concentration will V0=1.0 mmol/L/min?
A. 1.0 mM
B. 15.0 mM
C. 2.5 mM
D. 8.0 mM
E. 5.0 mM

The difference between the T and R states of hemoglobin is
A. the affinity of binding sites for O2
B. the relative positioning of the subunits
C. the tertiary structure of each subunit int he vicinity of the heme group
D. all of the above
E. none of the above

Back 37

C. the tertiary structure of each subunit int he vicinity of the heme group

Front 38

D-glucose cyclizes to the D-glucopyranose form via
A. the formation of a hemiacetal bond between carbons 5
and 1
B. the formation of a hemiketal bond between carbons 5 and 2
C. the formation of a hemiketal bond between carbons 5 and 1
D. the formation of a hemiacetal bond between carbons 6 and 1

Back 38

D. the formation of a hemiacetal bond between carbons 6 and 1

Front 39

Acetyl-coenzyme A, a thioester, has a higher free energy of hydrolysis than the corresponding oxygen ester because of
A. an enol-keto tautomerization in the coenzyme A product
B. resonance stabilization in the intact oxygen ester
C. resonance stabilization in the acetic acid product
D. resonance stabilization in the free coenzyme A product

Back 39

A. an enol-keto tautomerization in the coenzyme A product

Front 40

Which of the following statements about allosteric control of enzymatic activity is false?
A. Binding of the effector changes the conformation of the enzyme molecule.
B. Heterotropic allosteric effectors compete with substrate
for binding sites.
C. Allosteric proteins are generally composed of several
subunits.
D. allosteric eectors give rise to sigmoidal V0 vs. [S] kinetic
plots.
E. An effector may either inhibit or activate an enzyme.

Back 40

B. Heterotropic allosteric effectors compete with substrate for binding sites.

Front 41

The organic substrate of a cytochrome P450 enzyme
A. Is a target for general acid and/or general base catalysis
by enzyme amino-acid side chains
B. is chemically unchanged throughout most of the P450
reaction cycle steps
C. is converted to a free radical form immediately upon
binding to enzyme
D. forms a covalent bond with the enzyme

Back 41

A. Is a target for general acid and/or general base catalysis by enzyme amino-acid side chains

Front 42

The role of serine 195 in the chymotrypsin mechanism is
A. to alter the pKa of histidine 57
B. to form a covalent bond with the peptide substrate
C. to determine the substrate specicity of the enzyme
D. to form a hydrogen bond with the negative charge localized
on the carbonyk oxygen, thereby lowering the
free energy of the transition state

Back 42

B. to form a covalent bond with the peptide substrate

Front 43

An uncompetitive inhibitor I is defined as one for which
A. I can bind to ES to form ESI but cannot bind to E to
form EI
B. I can bind to E to form EI but cannot bind to ES to
form ESI
C. Both complexes ESI and EI are signicant
D. A permanent complex between I and the enzyme forms
E. I can interact directly with substrate in the absence of enzyme

Back 43

A. I can bind to ES to form ESI but cannot bind to E to
form EI

Front 44

A mechanism-based enzyme inhibitor:
A. undergoes the initial steps of catalysis before combining irreversibly with the enzyme
B. binds reversibly to the enzyme-substrate complex only
C. controls enzyme activity by binding at a site distant
from the active site
D. has a relatively high Ki

Back 44

A. undergoes the initial steps of catalysis before combining irreversibly with the enzyme

Front 45

The concerted MWC model of allosteric binding
A. applies only to proteins with an even number of binding
sites
B. considers the T-R transition as an "all-or-none" phenomenon
C. predicts a value of the Hill coecient equal to the number
of binding sites
D. neglects states in which T subunits bind O2 or R subunits
do not bind O2
E. all of the above
F. none of the above

Back 45

B. considers the T-R transition as an "all-or-none" phenomenon

Front 46

For the reaction
succinate + FAD -> fumarate + FADH2
what is Delta E' if [succinate]=5 mM, [fumarate]=2 mM,
[FADH2]=1.5 mM and [FAD]=6 mM?
A. -220 mV
B. -105 mV
C. -488 mV
D. -182 mV
E. -244 mV

Back 46

E. -244 mV

Front 47

For enzymes in which the slowest (rate-limiting) step is the reaction
ES -> P
Km becomes equivalent to
A. the dissociation constant Kd for the ES complex
B. the turnover number
C. the [S] where V0=Vmax
D. the maximum velocity

Back 47

A. the dissociation constant Kd for the ES complex

Front 48

If D-glucose is oxidized to a carboxylic acid at C-1 (the aldehyde carbon), the product is
A. N-acetylneuraminic acid
B. D-glucuronic acid
C. locked into the cyclic form
D. D-gluconic acid
E. explosive

Back 48

D. D-gluconic acid

Front 49

For some DNA or RNA polymerases, Mg2+ ions bound at the active site play a key role in the reaction mechanism. These
ions are referred to as
A. coenzymes, but not cofactors
B. cofactors, but not coenzymes
C. prosthetic groups
D. cosubstrates, but not coenzymes

Back 49

A. coenzymes, but not cofactors

Front 50

An amino-acid residue acting as a general base will often have a pKa similar to the ambient pH. Why?
A. to maximize te free energy released upon proton abstraction
B. to form as strong a hydrogen bond with substrate as possible
C. As a compromise between the greatest strength of the
base and the greatest fractional population of the basic form
D. to bind the reaction's transition state as selectively as possible

Back 50

C. As a compromise between the greatest strength of the
base and the greatest fractional population of the basic form

Front 51

The Delta G' for a reaction when reactants C and D and products A and B are at equilibrium is equal to
A. -RT ln Keq
B. zero
C. the sum of the nDelta;G' values for two component reactions
D. RT ln ([C][D]/[A][B])
E. none of the above

Back 51

A. -RT ln Keq

Front 52

Which of the following is a non-reducing sugar?
A. maltose
B. glucose
C. sucrose
D. fructose

Back 52

D. fructose

Front 53

Under what circumstances is the turnover number kcat equal
to Vmax/[Et]?
A. if the Michaelis-Menten kinetic scheme accurately describes the situation
B. always
C. if k-1 >> k2
D. if [S] << Km
E. under steady-state conditions
F. never

Back 53

A. if the Michaelis-Menten kinetic scheme accurately describes the situation

Front 54

Which of the following statements about the cytochrome P450 enzymes is not true?
A. They use molecular oxygen as a reactant.
B. Humans have several dozen different P450 enzymes expresed in their tissues.
C. Inhibition or activation of particular P450 enzymes is a major mechanism of drug-drug interactions.
D. Each P450 enzyme is extremely specific for a particular substrate molecule.

Back 54

D. Each P450 enzyme is extremely specific for a particular substrate molecule

Front 55

In the chymotrypsin-catalyzed hydrolysis of a p-nitrophenyl
ester, a rapid "burst phase" of product release corresponding to approximately one product molecule per enzyme molecule
was observed, followed by a slowdown to the steady-state
rate. This observation is taken as evidence for:
A. the critical role of a particular serine residue in catalysis
B. the use of general acid-general base catalysis by the
enzyme
C. a mechanism with a rapid step involving acylation of
the enzyme, followed by a slower hydrolysis of the acylenzyme intermediate
D. preferential stabilization of a transition state resembling the short-lived tetrahedral intermediate

Back 55

C. a mechanism with a rapid step involving acylation of
the enzyme, followed by a slower hydrolysis of the acylenzyme intermediate

Front 56

At a concentration very much higher than Km, an enzyme's
initial velocity will be approximately equal to
A. kcat*[S]
B. (Vmax/Km)*[S]
C. Vmax/2
D. Vmax

Back 56

D. Vmax

Front 57

The turnover number Kcat
A. is the number of substrate molecules converted to product
by one molecule of enzyme per time at saturation
B. is numerically equal to the rate constant k2 for an enzyme
following the simple Michaelis-Menten scheme
C. has units of 1/time
D. is dened as Vmax/[Et]
E. All of the above
F. None of the above

Back 57

E. All of the above

Front 58

The presence of an uncompetitive inhibitor will affect the apparent values of which kinetic constants relative to the uninhibited
case?
A. both Vmax and Km, but not the ratio Vmax/Km
B. neither Vmax nor Km
C. Km but not Vmax
D. Vmax, Km and the ratio Vmax/Km (all three)
E. Vmax but not Km

Back 58

A. both Vmax and Km, but not the ratio Vmax/Km

Front 59

An enzyme has an uninhibited Vmax of 2.3 mM/sec and a
Km of 0.15 mM. The reaction is studied in the presence of
0.5 mM of a competitive inhibitor with Ki=0.3 mM. What
apparent value of Km will be observed?
A. 0.25 mM
B. 0.4 mM
C. 0.15 mM
D. 0.075 mM

Back 59

D. 0.075 mM

Front 60

The kinetic hallmark of an allosteric enzyme is
A. an increase in the apparent Km relative to the noncooperative
case
B. a sigmoid rather than a hyperbolic shape to the V0 vs.
[S] plot
C. the initial rate continues to increase with increasing [S], rather than leveling out at Vmax
D. all of the above
E. none of the above

Back 60

D. all of the above

Front 61

The addition of a covalently linked phosphate group to an
enzyme, thereby decreasing its activity, is an example of
A. competitive inhibition
B. feedback inhibition
C. homotropic allosteric inhibition
D. all of the above

Back 61

A. competitive inhibition

Front 62

When two carbohydrates are epimers:
A. one is a pyranose, the other a furanose.
B. they differ only in the configuration around one carbon atom.
C. one is an aldose, the other a ketose.
D. they rotate plane-polarized light in the same direction.
E. they differ in length by one carbon.

Back 62

A. one is a pyranose, the other a furanose.

Front 63

Which of the following is an anomeric pair?
A. D-glucose and D-fructose
B. Alpha-D-glucose and Alpha-L-glucose
C. D-glucose and L-glucose
D. Alpha-D-glucose and Beta-D-glucose
E. D-glucose and L-fructose

Back 63

D. Alpha-D-glucose and Beta-D-glucose

Front 64

When the linear form of glucose cyclizes, the product is a(n)
A. hemiacetal
B. lactone
C. glycoside
D. oligosaccharide
E. anhydride

Back 64

A. hemiacetal

Front 65

D-Glucose is called a reducing sugar because it undergoes an oxidation-reaction at the anomeric carbon. One of the
products of this reaction is:
A. D-glucuronate
B. muramic acid
C. D-galactose
D. D-ribose
E. D-gluconate

Back 65

E. D-gluconate

Front 66

From the abbreviated name of the compound Gal(Beta-1-4)Glc,
we know that
A. C-4 of glucose is joined to C-1 of galactose by a glycosidic bond
B. the compound is a D-enantiomer
C. the glucose is the Beta anomer
D. the galactose residue is at the reducing end
E. the glucose is in its pyranose form

Back 66

A. C-4 of glucose is joined to C-1 of galactose by a glycosidic bond

Front 67

Which of the following statements about starch and glycogen is false?
A. Amylose is unbranched; amylopectin and glycogen contain
(Alpha- 1-6) branches.
B. Glycogen is more extensively branched than starch.
C. Both are homopolymers of glucose.
D. Both starch and glycogen are stored intracellularly as
insoluble granules.
E. Both serve primarily as structural elements in cell walls

Back 67

E. Both serve primarily as structural elements in cell walls

Front 68

When a mixture of 3-phosphoglycerate and 2-
phosphoglycerate is incubated at 25 C with the enzyme
phosphoglycerate mutase until equilibrium is reached, the
final mixture contains six times as much 2-phosphoglycerate
as 3-phosphoglycerate. Which of the following statements is
most nearly correct, when applied to the reaction as written?
(R=8.315 J/K/mol; T = 298 K)
A. Delta G is incalculably large and positive.
B. Delta G = -4.44 kJ/mol.
C. Delta G cannot be determined from the information given.
D. Delta G is zero.
E. Delta G = +12.7 kJ/mol.

Back 68

B. Delta G = -4.44 kJ/mol.

Front 69

During glycolysis, glucose-1-phosphate is converted to
fructose-6-phosphate in two successive reactions: Delta G for the overall reaction is
A. -8.8 kJ/mol
B. -5.4 kJ/mol
C. +5.4 kJ/mol
D. 8.8 kJ/mol
E. -7.1 kJ/mol

Back 69

B. -5.4 kJ/mol

Front 70

The hydrolysis of phosphoenolpyruvate proceeds with a Delta G of about -62 kJ/mol. The greatest contributing factors to this reaction are the destabilization of the reactants by electrostatic
repulsion and stabilization of the product pyruvate
by:
A. resonance
B. electrostatic attraction
C. polarization
D. tautomerization
E. ionization

Back 70

D. tautomerization

Front 71

If glucose labeled with 14C in C-1 were fed to yeast carrying out ethanol fermentation, where would the 14C label be in the products?
A. In C-2 of ethanol and CO2
B. In C-1 of ethanol only
C. In CO2 only
D. in C-1 of ethanol and CO2.
E. in C-2 (methyl group) of ethanol only

Back 71

E. in C-2 (methyl group) of ethanol only

Front 72

The conversion of 1 mol of fructose-1,6-bisphosphate to 2 mol of pyruvate by the glyclytic pathway results in a net formation of
A. 2 mol of NAD+ and 4 mol of ATP
B. 2 mol of NADH and 4 mol of ATP
C. 1 mol of NAD+ and 2 mol of ATP
D. 2 mol of NADH and 2 mol of ATP
E. 1 mol of NADH and 1 mol of ATP

Back 72

B. 2 mol of NADH and 4 mol of ATP

Front 73

In an anaerobic muscle preparation, lactate formed from glucose labeled in C-3 and C-4 would be labeled in
A. only the carboxyl carbon atom
B. the methyl and carboxyl carbon atoms
C. only the methyl carbon atom
D. only the carbon atom carrying the OH
E. all three carbon atoms

Back 73

A. only the carboxyl carbon atom

Front 74

When a mixture of glucose-6-phosphate and fructose-6-
phosphate is incubated with the enzyme phosphohexoseisomerase
(which catalyzes the interconversion of these two
compounds) until equilibrium is reached, the nal mixture
contains twice as much glucose-6-phosphate as fructose-6- phosphate. Which one of the following statements is most
nearly correct, when applied to the reaction below? (R=8.315 J/K/mol; T = 298 K)
A. Delta G is incalculably large and negative.
B. Delta G is incalculably large and positive.
C. Delta G is zero.
D. Delta G = +1.72 kJ/mol.
E. Delta G = -1.72 kJ/mol.

Back 74

D. Delta G = +1.72 kJ/mol

Front 75

In an anaerobic muscle preparation, lactate formed from glucose labeled in C-2 would be labeled in
A. only the carboxyl carbon atom
B. only the methyl carbon atom
C. all three carbon atoms
D. the methyl and carboxyl carbon atoms
E. only the carbon atom carrying the OH

Back 75

E. only the carbon atom carrying the OH

Front 76

The steps of glycolysis between glyceraldehyde-3-phosphate and 3-phosphoglycerate involve all of the following except
A. utilization of Pi
B. ATP synthesis
C. oxidation of NADH to NAD+
D. formation of 1,3-bisphosphoglycerate
E. catalysis by phosphoglycerate kinase

Back 76

C. oxidation of NADH to NAD+

Front 77

Galactosemia is usually a genetic error of metabolism associated with:
A. inability to digest lactose
B. defficiency of UDP-glucose:galactose-1-phosphate uridylyltransferase
C. defficiency of UDP-glucose
D. defficiency of galactokinase
E. excessive ingestion of glucose

Back 77

B. defficiency of UDP-glucose:galactose-1-phosphate uridylyltransferase

Front 78

In the alcoholic fermentation of glucose by yeast, thiamine
pyrophosphate is a coenzyme required by
A. pyruvate decarboxylase
B. hexokinase
C. aldolase
D. lactate dehydrogenase
E. transaldolase

Back 78

A. pyruvate decarboxylase

Front 79

In liver, fructose metabolism is initiated with the formation
A. of fructose-1-P and then cleavage to dihydroxyacetone-
P and glyceraldehyde
B. of fructose-6-P and then cleavage to glyceraldehyde-3-P
and dihydroxyacetone
C. of fructose-1-P and then formation of fructose-1,6-bis-P
D. of fructose-6-P and then conversion to glucose-6-P
which is metabolized
E. of fructose-6-P and then formation of fructose-1,6-bis-P.

Back 79

A. of fructose-1-P and then cleavage to dihydroxyacetone-
P and glyceraldehyde

Front 80

The label of C-1 of 3-phosphoglyceraldehyde is
A. converted to C-3 of dihydroxyacetone-P
B. randomized to C-1 and C-6 of fructose-1,6-bis-P upon
its reaction with triose-P isomerase and aldolase
C. randomized to C-2 of dihydroxyacetone-P
D. randomized to C-3 and C-4 of fructose-1,6-bis-P upon
its reaction with triose-P isomerase and aldolase
E. lost as CO2 during its conversion to pyruvate

Back 80

D. randomized to C-3 and C-4 of fructose-1,6-bis-P upon
its reaction with triose-P isomerase and aldolase

Front 81

In the list of enzymes below, three enzymes are essential and unique for gluconeogenesis. Starting with pyruvate as your
substrate, list those unique enzymes in the sequence of their conversion from pyruvate to glucose. Thus, the first unique
reaction of pyruvate in gluconeogenesis should be catalyzed by [enzyme #1], the next unique reaction needed for gluconeogenesis
should be catalyzed by [enzyme #2], and the
subsequent unique reaction catalyzed by a gluconeogenic enzyme should be listed for [enzyme #3].
A glyceraldehyde-3-P dehydrogenase
B phosphoglucoseisomerase
C phosphofructokinase 1
D enolase
E hexokinase
F lactate dehydrogenase
G fructose-1,6-bisphosphatase
H PEP carboxykinase
I pyruvate carboxylase
J phosphoglyceromutase
K None of the above
Enzyme #3
Enzyme #1
Enzyme #2

Back 81

Enzyme #3 - G fructose-1,6-bisphosphatase

Enzyme #1 - I pyruvate carboxylase

Enzyme #2 - H PEP carboxykinase