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MCMP 208 Exam II key - 1
Examination II Key
MCMP 208 – Biochemistry for Pharmaceutical Sciences I
March 9, 2015
Correct answers in multiple choice questions are indicated in RED and underlined.
Correct answers to essay questions are indicated in RED in comic book font.
In some cases and explanation is provided in BLUE/BLUE
MULTIPLE CHOICE. For problems 1 to 21, select from the list immediately following each question the
single most correct choice to complete the statement, solve the problem, or answer the question. Mark that
answer on your answer sheet. [3 points each]
1. Which monosaccharide is nutritionally significant as a component of milk sugar?
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fructose
lactose This is milk sugar, a disaccharide consisting of galactose and glucose
ribose
mannose
maltose
galactose
fucose
2. The sub-structure that involves the bond that holds D-ribose in a cyclic structure is called
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a ketal
an acetal The question is about D-ribose, not a ribose residue within a nucleotide
a hemiketal
a hemiacetal D-ribose is and aldose, so the furanose form involves a hemiacetal
a lactone
an ester
a thioester
an acid anhydride
3. The only structural difference between cellobiose and maltose is
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One contains D-glucose and the other contains L-glucose
One contains only D-glucose and the other contains D-glucose and D-fructose
One contains only D-glucose and the other contains D-glucose and D-galactose
One contains only D-glucose and the other contains only D-galactose
The linkage in one is α1,4 and in the other is α1,6
The linkage in one is α1,4 and in the other is β1,4 Both are disaccharides containing only glucose
The linkage in one is α1,6 and in the other is β1,4
The linkage in one is α1,6 and in the other is β1,6
MCMP 208 Exam II key - 2
4. The properties of glycosaminoglycans that are physiologically important result primarily from the fact
that glycosaminoglycans are
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branched
linear
anionic
cationic
branched and anionic
branched and cationic
linear and anionic These result in a long molecule with a large hydration volume.
linear and cationic
5. One of the two ways in which glycans are covalently linked to proteins is via an
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N-glycosidic bond to the side chain of lysine
N-glycosidic bond to the side chain of arginine
N-glycosidic bond to the amino terminus
N-glycosidic bond to the side chain of asparagine The other way is O-glycosides at serine
O-glycosidic bond to the side chain of tyrosine
O-glycosidic bond to the side chain of aspartate
6. The mechanism of the reaction catalyzed by phosphoglycerate mutase involves
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ene-diol intermediate bound to the enzyme
a phospho-enzyme state
a Schiff base with the side chain of a lysyl residue in the enzyme
instability of a beta-keto carboxylate
a small electron transport chain leading to reduction of NAD+
removal or addition of water to/from an olefin bond
hydrolysis of a phosphate ester
7. The primary allosteric regulator of glycolysis in the liver is
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glucose-6-phosphate
fructose-6-phpsphate
fructose-1,6-bisphosphate
fructose-2,6-bisphosphate
fructose-1-phosphate
glucose-1-phosphate
PEP
DHAP
pyruvate
8. Many different metabolites can be used to metabolically synthesize “new” glucose. The two groups of
metabolites from which the vast majority of “new” glucose is synthesized are
 fatty acids (from lipids) and other carbohydrates
 amino acids and other carbohydrates Fatty acids cannot be made into glucose and glycerol is minor
 fatty acids (from lipids) and glycerol (from triacylglycerols)
 fatty acids (from lipids) and amino acids
 amino acids and glycerol (from triacylglycerols)
MCMP 208 Exam II key - 3
9. The unique role of the oxidative phase of the pentose phosphate pathway is
 generation of NADH
 generation of ATP
 generation of ribose-5-phosphate This involves the non-oxidative part of the PPP and does not
actually require the oxidative part of the PPP
 generation of NADPH
 complete oxidation of glucose to carbon dioxide This requires the non-oxidative part of the PPP
10. If phosphofructokinase-1 and its opposing phosphatase are both active in the same cell at the same time,
this produces what is sometimes called a
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tightly regulated system
feedback control
nonsense control
somatic cell mutation
oxidative stress
futile cycle
respiratory control
11. The Cori cycle involves the cyclic interconversion of what two molecules?
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alanine and pyruvate
alanine and glucose
pyruvate and glucose
lactate and glucose
pyruvate and lactate
glycogen and glucose
lactate and glycogen
alanine and glycogen
pyruvate and glycogen
12. Concerning the two transferase enzymes in the pentose-phosphate pathway, which one of the following is
a valid description of the common aspects of the actions of these two enzymes?
 They shorten a phosphoaldose and simultaneously lengthen a phosphoketose The opposite is true
 They interconvert a phosphoketose into/from two shorter carbohydrates They never split 1 to form 2
 They interconvert a bis-phosphoketose into/from two shorter carbohydrates They never split 1 to
form 2
 They interconvert a phosphoaldose into/from two shorter carbohydrates They never split 1 to form 2
 They shorten a phosphoketose and simultaneously lengthen a phosphoaldose
 They always shorten the carbon chain length of phosphosugar molecules Some products are
lengthened
 They transfer carbons and a phosphate from one phosphosugar to another Phosphate is never
transferred
MCMP 208 Exam II key - 4
13. The enzyme that catalyzes the metabolic interconversion of galactose and glucose utilizes
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an ene-diol intermediate
the 6-phospho forms of galactose and glucose and an ene-dio intermediate
the 1-uridine diphosphoryl forms of galactose and glucose
the 4-uridine diphosphoryl forms of galactose and glucose
a phospho-enzyme mechanism
14. Muscle creates quite a lot of glycogen. Why does it do this?
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To help with blood glucose homeostasis during fasting Impossible in muscle
To utilize for bursts of anaerobic glycolysis
To supply the red blood cells and brain with glucose when needed Impossible in muscle
To use for its own ATP production during fasting Muscle mostly catabolizes fatty acids for ATP
It has to do something with glucose that it absorbs from the blood in the well-fed state While muscle
does absorb glucose to make glycogen when it is needed, this is not the primary reason why it makes
glycogen, and indeed, it would absorb less glucose in the well-fed state if it did not make glycogen.
15. Which one of the following is NOT a true DIFFERENCE between redox coenzymes containing
nicotinamide versus those containing flavin?
 Only flavins can participate in one electron reactions.
 Only flavins can function as a mononucleotide as well as a dinucleotide.
 Only nicotinamide coenzymes require a vitamin for their biosynthesis. Both can be made only from
vitamins
 Only flavin coenzymes can carry both of the protons associated with a reducing equivalent.
 Only flavin coenzymes are prosthetic groups.
 All of the above are true differences.
16. The reason why the addition of acetyl-CoA into the citric acid cycle is not reversible in cells is due to
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loss of carbon dioxide
the high ratio of NAD+ to NADH
the low concentration of coenzyme A
the hydrolysis of pyrophosphate
the hydrolysis of the thioester bond
the high concentration of pyruvate
the high concentration of oxaloacetate
the highly favorable energetics of the aldol condensation used in this reaction
17. A cytochrome is
 the same thing as heme
 any protein that participates in an oxidoreductase reaction
 any protein that participates in an oxidoreductase reaction but does not contain a flavin coenzyme
 any protein that participates in an oxidase reaction and also contains heme
 any molecule found in cells that is colored (in the visible light sepectrum)
 any protein that contains iron in any form
 any protein that participates in an oxidoreductase reaction and also contains iron in any form
 any protein that participates in an oxidoreductase reaction and also contains copper or zinc
 any protein that participates in an oxidoreductase reaction and also contains Mn2+ or Mg2+
 all of the proteins involved in mitochondrial electron transport
MCMP 208 Exam II key - 5
18. The chemiosmotic hypothesis postulated that utilization of electron transport for generation of ATP by
mitochondria requires
 a high energy phosphate intermediate This was never found and that fact was part the reason why this
hypothesis was made
 a chemical gradient as an intermediate
 a direct use of electron movement for ATP synthesis
 a battery-like set of reactions with oxidation on the inside and reduction on the outside
 an intermediate involving ADP that is transferred onto phosphate to generate ATP
19. The mitochondrial ATPase is considered to be a molecular motor because it
 rotates a large part of its structure while accomplishing real work in the physical sense Physical sense
of real work is to make a mass move (somewhat simplistically, but this will serve our purposes here).
 uses electricity like an electrical motor
 uses oxidation to drive its motion, as also happens with internal combustion motors
 the reaction it catalyzes in the mitochondria causes a rotation-like motion of some of its subunits
 uses electron transport through an unknown mechanism to produce ATP
20. Reactive oxygen species (ROS) are generated in cells
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always as the intended product of metabolic enzyme-catalyzed reactions Occasionally, but not always
mostly as a result of O2 being reduced in a chemical (non-enzyme catalyzed) reaction
by reactions of O2 with free-radical reactive molecules, e.g., alpha-tocopherol and ascorbic acid
generally by reactions utilizing the side-chain of lysyl residues in proteins
by reactions between O2 and reactive nitrogen species
21. Which one of the following statements about oxidative stress is NOT TRUE?
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Oxidative stress is theorized to be the major cause of aging.
Oxidative stress results in somatic cell mutations.
Oxidative stress results in damage to membrane lipids, proteins, and nucleic acids.
Oxidative stress cannot be avoided by human cells.
Cells have no mechanisms of dealing with ROS, so generation of ROS in cells always causes
oxidative stress. Cells do have coping mechanisms which deal with ROS or their consequences.
 Oxidative stress causes the increased expression of certain genes in cells.
 All of the above are true.
MCMP 208 Exam II key - 6
ESSAY PROBLEMS. Write your answers to problems 22 to 27 in the space immediately below each
problem.
22. [7 points] Structure drawing.
a. [2 points] Draw the conventional (anomeric carbon to the right, ring oxygen to the rear) Haworth
projection showing the structure of α-D-fructofuranose. All atoms other than hydrogens bound to
carbon MUST be explicitly indicated. Hydrogens bound to carbon MAY be explicitly indicated or
omitted.
b. [2 points] Draw the conventional (anomeric carbon to the right, ring oxygen to the rear) Haworth
projection showing the structure of β-D-glucopyranose. All atoms other than hydrogens bound to
carbon MUST be explicitly indicated. Hydrogens bound to carbon MAY be explicitly indicated or
omitted.
c. [3 points] In the space above, adjacent to your answer to part b, draw the structure of D-glucose that
must occur during the process of mutorotation leaving all the carbons in the same arrangement as
they are in the Haworth projection you drew for part b. On the structure you draw for part c, draw a
curved arrow around the bond that rotates during the mutorotation.
23. [6 points] If one has the ability to trace carbon 1 of glucose during glycolysis, for instance, with
radiocarbon labeling of carbon 1, which carbon in the product of glycolysis would be derived from
carbon 1 of glucose? You must unambiguously describe the product and the location of this carbon AND
explain how you reach this conclusion.
There are several ways to answer this, including the explanation. Any of the following or
similar are correct:
Answer: The product may be named (pyruvate or lactate) or the structure drawn. The
carbon may be indicated as carbon 3, the β carbon, the methyl, or it may be indicated (i.e.,
circled) in a drawn structure.
Some correct and adequate explanations:
Carbon 1 is phosphorylated and becomes carbon 1 of fructose by the end of the splitting
stage. After the splitting stage, the two phosphorylated carbons become carbon 3 of 3phosphoglyceraldehyde. During the final stage the aldehyde becomes a carboxylate, and
MCMP 208 Exam II key - 7
the other end of the molecule loses its phosphate and its alcohol during the formation of
PEP, resulting in a methyl group that persists in the final product.
OR
Carbons 3 and 4 in glucose become aldehydes during the splitting stage, and these become
oxidized during the energy extraction stage to a carboxylate. The carbons at the other
end of the resulting trioses, carbons 1 and 6 originally in glucose, become carbon 3 (or the
beta carbon) in glycerate that persists throughout the rest of the pathway to the final
product.
OR
(Full tracing through each intermediate) Carbon 1 of glucose becomes carbon 1 of G6P,
then of F6P, then of F1,6-bisP. When F1,6-bisP is split, carbon 1 becomes the
phosphorylated carbon in DHAP, which becomes carbon 3 (the phosphorylated carbon) in
3-phosphoglycerate, and also carbon 3 in 2-phosphoglycerate, and in PEP, and in pyruvate
(and lactate, if that is the product indicated).
24. [6 points] Glucose-6-phosphate is metabolized in four different carbohydrate metabolism pathways in the
liver. This means that there are 4 different enzymes that use Glucose-6-phosphate as a substrate in the
liver. For EACH of these 4 enzymes, indicate the name of the enzyme, the name of the product made by
this enzyme (from glucose-6-phosphate) and the name of the pathway that utilizes this enzyme to convert
glucose-6-phosphate into a product.
Enzyme: Glucose-6-phosphate isomerase
Pathway: Glycolysis
Product: Fructose-6-phosphate
Enzyme: Glucose-6-phosphatase
Pathway: Gluconeogenesis
Product: Glucose
Enzyme: Phosphoglucose mutase (aka phosphoglucomutase)
Pathway: Glycogenesis
Product: Glucose-1-phosphate
Enzyme: Glucose-6-phosphate dehydrogenase
Pathway: Pentose Phosphate Pathway
Product: 6-phosphoglucono-5-lactone (or delta lactone)
25. [6 points] Explain why, for nearly all of the glucose residues stored in glycogen in a cell, that there is one
additional ATP generated in a net fashion from glycolysis of these glucose residues compared to the
amount of net ATP generated by glycolysis of blood glucose.
Because of its highly branched structure, glycogen contains about 90% α1,4 linkages and
10% α1,6 linkages between glucoses. All of the α1,4 linkages are broken by phosphorolysis
which releases those glucoses with an α1,4 linkage (about 90% of the total glucose
released) as glucose-1-phosphate. Glucose-1-phosphate is converted without use of ATP
into Glucose-6-phosphate, which can enter glycolysis directly. Thus 90% of the glucose in
MCMP 208 Exam II key - 8
glycogen is released in a form which enters glycolysis as Glucose-6-phosphate, and
because of this it skips the first priming step catalyzed by hexokinase. Since hexokinase
uses on 1 ATP per glucose, only one ATP must be spent in priming glucose-6-phosphate (by
PFK-1). Since 4 ATPs are produced in the energy extraction stage, and only one is spent in
priming, then there is a net of 3 ATP produced, versus 2 net ATP produced from blood
glucose (which requires the hexokinase step).
26. [6 points] Enzymes are always named for one of their substrates or products. In the citric acid cycle there
is one metabolite that does not have its name as part of the name of any of the citric acid cycle enzymes.
Instead there is one enzyme with a name that does not include the name of any of the metabolites in the
citric acid cycle. What is the name of this enzyme? What reaction does it catalyze (use molecule names
and/or structures to indicate the reaction)? Why does this enzyme have this name?
Aconitase catalyzes the following reaction:
Citrate  [cis-aconitate] + water  iso-citrate
(structures may be used instead of any of the metabolite names)
This enzyme is named for the enzyme bound intermediate, cis-aconitate, which is the
product of the first reaction step and the substrate for the second reaction step. But
cis-aconitate is not considered metabolic intermediate of the cyclic part of the pathway
because it is not released from the enzyme.
27. [6 points] In mitochondrial electron transport, there are four proteins or protein complexes that reduce
coenzyme Q. (a) Identify these four, either indicating their name or providing a description that clearly
and uniquely identifies it. (b) Which of these pumps protons?
(a)
(b)
Complex I aka NADH Dehydrogenase
Complex II aka Succinate dehydrogenase
α-glycerol phosphate dehydrogenase
fatty acid dehydrogenase aka fatty acyl CoA dehydrogenase
Any of these may alternatively be indicated by describing the reaction that they
catalyze. In the case of FA-CoA DH, the reaction is to oxidize a C-C (single bond)
to an olefin (alkene) bond (C=C).
Only complex I pumps protons.