Exam #1
BMB 514 – Medical Biochemistry
9/16/11
STEP 1 - NAME (Print clearly) _________________ ____________________________
(last)
(first)
Circle your college and campus:
301 --- CHM-EL
302 --- CHM-GR
303 --- COM-EL
304 --- COM-DMC
305 --- COM-MUC
STEP 2 – Fill in your answer sheet with a #2 scoring pencil, as follows:
 Print your first and last name on the line provided
 Code in your Student Number (PID)
 Code in your section as corresponds to the above list
 Code in the correct FORM ..... This
is Form A
 Sign your name in the signature box. By signing the answer sheet for this exam, the student certifies
that he/she has adhered to the policies of academic honesty in the performance of this exam.
STEP 3 - Read these instructions:
 Page 2 of this exam contains information that may be useful to you: (a) abbreviations for the
amino acids; (b) pKa values of functional groups; and (c) table of logarithms.
 A simple calculator is supplied for your use during this exam. No other electronic or
computational devices are to be used. Turn off cell phones; keep them out of sight.
 The proctors have the authority/responsibility to assign any student a different seat at any
time, without implication and without explanation, before or during the examination, as they
deem necessary. Accomplish any relocation quietly and without discussion.
 Make sure your exam has 32 questions.
 We will not answer questions of clarification. However, if you think there is an error on your
exam, summon an exam proctor.
 Read each question very carefully. Choose the single, best answer and mark this answer
on your answer sheet. No points will be added for correct answers which appear on the
exam page but not on the answer sheet.
 When you finish, carefully follow the instructions at the end of the exam. When you leave
the exam room, please turn in your answer sheet AND your exam to the proctors standing
by the doors INSIDE the auditorium. Once you exit the auditorium, please leave the
building. Hallway conversations disturb those still taking the exam.
 There will be answer keys to this exam posted on the course website by 5:00 p.m. the day of the exam.
You may wish to copy your responses from your answer sheet onto the answer grid on the LAST page
of this exam so that you can check your results. You can tear off the last page and take it with you.
 You have 70 minutes to complete this exam. No additional time will be allowed for transfer of answers
from the exam to the answer sheet. We will close the exam promptly at 9:10 a.m. Once we withdraw
the boxes for the answer sheets from the doors, no additional answer sheets will be accepted.
STEP 4 – Wait until instructed to proceed with the exam!
INFORMATION THAT MAY BE USEFUL FOR THE EXAM
Body Mass Index = (weight in lbs) x 704/ (height in inches)2
CDC Weight Classes
Underweight:
Normal:
Overweight:
Obese:
<18.5
18.5-24.9
25-29.9
>30
2
1) The three-dimensional structure of an enzyme in complex with its substrate was determined by X-ray
crystallography. The structure revealed that a methionine residue in the active site of the enzyme is in close
proximity to an isoleucine residue on a substrate. Which of the following would be the predominant
interaction between these two amino acids?
A) covalent bond
B) disulfide bond
C) hydrogen bond
D) ionic interaction
E) hydrophobic interaction
2) Determine which of the following pairs of compounds represent an acid-conjugate base pair. (The
structures may not necessarily be written in the order of undissociated acid: conjugate base.)
A) a, b and c
B) a, b and d
C) a, c and d
D) a, c and e
E) a, b and e
3) Which of the following represents the predominant ionic species of aspartate at pH 11?
4) A new drug to treat ulcers of the stomach has a critical amino group and a carboxyl group with pKa values of
~9 and ~4. In order to be active, both groups need to be in their acid (HA) form. Would this drug likely be
effective if given orally? (The typical pH of the stomach is ~2.)
A) Yes, both groups will be in acid form.
B) No, only the amino group will be in acid form.
C) No, only the carboxyl group will be in acid form.
D) No, both groups will be in the conjugate base form.
E) Yes, both groups will be in the conjugate base form.
3
Questions 5 - 7 refer to the diagram shown below. Identify the letters A-E in the diagram with chemical
names. Then, match the chemical name with the description given in each question.
5) The product derived from the hydration of CO2 catalyzed by carbonic anhydrase
6) Carbamino hemoglobin
7) Oxygenated hemoglobin
8) The differences between maternal hemoglobin and fetal hemoglobin include:
A) maternal hemoglobin is a tetramer whereas fetal hemoglobin is a monomer.
B) maternal hemoglobin exhibits a sigmoidal O2 saturation curve while fetal hemoglobin exhibits
a hyperbolic curve.
C) maternal hemoglobin utilizes an Fe-containing prosthetic group while fetal hemoglobin
utilizes a Zn-containing prosthetic group.
D) maternal hemoglobin exhibits a lower degree of O2 saturation at all partial pressures of O2
below saturation.
E) all of the above
9) The main reason for treating severe carbon monoxide poisoning by placing the affected individual in an
oxygen tent is:
A) The individual has difficulty breathing.
B) Carbon monoxide poisons oxygen transport across the alveoli of the lung.
C) Carbon monoxide is a competitive inhibitor of oxygen binding to hemoglobin.
D) Carbon monoxide combines with oxygen to form carbon dioxide (CO + O2 —► CO2) and this
production of non-toxic carbon dioxide reduces the concentration of the poison.
E) In the presence of CO, the heme prosthetic group can form a "sandwich," resulting in the oxidation
of iron (Fe+2 —► Fe+3).
10) An18-month-old female is taken to ER because of persistent vomiting (20 times in the last 24 hours).
While on family vacation in Mexico, she was given vanilla ice cream that was sold by a street vendor (dairy and
meat products may harbor staphylococcal enterotoxins that produce food poisoining). You would predict:
A)
B)
C)
D)
E)
[bicarbonate] in blood
above normal
above normal
below normal
below normal
normal
primary problem
metabolic acidosis
metabolic alkalosis
metabolic acidosis
metabolic alkalosis
none
4
11) In this question, "increased" means higher than normal and "decreased" means lower than normal values
of pH = 7.4, [HCO3–] = 24 mM, and pCO2 = 40 mm Hg.
Which of the following best represents partially compensated metabolic alkalosis?
A)
B)
C)
D)
E)
pH
[HCO3–]
pCO2
increased
decreased
increased
decreased
decreased
increased
increased
increased
increased
decreased
increased
increased
decreased
decreased
decreased
12) A 3-year-old child was brought to the hospital with a cough, respiratory distress, and cyanosis (bluish skin
due to deoxygenated hemoglobin). Physical examination suggested a lower respiratory tract infection. Other
laboratory data available:
Patient
Normal
pO2 (mm Hg)
pCO2 (mm Hg)
pH
29
75
7.1
80-100
35-45
7.35-7.45
Other useful values: (a) pKa = 6.1 for CO2 - HCO3– buffer;
(b) solubility coefficient for CO2 at 37 oC, 0.03 mM/mm Hg.
What is the plasma bicarbonate concentration?
A) 8.7 mM
B) 22.5 mM
C) 24 mM
D) 29 mM
E) 75 mM
13) A 14-year-old boy who had never been immunized against poliomyelitis contracted the disease. He was
hospitalized and put on a respirator during the acute phase of his illness. When he appeared to be recovering,
he was taken off the respirator, with no apparent ill effects. Several days later, analysis of his blood revealed:
Na+ (mM)
K+ (mM)
Cl– (mM)
Total CO2 (mM)
pCO2 (mm Hg)
pH
Patient
Normal
136
4.5
92
36
70
7.32
136-145
3.5-4.6
100-106
26-27
35-45
7.35-7.45
Other useful values: (a) pKa = 6.1 for CO2 - HCO3– buffer;
(b) solubility coefficient for CO2 at 37 oC, 0.03 mM/mm Hg.
The normal value of the anion gap ranges 14-15 mM (mEq/L). Is the patient's anion gap:
A) in the normal range?
B) extremely elevated, relative to normal?
C) much below normal?
5
14) Which series of compounds is listed in order from the most reduced state to the most oxidized state?
A)
B)
C)
D)
E)
an acid, a ketone, an alcohol, and an alkane
an alkane, an alkene, an acid, and an aldehyde
an acid, an alkane, an alcohol, and an aldehyde
an alkane, an alcohol, an aldehyde, and an acid
an alkene, an acid, an aldehyde, and an alcohol
Questions 15 and 16 refer to the chemical reaction shown below. Data for the key reaction parameters
in the absence of any enzyme are also provided.
O
CH2OH
C H
C O
H C OH
CH2OPO3
2-
1
CH2OPO32-
2
ΔG’= +0.6 kcal/mol
EA = 25 kcal/mol
V = 2.1 x 10-7 sec-1
Keq = 0.05
15) If you were to add an enzyme to speed up the reaction, what type of enzyme would carry out this reaction?
A) Epimerase
B) Isomerase
C) Dehydrogenase
D) Kinase
E) Hydrolase
16) The data associated with the above reaction are the reaction parameters in the absence of an enzyme.
Which of the following correctly notes the changes that would occur to these parameters in the presence of the
appropriate enzyme?
A) ΔG’ is lowered to a negative value in order to make the reaction thermodynamically favorable.
B) EA is lowered in order to make the transition state more easily reached.
C) V is unchanged by the enzyme.
D) Keq is increased in order to have more of the product at equilibrium
17) Tryptophanyl-tRNA synthetase will charge a tRNA bearing the correct anticodon with L-tryptophan, but not
D-tryptophan nor any other amino acid in the process of protein biosynthesis. This is an example of which of
the following enzymatic characteristics?
A) Catalytic Power
B) Specificity
C) Transformation of Energy
D) Regulation
E) Competitive Inhibition
6
Consider the above Lineweaver-Burk plot for the following question. The solid line indicates data observed in
the absence of any inhibitor. The dotted lines labeled 1 and 2 indicate data observed in the presence two
different inhibitors.
18) Which of the following represents the kinetic values of the enzyme in the presence of a non-competitive
inhibitor?
A)
B)
C)
D)
Km
0.5
-2
1
0.5
Vmax
5
0.4
2.5
2.5
19) The amino acid sequence of an enzyme was determined to have a genetic mutation resulting in the amino
acid change cysteine  proline that maps to the location on the structure to the right highlighted by a box. The
active site is designated by a circle which contains a zinc cofactor shown as a black sphere and an inhibitor
shown as white sticks. Of the following options, what is the most likely effect of the mutation?
A) The mutant amino acid will directly interfere with catalysis.
B) The mutant amino acid is too far away to have any effect on the active site.
C) The mutant amino acid will alter interactions affecting the overall 3D enzyme structure.
D) The mutant amino acid will change the substrate specificity of the enzyme.
E) The enzyme will no longer bind its cofactor.
7
20) Given multiple enzymes that can catalyze the same reaction, which of the following would be the best
choice, given the kinetic parameters below?
A) Enzyme 1
B) Enzyme 2
C) Enzyme 3
D) Enzyme 4
E) Enzyme 5
Km
10
0.5
2
0.1
0.5
Vmax
10
1
1
10
5
21) Refer to the Lineweaver-Burk plot below, showing the kinetic data representing five similar but distinct
substrates of a single enzyme. Based on their kinetic parameters, which is the most preferred substrate of
the enzyme?
A) Substrate A
B) Substrate B
C) Substrate C
D) Substrate D
E) Substrate E
22) You are seeing a 19 yr old female patient who just tested
positive for pregnancy. She says she doesn’t need a prenatal
vitamin because she eats an “energy bar” every day that has lots
of vitamins in it. The nutrition label for her “energy bar” is shown to
the right. Of the following options, which of the statements below
would be sound advice for your patient?
A) “As long as you have one bar daily, you should be fine.”
B) “You will be at risk for developing scurvy.”
C) “Your baby will be at risk for neural problems.”
D) “You are not getting enough vitamin B5.”
E) “You may begin showing signs of Beri Beri.”
Nutrition Facts
Serving size: 1 bar (100 grams)
Servings per container: about 12
Amount per Serving
Calories per serving: 140
Calories from fat: 30
Vitamin
Amount
Thiamine.......................... 1.2 mg
Riboflavin......................... 1.3 mg
Niacin............................. 2.5 mg
Pantothenate...................... 20 mg
Pyridoxal........................... 0.4 mg
Folate.............................. 100 μg
Cobalamin.......................... 9.5 μg
Biotin............................... 30 μg
Ascorbate........................... 90 mg
% RDI
100
100
15
400
20
25
400
100
100
8
23) Your patient comes in for a checkup and you find that he has lost 5 lbs since his last visit. Where did the
lost mass (carbon) go?
A) It was burned up and released as heat.
B) It was converted to energy and used up.
C) It was exhaled as carbon dioxide.
D) It was excreted as waste (feces).
E) It’s still there; it just weighs less.
Questions 24 & 25 refer to the structures of the coenzyme derivatives labeled I – V below:
24) Which of the coenzyme derivatives above are carriers of carbon chains?
A) II only
B) III and IV
C) I and IV
D) I, II, and V
E) III only
25) Which of the coenzyme derivatives above has its active site appropriately highlighted by an oval?
A) I
B) II
C) III
D) IV
E) V
9
26) A 17 yr old male varsity wrestler is in your office for a sports physical. He is 5 feet 10 inches tall and
weighs 130 pounds. He expresses interest in losing 5 lbs in order to go down a weight class in competition
and seeks your approval. Which of the following statements would be the best advice for the patient?
A) “You are borderline underweight now; further weight loss is not recommended.”
B) “A little weight loss would be healthy, go ahead.”
C) “You are at an unhealthy low weight; you should probably gain a few pounds instead.”
D) “You could lose a few pounds. As you get taller, it will all even out.”
27) If ∆G0 for the chemical reaction, A + B ◄——► C + D, is -57 kcal/mol at 25oC, which of the following
statements is most accurate?
A) under standard conditions, equilibrium will be achieved when all concentrations are equal
B) under standard conditions, the equilibrium mixture will contain a predominance of reactants
compared to products
C) entropy is decreased as the reaction procedes to the right
D) under standard conditions, the equilibrium mixture will contain a predominance of products
compared to reactants
E) the reaction will always go to the left
28) Consider the reaction A + B
C + D which has a ΔG°’ of +1.2 Cal/mol. Which of the following
statements is true regarding this reaction?
A) The reaction will proceed forward as written under standard conditions.
B) Cellular concentrations of reaction components may make ΔG’ a negative value.
C) The reaction will occur slowly.
D) There will be more products than reactants at equilibrium.
E) This reaction could be used to generate ATP.
HO CH2
H
NH2
C
OH
CH2OH O
H
H
H
H
OH
OH
Molecule 2
N
C H
C C
N
H N
H
N
O
C
Molecule 1
HO CH2
H
O
OH
H
H
OH
H
H
Molecule 3
CH2OH
H
OH
OH
OH
H
O
Molecule 4
H
C
N
C H
C C
N
H2N N
H
N
C
Molecule 5
29) Which of the above molecules are components of RNA?
A)
B)
C)
D)
E)
Molecules 1, 2, and 3
Molecules 1, 4, and 5
Molecules 1, 3, and 5
Molecules 2, 3, and 5
Molecules 1, 2, and 5
10
CH2OH
OH
CH2OH
O
CH2OH
O
O
O
OH
OH
OH
OH
OH
OH
CH2OH O
OH
CH2OH
O
O
OH
O
OH
OH
Molecule 3
O
OH
OHCH OH
2
OH
CH2OH
OH
OH
OH
Molecule 2
Molecule 1
30) Which of the above molecules has (have) a reducing end?
A) Molecule 1
B) Molecule 2
C) Molecule 3
D) Both Molecules 2 and 3
E) Molecules 1, 2, and 3
CH2OH
C O
HO C H
H C OH
H C OH
CH2OH
Molecule 1
O
O
O
C H
C H
C H
H C OH
HO C H
HO C H
H C OH
HO C H
H C OH
HO C H
H C OH
HO C H
H C OH
H C OH
H C OH
CH2OH
CH2OH
CH2OH
Molecule 2
Molecule 3
Molecule 4
O
C H
H C OH
H C OH
H C OH
CH2OH
Molecule 5
31) In the above figure, which of the molecules are epimers?
A) Molecules 1 and 5
B) Molecules 2 and 3
C) Molecules 3 and 4
D) Molecules 2 and 4
E) Molecules 1 and 3
32) Food stuff oxidation, transfer of energy to ATP, and utilization of energy and amino acid building blocks to
synthesize a new protein are all part of what process?
A) Metabolism
B) Catabolism
C) Anabolism
D) Respiration
E) Digestion
11
END OF EXAMINATION
Tear off this sheet and save to check your answers.
Please remember to:


Write the letter corresponding to your FORM in the appropriate place on the answer sheet.
SIGN AND RETURN YOUR EXAMINATION to an instructor before leaving the exam room.
FORM: A
1. _______
11. _______
21. _______
31. _______
2. _______
12. _______
22. _______
32. _______
3. _______
13. _______
23. _______
4. _______
14. _______
24. _______
5. _______
15. _______
25. _______
6. _______
16. _______
26. _______
7. _______
17. _______
27. _______
8. _______
18. _______
28. _______
9. _______
19. _______
29. _______
10. _______
20. _______
30. _______
12
BMB 514 Exam I Answer Key (9/16/11)
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
25)
26)
27)
28)
29)
30)
31)
32)
Form A
Form B
Form C
Form D
E
C
C
A
C
B
E
D
C
B
A
B
A
D
B
B
B
D
C
D
E
C
C
B
C
A
D
B
E
D
B
A
C
C
A
E
C
B
E
D
B
A
E
A
C
C
A
A
A
C
D
D
E
C
C
B
C
D
C
A
D
D
A
E
C
A
E
C
C
B
E
D
A
D
D
E
B
B
E
D
E
C
D
D
E
C
C
B
C
C
B
E
C
D
E
D
A
E
C
C
C
B
E
D
E
C
C
D
A
A
D
C
D
D
C
D
E
C
C
B
C
B
A
D
B
D
D
C
Exam #2
BMB 514 – Medical Biochemistry
10/10/11
STEP 1 - NAME (Print clearly) _________________ ____________________________
(last)
(first)
Circle your college and campus:
301 --- CHM-EL
302 --- CHM-GR
303 --- COM-EL
304 --- COM-DMC
305 --- COM-MUC
STEP 2 – Fill in your answer sheet with a #2 scoring pencil, as follows:
 Print your first and last name on the line provided
 Code in your Student Number (PID)
 Code in your section as corresponds to the above list
 Code in the correct FORM ..... This
is Form A
 Sign your name in the signature box. By signing the answer sheet for this exam, the student certifies
that he/she has adhered to the policies of academic honesty in the performance of this exam.
STEP 3 - Read these instructions:
 Turn off cell phones; keep them out of sight.
 The proctors have the authority/responsibility to assign any student a different seat at any
time, without implication and without explanation, before or during the examination, as they
deem necessary. Accomplish any relocation quietly and without discussion.
 Make sure your exam has 32 questions.
 We will not answer questions of clarification. However, if you think there is an error on your
exam, summon an exam proctor.
 Read each question very carefully. Choose the single, best answer and mark this answer
on your answer sheet. No points will be added for correct answers which appear on the
exam page but not on the answer sheet.
 When you finish, carefully follow the instructions at the end of the exam. When you leave
the exam room, please turn in your answer sheet AND your exam to the proctors standing
by the doors INSIDE the auditorium. Once you exit the auditorium, please leave the
building. Hallway conversations disturb those still taking the exam.
 There will be answer keys to this exam posted on the course website by 5:00 p.m. the day of the exam.
You may wish to copy your responses from your answer sheet onto the answer grid on the LAST page
of this exam so that you can check your results. You can tear off the last page and take it with you.
 You have 70 minutes to complete this exam. No additional time will be allowed for transfer of answers
from the exam to the answer sheet. We will close the exam promptly at 9:10 a.m. Once we withdraw
the boxes for the answer sheets from the doors, no additional answer sheets will be accepted.
STEP 4 – Wait until instructed to proceed with the exam!
Dr. Otto Warburg proposed that cancer cells have an altered metabolism, one that is much more reliant on
glycolysis for ATP production, which explains their ability to grow and metastasize. In the 80 years since the
“Warburg Hypothesis” was presented, we have learned a lot about the biochemistry of cancer. The following
6 questions are focused on these findings.
1) Cancer cells have a higher rate of glycolysis than their neighboring normal cells. One reason for this
increased rate is the over-expression of hexokinase (HK). Given that most tumors have a limited supply of
glucose because of their inadequate vasculature, which statement below correctly describes a characteristic of
hexokinase that would explain why this increased HK concentration would be an advantage to the cancer?
A) Its low Km would allow it to bind and phosphorylate any available glucose
B) Its high Vmax would allow it to phosphorylate a large number of glucose molecules in a short time
C) The fact that glucose 6-phosphate has no effect on HK activity means it will not turn off in the presence
of high glucose concentrations
D) Its high Km means that it needs high glucose concentrations to become active
E) Its activity does not require ATP, making it better suited for tumor development
2) The cancer cell’s increased dependence on glycolysis for its energy needs also implies that which of the
following statements must also be true in a cancer cell?
A)
B)
C)
D)
E)
Fructose 2,6-bisphosphate will be low in the cancer cell
Phosphoenolpyruvate carboxykinase will be active
Glucose 6-phosphatase will be active
Phosphofructokinase 2 will be active
Pyruvate will be turned into oxaloacetate in the matrix of the mitochondria
3) Another phenotype of many cancer cells is the overexpression of pyruvate dehydrogenase kinase 1
(PDK1), the enzyme responsible for phosphorylating the pyruvate dehydrogenase complex. This increase in
PDK1 activity would result in which of the following?
A)
B)
C)
D)
E)
Trafficking of pyruvate into the mitochondria will increase
The level of lactate in the cell will increase
Citrate synthase activity will increase
The PDH complex will be responsive to direct activation by acetyl-CoA
The electron transport chain activity will be unaffected
4) Interestingly, inheriting a deleterious mutation in the succinate dehydrogenase (SDH) complex makes a
person prone to getting pheochromocytomas, a cancer of the adrenal gland. Which of the following would
NOT be an effect of SDH deficiency?
A)
B)
C)
D)
E)
Decreased levels of fumarate
Increased levels of ubiquinol (QH2)
Increased levels α-ketoglutarate
Decreased levels of malate
Decreased efficiency of complex III of the electron transport chain
5) As a cancer cell grows into a tumor, it needs a lot of nucleic acids (i.e. Ribose 5-P) and synthesis power
(i.e. NADPH). Which of the following enzymes are not required to meet these needs?
A)
B)
C)
D)
E)
Hexokinase
Glucose 6-phosphate dehydrogenase
Ribulose 5-phosphate isomerase
6-phosphogluconate dehydrogenase
Transketolase
2
6) One of the main reasons tumors become more dependent upon glycolysis is because they are hypoxic in
nature. This means they have a deficiency of oxygen. In fact, central portions of the tumor are almost anoxic,
completely lacking oxygen. Anoxia is capable of impacting the electron transport chain in the same manner as
cyanide. Which of the following statements would describe the mitochondria of cancer cells if they could be
isolated and tested under anoxic conditions?
A)
B)
C)
D)
E)
The addition of 2,4-dinitrophenol would restart the electron transport chain
Complex I would remain active
The potential across the inner mitochondrial membrane would be low
ATP production would be unaffected
Cytochrome c would be completely oxidized
7) A patient comes into clinic suffering from lack of energy and very low hemoglobin levels. You run some
tests and determine his red blood cells have a high level of phosphoenolpyruvate with little pyruvate produced
and decreased ATP levels. You quickly deduce that he has a mutation in which glycolytic enzymes?
A)
B)
C)
D)
E)
Glyceraldehyde 3-phosphate dehydrogenase
Glucokinase
Phosphofructokinase
Enolase
Pyruvate kinase
8) A patient suffering from glucose 6-phosphate dehydrogenase deficiency would be expected to have which
of the following phenotypes?
A)
B)
C)
D)
E)
Decreased risk of having Wernicke-Korsakoff syndrome
Increased cellular concentrations of 6-phosphogluconolactone
Normal levels of reduced glutathione
Experience hemolysis following exposure to antimalarial drugs
Normal NADPH-dependent cytochrome P450 enzyme activity
9) Fructose intolerance and galactose intolerance are similar in that they both:
A) fail to trap the sugar inside the cell
B) deplete the cell of reducing power
C) fail to split a 6-carbon sugar into 3-carbon units
D) effectively sequester inorganic phosphate
E) only affect infants
10) Lactate dehydrogenase (LDH) plays an essential role in an exercising muscle, especially when the level of
excursion surpasses the ability of circulatory systems ability to supply adequate oxygen. What is the main
reason LDH is so important to the muscle under these conditions?
A)
B)
C)
D)
E)
It produces one mole of ATP via substrate level phosphorylation.
It decreases pH thus decreasing the dissociation rate of oxygen from hemoglobin
It removes excess lactic acid from the muscle to create pyruvate
It produces NADH for energy while converting pyruvate into lactate
It resupplies NAD+ to glyceraldehyde 3-phosphate dehydrogenase
3
11) A 3 month infant is brought into the ER with an abnormally large liver and spleen. The infant is very small
for her age and her liver is already showing signs of progressive scarring. You quickly deduce that the little girl
has a glycogen storage disease. You analyze her glycogen enzymes and determine she has a branching
enzyme deficiency (Anderson’s Disease). If you were to analyze the structure and content of her glycogen
stores what is most likely what you would find:
A)
B)
C)
D)
E)
Normal amount, normal structure
Normal amount, fewer branches that are much longer than normal
Less than normal amount, fewer branches that are much longer than normal
Higher than normal amount, normal structure
Higher than normal amount, normal number of branches but they appear shorter
12) A patient suffering from an isocitrate dehydrogenase deficiency is most likely to exhibit which of the
following?
A)
B)
C)
D)
E)
Increased level of -ketoglutarate
Decreased electron transport chain activity
Increased levels of glutamate
Normal NADH levels within the matrix
Decreased levels of isocitrate
13) You isolate mitochondria from a patient suffering from muscle weakness and lactic acidosis. You
determine that the patient is UNABLE to oxidize ubiquinol, pump protons across the inner membrane if given
succinate as a carbon source, nor reduce cytochrome c. This patient most likely suffers from a defect in which
of the following protein complexes?
A)
B)
C)
D)
E)
Complex I
Complex II
Complex III
Complex IV
Complex V, ATP synthase
14) In a coupled mitochondria which of the following would you expect to observe?
A)
B)
C)
D)
E)
Oxygen consumption should stop when ADP is low
The addition of oligomycin will not affect oxygen consumption
The ratio ATP/O2 consumed (i.e. P/O ratio) is the same for FADH2 and NADH
The membrane potential will be unaffected by 2,4-DNP
Increased membrane potential upon exposure to rotenone
15) If the concentration of ATP is low, the availability of glucose and acetyl-CoA is high, and no other
metabolic demands are made on the cell, what is the most likely fate of oxaloacetate?
A) It is converted to phosphoenolpyruvate for gluconeogenesis to continue.
B) It is polymerized in glycogenesis.
C) It is converted to pyruvate.
D) It is combined with acetyl-CoA and enters the TCA cycle.
E) It is converted to malate through the reversal of a reaction in the TCA cycle.
4
Question 16 – 18 refer to the following diagram:
OAA
GTP
GDP
+
CO2
Metabolite #2
Enzyme #3
Metabolite #2
Enzyme #2
Enzyme #1
Pyruvate
Metabolite #1
Metabolite #3
Pyruvate
Pyruvate
Transporter
ATP
+
CO2
ADP + Pi
Mitochondria
16) Enzyme #1 is:
A)
B)
C)
D)
E)
Pyruvate carboxylase
Pyruvate Kinase
Lactate Dehydrogenase
Phosphoglycerate kinase
Pyruvate dehydrogenase
17) Metabolite #2 is:
A)
B)
C)
D)
E)
Lactate
Isocitrate
2-phosphoglycerate
Malate
Fumarate
18) Enzyme #3 is
A)
B)
C)
D)
E)
Pyruvate kinase
Phosphoglycerate kinase
Enolase
Malate dehydrogenase
Phosphoenolpyruvate carboxykinase
5
19) Glycogen metabolism relies on reciprocal regulation to ensure that your cells are not trying to make and
breakdown glycogen at the same time. Which of the following is NOT involved in this reciprocal regulation?
A)
B)
C)
D)
E)
Biological amplification
Cyclic AMP
Protein phosphorylation
Pyrophosphatase
Hormones
20) You have been hired as a consultant on the hit show “Royal Pains” and are asked to check the plausibility
of a storyline centered on antimycin toxicity. While reading the script you notice that the writers have Hank, the
lead character, ordering a mitochondrial functional test that shows the exposed patient’s mitochondria are not
consuming oxygen, but that it can be restored upon 2,4-dinitrophenol (2,4-DNP) treatment and the
mitochondria have a higher than normal level of ubiquinol. What would you tell the writer’s about their
storyline?
A) Antimycin toxicity would not affect oxygen consumption.
B) This is a great storyline and I would not change a thing.
C) Antimycin would cause a buildup of reduced cytochrome C, not ubiquinol.
D) 2,4-DNP would not restore oxygen consumption since antimycin inhibits complex III.
E) This whole storyline is unbelievable because Hank is not a smart enough doctor to order mitochondrial
testing.
21) What are the products of beta-oxidation of a C20 fatty acid?
A) 1 propionyl CoA, 9 acetyl CoA, 9 FADH2, and 9 (NADH + H+)
B) 9 acetyl CoA, 8 FADH2, 8 (NADH + H+)
C) 9 acetyl CoA, 9 FADH2, 9 (NADH + H+)
D) 10 acetyl CoA, 9 FADH2, 9 (NADH + H+)
E) 10 acetyl CoA, 10 FADH2, 10 (NADH + H+)
22) A patient has a defective cytosolic beta-ketothiolase enzyme. In this person’s liver cells, which of the
following pathways would be immediately affected?
A) ketone body synthesis
B) cholesterol synthesis
C) beta-oxidation of fatty acids
D) ketone body synthesis and beta-oxidation of fatty acids
E) ketone body synthesis, cholesterol synthesis, and beta-oxidation of fatty acids
23) Which of the following statements regarding the reciprocal regulation of fatty acid synthesis and betaoxidation is incorrect?
A) acetyl CoA carboxylase is activated by insulin.
B) Carnitine acyl transferase II (CAT II) is inhibited by malonyl CoA.
C) Leptin inhibits fatty acid synthesis.
D) Glucagon stimulates beta-oxidation of fatty acids.
E) Palmitoyl CoA is an inhibitor of fatty acid synthesis.
6
O
CH3
(CH2)12
C S
O
+
KS
-
O
O C CH2
molecule A
C S
ACP
molecule B
Reaction 1
[G]
CH3
(CH2)12
O
O
C CH2
C S
molecule C
ACP
[H]
Reaction 2
[I]
CH3
(CH2)12
molecule D
OH
O
C CH2
C S
ACP
H
Reaction 3
[J]
H
CH3
(CH2)12
O
C C C S
ACP
H
molecule E
[K]
Reaction 4
[L]
CH3
(CH2)12
CH2
CH2
O
C S
ACP
molecule F
The following 2 questions refer to the pathway drawn above. The letters in brackets [ ] represent
additional substrates and products for the reactions indicated.
24) Which of the following statements regarding the above pathway is correct?
A) Reactions 1 through 4 are oxidation, hydration, oxidation, and cleavage respectively.
B) Molecule F undergoes two more rounds of these four reactions to produce the normal final product of
this pathway.
C) Coenzyme A carries the intermediates to each of the enzymes in this pathway.
D) The enzymes that carry out reactions 2 and 4 are both reductases.
E) The fatty acid synthetase complex includes the enzymes of reactions 1 through 4.
25) Which of the following statements regarding the production of molecule B in the above pathway is correct?
A) Acetyl CoA carboxylase catalyzes the reaction that produces molecule B.
B) The enzymatic reaction that produces molecule B is readily reversible.
C) The enzymatic reaction that produces molecule B requires biotin and ATP.
D) Both A and C are correct.
E) All of the above are correct.
7
26) Malonyl CoA, which was 14C labeled (a radioactive isotope of carbon) at both carbons #1 and #2, and
unlabeled acetyl CoA were mixed together with the fatty acid synthase complex in a test tube. Which of the
carbons of the final product, palmitate, will be 14C labeled?
A) All of the carbons will be labeled
B) Only carbons #15 and #16 will be labeled
C) All of the even numbered carbons will be labeled, except for carbon #16
D) All of the odd numbered carbons will be labeled, except for carbon #15
E) Carbons #1 through #14 will all be labeled.
27) A patient has a low insulin/glucagon ratio. You need to determine her levels of ketone bodies in the blood
and urine using the nitroprusside test, which detects molecules with ketone groups. Which of the following
molecules will be detected?
A) acetone
B) β-hydroxybutyrate
C) acetoacetate
D) acetoacetate and acetone
E) β-hydroxybutyrate, acetoacetate, and acetone
28) Which of the following statements is correct?
A) Triacylglycerols (TAG) and phospholipids are synthesized by branches from a common intermediate.
B) ATP is used for activation in the salvage pathway of phospholipid synthesis.
C) Serine is a source used to create the backbone of phospholipids and triacylglycerols (TAG).
D) Breakdown of phospholipids yields important first messengers for signaling pathways.
E) Insulin inhibits triacylglycerol (TAG) synthesis.
29) Sphingomyelin is
A) a lipid which functions mainly as a storage form of energy.
B) synthesized using phosphatidate as the key intermediate of the pathway.
C) a major glycolipid of nerve cell membranes.
D) the major component of lung surfactant, and indicates fetal lung maturity.
E) a membrane lipid containing a sphingosine backbone, an amide linked fatty acid, and phosphoryl- choline
as the headgroup.
30) A 28-year-old white male complains of severe retrosternal pain radiating to his left arm and jaw. He has
not had a physical exam as an adult. His father died at a young age of a myocardial infarction. Physical exam
revealed that he is anguished and dyspneic (shortness of breath). There were elevated plaques on eyelids
(xanthelasmas), as well as xanthomas (pinkish nodules) of Achilles tendons and patellae (knee joint).
Although serum triglycerides and HDL (high density lipoprotein) were within the normal range, LDL (low density
lipoprotein) cholesterol was 650 mg/dL (normal ~130 mg/dL).
You suspect the following genetic defect and prescribe a drug.
genetic defect
A) pyruvate dehydrogenase
B) glucose 6-phosphate dehydrogenase
C) lactase
D) apoB-100
E) lipoprotein lipase
drug
thiamine
primaquine
lactose
statin
lecithin
8
31) A mother awakes after sleeping soundly for 8 hours for the first time since bringing her newborn daughter
home from the hospital. She goes to check on her infant and finds her covered with vomit, soaked in sweat,
and barely able to be aroused. The child is rushed to the emergency room. Initial tests rule out bacterial and
viral infection. The intern on duty suspects that she may have a metabolic disorder involving a defect in
medium-chain fatty acid oxidation, and orders a series of blood tests. Which set of laboratory findings would
confirm this hypothesis (normal serum values are in parentheses)?
A)
B)
C)
D)
E)
Glucose
(3.6 – 6.0 mM)
2.6
5.1
2.6
23
2.6
Fatty Acids
(0.2 – 0.6 mM)
6.1
6.1
0.1
0.5
0.5
Beta-hydroxybutyrate
(0.2 – 0.25 mM)
0.1
0.1
0.1
13
13
32) A 33-year old man with a BMI of 38 was prescribed orlistat (Xenical) as part of his treatment to reduce
obesity. Orlistat works in the small intestine to block the absorption of dietary fat. When taking orlistat he may
need to supplement his diet with several compounds, including:
A) linoleic acid
B) cholesterol
C) fat soluble vitamins
D) linoleic acid and fat soluble vitamins
E) linoleic acid, cholesterol, and fat soluble vitamins
9
END OF EXAMINATION
Tear off this sheet and save to check your answers.
Please remember to:


Write the letter corresponding to your FORM in the appropriate place on the answer sheet.
SIGN AND RETURN YOUR EXAMINATION to an instructor before leaving the exam room.
FORM: A
1. _______
11. _______
21. _______
31. _______
2. _______
12. _______
22. _______
32. _______
3. _______
13. _______
23. _______
4. _______
14. _______
24. _______
5. _______
15. _______
25. _______
6. _______
16. _______
26. _______
7. _______
17. _______
27. _______
8. _______
18. _______
28. _______
9. _______
19. _______
29. _______
10. _______
20. _______
30. _______
10
Fall 2011 BMB 514: Exam II—Answer Keys
Question
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Form A
A
D
B
B
E
C
E
D
D
E
B
B
C
A
D
A
D
E
D
D
D
B
B
D
D
E
D
A
E
D
A
D
Form B
C
D
D
B
B
B
D
A
D
D
C
D
A
D
C
B
D
B
C
A
E
B
C
B
D
E
B
C
A
C
E
D
Form C
C
D
C
B
D
B
D
A
E
D
D
B
C
C
D
C
D
E
D
D
A
D
D
C
A
B
D
B
E
C
D
B
Form D
D
C
B
D
A
D
B
A
C
B
B
E
E
B
D
B
C
D
B
C
E
C
D
B
C
D
B
D
E
D
B
B
Exam #3
BMB 514 – Medical Biochemistry
10/24/11
STEP 1 - NAME (Print clearly) _________________ ____________________________
(last)
(first)
Circle your college and campus:
301 --- CHM-EL
302 --- CHM-GR
303 --- COM-EL
304 --- COM-DMC
305 --- COM-MUC
STEP 2 – Fill in your answer sheet with a #2 scoring pencil, as follows:
 Code in your last name and first initial (F.I.)
 Code in your Student Number (PID)
 Code in your section as corresponds to the above list.
 Code in the correct FORM ..... This
is Form A
 Sign your name in the signature box. By signing the answer sheet for this exam, the student certifies
that he/she has adhered to the policies of academic honesty in the performance of this exam.
STEP 3 - Read these instructions:
 Page 2 of this exam contains information that may be useful to you: (a) abbreviations for the
amino acids; (b) pKa values of functional groups; (c) table of logarithms; and (d) CDC weight
classes related to Body Mass Index.
 A simple calculator is supplied for your use during this exam. No other electronic or
computational devices are to be used. Turn off cell phones; keep them out of sight.
 The proctors have the authority/responsibility to assign any student a different seat at any
time, without implication and without explanation, before or during the examination, as they
deem necessary. Accomplish any relocation quietly and without discussion.
 Make sure your exam has 64 questions.
 We will not answer questions of clarification. However, if you think there is an error on your
exam, summon an exam proctor.
 Read each question very carefully. Choose the single, best answer and mark this answer
on your answer sheet. No points will be added for correct answers which appear on the
exam page but not on the answer sheet.
 When you finish, carefully follow the instructions at the end of the exam. When you leave
the exam room, please turn in your answer sheet AND your exam to the proctors standing
by the doors INSIDE the auditorium. Once you exit the auditorium, please leave the
building. Hallway conversations disturb those still taking the exam.
 There will be answer keys to this exam posted on the course website by 5:00 p.m. the day of the
exam. You may wish to copy your responses from your answer sheet onto the answer grid on the
LAST page of this exam so that you can check your results. You can tear off the last page and take it
with you.
 You have 130 minutes to complete this exam. No additional time will be allowed for transfer of
answers from the exam to the answer sheet. We will close the exam promptly at 10:10 a.m. Once we
withdraw the boxes for the answer sheets from the doors, no additional answer sheets will be accepted.
STEP 4 – Wait until instructed to proceed with the exam!
INFORMATION THAT MAY BE USEFUL FOR THE EXAM
Body Mass Index = (weight in lbs) x 704/ (height in inches)2
CDC Weight Classes
Underweight:
Normal:
Overweight:
Obese:
<18.5
18.5-24.9
25-29.9
>30
2
1) In a patient with severe chronic obstructive pulmonary disease (COPD), COPD "flares" are common and
result in an inability to ventilate and the accumulation of carbon dioxide in the body, leading to a primary
respiratory acidosis. Of the following mechanisms, which is the most important for management of acid-base
status?
A) the carbon dioxide - bicarbonate equilibrium
CO2 + H2O ◄——► H2CO3 ◄——► H+ + HCO3– (pKa ~6.1)
B) the ammonia - ammonium ion equilibrium
NH4+ ◄——► H+ + NH3 (pKa ~9.3)
C) the dissociation of acetic acid
CH3COOH ◄——► H+ + CH3COO– (pKa ~4.8)
D) the ionization of β-hydroxybutyric acid
CH3CHOHCH2COOH ◄——► H+ + CH3CHOHCH2COO– (pKa ~4.4)
2) A medical student suffers an acute anxiety attack the night before the biochemistry final exam and
hyperventilates uncontrollably. Which of the following arterial blood gas results would most likely be observed?
pH
normal 7.35-7.45
A)
7.51
B)
7.50
C)
7.40
D)
7.22
E)
7.26
pCO2 (mmHg)
35 – 45
48
29
40
69
26
[HCO3-] (mM)
22 -26
38
22
24
27
11
3) Lipitor (a statin drug) inhibits the enzyme HMG-CoA Reductase in the pathway of cholesterol biosynthesis
via competitive inhibition. Normal kinetic parameters for this enzyme with HMG-CoA (without the drug) are:
Km = 8.1 µM and Vmax = 330 pmol min-1. Which of the following shows the expected changes in the kinetic
parameters for HMG-CoA in the presence of the drug?
A)
B)
C)
D)
E)
Km
8.1 µM
20.8 µM
20.8 µM
8.1 µM
2.3 µM
Vmax
120 pmol min-1
120 pmol min-1
330 pmol min-1
330 pmol min-1
330 pmol min-1
4) Asparaginase is used to reduce the level of asparagine in the blood in one treatment for leukemia. Which
isoform of asparaginase would be most useful if the patient’s blood asparagine level is 0.2mM?
Km
Vmax
A)
B)
C)
D)
E)
0.1mM;
0.2mM;
0.2mM;
2.0mM;
0.1mM;
0.5 mM/hr
0.1 mM/hr
0.5 mM/hr
0.1 mM/hr
0.1 mM/hr
5) The conversion of proinsulin to insulin requires the activity of two enzymes. Which of the following best
represents the classification of these two enzymes?
A) transferases
B) hydrolases
C) lyases
D) isomerases
E) oxidoreductases
3
6) The mature, active insulin protein contains two peptide chains held together by disulfide bonds. The side
chain of which amino acid is capable of forming this covalent linkage?
A) cysteine
B) hydroxyproline
C) isoleucine
D) lysine
E) alanine
7) A 33-year-old farm owner died while using an 11-horsepower gasoline-powered washer to clean the inside
of a 3420 cubic-foot swine farrowing area within a larger wooden structure. He had recently insulated this
farrowing room. He was working alone, the door was closed, and there was no other ventilation on this very
cold day. In the context of this vignette, an investigation by the local medical examiner's office during
postmortem analysis must necessarily include a determination of the farmer's level of :
A) 2,3-diphosphoglycerate
B) Hb AIC (Hb=hemoglobin)
C) insulin C-peptide
D) HbCO (Hb=hemoglobin)
E) acetone
8) The reaction Phosphoenolpyruvate (PEP) + ADP + Pi  Pyruvate + ATP is catalyzed in the cell by
pyruvate kinase. Which of the ratios given below would result in a ΔG’ = -4.7?
Given:
PEP  Pyruvate: ΔG°’ = -14.8
ATP  ADP + Pi: ΔG°’ = -7.3
ΔG’ = ΔG°’ + 1.4log (Products)
(Reactants)
A) [Pyruvate][ATP] = 102
[PEP][ADP][Pi]
B) [Pyruvate] = 10-2
[PEP]
C) [Pyruvate][ADP][Pi] = 102
[PEP] [ATP]
D) [Pyruvate][ATP] = 10-2
[PEP][ADP][Pi]
E) [ATP] = 102
[ADP][Pi]
9) A patient presents with poorly functioning Succinate Dehydrogenase, PDH complex E3, and Acyl-CoA
Dehydrogenase enzymes (amongst others). You suspect a vitamin deficiency. Which of the following vitamin
supplements would be of the most benefit to your patient?
A) Riboflavin (Vit B2)
B) Niacin (Vit B3)
C) Pyridoxal (Vit B6)
D) Biotin (Vit B7)
E) Thiamine (Vit B1)
4
10) A 40-year-old Caucasian gentleman is admitted to the hospital with a hematocrit of 14 (normal, 37-47). He
is noted to have a lemon-yellow waxy pallor. Neurological examination revealed parasthesias (skin sensation
of tingling, prickling, or itching), weakness, and an unsteady gait. A peripheral blood smear shows a
macrocytic anemia (MCV >100 fl). You suspect a deficiency in X and order administration of Y to test your
hypothesis.
Y
X
A)
B)
C)
D)
E)
vitamin B1 thiamine
vitamin B3 niacin
vitamin B12 cobalamin
vitamin C ascorbate
vitamin H biotin
transketolase
nicotinamide
intrinsic factor
collagen
pyruvate carboxylase
The next three questions deal with the following case:
A 2-year-old male born to consanguineous parents (parents are blood related or derived from the same
ancestor) is brought into the emergency room suffering from seizures. The patient suffers from episodic bouts
of hypoglycemia when he has not eaten. His lab values are below (PaCO2=pCO2):
Patient
Normal
Patient
Normal
pH
7.24
7.35‐7.45
Lactate
6 mM
0.5‐2.0
Pyruvate 0.23 mM
0.03‐0.08
PaCO2
36
38‐52 mm Hg
Lysine
Alanine
Proline
88‐205
158‐393
96‐272
HCO3
Na+
K+
Cl‐
14
140
4.3
111
19‐25 mEq/L
135‐145 mEq/L
3.5‐5.0 mEq/L
98‐108 mEq/L
89 uM
775 uM
217 mM
11) Knowing that the patient suffers from a detrimental mutation within a key metabolic enzyme and biotin
partially corrected this defect, which of the following enzymes is most likely affected by the mutation?
A)
B)
C)
D)
E)
Pyruvate kinase
Lactate dehydrogenase
Citrate synthase
Pyruvate dehydrogenase
Pyruvate carboxylase
12) What is the best way to describe the patient’s metabolic state?
A)
B)
C)
D)
E)
Metabolic alkalosis with respiratory compensation
Uncompensated metabolic alkalosis
Respiratory acidosis with partial metabolic compensation
Metabolic acidosis with partial (slight) respiratory compensation
Respiratory alkalosis with metabolic compensation
13) Given what you know about metabolism, which of the following would you expect to be elevated in this
patient's serum?
A)
B)
C)
D)
E)
Oxaloacetate
Malate
Glucose
Linoleic Acid
Beta-hydroxybutyrate
5
14) In a person with a deficiency of fructose 1,6-bisphosphatase, the predominant metabolic consequence is:
A)
B)
C)
D)
E)
failure to synthesize glucose from lactic acid
failure to split fructose 1,6-bisphosphate into triose phosphates
inability to degrade glycogen
inability to fix CO2 into organic linkages
lowered yield of ATP production per mole of glucose metabolized
15) What is the "activated" form of glucose used during the lengthening of a glycogen primer?
A) ATP- glucose
B) pyrophosphate
C) CDP-glucose
D) malonyl Co-A
E) UDP-glucose
16) The reciprocal regulation between gluconeogenesis and glycolysis involves all of the following EXCEPT:
A)
B)
C)
D)
E)
Phosphofructokinase 1
Fructose 1,6-bisphosphatase
Fructose 2,6-bisphosphate
Glucagon
Phosphoglucomutase
17) All the following key intermediates in energy metabolism are correctly paired with enzymes that would
directly consume or produce them except:
A) glucose-6-phosphate: glycogen phosphorylase
B) pyruvate: lactate dehydrogenase
C) acetyl CoA: pyruvate dehydrogenase complex
D) pyruvate: pyruvate carboxylase
E) glucose-6-phosphate: hexokinase
18) One hallmark of VonGierke’s Disease is hyperuricemia. Which of the following is an explanation for the
increased uric acid?
A)
B)
C)
D)
E)
Excess glucose 6-phosphate causes an increase in purine synthesis that is degraded to uric acid
Excess glucose 6-phosphate is converted to alanine that inhibits uric acid secretion
High circulating levels of glucagon inhibits the conversion of uric acid to lactate
Increased triglycerides are metabolized to uric acid
Excess uridine diphosphate not used in glycogen synthesis is excreted as uric acid.
19) You have just eaten some chocolate covered sugar O’s for breakfast. Which of the following enzymes
serves to protect your system from a dangerous spike in blood sugar after this meal?
A) Fructokinase
B) Glucokinase
C) Hexokinase
D) Galactokinase
E) Phosphofructokinase
6
The next two questions deal with the following case:
A farmer is rushed into the emergency room after collapsing on his farm. Initial and subsequent laboratory
data revealed signs of ischemic cardiac injury, abnormal coagulation profile, renal insufficiency, and slight
leukocytosis. Lab results (normal ranges in parenthesis):
arterial blood gas results:
pH
7.31 (7.35-7.45)
pCO2 44 mm Hg (38-52)
pO2
77 mm Hg (75-100)
oxygen saturation: 95% on inspired oxygen of 35%
serum chemistry:
BUN
43 mEq/L (7-21),
creatinine 2.6 mg/dL (0.5-1.4)
Na
135 mEq/L (135-145)
K
4.8 mEq/L (3.5-5)
Cl
105 mEq/L (98-108).
After further tests, you determine that he is not making enough ATP and his mitochondrial oxygen consumption
is very low. Using virtual technology you are able to deduce that the addition of 2,4-DNP to his mitochondria
does not rescue oxygen consumption. Finally, these purified mitochondria have an excess of reduced
cytochrome C.
20) To what mitochondrial poison was the farmer exposed?
A)
B)
C)
D)
E)
Oligmycin
Amytal
Antimycin
Hydrogen sulfide
Rotenone
21) What is the most likely cause of the acidosis
A)
B)
C)
D)
E)
Decreased activity of pyruvate kinase leading to excess phosphoenolpyruvate
Increased lactic acid caused by inhibition of TCA cycle
Decreased production of ketone bodies due to renal dysfunction
Excess protons from the mitochondrial inner membrane space being released into circulation
Increased activity of alanine transaminase leading to excess alanine
22) A 45-year-old man was treated for pneumonia (Pneumocystis carinii) with trimethoprim-sulfamethoxazole.
Two days after the therapy was started, he became slightly jaundiced, with the following blood profile on CBC
(complete blood count):
HCT: below normal
HGB: below normal
RBC: below normal
Retic: above normal
Direct bilirubin:  (above normal)
Indirect bilirubin:    (much above normal)
Upon observing his blood smear (see micrograph), you
immediately suspect that this patient has a genetic
deficiency in which of the following enzymes?
A) glucose 6-phosphate dehydrogenase
B) glycogen phosphorylase
C) phosphofructokinase-1
D) pyruvate kinase
E) cytochrome c oxidase
7
The next two questions deal with the following case:
A 37 year old man is currently being followed in the hematology clinic at Sparrow Hospital. His hemoglobin
levels were between 5-7 gm/dl (normal ~13.5 gm/dl in adult males). He occasionally has even more severe
decreases in his hemoglobin levels, usually precipitated by viral infections. Because of this and in an effort to
decrease hemolysis, he has had a splenectomy. (Erythrocytes are normally removed from the circulation by
the spleen.) Subsequently, his hemoglobin levels have ranged 6-9 gm/dl and he is usually asymptomatic from
his anemia. Metabolic analyses of his red blood cells show that he maintains less than 50% of the normal level
of ATP and has an elevated level of phosphoenolpyruvate in his red blood cells.
23) The patient most likely suffers from a deficiency in what enzyme?
A)
B)
C)
D)
E)
Phosphoenolpyruvate carboxykinase
Phosphoglycerate kinase
Pyruvate Carboxylase
Pyruvate Kinase
Glyceraldehyde 3-phosphate dehydrogenase
24) Surprisingly, the patient has an increased exercise tolerance in spite of his chronic anemia. The most
likely explanation for this increased tolerance is:
A) Increase phosphoenolpyruvate inhibits gluconeogenesis ensuring the TCA cycle is on
B) Increased phosphoenolpyruvate inhibits fructose 2,6-bisphosphatase ensuring glycoylsis stays active
C) Build up of 2,3-bisphosphoglycerate causes a right shift in hemoglobin-oxygen saturation curve
D) Decreased ATP slows metabolism leading to a decrease in harmful reactive oxygen species.
E) Increased phosphoenolpyruvate inhibits the pentose phosphate pathway, leading to a decrease of NADPH
needed for muscle contraction.
25) In the following question the abbreviations used are:
ADP, adenosine 5'-phosphate;
dADP, deoxyadenosine 5'-phosphate;
OMP, orotate monophosphate;
PRA, 5-phosphoribosylamine;
PRPP, 5-phosphoribosyl-1-pyrophosphate
Ribose 5-P, ribose 5-phosphate
Identify the two steps at which feedback inhibition controls de novo synthesis of purine nucleotides.
one step
A)
B)
C)
D)
E)
Ribose 5-P to PRPP
Ribose 5-P to PRPP
PRPP to OMP
PRPP to PRA
PRPP to OMP
another step
synthesis of carbamoyl phosphate
PRPP to PRA
Ribose 5-P to PRPP
ADP to dADP
PRPP to PRA
26) The direct (immediate) precursor of dTMP is:
A)
B)
C)
D)
E)
dCMP
dCDP
dGMP
dUMP
dAMP
8
27) A folate deficiency will most directly lead to a decreased rate of synthesis of some amino acids,
thymidylate AND:
A) glucose
B) palmitate
C) 5-phosphoribosyl-1- pyrophosphate (PRPP)
D) vitamin B12
E) adenosine monophosphate (AMP)
28) The inhibition of the synthesis of DNA by methotrexate results from direct inhibition of:
A)
B)
C)
D)
E)
the reduction of dihydrofolate to tetrahydrofolate
the reduction of ribonucleotides to deoxyribonucleotides
the synthesis of S-adenosylmethionine
thymidylate synthetase
a reaction in the pathway of purine nucleotide biosynthesis
29) Methotrexate is used to treat cancers such as leukemia. If you were to study your patient's cancer cells
after they had been exposed to methotrexate, you would find changes in the levels of compounds related to
one-carbon metabolism.
overall tetrahydrofolate
homocysteine
total cobalamin
A)
increased
decreased
no change
B)
decreased
increased
decreased
C)
decreased
increased
no change
D)
decreased
decreased
decreased
E)
increased
increased
increased
30) A 53-year-old man had adenocarcinoma in his large intestine. While the adenocarcinoma was being
surgically removed, nodules of metastatic cancer were found in the liver. After resection (complete removal) of
the tumor, therefore, the oncologist began treatment with 5-fluorouracil (5-FU), combined with other
chemotherapeutic agents. The 5-FU treatments aided in the killing of the metastatic cancer cells by
decreasing the intracellular concentration of:
A) deoxythymidine triphosphate (dTTP)
B) deoxyuridine triphosphate (dUTP)
C) ribose 5-phosphate
D) uridine triphosphate (UTP)
E) cytidine triphosphate (CTP)
31) Pyrimidine nucleotides are catabolized ...
A) to the respective bases, which are primarily salvaged
B) to carbon skeletons that are used for other metabolic pathways
C) only down to nucleosides
D) extensively in patients with gout
E) to uric acid, which is excreted
32) A 23-year-old woman was diagnosed with genital herpes. As a part of her treatment, she was prescribed
acyclovir (acycloguanosine). This drug works in herpes-infected cells by:
A) activating folate degradation
B) activating reactive oxygen species (H2O2) production
C) inhibiting DNA synthesis
D) inhibiting ribonucleoside diphosphate reductase (ribonucleotide reductase)
E) activating cAMP synthesis
9
33) An 18-month-old boy was brought to the clinic because of severe and repeated lip chewing and aggressive
tongue biting. A medical history revealed a normal pregnancy with little/no complications. But, a diagnosis of
muscular hypotonia (low muscle tone) was made at four months of age. A diagnosis of Lesch-Nyhan
syndrome was made on the basis of biochemical analysis and DNA sequencing. Which of the following
reactions is most likely to be deficient in this boy?
A) attachment of guanine to 5-phosphoribosyl-1-pyrophosphate (PRPP)
B) condensation of ornithine with carbamoyl phosphate
C) coupling of glycine and succinyl-CoA in initiating heme biosynthesis
D) hydroxylation of phenylalanine
E) removal of phosphate from glucose 6-phosphate
34) A 3-year-old boy is being evaluated for recurrent infections. He is found to be leukopenic and has
megaloblastic, hypochromic anemia. He is also noted for developmental retardation. Over the next couple of
months, his anemia is found to be unresponsive to iron, folic acid, or vitamin B12 supplementation. High levels
of orotic acid are found in his urine. What metabolic defect most likely could cause this?
A) a defect in carbohydrate metabolism
B) a defect in lipid metabolism
C) a defect in protein metabolism
D) a defect in purine metabolism
E) a defect in pyrimidine metabolism
35) A 3-year-old boy has been diagnosed with systemic carnitine deficiency. Which of the following statements
would be correct?
A) The patient will show fructose intolerance.
B) After a 24-hour fast, the patient will utilize ketone bodies as fuel.
C) Lipids will accumulate in the cytoplasm of liver cells.
D) During a fasting period of 30 hours, the blood glucose levels will stay constant.
E) The boy most likely has a defect in his liver beta-ketothiolase enzyme.
36) The four repeated steps of beta-oxidation of fatty acids, respectively, are:
A) condensation, reduction, dehydration, reduction
B) dehydrogenation, dehydration, dehydrogenation, cleavage
C) oxidation, hydration, oxidation, cleavage
D) reduction, hydration, reduction, cleavage
E) condensation, hydrogenation, hydration, hydrogenation
37) Which of the following statements correctly describes fatty acid synthesis and β-oxidation of fatty acids?
A) Fatty acid synthesis intermediates are covalently linked to coenzyme A (CoA), while β-oxidation
intermediates are linked to an acyl carrier protein (ACP).
B) Fatty acid synthesis occurs in the mitochondrial matrix and β-oxidation occurs in the cytosol of all cells.
C) The carboxylation of acetyl CoA to malonyl CoA is the committed step in β-oxidation of fatty acids.
D) The fatty acid chain is elongated by the sequential addition of 3 carbon units during fatty acid synthesis.
E) NADPH is a cofactor used in fatty acid synthesis, while NAD+ and FAD are used in β-oxidation.
38) Which one of the following statements about the absorption of lipids from the intestine is correct?
A) Dietary triacylglycerols are partially hydrolyzed and absorbed as free fatty acids and monoacylglycerol.
B) Dietary triacylglycerols must be completely hydrolyzed to free fatty acids and glycerol before absorption.
C) Release of fatty acids from triacylglycerols in the intestine is inhibited by bile salts.
D) Lipoprotein lipase (LPL) degrades the dietary lipids for absorption by the intestinal mucosal cells.
E) Formation of chylomicrons does not require protein synthesis in the intestinal mucosa.
10
39) What is the "activated" form of a fatty acid used during the synthesis of triacylglycerol from glycerol 3phosphate?
A) ATP-linked fatty acid
B) acyl-CoA
C) CDP-linked fatty acid
D) acetyl-CoA
E) UDP-linked fatty acid
40) Which of the following is directly involved in the synthesis of phosphatidylcholine from
phosphatidylethanolamine?
A) 3-hydroxy-3-methyl-glutaryl CoA (HMG CoA)
B) mevalonate
C) 5-phosphoribosyl-1-pyrophosphate (PRPP)
D) S-adenosylmethionine (SAM)
E) ceramide
The following 2 questions refer to the clinical scenario below:
A young girl with a history of severe abdominal pain was taken to her local hospital at 5 AM in severe distress.
Blood was drawn, and the plasma appeared milky, with the triacylglyceride (TAG) level in excess of 2000 mg/dl
(normal = 4-150 mg/dl). The patient was placed on a diet severely limited in fat, but supplemented with
medium-chain length fatty acids.
41) Which of the following lipoprotein particles are most likely responsible for the appearance of the patient’s
plasma?
A) Very low density lipoproteins (VLDL)
B) Intermediate density lipoproteins (IDL)
C) Low density lipoproteins (LDL)
D) High density lipoproteins (HDL)
E) Chylomicrons
42) Medium-chain length fatty acids are given because they
A) enter directly into the portal blood for metabolism by the liver.
B) are activators of lipoprotein lipase.
C) are more efficiently packed into serum lipoprotein particles.
D) can be converted into a variety of gluconeogenic precursors.
E) provide more calories than long-chain fatty acids.
43) Which of the following statements about bile acids and bile salts is correct?
A) Conjugation of the bile salts with taurine or glycine produces bile acids.
B) The addition of taurine or glycine makes these molecules more insoluble in water.
C) Bile acids and bile salts are synthesized in the gall bladder.
D) The majority of bile acids and bile salts are excreted from the body daily.
E) They function as detergents because they are amphipathic.
44) Which of the following conditions would activate the pathway of cholesterol synthesis within a liver cell?
A) Increased concentrations of cholic acid.
B) Increased numbers of LDL receptors at the cell surface.
C) Dephosphorylation of HMG-CoA reductase.
D) Activation of proteases that degrade HMG-CoA reductase.
E) Increased concentrations of malonyl CoA, the substrate of cholesterol synthesis.
11
45) Lipoprotein lipase is:
A) activated by a protein kinase-driven phosphorylation
B) released from the pancreas to catabolize dietary triacylglycerols in the small intestine.
C) requires co-lipase for activation.
D) an extracellular lipase that catabolizes triacylglycerols in chylomicrons and VLDLs.
E) responsible for releasing fatty acids from adipocyte's stores of triacylglycerols.
The next two questions relate to the following clinical scenario: You have an overweight patient with a
great deal of adipose tissue (adipocytes). Her diet, though, is mostly carbohydrates with a moderate fat intake.
46) Which of the following statements is the best information that you can tell your patient?
A) She should completely eliminate sugar from her diet to force her body to convert her fat stores back to
sugar.
B) She should continue eating her high carbohydrate diet because that is not causing her weight gain.
C) You are going to prescribe her 2,4-dinitrophenol (2,4-DNP) to help her lose the weight by uncoupling her
mitochondria.
D) Her liver is converting the excess carbohydrate in her diet to fatty acids for storage as triacylglycerols
(TAG), which is the cause of her weight gain.
E) Her increased amount of fat cells (adipocytes) results in a decreased amount of circulating leptin, which is
continually making her hungry.
47) Under the conditions of excess carbohydrate intake by your patient, which of the following regulatory
effects would be occurring in liver cells?
A) The acetyl CoA formed from the pyruvate dehydrogenase (PDH) complex would activate pyruvate
carboxylase for gluconeogenesis to occur.
B) Carnitine acyl transferase I (CAT I) would be inhibited by high concentrations of malonyl CoA.
C) All 8 enzymes of the TCA cycle would be active to generate oxaloacetate (OAA) for shuttling acetyl CoA
units to the cytosol.
D) Glycogenolysis (glycogen breakdown) would occur to run glycolysis for ketone body production.
E) NADPH production by the pentose phosphate pathway is necessary to run the electron transport chain for a
continual supply of ATP needed for fatty acid synthesis.
48) Enteropeptidase deficiency is an inborn error of metabolism that causes malabsorption of protein. The
most likely explanation for protein malabsorption is that in the absence of this enzyme, the only active
protease is
A) pepsin
B) carboxypeptidase
C) trypsin
D) chymotrypsin
E) elastase
49) Digestion and absorption of proteins
A) occurs only in the presence of bile salts
B) is more effective if the protein has a high content of essential amino acids
C) occurs by hydrolysis of peptide bonds by proteases that are stored as zymogens
D) occurs only by removal of amino acids from the ends of chains (N-terminal or C-terminal)
E) does not occur in the stomach.
12
50) Which of the following statements regarding protein degradation of endogenous proteins is correct?
A) The lysosomal pathway primarily degrades proteins taken up by a cell via endocytosis.
B) The attachment of ubiquitin to a protein does not require ATP.
C) Enzymes targeted for destruction require the attachment of only one molecule of ubiquitin.
D) Lysosomes degrade ubiquitin-labeled proteins to peptide fragments.
E) The lysosomal pathway degrades the peptides generated by the proteasome complex.
51) A 2-year-old girl, daughter of a recently immigrated African family, is admitted to the pediatric ward owing
to an increase in abdominal girth and failure to thrive. She was breast-fed until 1 year of age, at which time her
mother ran out of milk. The mother then fed her bottles of liquid gelatin and believed that she was getting
enough calories. On physical examination, hepatomegaly was evident as was depigmentation of both skin and
hair: thinning of hair; dry skin. Height and weight in the fifth percentile. Loss of muscle in appearance,
confirmed by lab data indicating hypoproteinemia and hypoalbuminemia. She is apathetic and irritable and has
been having frequent episodes of diarrhea. Pathology lab reports intestinal mucosal atrophy with loss of brush
border enzymes; also atrophy of pancreatic islet cells that secrete digestive enzymes. This girls suffers from:
A) Scurvy
B) Pellagra
C) Marasmus
D) Hypercholesterolemia
E) Kwashiorkor
For the next three questions, identify the chemical or enzyme name corresponding to the letters A, B,
C, D, and E in the diagram below. Then, choose the letter that best fills the blanks (with Question
Number) in the following paragraph.
Processing of the amino groups of the amino acids produces ammonia, which is toxic in its free form. In most
tissues, __Question 52___, combines free ammonia with glutamate to produce nontoxic __Question 53___ ;
while muscle cells will export their amino groups as ___Question 54____ to the liver.
52) Fill in the blank designated as Question 52 in paragraph above.
53) Fill in the blank designated as Question 53 in paragraph above.
54) Fill in the blank designated as Question 54 in paragraph above.
13
55) Ketone bodies can NOT be used for energy by
A)
B)
C)
D)
E)
skeletal muscle cells
kidney cells
brain cells
red blood cells
cardiac muscle cells
56) An insulinoma is a type of pancreatic tumor that results in increased insulin production. Which of the
following would most likely be seen in an untreated patient with an insulinoma?
A) increased serum fatty acids
B) polyuria (frequent urination)
C) reduced liver glycogen stores
D) ketosis
E) hypoglycemia
57) A long distance runner is several hours into a race. His metabolism is dominated by the influence of
epinephrine and glucagon. Which of the following correctly describes metabolism occurring in the liver,
muscle, and adipose tissue?
A) Concentrations of cAMP are decreased in both the liver and muscle.
B) Muscle tissue increases glucose uptake from the blood.
C) HMG CoA reductase is active in the liver.
D) Glycogen phosphorylase is phosphorylated and active in both liver and muscle.
E) Triacylglycerol breakdown is inhibited in adipose tissue.
58) After five weeks of starvation, which of the following statements would correctly describe the changes in
levels of circulating fuel compared to the well-fed state?
A) lactate, pyruvate, and alanine are higher
B) glucose is higher
C) overall ATP equivalents of circulating fuel is lower
D) fatty acids are higher
E) ketone bodies are lower
59) A newborn girl appeared normal at birth, but within 24 hours she developed lethargy, hypotonia, and
apnea. Initial tests showed that she had low levels of blood urea nitrogen (BUN) and elevated ammonia. A
urea cycle defect was suspected, and further tests were performed. Urinalysis results: high glutamine and
orotic acid, but undetectable levels of citrulline. The defective enzyme is most likely:
A) carbamoyl phosphate synthetase II
B) argininosuccinate synthetase
C) argininosuccinate lyase
D) arginase
E) ornithine transcarbamoylase
14
The next five questions relate to the following clinical scenario: Sparty has type 1 diabetes mellitus. He
has just been admitted to the hospital with symptoms of Kussmaul respirations (rapid and deep breathing),
polyuria (frequent urination) and polydipsia (frequent thirst). Initial lab data indicated elevated blood glucose,
and the presence of glucose and ketone bodies in the urine.
60) Which of the following statements is most likely the cause of Sparty’s abrupt symptoms of polyuria and
polydipsia?
A) He injected too much insulin to compensate for a carbohydrate-rich meal.
B) His RBC are lysing, due to lack of glucose uptake, releasing too much water into his plasma.
C) Excess glucose in his urine causes him to excrete excess water, making him drink more for compensation.
D) The increased rate of beta-oxidation causes the electron transport chain to produce excess water.
E) His rapid and deep breathing to blow of excess CO2 causes him to retain water.
61) At the time of Sparty’s admission to the hospital, which of the following conditions is most likely correct?
A) Protein degradation in his muscle will be inhibited.
B) His ketone body levels will be low.
C) Most of his key regulated enzymes in the liver will be phosphorylated.
D) His HbA1C levels in the blood will be low.
E) His blood pH will be high
62) Which one of Sparty’s liver enzyme activities decreases when he is treated with insulin?
A) Fructose 1,6-bisphosphatase
B) Pyruvate kinase
C) Pyruvate dehydrogenase complex
D) Phosphofructokinase 1 (PFK1)
E) Glucokinase
63) Why does Sparty’s type 1 diabetes cause ketoacidosis, but general starvation conditions would not lead to
ketoacidosis?
A) In diabetes, all of the excess glucose is converted to ketone bodies by the liver.
B) In diabetes, tissues do not have to resort to using the ketone bodies produced.
C) In starvation conditions the circulating fatty acids are used by the tissues for fuel, so the liver does not have
to make ketone bodies.
D) In starvation conditions, the liver uses the acetyl CoA produced for the TCA cycle rather than ketone body
production.
E) In diabetics, muscle tissue also releases ketone bodies to the blood for use by other tissues.
64) Sparty must use a mixture of insulin analogs to maintain his blood glucose due to the lack of production of
insulin by his pancreas. Which of the following statements correctly describes native human insulin?
A) Insulin is an eicosanoid hormone.
B) Insulin is activated by cleavage of the C-peptide from proinsulin
C) Insulin stimulates phosphorylation of many key regulatory enzymes in metabolism.
D) Insulin binds to G-protein coupled receptors.
E) Insulin is released from α-cells of the pancreas.
15
END OF EXAMINATION
Tear off this sheet and save to check your answers.
Please remember to:


Write the letter corresponding to your FORM in the appropriate place on the answer sheet.
SIGN AND RETURN YOUR EXAMINATION to an instructor before leaving the exam room.
FORM: A
1. _______
21. _______
41. _______
61. _______
2. _______
22. _______
42. _______
62. _______
3. _______
23. _______
43. _______
63. _______
4. _______
24. _______
44. _______
64. _______
5. _______
25. _______
45. _______
6. _______
26. _______
46. _______
7. _______
27. _______
47. _______
8. _______
28. _______
48. _______
9. _______
29. _______
49. _______
10. _______
30. _______
50. _______
11. _______
31. _______
51. _______
12. _______
32. _______
52. _______
13. _______
33. _______
53. _______
14. _______
34. _______
54. _______
15. _______
35. _______
55. _______
16. _______
36. _______
56. _______
17. _______
37. _______
57. _______
18. _______
38. _______
58. _______
19. _______
39. _______
59. _______
20. _______
40. _______
60. _______
16
Fall 2011 BMB 514: Exam 3—Answer Keys
Question #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
Form A
A
B
C
A
B
A
D
A
A
C
E
D
E
A
E
E
A
A
B
D
B
A
D
C
B
D
E
A
C
A
B
C
A
E
C
C
E
A
B
D
E
A
E
Form B
A
B
B
E
A
E
D
A
E
C
D
C
D
E
E
A
A
B
A
C
A
E
D
C
A
C
D
E
C
E
A
B
A
E
C
E
A
C
B
C
D
E
D
Form C
A
B
A
D
E
D
D
A
D
C
C
B
C
E
A
A
B
A
E
B
E
D
D
C
E
B
C
D
C
D
E
A
A
E
E
A
C
C
B
B
C
D
C
Form D
A
B
D
B
C
B
D
A
B
C
A
E
A
B
A
E
E
A
A
E
C
B
D
C
C
E
A
B
C
B
C
D
A
E
A
C
C
E
B
E
A
B
A
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
C
D
D
B
A
C
A
E
D
E
A
D
E
D
D
E
C
C
A
B
B
B
D
D
B
A
C
A
D
D
E
A
E
D
D
E
D
C
C
A
B
B
A
D
D
B
A
C
A
C
D
E
A
D
D
E
D
E
C
C
A
B
B
D
D
D
B
A
C
A
A
D
E
A
E
D
E
D
D
C
C
A
B
B