Download NAME_________________ 1 BIO 451 13th

NAME_________________
1
13th December, 2002
BIO 451
FINAL EXAM KEY
This exam will be taken apart for grading. Please PRINT your name on each page.
If you do not have sufficient room for your answer in the space provided, please continue on the back of the
page on which the question appears.
Question
I.
Maximum Points
Earned Points
13
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II.
8
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III.
8
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IV.
4
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V.
12
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VI.
8
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VII.
10
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VIII.
12
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IX.
7
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X.
16
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XI.
10
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XII.
10
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XIII.
8
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XIV
7
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==================================================================
TOTAL 133
Normalized
I
II
III
Score on :
Total* = Sum of two best scores + points earned on the Final
[COURSE GRADE ON REVERSE SIDE]
FINAL
NOTE: FULL CREDIT WILL BE GIVEN FOR THOSE ANSWERS WHICH CLEARLY ADDRESS
ALL RELEVANT ASPECTS OF THE QUESTION S IN THE CLEAREST AND MOST
CONCISE MANNER.
NAME_________________
I.
[13 Points:1 point for each correct response]
Match the metabolic pathways below with the cellular compartments in which they occur.
A Cytosol
B. Inner mitochondrial membrane
C. Mitochondrial matrix
D. Mitochondrial intermembrane space
E. Endoplasmic reticulum
____A____Glycolysis
_____A___Lactic fermentation
______C__Pyruvate dehydrogenation
_______A,C______ Amino acid degradation
________A,C_____Urea cycle
_________A,C____Gluconogenesis
_______A___ Cholesterol synthesis
II.
_____C_______Palmitoyl-coA Oxidation
______A_______ Palmitate synthesis
_______C______ Citric acid cycle
____B____Oxidative phosphorylation of ADP
____A____Pentose phosphate pathway
___F_____ Fatty acid elongation and desaturation
[8 Points] Answer Either A or B not both. ONLY THE FIRST ANSWER WILL BE GRADED
A. How does an increase in blood glucose affect triacylglycerol metabolism in adipocytes?
Increasing levels of blood glucose favor TG synthesis as the rate of glucose uptake by fat cells
increases. The 3-carbon backbone of TG’s is derived from DHAP, an intermediate of glycolysis.
DHAP is converted to Glycerol-3-Phosphate to favor FA esterification.
B. You obtain a liver homogenate from a fasting mouse and "spike" it with a high concentration of
glucose. In what form would you expect glyogen phosphorylase?
The addition of a large amount of glucose shifts the T/R equalibrium for phosphorylase towad the T
state. Stabilization of the T state by glucose binding promotes dephosphorylation of Ser 14, which
converts the enzyme to the less active phophorylase b.
2
NAME_________________
III.
[8Points]
A.
During G- protein activation, which subunit exchanges GDP for GTP? What is the intermediate
consequence of this exchange? (4 pts)
3
When G-protein binds to a hormone-receptor complex, the Gα subunit exchanges GDP for GTP.
Binding of GTP induces a conformational change in Gα that causes it to dissociate from Gβδ . GTP
binding also increases the affinity of Gα for adenylate cyclase, which is thereby activated.
B.
Describe the intracellular signaling cascade mediated by phospholipase C activity. How is
phospholipase C activated? (4pts)
SEE ANSWER TO CHAPTER 21 OF COMPANION PAGES 276 & 277.
IV.
[4 points]
List the order in which the following energy sources are used by skeletal muscle to, produce ATP:
protein, phosphocreatine, fatty acids, glycogen.
Phosphocreatine, Glycogen, FA’s, Protein.
NAME_________________
V.
4
[12 Points, 1.5 pts each]
This question is designed to test your familiarity with heme biosynthesis and catabolism as well as
inter tissue cooperation by writing the appropriate item beside each description.
A. Principal site of red blood cell production in adult humans
Bone marrow
B. In mature red blood cell, aerobic; makes globin, heme and purine nucleotides
C. Involved in transport of billirubin from the spleen to the liver
reticulocyte
Serum albumin
D.Degrades worn out red blood cells, part of the reticuloendothelial system. Spleen
E. Required for removal of glucuronic acid residues from billirubin diglucuronide. Enyzmes of intestinal
bacteria
F. Light-sensitive heme precursor that accumulates when urogen III cosynthase is defective.
Uroporphirinogen I or Urogen I
G. Storage form of iron in the bone marrow tissue. ferritin
H. Principal site of feedback regulation of heme synthesis. ALA synthase
VI.
[8 points]
1.
Malonic acid is a structural analog of succinic acid. Addition of malonate to a suspension of
respiring, intact mitochondria is followed by a rapid cessation of O2 consumption. Explain; the
correct answer is short but you must be specific. (4pts)
O2 consumption depends on a functioning TCA cycle; malonate is a competitive inhibitor of succinic
dehydrogenase and will therefore inhibit the cycle.
2.
Short of removing the malonate, how might you restore respiration and coupled phosphorylation?
Your assumptions and rationale must be explicitly stated. [Note: Conversion of the malonate to
malonyl-SCoA is not an acceptable option.] Explain. (4pts)
Add succinate in excess of malonate
NAME_________________
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VII. [10 points]
Answer Either A or B not both. ONLY THE FIRST ANSWER WILL BE GRADED
A.
A sample of liver tissue was obtained post mortem from the body of a person believed to be genetically
deficient in one of the enzymes of carbohydrate metabolism. A homogenate of the liver sample had the
following characteristics. 1) It degraded glycogen to produce G-6-P. 2) It did not synthesize glycogen from
any sugar, nor did it utilize galactose as an energy source. 3) It synthesized G-6-P from lactate. Which of
the following enzymes was deficient? Give specific reasons for your answer. You must also state
specifically the basis for elimination of two choices.
1) glycogen phosphorylase
#1 says this enzyme is OK
2) fructose-1,6-phosphatase
#2 says that gluconeogenesis works, so FBPase-1 is OK
3) UDP-glucose pyrophosphorylase Required for glucogen synthesis and Glu to Gal,
and both are non functional, the lesion is here.
B.
A weight-reducing diet heavily promoted several years ago required the daily intake of "liquid
protein" (soup of hydrolyzed gelatin; a collagen product), water and an assortment of vitamins. All other
food and drink were to be avoided. People on this diet typically lost 10 - 14 lb. in the first week.
A number of people on this diet died. What are some of the dangers inherent in the diet and how can they
lead to death? [Hint: It is not acceptable to invoke contamination or experimental artifacts. Consider
ammonia toxicity and why this is likely in this case, as well as the composition of collagen.]
The individuals are deficient in essential amino acids; collagen is 1/3 glycine and very poor in Lys, Trp,
etc. There would also be extensive breakdown of body protein and a huge ammonia load to deal with,
perhap more than can be handeled by te urea cycle
NAME_________________
VIII. [ 12 points; 1 pt each]
For each description (below) select the ONE most appropriate vitamin; there are two parts for which there
are two possibilities – you are to provide either of them.
1. Required for oxidative decarboxylation of "-keto acids __D or K_____
2. Its synthesis is inhibited by sulfanilamide ___F___
3. Participates in the conversions involving free radicals ____B___
4. Participates in 1C transfers at the level of a formyl group __F____
5. Participates in 1C transfers at the level of a carboxyl group __A____
6. Participates in hydride ion transfers ___K___
7. Participates in the transfer of two hydrogen atom transfers,
each with one electron __E or C_____
8. Participates in postranslational hydroxylation __C____
9. A derivative of cholesterol ___H___
10. The precursor for FMN ___E___
11. Contains a thiazoline ring ___D___
12. Contains a redox active disulfide __L____
A. Biotin
B. Vitamin B12
C. Ascorbic acid
D. Thiamine
E. Riboflavin
F. Folic acid
G. Vitamin A
H. Vitamin D
I. Vitamin K
J. Vitamin E
K. Niacin
L. Lipoic acid
6
NAME_________________
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IX. [7 points]
For each of the following, choose the ONE best answer
A. Hormonal stimulation of the second messenger inositol 1,4,5-triphosphate [IP3] quickly leads to the
release of which intracellular second messenger? __d___
a. cGMP
b. cAMP
c. prostaglandin
d. calcium
e. leukotriene
B. A strong cup of coffee would be expected to ___c___
a. interfere with the synthesis of prostaglandins
b. decrease the effects of glucagon
c. enhance the effects of epinephrine
d. provide the vitamin niacin
e. none of the above
C. During starvation, ketone bodies are synthesized in ____c__
a. adipose tissues
b. brain
c. liver
d. muscles
e. thymus
D. After an injection of insulin in a diabetic patient with hyperglycemia, there is a prompt normalization of
plasma glucose, due to the recruitment of which of the following transport proteins to the plasma
membrane? ___d___
a. GLUT 1
b. GLUT 2
c. GLUT 3
d. GLUT 4
e. GLUT 5
E. Glycolysis is the only ATP-producing pathway in ___a__
a. erythrocytes
b. lymphocytes
c. reticulocytes
d. hepatocytes
e. neurons
f. adipocytes
F.
In the normal resting state of humans, most of the blood glucose burned as fuel is consumed by___b__
a. the liver
b. the brain
c. the kidneys
d. adipose tissue
e. muscle
NAME_________________
G. Elevation of cytosolic calcium from intracellular stores can be caused by ___d___
a. cAMP
b. cGMP
c. cCDP
d. inositol 1,4,5-triphosphate [IP3]
e. diacylglycerol
8
NAME_________________
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X. [16 points]
This question is presented in the form of a crossword puzzle. It is designed to test your familiarity with
terms and concepts associated purine nucleotide metabolism. As with most crossword puzzles, following
the clues is a parenthetical expression which indicates the number of letters/numbers required for a
particular answer; where answers are to be given in terms of abbreviations this is also indicated. You
cannot possibly solve the entire puzzle in the time allotted; therefore, choose only 8 items. It is important,
as with most crossword puzzles, that the answers are spelled properly. If you enter an answer and later
decide that the answer is wrong cross it out or erase it. Only your first 8 answers will be graded. It is
essential that you write legibly. Full credit will be awarded for correct, complete, legible, correctly-spelled
answers. 2 points will be awarded for each correct answer therefore total credit for this question is 16
points.
NAME_________________
10
NAME_________________
11
NAME_________________
XI. [10 Points]
Identify ONE specific example of a genetic defect in metabolism that have been considered in class or in
the text, and for which the biochemical basis is clear.
You must describe BOTH the biochemical basis of the lesion as well as the metabolic/physiological
consequences of the defect in as much detail as you are able.
SEE CLASS NOTES/TEXT
12
NAME_________________
XII.
13
[10 points]
A. Describe the biochemical and cellular processes that are involved in glucose
stimulated insulin secretion (GSIS). (5pts)
Insulin is secreted by the $-cells of the pancreas. Glucose is taken up via GLUT 2, a low
affinity glucose transporter. The first stem in its metabolism is conversion to G6P via glucokinase (GK);
subsequent catabolic processes, especially OxPhos produces ATP. ATP inhibits the ATP-dependent
potassium channel. This depolarizes the membrane and allows calcium ions to enter the cell via the
calcium channel. The influx of calcium ions enhances insulin secretion.
B.
kCAT
Km
Normal
8.4mM
54.4moles.mole!1.sec!1
Mutant (Val455Met)
2.9mM
50.2 "
"
"
"
The table above provides values for relevant kinetic parameters for glucokinase from $cells from normal individuals and patients having a mutation at residue 455 of the
polypeptide. Keeping the normal processes involved in GSIS in mind, what would the
effect of this mutation be on levels of insulin and glucose in the blood? Explain your
rationale in as much detail as you are able. (5pts)
The mutant GK has a significantly higher affinity for glucose, this means that for a given concentration
of glucose from the blood, the GK activity is higher in the patients carrying the mutation, thus producing
more ATP and increasing insulin secretion more than in normal individuals.
These individuals will show hyperinsulinemia and hypoglycemia (insulin stimulates glucose uptake).
NAME_________________
1) Consider the situation where you want to check if two proteins A and
B have a direct interaction using fluorescence resonnance energy transfer
(FRET) technique. You have the options to use any of the fluorophores
provided in the table. Which pair would you use and why? (6 points)
The right pair to use if ECFP/ EYFP. However, Alexa488/ECFP, Bodipy/
FITC, Bodipy/EYFP, ECFP/Cy3 deserve 2 points.
The selected pair is used because the emission wavelength of one
fluorophore is close enough to excite the second fluorophore.
2) a- Why is X-ray crystallography important? (2 points)
Insight into 3D structure of protein
Better way to design drugs
Understand Protein- Protein interaction
b- What steps do you experimentally take to generate a 3D strucure? (4
points)
Purify protein (higher than 98%)
Grow crystal using the hanging drop method
Collect diffraction data
Generate electron density map
Solve structure
c- Which step is the most limitting and why? (2 points)
Protein purification and/ or crystal growing step.
XIII. [8
points]
Consider the situation where you want to check if two proteins A and B have a direct
interaction using fluorescence resonance energy transfer (FRET) technique. You have
options to use any of the fluorophores provided in the table. Which pair would you use
and why?
Florophores
Alexa 488
Bodipy 564/570
ECFP
Cy3
FITC
EYFP
GFP
Absorption
wavelength (nm)
492
564
436
514
490
517
475
Emission
wavelength (nm)
520
570
488
566
520
528
509
14
NAME_________________
XIV. [7
Points]
a)
Why is X-ray crystallography important? (2 pts)
b)
What steps do you experimentally take to generate a 3D structure? ( 3pts)
c)
Which step is the most limiting and why? (2 pts)
15