Download Name 1 Bio 451 12th November, 1999 EXAM III This

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Name ____________________________
12th November, 1999
Bio 451
EXAM III
This exam will be taken apart for grading. If you expect to receive proper credit for your
answers it is essential that you PRINT your name clearly at the top of 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.
NOTE: FULL CREDIT WILL BE GIVEN FOR THOSE ANSWERS THAT CLEARLY
ADDRESS ALL RELEVANT ASPECTS OF THE QUESTIONS C IN THE CLEAREST
AND MOST CONCISE MANNER.
QUESTION
I
MAXIMUM POINTS
EARNED POINTS
9
II
10
III
5
IV
5
V
6
VI
11
VII
10
VIII
18
IX
10
X
6
XI
10
TOTAL
100
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I. [ 9 Points]
Respiration of mitochondrial suspensions can be assessed with an oxygen electrode. The following plot
illustrates what happens to the oxygen concentration in the surrounding medium under various
experimental conditions.
Explain the effect of adding each of the following compounds, in turn, to the same suspension; ADP,
oligomycin, 2,4-dinitrophenol. Please ignore the slight blips.
Begin by stating, according to the graph, what effect ADP has on the rate of oxygen consumption.
Why?
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CONTINUED
Does oligomycin alter oxygen the rate of consumption, according to the graph ? In what way ?
Why?
Answer the all the same questions for DNP.
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II. [ 10 points]
Match the following enzyme or other molecule with its location.
_____ Pyruvate dehydrogenase
_____ 3-Phosphoglycerate dehydrogenase
_____ Flavoprotein dehydrogenase
_____ Malate dehydrogenase
_____ Cytochrome c
_____ Fatty acid oxidation enzymes
_____ ADP-ATP translocator
_____ Mitochondrial porin
_____ ATP-Citrate lyase
A. Cytosol
B. Mitochondrial outer membrane
C. Mitochondrial inner membrane
D. Mitochondrial inner membrane space
E. Mitochondrial matrix
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III. [ 5 points]
Indicate whether the following statements are true (T) or false (F):
a) Proteins with the sequence Lys-Phe-Glu-Arg-Gln are selectively degraded by
proteasomes.
b) Proteins containing sequences rich in Pro, Glu, Ser and Thr often have short halflives.
c) The additionof ubiquitin protects segments of a protein from proteolysis.
d) Lysosomal proteases degrade only extracellular proteins that enter the cell by endocytosis.
e) The ubiquitin-transfer reactions catalyzed by E2 and E3 do not require the input of free
energy in the form of ATP.
IV. [ 5 points]
Match each item on the left with its description on the right.
_____ Bile acid
_____ Albumin
A. Helps bind lipase to the lipid-water interface
_____ Phospholipase A2
B. Hydrolyzes phospholipids to yield
lysophospholipids and free fatty acids
_____ Colipase
C. Facilitates the digestion of water-insoluble
triacylglycerols
_____ Chylomicrons
D. Tranports lipid digestion products through
the lymphatic system and then the bloodstream
to the tissues.
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Name ____________________________
E. Transports free fatty acids released from
adipose tissues stores through the bloodstream
V. [ 6 points]
Briefly, but clearly, define and illustrate your awareness of the metabolic relevance of the items listed
below. CHOOSE 5. Only the first 5 answers will be graded.
CDP-choline
Mevalonic acid
CytochromeP450
N-acetylglutamic acid
Condensing enzyme
ATP-citrate lyase
SAM
Tetrahydrofolic acid
Serine hydroxymethyltransferase
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Name ____________________________
VI. [ 11 points ]
Match the reactant or characteristic in the right column with the appropriate pathway in the left column.
1) Acyl-CoA
a) Fatty acid oxidation _____________
2) Occurs in the mitochondria
b) Fatty acid synthesis ______________
3) NAD+-dependent
4) Three unique thiols are involved
5) ACP involved
6) Synthesis requires cooperation between
sites on two identical polypeptide
chains
7) FAD-dependent
8) NADPH-dependent
9) Committed step regulated by hormonemediated phosphorylation
10) Malonyl-CoA
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Name ____________________________
VII. [10 points]
A. Which of the following events occur in the receptor-mediated endocytosis pathway?
Place them in their proper sequential order.
1) breakdown of LDL involving lysosomes
2) endocytosis of LDL along with LDL receptors
3) regulation of the biosynthesis of HMG-CoA reductase by cholesterol and/or cholesterol
metabolites
4) degradation of LDL receptors
5) binding of LDL to LDL receptors.
B. From the following compounds, identify the intermediates in the synthesis of
cholesterol and list them in their proper sequential order.
1) Geranyl pyrophosphate
2) Squalene
3) Isopentenyl pyrophosphate
4) Glycocholyl-CoA
5) Farnesyl pyrophosphate
6) Lanosterol
7) Mevalonic acid
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8) $-hydroxybutyric acid
VIII. [18 points ]
Choose statements which are completely correct. 18 correct choices are possible. You will lose ½
point for each incorrect guess.
=====================
___Loss of function is associated with extreme light sensitivity
PBG deaminase
___ Participates in the synthesis of Uroporphyrinogen III
=====================
)-Aminolevulinic acid [ALA]
synthase
___The committed step in heme biosynthesis
___Substrates are glycine and succinyl-CoA
___Encoded by mitochondrial genes but synthesized on cytoplasmic
ribosomes
=======================
___Overproduction associated with light sensitivity when uro’gen
III cosynthase is defective
Uroporphyrinogen I [Uro’gen I]
___An essential precursor for heme biosynthesis
=======================
___ Regulates its own synthesis at several different levels
Heme
___ Formed in the mitochondria by the addition of Fe (III) to
protoporphyrin IX
=======================
___ Individuals homozygous for a complete deficiency of this enzyme
are not found
Uro’gen III Cosynthase
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___ Required for the translocation of ALA synthase to the
cytosol
=======================
_____ are synthesized in the liver but cannot be used as an
energy source for hepatocytes due to their lack of thiolase.
Ketone bodies
_____ HMG-CoA is a common intermediate in the synthesis of
both cholesterol and ketone bodies.
_____ are preferred carbon sources for heart tissue
====================
====================
_____ contain B-100 protein, transport endogenously synthesized
cholesterol and triacylglycerols, and are modified by lipoprotein lipase
VLDL
_____ are exported by the liver; they are the largest of the
major lipoprotein particles
===================
_____ the smallest of the lipoprotein particles, thought to help
remove cholesterol from the body, contain bile salts
HDL
_____ produced by conversion of IDL particles
===================
_____ a protein containing bound lipid, like serum albumin
Lipoprotein
_____ a particle containing triacylglycerols, cholesterol esters and
proteins, as well as phospholipids.
====================
_____ a disorder is characterized by elevated serum cholesterol, most
of which is represented by LDL.
Familial Hypercholesterolemia
_____ associated with early onset coronary artery disease
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Name ____________________________
_____ the major biochemical defect is the absence of B-100 on
LDL
====================
_____ the function of the glycosylated domains is the most clearly
understood
LDL Receptor Domains
_____ deletion of the membrane-spanning domain leads to aberrant
secretion of the receptor
_____ the cytoplasmic domain can be largely deleted without
affecting receptor function.
====================
====================
_____ catalyze the oxidative deamination of of Glu
_____ catalyze the transfer of the " -amino group of glutamate to
enzyme-bound pyridoxal phosphate
Aminotransferases (Transaminases)
_____ catalyze the transfer of an enzyme-bound amino group from
pyridoxamine phosphate to pyruvate
_____ catalyze the deamination of branched-chain amino
acids
====================
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Name ____________________________
IX
[10 points]
Answer A OR B . If more than one question is answered, only the first answer will be graded.
A. A small number of individuals who have phenylketonuriaa (PKU) have normal levels of
phenylalanine hydroxylase activity. On normal (Phe-containing) diets they continue to
accumulate phenyl pyruvate, phenyl acetate, and phenyl lactate. They also have high levels of
dihydrobiopterin. What is the probable enzyme deficiency in these individuals ? Explain.
B. In muscle, glutamine synthetase (GS) is very active, catalyzing the ATP-dependent formation of
glutamine from glutamate and ammonia. In liver, GS activity is very low; however, the activity of
glutaminase, which catalyzes the hydrolysis of glutamine to ammonia and glutamate, is high.
Explain the metabolic significance of these tissue-specific differences in enzyme levels.
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X. [6 points]
The catabolism of the carbon chain of isoleucine produces the following intermediates:
CH3-CO-S-CoA
CH3-CH2-CO-S-CoA
A defect in the metabolism of the compound on the right is correlated with hypoglycemia [low blood
glucose].
a) What is the first step in the catabolism of CH3-CH2-CO-S-CoA?
b) Why would a defect in this enzyme be associated with hypoglycemia?
c) Would you expect a deficiency in vitamin B12 to be correlated with hypoglycemia as well?
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Name ____________________________
XI [ 10 points]
Answer A or B, but not both. Only your first answer will be graded.
A. NOTE: This question does NOT require you to draw the structure of F1F0ATPase, or to describe
the binding-change mechanism in detail.
1. Describe the subunit structure of the F1 portion of ATP synthase; do NOT include a description of
the entire ATP synthase.
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Name ____________________________
2. Two lines of evidence in support of the binding-change model for ATP-synthase were described in
class. Both were based on studies of F1ATPase. One was based on studies of molecular models and
the other was based on direct observation of functional F1ATPase. Describe ONE of these studies and
indicate clearly how this study supports an essential feature of the binding-change model.
Continued
B.
1. How do studies of bacteriorhodopsin relate to the mechanism of chemiosmosis?
2. Outline the essential features of one cycle of bacteriorhodopsin, including the roles of Asp85 and Asp
92.
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Name ____________________________
Extra Credit [5 points]
Asp92 was replaced by Asn, by site directed mutagenesis. What effect would you expect this to have
on the function of bacteriorhodopsin as a proton pump? Explain.