BIOC*2580 Fall 2007 Final Examination
Friday December 7, 2007; 8:30 a.m. Instructor: Dr. David Josephy
Instructions: No written aids or programmable calculators may be brought into the exam. Electronic
communication devices (such as cellular telephones) are strictly prohibited. This exam. determines
45% of the final course grade. Total marks for this paper = 80. Time allotted = 2 hours (120 minutes).
Section A: True/False questions. Please mark your answers on the “Scantron” card. Answer A if the
statement is true; answer B if the statement is false. One mark each × 11 questions = 11 marks.
(No marks will be deducted for wrong answers.)
1. Enzymes are biochemical catalysts.
2. Phosphatidylglycerol is a form of “storage fat”.
3. The conversion of an aldehyde to an acid is an oxidation reaction.
4. Thymine is a normal base constituent of both DNA and RNA.
5. The two strands of the DNA double helix are anti-parallel.
6. Glucose is a reducing sugar.
7. Succinic acid is a tricarboxylic acid.
8. Lester B. Pearson won the Nobel Prize for explaining the significance of ATP in bioenergetics.
9. Each of the first three reactions of glycolysis consumes one molecule of ATP.
10. “GLUT” proteins are transporters that catalyze the import of glucose into cells.
11. Oxidative phosphorylation occurs in eukaryotic cells but not in bacterial cells.
Section B: Multiple-choice questions. Please mark your answers on the “Scantron” card.
One mark each × 25 questions = 25 marks. (No marks will be deducted for wrong answers.)
12. The activities of many proteins are regulated by phosphorylation: the enzyme-catalyzed addition of
phosphate groups to specific amino acid residues in the protein. The most likely donor of these
phosphate groups is:
A) ATP; B) phosphatidylcholine; C) acetyl CoA;
D) NADH; E) NADPH.
13. Phosphorylation of proteins (see previous question) can occur on either serine, threonine, or
tyrosine residues. These amino acids share the property that their side chains are ...
A) very hydrophobic; B) negatively (-) charged at physiological pH;
C) positively (+) charged at physiological pH; D) alcohols; E) aromatic rings.
14. The complete hydrolysis of one mole of phosphatidylglycerol yields the components
glycerol, fatty acid, and inorganic phosphate, in which of the following respective molar ratios?
A) 1 : 1 : 1 B) 1 : 2 : 1 C) 2 : 2 : 1
D) 2 : 1 : 2 E) 1 : 2 : 2
15. The linkage between the alpha and beta phosphate groups in ATP is best described as a ...
A) thioester linkage; B) glycosylic linkage; C) phosphate ester linkage;
D) phosphodiester linkage; E) phosphoanhydride linkage. 16. The Fischer structures shown at right represent ...
A) two different representations “on paper”
of the same sugar molecule;
B) a pair of epimeric aldopentoses;
C) a pair of anomeric aldopentoses;
D) a pair of anomeric ketopentoses;
E) none of the above answers is correct.
17. The sugar known as sedoheptulose is shown at right.
The anomeric carbon atom is atom:
A) A B) B C) C D) D E) none of the above.
18. Melibiose, a disaccharide, is designated “galactose á(166) glucose”.
In the structure of melibiose, a glycosidic bond links (via an O atom), the ...
A) anomeric C atom of galactose, in the beta configuration, to the C6 atom of glucose;
B) anomeric C atom of galactose, in the alpha configuration, to the C6 atom of glucose;
C) anomeric C atom of galactose, in the alpha configuration, to the anomeric C atom of glucose;
D) C6 atom of galactose to the anomeric C atom of glucose;
E) C6 atom of galactose to the C6 atom of glucose.
19. A chemical reaction has a positive enthalpy change and a positive entropy change.
This reaction ...
A) will always be spontaneous;
B) will always be non-spontaneous;
C) could be either spontaneous or non-spontaneous, depending on the temperature;
D) must be an oxidation-reduction reaction;
E) can only occur in the presence of a catalyst.
© 2007 P.D. Josephy unauthorized reproduction prohibited -2- 20. A biosynthetic metabolic pathway functions in the following manner:
ñ ó ô õ
A 6 B 6 C 6 D 6 E
where A, B, C, D, and E are metabolites, and ñ, ó, ô, and õ are the enzymes that catalyze the indicated
steps in the pathway. In order to maintain a steady level of operation of the pathway, which of the
following regulatory mechanisms would be most appropriate?
A) Synthesis (i.e., gene expression) of the four enzymes occurs only in the presence of metabolite E;
B) Metabolites B, C, and D are inhibitors of enzyme õ;
C) Metabolite E is an inhibitor of enzyme ñ;
D) Metabolite A is an inhibitor of enzyme õ;
E) Metabolite A is also converted into metabolite E by a different, ATP-dependent pathway.
21. The following thermodynamic data are available for the conversion of A to B:
(uncoupled reaction) A W B K eq10 -3
(ATP-coupled reaction) A + ATP W B + ADP + P i K eq200
In the living cell, the steady state ratio of [ATP] / ([ADPi [P]) = 5 ×10 . By approximately
what factor will the coupling to ATP hydrolysis increase the ratio of [B] / [A], relative to the value for
the uncoupled reaction?
A) 10 9 B) 2 × 108 C) 108 D) 2 × 105
E) 1 (i.e, the ratio will be unchanged)
22. The glycosylic (also called “glycosidic”) bonds in nucleic acids ...
A) connect bases to one another; B) connect sugars to bases;
C) connect sugars to one another; D) are also known as “phosphodiester linkages”;
E) none of the above statements is true.
23. All of the following enzymes would be found in the mitochondria of a human intestinal
epithelial cell, except:
A) succinate dehydrogenase; B) carnitine acyltransferase;
C) enoyl-CoA hydratase; D) pyruvate dehydrogenase; E) pyruvate kinase.
24. The mechanism of the reaction catalyzed by the beta-oxidation enzyme enoyl-coA hydratase
is similar to that of the citric acid cycle enzyme ...
A) malate dehydrogenase; B) alpha-ketoglutarate dehydrogenase; C) aconitase;
D) fumarase; E) citrate synthase.
25. Within the cell, ATP exists mainly as a complex with:
A) K ; B) Na ; C) Ca ; D) Mg ; E) Fe . ++
© 2007 P.D. Josephy unauthorized reproduction prohibited -3- 26. All but one of the following metabolic transformations can be accomplished without making
or breaking any carbon-carbon bonds. The one exception is:
A) glutamate W glutamine;
B) alpha-ketoglutarate W glutamate;
C) oxaloacetate W aspartate;
D) citrate W isocitrate;
E) isocitrate W alpha-ketoglutarate.
27. Fatty acids are usually transported across the inner mitochondrial membrane in the form of:
A) coenzyme A thioesters; B) glycerol esters; C) carnitine esters;
D) mixed anhydrides with ATP; E) none of the above answers is correct.
28. The complete oxidation of arachidic acid requires X rounds of beta oxidation and Y rounds of the
citric acid cycle, where X and Y =
A) 9 and 10; B) 8 and 9; C) 9 and 9;
D) 10 and 10; E) none of the above; ...
29. Considering the metabolic processes we have discussed in this course, which one of the following
molecules is a substrate for an oxidation reaction?
A) fructose-1,6-bisphosphate; B) dihydroxyacetone phosphate;
C) glyceraldehyde-3-phosphate; D) phosphoenol pyruvate;
30. Oxidative phosphorylation and electron transport are said to be "coupled". By this, we mean that, in
A) neither process can occur without the other;
B) oxidative phosphorylation requires electron transport, but not vice versa;
C) electron transport requires oxidative phosphorylation, but not vice versa;
D) the same proteins catalyze both processes;
E) chemical "uncouplers" stop both processses.
© 2007 P.D. Josephy unauthorized reproduction prohibited -4- 31. Which one of the following statements concerning electron transport and ATP synthesis
in the mitochondrion is false?
A) Electron transfer by the electron transport chain is coupled to H transport out of the matrix.
B) Reduced coenzymes donate electrons to the electron transport chain.
C) ATP synthesis occurs on the matrix side of the membrane.
D) Oxygen is reduced to wa-er by the respiratory electron transport chain.
E) Cytochrome c carries e between Complexes I and III, and also between Complexes III and IV.
32. The “half-channel” structures, which allow protons to move from the inter-membrane space into
the ATP synthase, and from the ATP synthase into the mitochondrial matrix, are located in the ...
A) a; B) b; C) c; D) ã; E) å ... subunit(s) of the enzyme.
33. A vintner (winemaker), wishing to get his wine into the liquor stores sooner after the grape
harvest, tries bubbling oxygen gas into the fermentation vats. To his satisfaction, he finds that this
change to the winery’s standard operating procedures makes the yeast cultures multiply much more
rapidly. The final product (i.e., the wine) would be ...
A) produced more quickly, bringing commercial advantage to the winery;
B) undrinkable, and almost alcohol-free;
C) unacceptably high in alcohol;
D) unacceptably sweet;
E) little different from the standard product, making the process change a waste of effort.
34. The oxidation of a fatty acyl CoA to an enoyl CoA, catalyzed by acyl CoA dehydrogenase, uses the
oxidizing agent: A) FAD; B) NAD ; C) NADP ; D) O ; E) 2 O . 2 2
35. According to the mechanism of ATP synthase catalysis proposed by Paul Boyer, the energy
released by the proton motive force is used mainly to promote the ...
A) binding of the alpha subunits to the beta subunits, to form the catalytic active sites;
B) binding of ADP to the enzyme;
C) condensation of ADP with inorganic phosphate to form ATP;
D) release of ATP from the enzyme;
E) none of the above.
36. Which of the following statements about glucose is false?
A) The glucose concentration in the blood plasma of a well-nourished human is about 5 mM;
B) Glucose enters human cells readily, by passive diffusion across the cell membrane;
C) Upon entry into most cells, glucose is rapidly phosphorylated;
D) Glucose can be catabolized under either aerobic or anaerobic conditions;
E) Glucose can bind covalently to some proteins in the blood.
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CORRECT ANSWERS: 121211222 1214352423 3125445313 1512142
© 2007 P.D. Josephy unauthorized reproduction prohibited -5- Student name: ID number:
Section C: Short answers. 20 marks total for Section C.
Note: Sections C and D are reproduced here twice - first without the answers, and then with the
answers filled in.
1. Next to the name of the substrate shown on the left, write the name of the enzyme which catalyzes
its metabolism (catabolism). 5 marks.
substrate enzyme name
2. “Pas de deux”. Each of the catabolic enzymes listed below acts on two substrates. One of the
substrates is given; name the other substrate. (Do not name the products of the reaction; do not draw
any chemical structures.) The first question is completed for you, as an example. 4 marks.
enzyme substrate 1 substrate 2
hexokinase glucose ATP
pyruvate kinase ADP
lactate dehydrogenase pyruvate
© 2007 P.D. Josephy unauthorized reproduction prohibited -6- Student name: ID number:
3. “Sweet success”. Fill in the six missing entries in the following tabl