Bioc3321 Spring 2012 Exam 2
Name:______________________________________
Biochemistry (Bioc3321 Spring 2012)
Exam 2. Biomolecules (4/2/12)
Instructions
1. This exam consists of 7 pages. If a page is missing return the exam immediately.
2. PRINT your name NOW in the spaces at the top of ALL pages
3. The exam should be easy to complete in 45 minutes. However, you have 60 minutes
to finish it. Some advice, save the more difficult problems for the end.
4. Please, show all your work and be certain that all your explanations are given
as complete sentences and that all your calculations contain the right units. No
credit is given to the right answer for the wrong reason.
5. The last page is a blank sheet for you to use for calculations. Do not write any results
in there, it will NOT be graded. If you run out of space, write in the back of the page.
Good luck!!
Please sign:
Honor code: By the definition of academic integrity, the exam I am handling in is solely my
own work and truthfully represents work I have done.
___________________________________
Signature
Question 1. Bioenergetics
Question 2. Catabolism of carbohydrates
Question 3. Catabolism of carbohydrates
Question 4. Catabolism of lipids
Question 5. Catabolism of amino acids
Total
/45
/45
/20
/45
/45
/200
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Bioc3321 Spring 2012 Exam 2
Name:______________________________________
1. One of the steps of the steps of the citric acid cycle is the following reaction
Malate + NAD+ <--> oxaloacetate + NADH + H+
At T=262.6K: ∆G’o = 9 kJ/mol
The ∆G in cells = -1 kJ/mol [NADH]/[NAD+] = 1 in
cells
If you don’t want to use a calculator: RTln = 2.3RTlog. At 310K: 2.3RT = 5 kJ/mole
Which of the following conclusions is True, False, or cannot be determined from the
information above? Put an X under “”True” if the conclusion is true given the
information above. Put an X under “False” if the conclusion is false given the
information above. Put an X under “Inconclusive” if there is insufficient information
to determine if the statement is true or false.
True
False
Inconclusive
_________
___________
___________
The reaction in the cell is very fast.
__________
___________
___________
[malate] is 9 times greater than
[oxaloacetate] in the cell.
___________
___________
The ratio of [oxaloacetate][NADH]
/[malate][NAD+] found in the cell is equal
to K’eq.
_________
_________
[malate] is 100 times greater than
[oxaloacetate] in the cell.
___________
___________
_________
___________
___________
The ratio of
[oxaloacetate][NADH]/[malate][NAD+] at
biochemical standard state is equal to K’eq.
_________
___________
___________
The reaction is exergonic inside cells.
_________
___________
___________
When starting from the standard state,
more malate will be made.
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Bioc3321 Spring 2012 Exam 2
Name:______________________________________
2. You discover a new aldolase enzyme that uses fructose 6-phosphate as the
substrate. Given what you know about glycolysis, answer the following questions.
a. Draw the structures of the products (don’t specify stereochemistry).
b. Name the products. Do not use abbreviations.
c. When the new aldolase uses fructose 6-phosphate as its substrate,
two steps of glycolysis are not used. Name the reactants of the 2 steps
in glycolysis that are unused? (other than the new aldolase, the rest of
the glycolysis enzymes are the same)
d. What is the net production of ATP per glucose molecule if aldolase
uses fructose 6- phosphate as its substrate?
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Bioc3321 Spring 2012 Exam 2
Name:______________________________________
3. Answer the following questions.
a. Assign oxidation numbers for each carbon in the blank below that carbon
and write the chemical structure of pyruvate.
Oxidation state
on carbon:
___ ___
(acetyl CoA)
___ ___ ___
lactic acid
____ ____ ____
pyruvate(*)
(*) If you don’t remember the structure of pyruvate remember that pyruvate is
reduced to lactate with two electrons and that acetyl-CoA is obtained when
pyruvate is oxidized and decarboxylated and it reacts with CoA-SH.
b. Fill in the blanks or circle the right answer (in bold)
i. ____ molecules of NAD+ or NADH are needed to convert pyruvate into
lactate.
ii. Under anaerobic conditions when glucose is turned into lactate the
overall yield of glycolysis is ____ molecules of ATP and ____ molecules
of NAD+ or NADH.
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Bioc3321 Spring 2012 Exam 2
Name:______________________________________
4. Below is a list of the steps required to convert three fatty acids to acetyl CoA.
 Fatty acid A requires the following steps to be oxidized to acetyl CoA. 1x
(activation)
2x (FAD-dehydrogenase, hydratase, NAD-dehydrogenase,
thiolase) 1x (isomerase, hydratase, NAD-dehydrogenase, thiolase)
2x (FADdehydrogenase, hydratase, NAD-dehydrogenase, thiolase)

Fatty acid B requires the following steps to be oxidized to acetyl CoA 1x
(activation)
3x (FAD-dehydrogenase, hydratase, NAD-dehydrogenase,
thiolase)
1x (FAD-dehydrogenase, reductase, isomerase, hydratase, NADdehydrogenase, thiolase) 2x (FAD-dehydrogenase, hydratase, NADdehydrogenase, thiolase)

Fatty acid C requires the following steps to be oxidized to acetyl CoA 1x
(activation)
3x (FAD-dehydrogenase, hydratase, NAD-dehydrogenase,
thiolase)
1x (FAD-dehydrogenase, reductase, isomerase, hydratase, NADdehydrogenase, thiolase) 2x (FAD-dehydrogenase, hydratase, NADdehydrogenase, thiolase)
1x (isomerase, hydratase, NAD-dehydrogenase,
thiolase)
4x (FAD-dehydrogenase, hydratase, NAD-dehydrogenase, thiolase)
From the above information, fill in the table below for each fatty acid.
Fatty acid
# of Carbons in fatty acyl
chain
A
B
C
Net # of NADH produced
Net # of FADH2 produced
# of unsaturated bonds
Position of unsaturated
bond(s) (0 if no unsaturated)
Only two fatty acids will be graded. If you fill up three the best two will count
for your grade
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Bioc3321 Spring 2012 Exam 2
Name:______________________________________
5. Aminotransferases transfer the amino group of amino acids to -ketoglutarate
yielding as products glutamate and the corresponding -ketoacid
a. Draw the structures of this reaction:

amino acid
-ketoglutarate

-ketoacid
glutamate
b. -ketogluatarate is recovered when glutamate dehydrogenase acts on
glutamate to yield one molecule of -ketoglutarate and ammonium cation.
However, in this case, unlike the aminotransferase reaction, a NADH
molecule is also synthesized.
glutamate + NAD+  -ketoglutarate + NADH + NH4+
Explain why NADH wasn’t needed in the aminotransferase reaction
c. Glutamate dehydrogenase is an allosteric enzyme that can bind ADP and GTP
modulators. From what you know about catabolism of amino acids, circle the
right option:
Modulator
ADP
GTP
Positive
Positive
Effect on enzyme activity
Negative
Negative
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Bioc3321 Spring 2012 Exam 2
Name:______________________________________
Use this page for your own thoughts and calculations. This page WILL NOT BE
GRADED
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