Biochemistry II (CHEM 4420)
Sample questions for Exam 1:
1. Thiamine deficiency results from several causes, and severe deficiencies cause a
disease called Beri-Beri.
- What is one cause of a thiamine deficiency?
- Why is thiamine an essential vitamin?
- Discuss an example of its role as a cofactorin the function of an enzyme. Please be specific about naming the enzyme, the full name of the cofactor and the reaction that it catalyzed, you do not have to push electrons or draw the structure of the thiamine containing cofactor.
2. Why does citric acid cycle only operate when there is oxygen present? Be sure to
include the regulatory mechanisms of the cycle in your discussion.
3. Red blood cells have an alternate pathway for glycolysis, that produces an
intermediate that is essential for the function of the red blood cell. This detour
bypasses an ATP generating step. Discuss this detour in terms of the intermediate
that is generated and the function of red blood cells.
4. The patient complains of gastric discomfort upon consuming milk. The patient also
shows signs of liver, kidney and brain dysfunction. This dysfunction is due to
the build up of the toxic compound, galactose-1-P.
- What enzyme is the patientlacking?
- What reaction is not being catalyzed?
- Suggest a possible recommendation for the patient to follow in order to avoid further tissue damage.
3. Several of the reactions in glycolysis and the TCA cycle have positive
(delta) Gø' values, yet the reactions are still driven towards the products. There are
several different ways that can compensate for these standard state free energy
values. Pick one of the following and discuss its effect on Grxn and give an
example of a reaction in glycolysis or the TCA cycle where the effect you chose
occurs. Be sure to show all equations that are relevant.
1. The effect of concentration.
or
2. The effect of shared intermediates.
Multiple choice section:
1. What type of enzyme catalyzes the reaction below?
a. kinase b. isomerase c. mutase d. aldolase e. dehydrogenase
2. The oxidation of 1 mole of glucose by anaerobic glycolysis in yeast yields:
a. 2 moles of lactate and 2 moles of ATP
b. 2 moles of ethanol, 2 moles of carbon dioxide and 2 moles of ATP
c. 2 moles of ethanol, 2 moles of carbon dioxide and 4 moles of ATP
d. 2 moles of pyruvate, 2 moles of NADH++ H+, and 2 moles of ATP
e. 2 moles of lactate, 2 moles of NADH++ H+, and 2 moles of ATP
3. What kind of linkages are present in between glucose units of glycogen?
a. beta-1,4 only
b. beta -1,6 only
c. beta -1,6 and beta -1,4
d. alpha-1,4
e. alpha-1,4 and alpha-1,6
4. Humans can not make use of the complex carbohydrate found in plant cell walls
as an energy source. This is due to the fact that vertebrates do not have the
enzyme __________ , that degrades the ____________ linkages found in this complex
carbohydrate.
a. trehalase, alpha-1,4
b. cellulase, beta -1,6
c. chitinase, beta-1,6
d. cellulase, beta-1,4
e. none of these
5. How many ATP molecules are generated from the energy of complete anaerobic
oxidation of a molecule of glucose?
6. Which of the following enzymes catalyzes a reaction that involves a
decarboxylation reaction?
a. pyruvate dehydrogenase
b. isocitrate dehydrogenase
c. à-keto glutarate dehydrogenase
d. all of the above
e. only a and c
7. Malonate is an inhibitor of a Kreb's cycle enzyme because it is structurally
similar to the substrate for that enzyme. How many ATP molecules could be
generated under aerobic conditions from one molecule of pyruvate if the inhibitor,
malonate is present? The structure of malonate is:
a. 7
b. 10
c. 4
d. 20
e. none of these
8. By doing site directed mutagenesis, researchers are able to generate mutants of
proteins that have specific changes in their primary amino acid sequence. The
sequence of the active site of phosphoglycerate mutase was being investigated using
this technique. Based upon what you know about the enzyme mechanism, which
of the following mutants will have no activity?
The normal sequence (full activity) of the active site is:
gly-gly-glu-his-gly-cys-ser-gly
The active site mutant with no activity is
a. gly-lys-glu-his-gly-cys-ser-gly
b. gly-gly-glu-glu-gly-cys-ser-gly
c. gly-gly-glu-his-gly-lys-ser-gly
d. gly-gly-glu-his-gly-cys-his-gly
e. none of the above
9. Anaplerotic reactions are those that result in replenishing intermediates in the
TCA cycle. Which of the following enzymes catalyzes an anaplerotic reaction?
a. malate dehydrogenase
b. pyruvate carboxylase
c. pyruvate kinase
d. citrate synthase
e. none of the above
10. In the catalysis of a reaction, an enzyme
a. increases the Keq.
b. decreases the Keq.
c. increases the rate and decreases the activation energy of the reaction.
d. increases the rate and increases the activation energy of the reaction.
e. makes the (delta) G more negative for the reaction.
Problems with the problems? Please send EMAILto koni@chem.csustan.edu.
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This page was created March 8, 1996 by Koni Stone