BIOC 384 EXAM 4 UPDATED ACTUAL QUESTIONS AND
CORRECT ANSWERS
Question:
1. order the following steps in the pyruvate dehydrogenase
reaction
Answer:
1.pyruvate and thiamine pyrophosphate react form hydroxyethyl-TPP, CO2 is
released
2. an acetyl group is added to a coenzyme bound to PDH, forming acetyl-
dihydrolipoamide
3. the acetyl group is transferred to CoA, forming acetyl-CoA
4.the reduced coenzyme bound to PDH is reoxidized using electrons from FAD
5. electrons from FADH2 are transferred to NAD+ forming NADH and H+
Question:
2. In two turns of the citrate cyle, how many electrons are
transferred from the citrate cycle intermediates to NAD+
and FAD?
Answer:
16
Question:
3. Match the citrate cycle enzyme with the type of
biochemical rxn it catalyzes
1. condensation rxn
2. dehydrogenation rxn
3. oxidative decarboxylation rxn
4. dehydration rxn
5. substrate level phosphorylation rxn
Answer:
1. citrate synthase
2. malate dehydrogenase
3. isocitrate dehydrogenase
4. Aconitase
5. succinyl-CoA synthase
Question:
4. how is the pyruvate dehydrogenase rxn regulated?
Answer:
allosteric control and covalent modification
,Question:
5. the disease berberi is caused by a nutritional defiiency in
vitamin B(thiamin). what key mitochondrial enzyme uses
thiamin as a coenzyme in a rxn that generates acetyl-
CoA, CO2 and NADH + H+ as products and why is this
condition rare in developed countries?
Answer:
pyruvate dehydrogenase, berberi is rare because many common foods are
vitamin fortified
Question:
6. what is the biochemical explanation for the observed
toxic effects of arsenic contaminated well water in
bangladesh?
Answer:
the arsenic contaminated well water caused inhibition of dihydrolipoyl
transacetylase, which is an enzyme subunit required for metabolism of rice starch,
the source of 70% of their daily caloric intake.
Arsenic is converted to arsenite, which covalently modifies reduced lipoamide,
thereby inhibiting activity of the pyruvate dehydrogenase complex and blocking
conversion of pyruvate to acetyl-CoA
Question:
7. two best correct statements describing the citrate cylce
Answer:
atp is an indirect product of the citric acid cycle
the pool of mitochondrial ocaloacetate can be increased by pyruvate
Question:
8. what are the principle physiological electron donors for
the mitochondrial electron transport pathway?
Answer:
FADH2 and NADH
Question:
9. which one of the statements below describes the
mechanism of proton translocation by the electron
transport system using a redox loop mechanism
exemplified by the Q cycle?
Answer:
none of the answer are correct
, Question:
10. which of the statements below best describes the
mechanism of proton translocation via a redox driven
conformational change?
Answer:
matrix derived protons are translocated across the mitochondrial membrane by
altering pka values of functional groups located on the inner and outer faces of
the membrane
Question:
11. approx how many more ATPs are made from one glucose
molecule under aerobic conditions with oxidative
phosphorylation than under anaerobic conditions?
Answer:
30
Question:
12. a characteristic of complex III is that is
Answer:
uses the Q cycle mechanism to oxidize ubiquinone
Question:
13. for one electron entering the electron transport chain at
complex I, how may times is it handed off between redox
active cofactors on its way through the enzyme
complexes to end up on O2?
Answer:
~20
Question:
14. which is the only electron carrier in the electron transport
system that is not embedded in a membrane?
Answer:
cytochrome c
Question:
15. which statement best describes the chemiosmotic theory
proposed by peter mitchell?
Answer:
conversion of redox energy o rlight energy into potential energy as an
electrochemical proton gradient
CORRECT ANSWERS
Question:
1. order the following steps in the pyruvate dehydrogenase
reaction
Answer:
1.pyruvate and thiamine pyrophosphate react form hydroxyethyl-TPP, CO2 is
released
2. an acetyl group is added to a coenzyme bound to PDH, forming acetyl-
dihydrolipoamide
3. the acetyl group is transferred to CoA, forming acetyl-CoA
4.the reduced coenzyme bound to PDH is reoxidized using electrons from FAD
5. electrons from FADH2 are transferred to NAD+ forming NADH and H+
Question:
2. In two turns of the citrate cyle, how many electrons are
transferred from the citrate cycle intermediates to NAD+
and FAD?
Answer:
16
Question:
3. Match the citrate cycle enzyme with the type of
biochemical rxn it catalyzes
1. condensation rxn
2. dehydrogenation rxn
3. oxidative decarboxylation rxn
4. dehydration rxn
5. substrate level phosphorylation rxn
Answer:
1. citrate synthase
2. malate dehydrogenase
3. isocitrate dehydrogenase
4. Aconitase
5. succinyl-CoA synthase
Question:
4. how is the pyruvate dehydrogenase rxn regulated?
Answer:
allosteric control and covalent modification
,Question:
5. the disease berberi is caused by a nutritional defiiency in
vitamin B(thiamin). what key mitochondrial enzyme uses
thiamin as a coenzyme in a rxn that generates acetyl-
CoA, CO2 and NADH + H+ as products and why is this
condition rare in developed countries?
Answer:
pyruvate dehydrogenase, berberi is rare because many common foods are
vitamin fortified
Question:
6. what is the biochemical explanation for the observed
toxic effects of arsenic contaminated well water in
bangladesh?
Answer:
the arsenic contaminated well water caused inhibition of dihydrolipoyl
transacetylase, which is an enzyme subunit required for metabolism of rice starch,
the source of 70% of their daily caloric intake.
Arsenic is converted to arsenite, which covalently modifies reduced lipoamide,
thereby inhibiting activity of the pyruvate dehydrogenase complex and blocking
conversion of pyruvate to acetyl-CoA
Question:
7. two best correct statements describing the citrate cylce
Answer:
atp is an indirect product of the citric acid cycle
the pool of mitochondrial ocaloacetate can be increased by pyruvate
Question:
8. what are the principle physiological electron donors for
the mitochondrial electron transport pathway?
Answer:
FADH2 and NADH
Question:
9. which one of the statements below describes the
mechanism of proton translocation by the electron
transport system using a redox loop mechanism
exemplified by the Q cycle?
Answer:
none of the answer are correct
, Question:
10. which of the statements below best describes the
mechanism of proton translocation via a redox driven
conformational change?
Answer:
matrix derived protons are translocated across the mitochondrial membrane by
altering pka values of functional groups located on the inner and outer faces of
the membrane
Question:
11. approx how many more ATPs are made from one glucose
molecule under aerobic conditions with oxidative
phosphorylation than under anaerobic conditions?
Answer:
30
Question:
12. a characteristic of complex III is that is
Answer:
uses the Q cycle mechanism to oxidize ubiquinone
Question:
13. for one electron entering the electron transport chain at
complex I, how may times is it handed off between redox
active cofactors on its way through the enzyme
complexes to end up on O2?
Answer:
~20
Question:
14. which is the only electron carrier in the electron transport
system that is not embedded in a membrane?
Answer:
cytochrome c
Question:
15. which statement best describes the chemiosmotic theory
proposed by peter mitchell?
Answer:
conversion of redox energy o rlight energy into potential energy as an
electrochemical proton gradient
