Download C O CH3 CoAS

BICH-411
EXAM II
March 3, 2003
KEY
Scantron Section
1.) The citric acid cycle is an example of an amphibolic pathway. (A) True (B) False
2.) Which of the following takes place during electron transport?
(A) Protons are pumped from the matrix into the intermembrane space.
(B) Protons are pumped from the intermembrane space into the cytosol.
(C) Protons are pumped for the intermembrane space into the matrix.
(D) Electrons are pumped from the matrix into the intermembrane space.
(E) Electrons are pumped from the intermembrane space into the matrix.
3.) Cyanide has been used for years to commit murder and is used in gas chambers in executions.
Cyanide:
(A) Inhibits electron transport in Complex III.
(B) Uncouples electron transport from oxidative phosphorylation.
(C) Inhibits ATP synthase.
(D) Coordinates tightly with the heme iron of cytochrome a3.
(E) Is a competitive inhibitor of enzymes that utilize NAD+ as an oxidizing agent.
4.) Acetyl-CoA labeled with 14C as shown below is allowed to enter the citric acid cycle. Assuming that
all of the acetyl-CoA enters the cycle, what fraction of the label will be present in oxaloacetate at the
end of one turn of the cycle?
(A) 100%
O
(B) 75%
(C) 50%
14
CoAS
C
CH3 (D) 25%
(E) 0%
5.) Consider the information in Question 4. Which carbons in the oxaloacetate formed by one turn of the
cycle would contain the radiolabel?
(A) C1
C3 C2 C1
C4
(B) C2
O2C
C
C
CO2(C) C1 and C4
H2
(D) C2 and C3
O
(E) No radiolabel present.
6.) Consider the information in Questions 5 & 4. What fraction of the original radiolabel present in the
acetyl-CoA will be present in oxaloacetate at the end of two turns of the citric acid cycle?
(A) 100%
(B) 50%
(C) 25%
(D) 12.5%
(E) 0%
7.) In mammalian tissues, isocitrate dehydrogenase is allosterically stimulated by:
(A) A high ATP/ADP ratio
(B) A high NAD+/NADH ratio
(C) A low NAD+/NADH ratio
(D) A low acetyl CoA/CoA ratio
(E) A decrease in Ca2+ concentration.
8.) The mitochondrial inner membrane contains a transporter for:
(A) NADH. (B) Oxaloacetate.
(C) Phosphate (D) Acetyl-CoA
(E) All of the above.
1
BICH-411
EXAM II
March 3, 2003
KEY
9.) Which of the following enzyme activities would not be decreased by a thiamine deficiency?
(A) α-Ketoglutarate dehydrogenase.
(B) Pyruvate carboxylase.
(C) Pyruvate dehydrogenase.
(D) Transketolase.
(E) All of these enzyme activities would be decreased.
10.) The protein complexes in the electron transport chain that transfer electrons from succinate to O2 are:
(A) Complex I, Complex II, Complex III, and Complex IV.
(B) Complex I, Complex III, and Complex IV.
(C) Complex II, Complex III, and Complex IV.
(D) Complex I, Complex II and Complex III.
(E) None of the above
11.) Which enzyme is unique to the glyoxylate cycle?
(A) Malic enzyme
(B) Malate dehydrogenase
(C) Citrate-ATP lyase
(D) isocitrate lyase
(E) Pyruvate carboxylase
Order the following intermediates according to their formation in the pyruvate dehydrogenase complex.
12.) (B) Hydroxyethyl-TPP
13.) (E) Acetyl-lipoamide
14.) (D) Acetyl CoA
15.) (A) FADH2
16.) (C) NADH
17.) Fluoroacetate inhibits the citric acid cycle. Fluoroacetate is metabolized into a product that inhibits:
(A) Pyruvate dehydrogenase
(B) Acetyl-CoA synthetase
(C) Citrate Synthase.
(D) Succinate dehydrogenase
(E) Aconitase
18.) Which of the following enzymes catalyzes an oxidative decarboxylation reaction?
(A) Citrate synthase
(B) Isocitrate dehydrogenase
(C) Succinyl-CoA synthetase
(D) Succinate dehydrogenase
(E) Malate dehydrogenase
19.) The activated form of eukaryotic pyruvate dehydrogenase complex is the phosphorylated form.
(A) True (B) False
20.) Which one of the following enzymes of the citric acid cycle catalyzes an irreversible step?
(A) Succinyl-CoA Synthetase
(B) Succinate dehydrogenase
(C) Aconitase
(D) Fumarase
(E) Citrate Synthase
2
BICH-411
EXAM II
March 3, 2003
KEY
21.) How many electrons are required to reduce O2 into 2 H2O?
(A) 1
(B) 2
(C) 3
(D) 4
(E) 8
Match the following
22.) Which complex produces ferrous cytochrome c?
23.) Which complex generates ubiquinone?
24.) Which complex requires copper ions as cofactors?
25.) Which complex generates NAD+?
26.) Which complex requires FAD as a cofactor?
27.) Which complex is inhibited by Oligomycin?
(C) Complex III
(C) Complex III
(D) Complex IV
(A) Complex I
(B) Complex II
(E) Complex V
28.) The final electron acceptor in the electron transport pathway is:
(A) NAD+
(B) NADP+
(C) Coenzyme Q
(D) O2
(E) ADP
29.) Dinitrophenol:
(A) Is a competitive inhibitor of NAD+-requiring enzymes.
(B) Inhibits electron transport at Complex I.
(C) Inhibits electron tansport at Complex III at cytochrome bH.
(D) Inhibits ATP synthase.
(E) Facilitates the passive transport of hydrogen ions across the inner mitochondrial membrane.
30.) Which of the following enzymes catalyzes an anaplerotic reaction?
(A) Isocitrate lyase
(B) Malate synthase
(C) Citrate synthase
(D) Pyruvate dehydrogenase
(E) Pyruvate Carboxylase
31.) Which of the following can function as a 2 electron carrier?
(A) Cytochrome c
(B) Fe-S iron sulfer cluster
(C) 2Fe-2S iron sulfer cluster
(D) 4Fe-3S iron sulfur cluster
(E) Coenzyme Q
32.) Which of the following is a lipophillic free radical scavenger that protects lipids for peroxidation in
biological membranes?
(A) Glutathione
(B) Vitamin E
(C) Vitamin C
(D) Vitamin D
(E) Coenzyme Q
3
BICH-411
EXAM II
March 3, 2003
KEY
33.) Which of the following statements about ATP synthase is correct?
(A) The α3β3 subunits of the F1 complex extend in the intermembrane space.
(B) ATP synthase has two ATP active sites per complex.
(C) Hydrogen ions are required to release ATP from the complex.
(D) The active sites are found on the α subunits.
(E) All of the above statements are correct.
34.) Myxothiazol is an antifungal agent shown below.
OCH3
OCH3
CH3
CH3
N
H2N
C
N
CH3
S
CH3
S
O
Myxothiazol
Adding myxothiazol to a suspension of mitochondria inhibits oxygen consumption. The myxothiazol
treated mitochondria have high concentrations of NADH, FMNH2, Succinate, FADH2, QH2, Fe3+cytochrome bL, Fe3+-cytochrome bH, Fe3+-cytochrome c1, Fe3+ -cytochrome c, CuA2+ ,Fe3+ - cytochrome a
,Fe3+-cytochrome a3, and CuB2+. Based on this information at which electron transport complex is
inhibited by myxothiazol?
(A) Complex I (B)Complex II
(C)Complex III
(D) Complex IV
(E) Complex V
4
BICH-411
EXAM II
March 3, 2003
KEY
End of Scantron Section.
35.) (5 pts) What is the net yield of ATP when glyceraldehyde 3-phosphate is completely oxidized into
CO2 via glycolysis, citric acid cycle, electron transport and oxidative phosphorylation. (a) Using the
Aspartate-Malate shuttle? (b) using the Glycerophosphate shuttle?
Cytosolic ATP equivalents
(a) Aspartate-Malate
(b) Glycerol 3-P
Glyceraldehyde 3-P
Pi + NAD+
1 X 2.5ATPs/NADH
NADH + H
1 X 1.5ATPs/NADH
+
1,3-Bisphosphoglycerate
+
+
1 ATP
1 ATP
+
+
1ATP
1 ATP
= 4.5 ATPS
3.5 ATPS
ADP
ATP
3-Phosphoglycerate
2-Phosphoglycerate
H2O
PEP
ADP
ATP
Pyruvate
CoA + NAD
+
NADH + H+
+ ATP equivalents generated in the matrix
2.5ATP
Acetyl-CoA
3 NADH
1 FADH2
GTP
2 CO2
+
3 X 2.5 = 7.5 ATP
+
1 X 1.5 = 1.5 ATP
+
1 GTP = 1 ATP
(a) 12.5 + 4.5 = 17 ATPS
(b) 12.5 +3.5 =16 ATPS
5
BICH-411
EXAM II
March 3, 2003
KEY
36.) (5 pts) Draw the mechanism for the enzyme citrate synthase. Draw the structure of any
relevant intermediates. You may use B—H and B: for the general acid / base groups. PUSH
ARROWS!
B
H
O H
CoA
S C C H
H
B:
CoA
:B
O
H
O H
S C C
C OH B
C O
H
CH2
C OO
B
H
CoA
O
C O-
O H
S C C
C O
H
H :B
CH2
C OO
H2O
CO2-
CoA
CH2
HO C CO2CH2
CO2-
37.) Name my Favorite Biomolecules (3 Pts)
H
HO
C
HO
C
H2
O
O
Asorbic Acid, Vitamin C
H
OH
HO
O
Glyoxylate
O
H3C
N
NH
H3C
N
O
N
CH2
H
C
OH
H
C
OH
H
C
OH
O
O
P
H 2C
FMN
O-
O-
6
O
O
C
CH
BICH-411
EXAM II
March 3, 2003
KEY
38.)(10 pts) The Pyruvate Dehydrogenase complex converts pyruvate into acetyl-CoA and CO2. The E1
enzyme, pyruvate dehydrogenase, converts pyruvate into acetyl-lipoamide. Beginning with pyruvate,
lipoamide and TPP in the ylid form, draw the mechanism of the formation of acetyl-lipoamide. Draw the
structure of any relevant intermediates. You may use B—H and B: for the general acid / base groups.
PUSH ARROWS!
H3 C
O
R'
+
E2
N
S
:
-C
H
S
+
N
-C S
R'
O
C
N
C
H
B:
B
H3C
C
-
O
R'
C C
CO2
S
R
+
N
R
O
H
H
H3C
R
C S
S
C
SH
O
N
S
C
CH3
-
S
H
R
B:
B
C S
B
H
-
:
C
O
O
H
H
CH3
H3C
R'
S
C
SH
O
CH3
+
R
N
- C
S
R
7
:C
O
S
H
R
R'
+
N
R'
R
C
H3C
R'
CH3
O
N
CH3
H
H C CH3
C
R'
O
H
CH3
N
C
O O
R
S
C
H3 C
R'
C S
CH3
H3C
N
H
H
+
N
R
S
C
O O
R
R'
+
R
C S
C CH3
H3C
H3C
R'
R'
+
N
R
:
-
H3 C
H3C
H3C
R
S
N
H
:
R
H
S
CH3
BICH-411
EXAM II
March 3, 2003
KEY
39.) (15 pts). Draw the citric acid cycle. Show the structures and names of all reactants and products, as
well as the names of the enzymes. You do not need to draw the structures of ATP, NAD+, CoA, etc.,
but do show them as reactants or products in the appropriate places. You do not need to show the
mechanisms of the enzymes
O
NADH + H+
CO2-
C SCoA
Malate
H2O
CO2-
CoA
CH2
CH2
Citrate Synthase
-
CO2-
H2O
H3C
C O
+
HO C H NAD
CH2
CO2
-
CO2
Malate
Dehydrogenase
Oxaloacetate
-O2C
C OH
CH2
CO2-
Citrate
Fumarase
Aconitase
CO2C H
CO2-
H C
HO
CO2-
H
Fumarate
FADH2
FAD
C
H
C
CO2-
CH2
CO2-
Succinate
Dehydrogenase
Isocitrate
CO2-
Isocitrate
Dehydrogenase
CH2
CH2
CO2-
CO2-
Succinate
α-ketoglutarate
Dehydrogenase
Succinyl-CoA
Synthetase
GDP + Pi
CH2
CO2-
CH2
CO2-
C O
CH2
CO2 + NADH + H+
CH2
SCoA
GTP + HSCoA
C O
NAD+
α-ketoglutarate
HS-CoA + NAD+
CO2 + NADH
Succinyl-CoA
8