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Islamic University of Gaza
Faculty of Science
Biological Sciences Department
Advanced Biochemistry
Midterm Exam
14. 11.2010
Time: 2 hours
A. Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
i) ADP
b) nicotinamide
c) ATP
d) amphibolic
e) CO2
f) Coenzyme A
g) flavin
(4 points)
h) FAD
j) NADPH k) chemotrophs
1. Pathways that can be either anabolic or catabolic depending on the energy conditions of the cell.
Answer: d
2. In aerobic respiration the ultimate acceptor of electrons is _________.
Answer: a
3. The product of aerobic respiration.
Answer: e
4. NADH is an electron carrier that contains the ______ ring as redox active group.
Answer: b
5. Used for reductive biosynthesis.
Answer: j
6. A carrier of two carbon acyl groups.
Answer: f
7. An electron carrier of hydrogen atoms
Answer: g and h
8. Required for many ligation reactions.
Answer: c
----------------------------------------------------------------------------------------------------B. Choose the correct answer from the following
1. Reaction pathways that transform fuels into cellular energy:
A) anabolic
B) catabolic
C) allobolic
D) all of the above
(7 points)
E) none of the above
Answer: B
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2. Electron carrier(s) that contain(s) portions of ATP:
A) NAD+
B) FAD
C) Riboflavin
D) a and b
E) a, b, and c
Answer: D
3. The free energy change for hydrolysis of ATP to ADP is:
A) -2.2 kcal/mol.
B) 33 kcal/mol.
C) -7.3 kcal/mol.
D) -14.6 kcal/mol.
E) 7.6 kcal/mol.
Answer: C
4. Molecule(s) with a higher phosphoryl transfer potential than ATP:
A) phosphoenolpyruvate
B) creatine phosphate
C) 1,3 bis-phosphoglycerate
E) a, b, and c
D) a and b
Answer: E
5. A typical concentration of ATP in resting muscle is
A) 150 mM.
B) 4 mM.
C) 0.03 mM.
D) 25 M.
Answer: B
E) none of the above.
6. Fats are a more efficient energy source than carbohydrates because they are more
A) oxidized.
B) polarized. C) reduced.
D) all of the above.
E) none of the above.
Answer: C
7. The reduced form of flavin adenine dinucleotide is
A) FADH.
B) FAD.
C) FADH2+.
D) FADH2.
E) none of the above.
Answer: D
8. An example of an oxidation reaction would be
A) the conversion of succinate to fumarate using FAD.
B) the addition of carbon dioxide to pyruvate to form oxaloacetate.
C) the conversion of citrate to isocitrate.
D) the hydrolysis of a peptide bond.
E) none of the above.
Answer: A
9. An example of an isomerization reaction would be
A) the conversion of succinate to fumarate using FAD.
B) the addition of carbon dioxide to pyruvate to form oxaloacetate.
C) the conversion of citrate to isocitrate.
D) the hydrolysis of a peptide bond.
E) none of the above.
Answer: C
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Islamic University of Gaza
Faculty of Science
Biological Sciences Department
Advanced Biochemistry
Midterm Exam
14. 11.2010
Time: 2 hours
10. Catalytic reactions in metabolism proceed _______ depending on the standard free energy and
the concentrations of the substrates and reactants.
A) in the reverse direction
B) in the forward direction
C) in either direction
D) all of the above
E) none of the above
Answer: C
11. Which activated carriers contain adenosine phosphate units?
A) NADH
B) FADH2
C) Coenzyme A
D) a and b
E) a, b, and c
Answer: E
12. How can the amounts of enzymes be controlled?
A) transcriptional regulation
B) protein breakdown
D) a and b
E) a, b, and c
C) allosteric control
Answer: D
13. Groups that are carried by one or more than one activated carrier:
A) electrons B) one-carbon units C) acyl D) Glucose E) all of the above
F) none of the above
Answer: E
14. Some of the mechanisms for enzymatic control include
A) allosteric control. B) feedback inhibition. C) covalent modification.
D) a and c
E) a, b, and c.
Answer: E
----------------------------------------------------------------------------C. How does a chemically coupled pathway influence metabolism?
(1 point)
Answer: The free-energy changes of the individual steps in a pathway are summed to determine the
overall free-energy change. Thus, a step that might not normally occur can be driven if it is coupled to a
thermodynamically stable reaction.
D. Why is ATP frequently complexed with magnesium or manganese ions?
(1 point)
Answer: These divalent ions complex to the negatively charged oxygens found on the phosphate groups.
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E. Why is ATP an energy rich molecule?
(1 point)
Answer: ATP contains two phosphoanhydride bonds. One must compare the free energy of the molecule
and its hydrolysis products.
F. How are a change in conformation and mechanical energy related?
(1 point)
Answer: ATP may be bound to a protein, inducing a conformational change, which can store free energy.
This change in conformation is actually the mechanical energy of movement such as muscle contraction.
G. What general factors contribute to the high phosphoryl-group transfer of ATP?
(2 points)
Answer: Resonance stabilization, electrostatic repulsion, and stabilization due to hydration are
important.
H. How much ATP is used daily by a typical human? How is it regenerated?
Answer: A human uses 40 kg of ATP per day. There is only about 100 g ATP available,
(1 point)
thus the ATP is used and regenerated rapidly. ATP is regenerated from ADP and Pi, using the energy
from catabolic processes.
I. Compare ATP to Acetyl CoA.
(1 point)
Answer: Both are activated carriers: Acetyl CoA carries acetyl groups, with high acetyl group-transfer
potential, whereas ATP carries phosphate groups with high phosphorylgroup transfer. Both molecules
are common to several pathways.
J. How are metabolic processes unified? How can you use this to help learn and understand
biochemistry?
(1 point)
Answer: Common molecules and mechanisms are evident in motifs and patterns throughout metabolic
pathways. Understanding the logic of catabolic and anabolic paths, and knowing common molecules
(such as ATP) and mechanisms (oxidation-reduction) makes it simpler to understand the myriad paths of
metabolism.
K. Which of the metabolic chemical reactions is most commonly used to break down foodstuffs?
(1 point)
Answer: Hydrolysis reactions are commonly used to break down molecules into smaller components.
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Islamic University of Gaza
Faculty of Science
Biological Sciences Department
Advanced Biochemistry
Midterm Exam
14. 11.2010
Time: 2 hours
L. How is metabolism controlled?
(1 point)
Answer: The amounts of enzymes and their catalytic activity are two controllable aspects of metabolism.
Substrate accessibility is also important.
M. If many compounds are common to both anabolic and catabolic paths, how can
metabolism be controlled?
(1 point)
Answer: The enzymes and their activities can be controlled. Moreover, the biosynthetic and degradative
paths are different from each other, thus substrate concentrations can be controlled independently.
N. How are hormones used in metabolism?
(1 point)
Answer: Hormones serve critical functions in the regulation of enzymes and signal transduction
cascades, and are used in second messenger paths. All of these processes have dramatic effects on
metabolism regulation.
O. Substrate cycles are biologically important. Give more details?
(3 points)
1. Substrate cycles amplify metabolic signals: This amplification is made possible by the rapid
hydrolysis of ATP. If an allosteric effector reciprocally increases A to B and decreases B to A by
20% each, then a 20% change in the rates of the opposing reactions has led to a
480%(=100x48/10) increase in the net flux.
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2. Generation of heat produced by the hydrolysis of ATP.
P. One of the citric acid cycle’s enzymes requires five coenzymes for its activity. (3 points)
1. Name the enzyme.
Pyruvate dehydrogenase complex
2. What are these 5 coenzymes?
– Thiamine pyrophosphate (TPP)
– Lipoic acid
– FAD
– CoA
-
NAD+
3. Do these coenzymes belong to same category. Explain?
•
Catalytic cofactors: Thiamine pyrophosphate (TPP), Lipoic acid, FAD
•
Stoichiometric cofactor: CoA, NAD+
-------The End-------
Dr. Tarek M. Zaida
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