Chapter Fifteen: Metabolism: Basic Concepts and Designs
Use the following to answer questions 1-10:
Choose the correct answer from the list below. Not all of the answers will be used.
a) O2
b) nicotinamide c) phototrophs
f) Coenzyme A g) flavin
h) amphibolic
k) chemotrophs l) FAD
d) ATP
i) ADP
e) CO2
j) NADPH
1. Organisms that use energy of sunlight and convert it to chemical energy.
Answer: c
2. Organisms that obtain chemical energy from oxidation of foodstuffs.
Answer: k
3. Pathways that can be either anabolic or catabolic depending on the energy conditions of
the cell.
Answer: h
4. In aerobic respiration the ultimate acceptor of electrons is _________.
Answer: a
5. The product of aerobic respiration.
Answer: e
6. NADH is an electron carrier that contains the ______ ring as redox active group.
Answer: b
7. Used for reductive biosynthesis.
Answer: j
8. A carrier of two carbon acyl groups.
Answer: f
9. A electron carrier of hydrogen atoms
Answer: g and l
10. Required for many ligation reactions.
Answer: d
11. The major purpose(s) for which organisms require energy:
A) performance of mechanical work
D) a and c
B) active transport
E) a, b, and c
C) synthesis of biomolecules
Answer: E
12. Reaction pathways that transform fuels into cellular energy:
A) anabolic
B) catabolic
C) allobolic
D) all of the above
Answer: B
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E) none of the above
13. Reaction pathways that require energy, often biosynthetic processes:
A) anabolic
B) catabolic
C) allobolic
D) all of the above
E) none of the above
Answer: A
14. Electron carrier(s) that contain(s) portions of ATP:
A) NAD+
B) FAD
C) Riboflavin D) a and b
Answer: D
E) a, b, and c
15. The free energy change for hydrolysis of ATP to ADP is:
A) -2.2 kcal/mol.
D) -14.6 kcal/mol.
B) 33 kcal/mol.
E) 7.6 kcal/mol.
C) -7.3 kcal/mol.
Answer: C
16. Molecule(s) with a higher phosphoryl transfer potential than ATP:
A) phosphoenolpyruvate
D) a and b
B) creatine phosphate
E) a, b, and c
C) 1,3 bis-phosphoglycerate
Answer: E
17. 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.
18. Fats are a more efficient energy source than carbohydrates because they are more
A) oxidized.
D) all of the above.
B) polarized.
E) none of the above.
C) reduced.
Answer: C
19. Carbon oxidation of compounds can be coupled to ATP synthesis. An example is:
A) The oxidation of glyceraldehyde 3-phosphate to 3-phosphoglyceric acid
B) The oxidation of glyceraldehyde 3-phosphate to 1,3 bisphosphoglycerate
C) The oxidation of acetic acid to acetaldehyde.
Answer: A
20. This energy source powers most ATP synthesis.
A) electrochemical potential of ion gradients
B) electrochemical potential of stored glycogen
C) high-energy intermediates
D) all of the above
E) none of the above
Answer: A
21. The reduced form of flavin adenine dinucleotide is
A) FADH.
B) FAD.
C) FADH2+.
D) FADH2.
Answer: D
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E) none of the above.
22. Activated electron carriers provide electrons for
A) reductive biosynthesis.
D) b and c.
B) fuel oxidation.
E) a and b.
C) methyl group transfer.
Answer: E
23. Groups that are carried by one or more than one activated carrier:
A) electrons
D) Glucose
B) one-carbon units
E) all of the above
C) acyl
F) none of the above
Answer: E
24. Types of chemical reactions include
A) isomerization.
D) all of the above.
B) group transfer.
E) none of the above.
C) ligation requiring ATP.
Answer: D
25. 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
26. 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
27. Catalytic reactions in metabolism proceed _______ depending on the standard free
energy and the concentrations of the substrates and reactants.
A) in the reverse direction
D) all of the above
B) in the forward direction
E) none of the above
C) in either direction
Answer: C
28. Which activated carriers contain adenosine phosphate units?
A) NADH
B) FADH2
C) Coenzyme A
D) a and b
Answer: E
29. How can the amounts of enzymes be controlled?
A) transcriptional regulation
D) a and b
B) protein breakdown
E) a, b, and c
C) allosteric control
Answer: D
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E) a, b, and c
30. Some of the mechanisms for enzymatic control include
A) allosteric control.
D) a and c
B) feedback inhibition.
E) a, b, and c
C) covalent modification.
Answer: E
31. How does a chemically coupled pathway influence metabolism?
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.
32. Sum up the units that make up ATP.
Answer: The structure should contain the triphosphate, base, and ribose portions. An example can
be found in Figure 14.3 in the textbook.
33. Why is ATP frequently complexed with magnesium or manganese ions?
Answer: These divalent ions complex to the negatively charged oxygens found on the phosphate
groups.
34. Why is ATP an energy rich molecule?
Answer: ATP contains two phosphoanhydride bonds. One must compare the free energy of the
molecule and its hydrolysis products.
35. How are a change in conformation and mechanical energy related?
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.
36. What general factors contribute to the high phosphoryl-group transfer of ATP?
Answer: Resonance stabilization, electrostatic repulsion, and stabilization due to hydration are
important.
38. 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,
thus the ATP is used and regenerated rapidly. ATP is regenerated from ADP and Pi, using the
energy from catabolic processes.
39. What is an ion gradient? Provide an example of an ion found in a gradient.
Answer: Difference in concentration of a charged molecule, on opposite sides of a membrane.
Examples include protons and sodium, potassium, and calcium ions.
40. What is oxidative phosphorylation?
Answer: The process of making ATP by using a proton gradient.
41. What are the stages for extracting energy from food?
Answer: There are three stages: 1) Large food molecules are broken down into smaller units, such
as amino acids, carbohydrates, and fatty acids. 2) The small units are further broken down to a
subset of small molecules that are critical to metabolism, such as acetylCoA. 3) ATP is produced
by oxidation of the acetyl units.
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42. What is an active carrier? Provide two examples.
Answer: Activated carriers are molecules that are used as the carrier molecules of a particular
molecule, atom, electron, or protons. One example would be ATP, which is the activated carrier
of phosphoryl groups. Flavin derivatives (FAD) would be examples of activated carriers of
electrons.
43. Compare ATP to Acetyl CoA.
Answer: Both are activated carriers: Acetyl CoA carries acetyl groups, with high acetyl grouptransfer potential, whereas ATP carries phosphate groups with high phosphorylgroup transfer.
Both molecules are common to several pathways.
44. Why is the stability of the activated carriers important?
Answer: All are extremely stable, therefore they are kinetically stable, and are unlikely to
undergo chemical reactions such as hydrolysis or oxidation without catalytic assistance. Thus,
energy flow and reductive power can be controlled.
45. How are metabolic processes unified? How can you use this to help learn and
understand biochemistry?
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.
46. What are the precursors for the activated carriers that are derived from vitamins?
Answer: Niacin, riboflavin, pantothenate, thiamine, biotin, and folate.
47. Which of the metabolic chemical reactions is most commonly used to break down
foodstuffs?
Answer: Hydrolysis reactions are commonly used to break down molecules into smaller
components.
48. How is metabolism controlled?
Answer: The amounts of enzymes and their catalytic activity are two controllable aspects of
metabolism. Substrate accessibility is also important.
49. If many compounds are common to both anabolic and catabolic paths, how can
metabolism be controlled?
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.
50. How are hormones used in metabolism?
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.
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