Download Chapter 1 Review Key

Chapter 1 Review, pages 64–69
Knowledge
1. c
2. d
3. b
4. d
5. d
6. b
7. a
8. d
9. a
10. b
11. a
12. b
13. a
14. b
15. a
16. a
17. c
18. c
19. c
20. a
21. False. Radioactivity occurs when a radioactive isotope decays into an atom of another
element.
22. False. A bond is less polar when the electronegativity values of the atoms are closer together.
23. True
24. False. A buffer is a weak acid or base that can be used effectively to regulate the pH of a
solution.
25. False. Hydrogen bonding is completely responsible for the ability of water to dissolve ionic
substances in the blood.
26. True
27. False. The orientation of the bond between carbon and hydrogen in methane, CH4, forms
109.5° angles.
28. False. A gram of fat carries more than twice the energy of a gram of simple sugar.
29. True
30. False. Cutin is a wax that prevents water evaporation from the leaves of plants.
31. False. Cutin is a wax that waterproofs the skin of fruits and vegetables.
32. False. RNA carries the genetic blueprint for some viruses.
33. False. Proteins are the most diverse group of biological molecules in human cells.
34. True
35. True
36. True
37. False. An enzyme can bind with only one substrate.
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Chapter 1: The Biochemical Basis of Life
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38. (a) ii
(b) iv
(c) i
(d) iii
39. (a) iv
(b) iii
(c) ii
(d) i
40. (a) ii
(b) iii
(c) i
41. carbon; hydrogen; oxygen; nitrogen
42. Covalent or molecular bonds join two atoms together into a molecule by sharing electrons.
Intermolecular forces are forces of attraction between molecules (e.g., weak van der Waal forces,
hydrogen bonding).
43. When atoms bond they “fill” or empty their outer electron orbital (shells), which results in
their most stable conformation. This can be achieved by sharing (molecular bonding) or
transferring electrons (ionic bonding).
44. A redox reaction is an exchange of electrons. One atom loses electrons and another gains
electrons. In the combustion of methane, CH4 + 2O2  CO2 + 2H2O, the oxygen atom starts with
a zero oxidation state and becomes –2. The oxidation state of carbon changes from –2 to +4.
45. When there is a large electronegativity difference between two atoms, they are likely to form
an ionic bond. Two non-metals have a smaller electronegativity difference and form a covalent
bond.
46. Table 1
Strong
Weak
• dissociates completely
• does not dissociate completely
Acid
• HNO3 or H2SO4
H2CO3
Base
• dissociates completely
• NaOH
• does not dissociate completely
• HCO3
47. Water molecules are polar with the electrons spending the most time near the partially
negative oxygen atom. This causes the bent shape of the molecule.
48. (a) bases, pH greater than 7, bitter, corrosive, slippery
(b) acids, pH less than 7, corrosive, sour
49. carbon, hydrogen, oxygen
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50.
51. The four main classes of biological molecules are carbohydrates, lipids, proteins, and nucleic
acids.
52. A glycosidic bond is a type of covalent bond that joins a carbohydrate (sugar) molecule to
another group, which may or may not be another carbohydrate.
53. (a) The two forms of glucose are isomers and differ in the arrangement of an OH group.
(b) α-glucose forms starch polymers, which are digestible, but β-glucose forms cellulose, an
indigestible polymer.
54. A triglyceride is made of three fatty acid molecules joined to a glycerol molecule. A
trisaccharide is three sugar monomers joined together to make one larger sugar polymer.
55. A monomer and a polymer are both molecules. A monomer is a small reactive molecule that
can chemically bond to other monomers to form a polymer. A polymer is a larger molecule
composed of many repeated units (monomers).
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56. T-charts may vary but the following information about protein structure should be included:
The primary structure is the linear sequence of its amino acids in the protein chain.
The secondary structure is the folding and interactions between peptide groups due to hydrogen
bonding.
The tertiary structure is the overall shape of a protein due bonding between the R groups of the
amino acids.
The quaternary structure describes the organization of multiple polypeptide chains in proteins
that have more than one.
57. A prosthetic group is a non-amino acid component that a protein needs to function. An
example of a prosthetic group would be a tightly-bound cofactor such as an iron atom in a heme
group of the hemoglobin.
58. (a) The five bases found in a nucleic acid are uracil, thymine, cytosine, adenine, and guanine.
(b) Each nucleotide contains the nitrogen-containing base, a 5-carbon sugar (ribose or
deoxyribose), and a phosphate group.
(c) Nucleotides are held bonded together by a covalent ester bonds between nucleotide phosphate
on the 3-carbon of one pentose sugar and a covalent ester bond between the phosphate and the 5carbon of another nucleotide. This linkage is called a phosphodiester bond.
59. A cofactor is a non-protein group or atom that is required for a protein (or enzyme) to
function. An example of this is flavin adenine dinucleotide (FAD), which is a redox cofactor
used by oxidoreductase enzymes.
60. (a) An allosteric site is where a regulatory molecule can bond to an enzyme.
(b) Allosteric regulation controls enzyme function at a site other than the active site by changing
the conformation of the enzyme to stabilize or destabilize the active form of the enzyme.
Understanding
61. (a) Atoms with the same number of protons but different number of neutrons are isotopes.
Isotopes are unstable if they have too many or too few neutrons. Radioisotopes are unstable
isotopes that will decay at a steady known rate into smaller particles. Stable isotopes have a
stable number of neutrons. The chemical behaviour of stable isotopes is the same as
radioisotopes except that they do not decay.
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(b) The radiation from radioisotopes may be dangerous to humans, causing mutations to genetic
material. Radiation can also be very useful, for example, in medical diagnosis with X-rays or in
treatments such as chemotherapy.
62. (a) Carbon has four valence electrons that are unpaired, and hence it is able to form four
bonds. It can form two double bonds, one single and one triple, or four single bonds.
(b) Since the four valence electrons in carbon’s outer shell are unpaired, as shown in the
diagram, each one can take part in a covalent bond with another atom. In a covalent bond, one or
more electrons in carbon’s outer and one or more electrons in another atom’s outer shell would
be shared between both atoms.
63. (a) Elements that are most essential to human life include carbon, oxygen, hydrogen,
nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, iodine, iron,
manganese, molybdenum, nickel, selenium, zinc, copper, cobalt, and chromium.
(b) Answers may vary. Sample Answer: You can supply your body with these elements through
dietary sources. Water is made of hydrogen and oxygen. Potatoes contain potassium. Seaweed
contains iodine and iron.
64. Each carbon atom has four valence electrons allowing it to form up to four single bonds with
other atoms. Its structure also allows it to form straight chains, branched chains, and rings,
resulting in a variety of different structures.
65. Polarity is the uneven sharing of electrons in a covalent bond. Hydrogen bonds are the result
of the partial charges from polar covalent bonds.
66. Answers may vary. Sample answer: pH is critical to all organisms and their environments. A
change of 0.1 or even 0.01 in pH can drastically alter biological reactions and the structure of
proteins. pH must be maintained in the stomach for proper food digestion. pH in freshwater
ecosystems can drastically alter the health of species who live in or rely on water sources. The
pH of the ocean is about 8, but if too much carbon dioxide, CO2, is absorbed, it becomes too
acidic. An acidic environment alters the shells of molluscs and the health of many other marine
organisms.
67. (a) A buffer system contains a weak acid or a weak base or a combination of the two.
(b) A buffer system can compensate for changes in pH by donating hydroxide ions or hydrogen
ions.
(c) Answers may vary. Sample Answer: An example of a buffer system is blood which contains
hydrogen ions, H+, carbonic acid, H2CO3, and hydrogen carbonate, HCO3, in H2O.
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68. Answers may vary. Sample Answer: Polymerization of biological molecules allows for
efficient storage molecules, which can be broken down into useful smaller molecules when
needed. Polymerization allows for building complex protein molecules for a variety of functions
and structures, DNA as storage of genetic information, and RNA as interpreter of that genetic
information.
69. Answers may vary. Sample Answer: Carbon can covalently bond with four other atoms.
Carbon can form straight chains, branching chains, and rings, which allow for a great variety of
shapes and sizes in molecules. Carbon can form single, double, or triple bonds, forming
structures of various strengths.
70. A dehydration reaction removes a water molecule to join two smaller molecules into one
larger one (also called condensation). A hydrolysis reaction adds a water molecule to split a large
molecule into two smaller molecules.
71. Peptide bonds and glycosidic bonds are both covalent bonds. A glycosidic bond is a bond
between a sugar and another molecule while a peptide bond is a bond between two amino acids.
72. (a) The diagram represents a monosaccharide.
(b) The chemical formula for the monosaccharide is C5H10O5.
(c) A monosaccharide belong to the group of carbohydrates.
73. T-charts may vary. Diagrams should include the following information:
Saturated fats have no double bonds between carbons in the fatty acid side chains. They tend to
have higher melting points. Unsaturated fats have fewer than the maximum number of hydrogen
atoms for the number of carbon atoms because they have one or more double bonds in their fatty
acid chains. They have lower melting points.
74. Answers may vary. Sample answer:
Table 2
Steroid
Purpose
cholesterol
helps to keep cell membranes fluid
testosterone
controls the development of male
sexual traits
progesterone
involved in pregnancy
75. Answers may vary. Sample Answer: Plants make the wax cutin, to waterproof their surfaces.
Birds make a kind of wax to keep their feathers dry. Bees make wax to store honey and their
developing young.
76. (a) Fatty acids in living things are at least 4 carbons long, and typically 14-22 carbons per
chain.
(b) As carbon chain length increases, fatty acids become less water-soluble.
77. (a) Phospholipids are composed of a glycerol molecule to which two fatty acids and a
phosphate group are linked by dehydration synthesis.
(b) All biological membranes are made of phospholipids.
78. Answers may vary. Student responses should indicate that structural proteins provide
supportive frameworks for cells (e.g., the hairs on your head), defensive proteins help fight off
infection (ex. antibodies), hormones signal your body to make changes (e.g., insulin), transport
proteins carry substances in your blood and through your body (e.g., hemoglobin), storage
proteins provide nutrition where needed (e.g., albumin in egg whites), receptor and recognition
proteins help differentiate cells (e.g., MHC in immune reactions), motile proteins help cells
move (e.g., flagella), and enzymes—help reactions to occur (ex. salivary amylase).
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79. (a) In competitive inhibition, an inhibitory molecule competes with the substrate for binding
at the active site. In noncompetitive inhibition, an inhibiting molecule does not compete with the
substrate for the active site but modulates the enzymes activity form an alternate site.
(b) In biological pathways, noncompetitive inhibition is used to regulate negative feedback
mechanisms, in which the product of a metabolic pathway inhibits upstream enzyme activity by
binding to an allosteric site. Competitive inhibition occurs when multiple metabolites compete
for the same enzyme, when the concentration of the inhibiting molecule is high enough the rate
of enzyme activity is decreased.
80.
Analysis and Application
81. Answer may vary. Sample answer: Isotopes behave similarly in chemical reactions because
they maintain a similar electronic environment. Neutrons carry no electrical charge and are not
involved in chemical reactions.
82. (a)
(b) The rigid lattice structure of ice means the water has a density as a solid that is lower than its
density as a liquid. This means that ice floats on the water, and in the winters, forms an
insulating layer preventing the lake from freezing all the way to the bottom so species, such as
carp, can survive in deep lakes by living in the lower layers.
83. (a) a lipid bilayer membrane
(b) Hydrophilic molecules are strongly attracted to water and readily mix with water.
Hydrophobic molecules are not strongly attracted to water and will tend to separate from water.
The water-soluble heads of the lipid bilayer line up toward the outside of the membrane. Watersoluble molecules do not freely pass through the hydrophobic inner membrane, however.
84. (a) Answers may vary. Sample answer: Solid water is less dense than liquid water causing
ice to float and hydrogen bonding of water results in high surface tension.
(b) If ice did not float, fish in northern lakes would die during the winter. The surface tension of
water lets bugs walk on top. The ability of water to contain so many solutes helps make the
oceans and our bodies work as they do. The heat of vaporization helps our bodies use
perspiration to cool down.
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85. (a) Omega-3 fatty acids are suspected to counteract the effects of triglycerides and to have a
good effect on heart, brain, joint, and digestive health.
(b) You should eat more enhanced eggs, salmon, winter squash, flax seeds, and olives to make
sure you get enough Omega-3 fatty acids.
86. The functional advantage of fats containing several fatty acid chains is an increased capacity
for energy storage.
87. As the fats get digested the fatty acids are released from the triglycerides. This in
combination with the gastric acidic secretions used to solubilize the fat cause heartburn.
88. (a) Answers may vary. Sample Answer: An R group is a functional side chain associated
with amino acids. They give amino acids structural and functional diversity. Methyl indole is the
R group in tryptophan. (Students might mention any of the R groups found in Figure 2, page 40
of the student textbook.)
(b) The OH and a H are removed from an amino acid in a dehydration reaction to form peptide
bonds.
89. DNA has thymine; RNA has uracil. DNA is double-stranded and arranged as a helix; RNA is
a single strand. Both structures have the nucleotides adenine, guanine, and cytosine. DNA
primarily serves as the storage material for genetic information; RNA can function as a carrier of
genetic information, catalyst of biochemical reactions, and acts as a structural molecule in
cellular organelles.
90.
91. (a) 38 °C
(b) 8.5
(c) 4
92. No, only a sugar molecule would fit into an active site of the enzyme. The enzyme-substrate
complex is like a lock and key. A protein would not fit into this active site as it is configured
differently.
93. As the sugar is catalyzed into different substances, the substrate concentration is gradually
reduced. This reduction in the substrate concentration decreases the rate of reaction.
Evaluation
94. Since water in its solid state is less dense than its liquid state, the water in ponds and lakes
freeze from the top down. The water will not freeze all the way through because the solid water
will float on the surface protecting the remaining water from the elements allowing it to remain
warm enough to stay in its liquid state. All but the smallest ponds can remain partly liquid.
Aquatic animals can survive in this water until the ice thaws in the spring.
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95. The marathon runner should consume foods containing complex carbohydrates like pasta and
grains as they can be stored in the muscles and will break down more slowly than simple
carbohydrates.
96. Disaccharides need to break only one bond to release a monosaccharide allowing them to
provide a quick source of energy. Polysaccharides contain multiple bonds that need to be broken
to release the monosaccharides. The monosaccharides are a longer-term source of energy.
97. Cerumen can have a water-proofing effect that controls the amount of water that enters the
ear canal. It is also “sticky,” trapping dirt and debris so that it does not enter the ear canal.
98. A dehydration reaction can take place on any of the carbons with available OH groups. The
carbon at the 5 position is hindered and will not form glycosidic linkages.
99. Enzymes depend on water to reach their substrates and bind to them. Many active sites use
water to form hydrogen-bonding networks critical to the function of the enzyme.
100. The breakdown of organs and tissues after death is catalyzed by enzymes. Cooling organs
and tissues for transplant reduces this enzyme activity, slowing the natural decomposition
process. Cooling also slows the normal metabolic processes and reduces the degradation of the
structures.
101. The recommendation to run the reaction with a substrate concentration that allows
saturation of the available enzymes would lead to a stable production rate.
102. Answers may vary. Sample answer: Students’ answers should include a discussion of
functional groups that distinguish the function of each molecule and give clues to which
biological category it falls into. If the ratio of molecule’s carbon-hydrogen-oxygen ratio is 1:2:1,
it is a carbohydrate. If the molecule has many portions that are hydrocarbons and lower oxygen
content, then it is a lipid. If the molecule contains nitrogen and exhibits a pattern of repeating
peptide linkages such as, –C–C–N–C–C–N, then it is a protein. Nucleic acids will have repeating
sugar/phosphate arrangements.
Reflect on Your Learning
103. Answers may vary. Sample answer: Students should indicate that proteins have the greatest
diversity in roles, including enzyme production, transport, immunity, structure, recognition, and
other functions due to the large number of amino acid combinations and functional groups.
104. Answers may vary. Sample Answer: Understanding about the biological molecules and how
they function in cells can make us more aware how a healthy diet contributes to overall health,
and help us make healthy nutrition choices. I will eat fewer saturated fats, such as butter and
cheese, and more polyunsaturated fats such as avocados and olive oil to keep membranes fluid
and functioning optimally. I will make sure I eat protein with every meal to make sure my body
gets enough amino acids for building a strong body, defending against disease, and enzyme
function.
105. Answers may vary. Sample answer: The polarity of water contributes to many of its unique
properties, and this chemical perspective is essential to understanding these properties. The
physics of how water can move against gravity and how the molecules interact relates to the
roles water plays in living things and ecosystems.
106. Answers may vary. Sample answer: Students should provide explanations of how specific
diagrams or images were helpful. For example, they might explain how seeing the shape of the
molecules helped them to visualize the processes in the body. They should create some kind of
sketch of a six-membered simple sugar, and understand the idea of the basic monomers of the
amino acids and nucleic acids.
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Chapter 1: The Biochemical Basis of Life 1-10
107. Answers may vary. Sample answer: Students should choose a topic and describe its
importance in their life. For example, a student might describe how learning about the roles of
lipids, carbohydrates, and amino acids, and how this makes them more aware of the molecules
they are putting into their diet.
Research
108. Students’ research should include relevant facts about how radioactive iodine is used to
diagnose thyroid disease.
109. Answers may vary. Sample answer: Students’ research should include relevant facts about
how Co-60, I-131, and Tc-99 are used.
110. Answers may vary. Sample answer: Students may mention lactose intolerance due to a lack
of lactase enzyme (sufferers experience abdominal pain as gas builds up). Students may mention
sucrase-isomaltase deficiency affecting ones ability to digest table sugar. Treatments for
digestive issues may include taking a regimen of enzymes and avoiding certain foods.
111. Answers may vary. Sample answer: The essential fatty acids are omega-3, which is
important in maintaining brain function, as well as normal growth and development, omega-6,
which stimulates skin and hair growth, maintains bone health, maintains the reproductive system
and regulates metabolism. Dietary sources include: flax seeds, olive oil, and fish oils.
112. Answers may vary. Sample answer: The essential amino acids are phenylalanine, valine,
threonine, tryptophan, isoleucine, methionine, leucine, lysine, and histidine. Additionally,
cysteine (or sulphur-containing amino acids), tyrosine (or aromatic amino acids), and arginine
are required by infants and growing children. Diets that include red meat include all of the
essential amino acids, but vegetarians can also ensure that they get all of them by pairing their
foods carefully. For example, the combination of rice and beans makes a “complete protein”
meal.
113. Answers may vary. Sample answer: Excess triglycerides in a diet contribute to chronic heart
disease and stroke. To minimize the effects of a high triglyceride diet, one should limit the
amount of simple sugars ingested and exercise regularly.
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