Download CHAPTER 2- The Chemical Level of Organization

CHAPTER 2- The Chemical Level of Organization
Choose the best answer to each of the following questions.
1) The four elements making up about 96% of the body's mass are represented by the symbols:
A) O, Ca, H, Na
B) O, C, H, N
C) O, C, He, Na
D) O, H, K, N
E) O, Ca, H, Ni
Answer: B
Reference: 2.1
Level of Difficulty: Easy
2) Which statement about an atom is not true?
A) an atom has the characteristics of the element
B) the nucleus of an atom is make up of protons and neutrons
C) the proton has a positive charge and the neutrons has no charge
D) electrons are found in shells around the nucleus
E) a neutral atom has more neutrons than protons and electrons
Answer: E
Reference: 2.1
Level of Difficulty: Medium
3) The smallest unit of matter that retains the properties and characteristics of an element is the:
A) atom.
B) molecule.
C) proton.
D) nucleus.
E) electron.
Answer: A
Reference: 2.1
Level of Difficulty: Easy
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4) Which of the following carry a negative charge?
A) protons only
B) neutrons only
C) electrons only
D) both protons and electrons
E) both electrons and neutrons
Answer: C
Reference: 2.1
Level of Difficulty: Easy
5) An atom of one element is distinguished from an atom of another element by the number of:
A) neutrons in the nucleus.
B) electrons in the nucleus.
C) protons in the nucleus.
D) electrons orbiting the nucleus.
E) electrons it can lose when bonding.
Answer: C
Reference: 2.1
Level of Difficulty: Medium
6) Isotopes are
A) charged atoms that gained or lost electrons.
B) atoms of different elements that have the same atomic mass.
C) able to release radiation if their nuclei are unstable.
D) atoms with unpaired electrons in their outermost shells.
E) atoms with the same numbers of neutrons but different numbers of protons.
Answer: C
Reference: 2.1
Level of Difficulty: Medium
7) What determines the atom’s chemical properties?
A) protons
B) neutrons
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C) electrons
D) the nucleus
E) all of the above
Answer: C
Reference: 2.1
Level of Difficulty: Medium
8) Which of the following is an ion and why?
A) O2- because it contains an unpaired electron in its outer shell.
B) Na+ because it has lost an electron.
C) Co-60 because it is radioactive.
D) H2 because it is sharing electrons.
E) H-3 because it has two extra neutrons.
Answer: B
Reference: 2.1
Level of Difficulty: Medium
9) A manufacturing company uses a very effective solvent that is composed of groups of atoms
with unpaired electrons in their outermost electron shells. Which of the following is true?
A) The solvent’s atoms are isotopes with unstable nuclei that releases radioactivity.
B) Workers using the solvent have decreased risk of cataracts, atherosclerosis, or cancers.
C) Inclusion of antioxidants in workers’ diets may help protect them from effects of the solvent.
D) The solvent is electrically neutral and therefore poses no risks to workers.
E) The unpaired electrons in the solvent atoms will stabilize molecules in the workers’ bodies.
Answer: C
Reference: 2.1
Level of Difficulty: Hard
10) Which of the following is true of the chemical formula, H2O2?
A) The formula represents four atoms sharing electrons.
B) The formula represents an element.
C) The formula represents two ions of hydrogen and two ions of oxygen.
D) The formula indicates the presence of two molecules each of hydrogen and oxygen.
E) The formula indicates the transfer of electrons from hydrogen to oxygen.
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Answer: A
Reference: 2.1
Level of Difficulty: Medium
11) Which of the following does NOT indicate a compound?
A) CO2
B) N2
C) HCl
D) H2O
E) NaCl
Answer: B
Reference: 2.1
Level of Difficulty: Medium
12) A free radical
A) is a stable compound, such as vitamin C
B) is an electrically neutral compound
C) can break apart important body molecules
D) is caused by exposure to the sun
E) all of the above
Answer: C
Reference: 2.1
Level of Difficulty: Medium
13) Which of the following is true?
A) Chemical bonds are repulsive forces between the atoms of molecules.
B) The valence electrons involved in bonding are found in an atom’s innermost shell.
C) Atoms tend to react to decrease the stability of the arrangement of their electrons.
D) The most reactive atoms already have 8 valence electrons.
E) Atoms tend react so that they acquire eight electrons in their outermost shell.
Answer: E
Reference: 2.2
Level of Difficulty: Medium
14) Salts are formed by the exchange of electrons between atoms that tend to form cations and
those that tend to form anions. Which of the following pairs of ions would likely form a salt?
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A)
B)
C)
D)
E)
potassium ion, iodide ion
chloride ion, iodide ion
magnesium ion, calcium ion
sodium ion, iron (II) ion
calcium ion, hydrogen ion
Answer: A
Reference: 2.2
Level of Difficulty: Hard
15) All of the following are true of ionic compounds EXCEPT
A) Many ionic compounds exist as crystalline solids.
B) Ionic compounds have consistent ratios of cations to anions.
C) Solid ionic compounds are found primarily in the soft tissues of the body.
D) Ionic compounds have a neutral electrical charge.
E) Ionic compounds conduct electricity when dissolved in water.
Answer: C
Reference: 2.2
Level of Difficulty: Medium
16) Covalent bonds are found in
A) carbohydrates
B) proteins
C) lipids
D) A and B
E) A, B, and C
Answer: E
Reference: 2.2
Level of Difficulty: easy
17) Each molecule of oxygen gas is composed of two atoms of oxygen sharing two pairs of
electrons equally. Which of the following best describes the chemical bond between the oxygen
atoms?
A) covalent bond
B) polar bond
C) double bond
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D) nonpolar bond
E) double nonpolar covalent bond
Answer: E
Reference: 2.2
Level of Difficulty: Medium
18) Which of the following compounds is polar covalent?
A) O2
B) H2O
C) NaCl
D) CH4
E) KI
Answer: B
Reference: 2.2
Level of Difficulty: Medium
19) Hydrogen bonds
A) are stronger than either covalent or ionic bonds.
B) tend to destabilize large molecules such as proteins.
C) are relatively uncommon between molecules in the body.
D) form between hydrogen and nitrogen or oxygen atoms.
E) enhance gas exchange in the lungs.
Answer: D
Reference: 2.2
Level of Difficulty: Medium
20) Between which of the following pairs would H bonds be likely to form?
A) H2 and CH4
B) H2O and NH3
C) CO2 and H2O
D) A, B and C are correct.
E) Only B and C are correct.
Answer: E
Reference: 2.2
Level of Difficulty: Hard
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21) In a chemical reaction,
A) the starting materials are called products.
B) the ending substances are called reactants.
C) electrons are exchanged or shared to make atoms more stable.
D) matter is created or destroyed.
E) the starting and ending materials have identical properties.
Answer: C
Reference: 2.3
Level of Difficulty: Medium
22) The sum of all of the chemical reactions that occur in the body is called
A) metabolism
B) anabolism
C) synthesis
D) catabolism
E) exchange
Answer: A
Reference: 2.3
Level of Difficulty: Easy
23) All of the following are true EXCEPT
A) Energy is the capacity to do work.
B) The energy stored in body fat is potential energy.
C) The energy transferred to a ball by a swinging foot is kinetic energy.
D) Chemical energy is a form of kinetic energy.
E) Energy cannot be created or destroyed, only converted from one form to another.
Answer: D
Reference: 2.3
Level of Difficulty: Medium
24) Glycolysis is the catabolism of glucose to pyruvate. It requires the hydrolysis of 2 ATP
molecules, but ultimately generates 4 ATP molecules. Glycolysis is best described as a __
process.
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A) exergonic
B) endergonic
C) energy neutral
D) physiologically improbable
E) anabolic
Answer: E
Reference: 2.3
Level of Difficulty: Hard
25) The kinetic energy needed to break the chemical bonds in reactant molecules is called
A) chemical energy
B) positional energy
C) activation energy
D) conservation energy
E) potential energy
Answer: C
Reference: 2.3
Level of Difficulty: Easy
26) Which of the following influence the rate of a chemical reaction?
A)
B)
C)
D)
E)
the concentration of the reactants
the temperature
the presence of catalysts or enzymes
Both A and B are correct.
A, B and C are correct.
Answer: E
Reference: 2.3
Level of Difficulty: Medium
27) The function of a catalyst is to:
A) convert strong acids and bases into weak acids and bases.
B) store energy released during exergonic reactions.
C) act as the chemical link between atoms in a covalent bond.
D) lower the activation energy needed for a chemical reaction to occur.
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E) keep particles in a colloid from settling out.
Answer: D
Reference: 2.3
Level of Difficulty: Easy
28) Which of the following is true of a catalyst?
A) It is changed by the chemical reaction in which it participates.
B) It helps orient colliding molecules so that a reaction is more likely to occur.
C) It raises the activation energy required for a reaction to occur.
D) It prevents chemical reactions from occurring under physiological conditions.
E) It changes the difference in potential energy between reactants and products.
Answer: B
Reference: 2.3
Level of Difficulty: Medium
29) Which of the following is true of anabolic reactions in the body?
A) They are exergonic.
B) They are used to release energy from structural molecules.
C) They may be represented as A + B  AB.
D) They are decompositions.
E) They convert large molecules to smaller ones.
Answer: C
Reference: 2.3
Level of Difficulty: Medium
30) The body converts starch to glucose, which is then ultimately to converted to CO2, H2O, and
energy. These conversions are
A) catabolic.
B) exergonic
C) anabolic
D) Both A and B are correct.
E) Both B and C are correct.
Answer: D
Reference: 2.3
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Level of Difficulty: Medium
31) Which of the following is an exchange reaction?
A) H2CO3  H2O + CO2
B) NaCl + KI  NaI + KCl
C) HCl + NaOH  H2O + NaCl
D) B and C are correct.
E) A, B and C are correct.
Answer: D
Reference: 2.3
Level of Difficulty: Medium
32) Inorganic molecules
A) are usually structurally complex.
B) contain no carbon atoms.
C) include glucose, amino acids and triglycerides.
D) are not water soluble.
E) contain only covalent bonds.
Answer: B
Reference: 2.4
Level of Difficulty: Medium
33) CO2 and HCO3- are considered inorganic compounds even though they each contain a carbon
atom. Based on this observation, how could the definition of an inorganic compound best be
modified?
A) Inorganic compounds contain carbon atoms only if they also contain oxygen atoms.
B) Inorganic compounds contain no chains of carbon atoms.
C) Inorganic compounds contain carbon atoms only if they also contain hydrogen atoms.
D) Both A and B are correct.
E) Both A and C are correct.
Answer: B
Reference: 2.4
Level of Difficulty: Hard
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34) The most abundant and important inorganic compound found in living systems is
A) O2
B) CO2
C) HCO3D) H2O
E) C6H12O6
Answer: D
Reference: 2.4
Level of Difficulty: Medium
35) Hydrophilic solutes are those that:
A) dissolve easily in lipids because they contain nonpolar covalent bonds.
B) dissolve easily in water because they contain polar covalent bonds.
C) dissolve easily in water because they contain nonpolar covalent bonds.
D) dissolve poorly in water because they contain polar covalent bonds.
E) dissolve poorly in water because they contain nonpolar covalent bonds.
Answer: B
Reference: 2.4
Level of Difficulty: Medium
36) Water
A) serves as the Medium for most chemical reactions in the body.
B) is added to small molecules to join them into larger molecules.
C) is removed from large molecules to break them into smaller molecules.
D) has a limited ability to absorb or release heat without changing temperature.
E) provides friction that resists movement between membranes in body cavities.
Answer: A
Reference: 2.4
Level of Difficulty: Medium
37) A second semester anatomy and physiology student is taking a test that includes questions
about the blood. One question asks the student to characterize blood plasma, which contains
protein particles large enough to scatter light slightly but small enough to remain suspended in
water. The student knows that plasma also contains dissolved sugars, salts and other small
molecules too small to scatter light. Based on this knowledge, the student characterizes plasma
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as
A) a suspension.
B) a solution.
C) a colloid.
D) a suspension and solution.
E) a solution and colloid.
Answer: E
Reference: 2.4
Level of Difficulty: Hard
38) An acid
A) dissociates into H+ ions and cations in water.
B) is a proton acceptor.
C) has a pH < 7.
D) A and B are correct.
E) A, B and C are correct.
Answer: C
Reference: 2.4
Level of Difficulty: Medium
39) A salt
A) dissociates into H+ and OH- in solution.
B) prevents drastic changes in pH in body fluids.
C) is a proton donor.
D) is a product of the reaction of an acid with a base.
E) is the product of a decomposition reaction.
Answer: D
Reference: 2.4
Level of Difficulty: Medium
40) Which of the following never has an alkaline pH in a healthy person?
A) gastric juice
B) urine
C) semen
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D) blood
E) pancreatic juice
Answer: A
Reference: 2.4
Level of Difficulty: Medium
41) Which of the following is TRUE regarding this situation: Solution A has a pH of 7.48 and
Solution B has a pH of 7.39:
A) Solution B is more acidic than Solution A.
B) The pH of Solution A falls within the homeostatic pH range for extracellular body fluids, but
the pH of Solution B does not.
C) Solution A contains a higher concentration of hydrogen ions that Solution B.
D) Solution B contains a higher concentration of hydrogen ions than Solution A.
E) Both B and C are correct.
Answer: D
Reference: 2.4
Level of Difficulty: Hard
42) Buffers
A) convert weak acids or bases into strong ones.
B) help destabilize pH.
C) can absorb OH- if the pH is too low.
D) can release H+ if the pH is too high.
E) include the HCl – KOH system.
Answer: D
Reference: 2.4
Level of Difficulty: Medium
43) A common buffer found in extracellular fluid is
A) glucose.
B) bicarbonate ion.
C) sodium ion.
D) a triglyceride.
E) ATP
Answer: B
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Reference: 2.4
Level of Difficulty: Medium
44) Specific arrangements of atoms that cause organic molecules to have particular chemical
properties are called
A) functional groups
B) macromolecules
C) monomers
D) isomers
E) polymers
Answer: A
Reference: 2.4
Level of Difficulty: Medium
45) ALL of the following are organic molecules EXCEPT:
A) ATP
B) glucose
C) DNA
D) enzymes
E) O2
Answer: E
Reference: 2.4
Level of Difficulty: Medium
46) Carbohydrates
A) are stored in the liver and muscles in the form of triglycerides
B) contain C, H, and O in a 1:2:1 ratio.
C) are primarily used for structural support.
D) are composed of subunits called polysaccharides.
E) include RNA and DNA.
Answer: B
Reference: 2.4
Level of Difficulty: Medium
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46) Carbon can bond with how many other atoms?
A) 1
B) 2
C) 3
D) 4
E) 5
Answer: D
Reference: Intro
Level of Difficulty: Easy
47) An example of a polysaccharide stored in humans is
A) cellulose.
B) lactose.
C) glucose.
D) glycogen.
E) mannose
Answer: D
Reference: 2.5
Level of Difficulty: Medium
49) Which of the following is NOT true of lipids?
A) may be stored as triglycerides to provide chemical energy later
B) usually dissolve freely in blood
C) include steroids and eicosanoids
D) usually dissolve freely in blood plasma
E) usually have large numbers of C and H atoms, but few O atoms.
Answer: B
Reference: 2.7
Level of Difficulty: Medium
50) Glycerol is the backbone molecule for:
A) disaccharides.
B) DNA.
C) peptides.
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D) triglycerides.
E) ATP.
Answer: D
Reference: 2.7
Level of Difficulty: Medium
51) A fatty acid with only single covalent bonds is said to be:
A) oxidized.
B) reduced.
C) saturated.
D) denatured.
E) hydrolyzed.
Answer: C
Reference: 2.7
Level of Difficulty: Medium
52. Which statement is not true of a steroid?
A) The structure of a steroid is four rings of carbon
B) Common steroids are cortisol, vitamin D, estrogen
C) Body celss make steroids from polysaccharides
D) Anabolic steroids increase muscle size
E) All of the above statements are true
Answer: C
Reference: 2.7
Level of Difficulty: Medium
53) Peptide bonds are found in:
A) carbohydrates.
B) lipids.
C) proteins.
D) inorganic compounds.
E) any type of molecule.
Answer: C
Reference: 2.8
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Level of Difficulty: Easy
54) Enzymes and antibodies are examples of
A) carbohydrates.
B) lipids.
C) amino acids
D) nucleic acids.
E) proteins.
Answers: E.
Reference: 2.8
Level of Difficulty: Medium
55) In proteins, the folding of the unit on itself is referred to its
A). Primary structure.
B) Secondary structure
C) Tertiary structure
D) Quaternary structure
E) All answers are correct
Answer: C
Reference: 2.8
Level of Difficulty: Medium
56) Which of the following is NOT a function of a protein?
A) The mechanism that shortens muscles
B) Regulates nervous system as neurotransmitters
C) Defenses the body by forming antibodies
D) Is used to make visual pigments in the eye
E) Hemoglobin transports oxygen and some carbon dioxide
Answer: D
Reference: 2.6
Level of Difficulty: Mediium
57) Enzymes are
A) biological catalysts.
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B) usually large proteins.
C) specific for a single substrate.
D) A and B are true.
E) A, B and C are true.
Answer: E
Reference: 2.8
Level of Difficulty: Medium
58) Nucleotides contain
A) amino acids.
B) five carbon sugars.
C) fatty acids.
D) dipeptides.
E) disulfide bonds
Answer: B
Reference: 2.9
Level of Difficulty: Medium
59) Which of the following is NOT found in RNA?
A) ribose
B) phosphate
C) adenine
D) cytosine
E) thymine
Answer: E
Reference: 2.9
Level of Difficulty: Medium
60) Which of the following is NOT true of DNA?
A) It is the molecule of heredity.
B) It contains purines.
C) It contains deoxyribose and phosphate.
D) It is single stranded.
E) It contains pyrimidines.
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Answer: D
Reference: 2.0
Level of Difficulty: Medium
Choose the answer from the column on the right that best matches the description or term
on in the column on the left.
61) found in different energy levels outside
of the nucleus
A) atoms
B) electrons
62) fundamental particles of elements
C) molecules
D) neutrons
63) subatomic particle with no charge
E) protons
61) Answer: B
Reference: 2.1
Level of Difficulty: Medium
62) Answer: A
Reference: 2.1
Level of Difficulty: Medium
63) Answer: D
Reference: 2.1
Level of Difficulty: Medium
66) occurs between N-bases of DNA
64) occurs between two atoms that share
electrons equally
A) double covalent bonding
B) hydrogen bonding
65) occurs when one atom transfers
electrons to another
C) ionic bonding
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D) nonpolar covalent bonding
E) polar covalent bonding
64) Answer: D
Reference: 2.2
Level of Difficulty: Medium
65) Answer: C
Reference: 2.2
Level of Difficulty: Medium
66) Answer: B
Reference: 2,2
Level of Difficulty: Medium
67) glucose + galactose  lactose
A) activation energy
B) decomposition reaction
68) required to break chemical bonds in
reactants
C) exchange reaction
D) kinetic energy
69) sodium chloride + potassium iodide 
potassium chloride + sodium iodide
E) synthesis reaction
67) Answer: E
Reference: 2.3
Level of Difficulty: Medium
68) Answer: A
Reference: 2.3
Level of Difficulty: Medium
69) Answer: C
Reference: 2.3
Level of Difficulty: Medium
70) protein fount in connective tissues and skin
A) ATP
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71) most abundant lipids in the body
B) collagen
72) primary energy transfer molecule of body
C) fatty acids
D) starch
E) triglycerides
70) Answer: B
Reference: 2.8
Level of Difficulty: Medium
71) Answer: E
Reference: 2.7
Level of Difficulty: Medium
72) Answer: A
Reference: 2.10
Level of Difficulty: Medium
Write the word or phrase that best completes the sentence.
73) Protons, neutrons and electrons are classified as _____ particles.
Answer: subatomic
Reference: 2.1
Level of Difficulty: Medium
74) Atoms that share the same atomic number, but have different mass numbers are called
_____.
Answer: isotopes
Reference: 2.1
Level of Difficulty: Medium
75) The _____ predicts that atoms will react with each other to become more stable by filling
their valence shells with eight electrons.
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Answer: octet rule
Reference: 2.2
Level of Difficulty: Medium
76) Substances that dissociate into electrolytes in water are held together by _____ bonds.
Answer: ionic
Reference: 2.2
Level of Difficulty: Medium
77) In a double covalent bond, _____ of electrons are shared.
Answer: two pairs
Reference: 2.2
Level of Difficulty: Medium
78) _____ bonds maintain the complex shapes of large molecules such as proteins and nucleic
acids.
Answer: Hydrogen
Reference: 2.2
Level of Difficulty: Medium
79) Substances containing _____ bonds are water-soluble.
Answer: polar covalent
Reference: 2.2
Level of Difficulty: Medium
80) ____ occur when bonds are broken or created between atoms.
Answer: Chemical reactions
Reference: 2.3
Level of Difficulty: Medium
81) _____ reactions release energy.
Answer: Exergonic
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Reference: 2.3
Level of Difficulty: Medium
82) The two primary factors influencing activation energy are temperature and _____.
Answer: concentration
Reference: 2.3
Level of Difficulty: Medium
83) Products can be converted back into reactants in _____ reactions.
Answer: reversible
Reference: 2.3
Level of Difficulty: Medium
84) _____, or nonpolar covalent, compounds cannot dissolve in water because of their atoms
share electrons equally.
Answer: Hydrophobic
Reference: 2.4
Level of Difficulty: Medium
85) In a ____ reaction, a water molecule is used to split a large molecule into smaller molecules.
Answer: hydrolysis
Reference: 2.4
Level of Difficulty: Medium
86) An acid has a pH range of ____ .
Answer: 1-7
Reference:
Level of Difficulty: Medium
87) _____ are chemical compounds that help the body maintain homeostasis by preventing
drastic changes in the pH of body fluids.
Answer: Buffers
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Reference: 2.4
Level of Difficulty: Medium
88) Glycogen and starch are examples of complex carbohydrates called _____.
Answer: polysaccharides
Reference: 2.6
Level of Difficulty: Medium
89) _____ fats are triglycerides that contain only single covalent bonds between carbon atoms.
Answer: Saturated
Reference: 2.7
Level of Difficulty: Medium
90) The particular sequence of amino acids found in a protein is its _____ structure.
Answer: primary
Reference: 2.8
Level of Difficulty: Medium
91) When 2 amino acids bond, a _____ is formed.
Answer: dipeptide
Reference: 2.9
92) _____ are the monomers of nucleic acids.
Answer: Nucleotides
Reference: 2.9
Level of Difficulty: Medium
Write a short paragraph that answers each of the following questions.
93) Describe/discuss the structural arrangement of the subatomic particles of an atom.
Answer: The positively charged protons and the uncharged neutrons are located in the nucleus of
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the atom. Negatively charged electrons, equal in number to the protons, orbit the nucleus in
various energy levels, depending on the total number of electrons.
Reference: 2.1
Level of Difficulty: Medium
94) Distinguish between ions, molecules, free radicals and compounds.
Answer: Ions are atoms that have electrical charges because they have gained or lost electrons.
Atoms that lose electrons and become positively charged are called cations. Atoms that gain
electrons and become negatively charged are called anions. Some ions have an unpaired electron
in their outermost energy shell. Those ions are free radicals, which can damage other molecules
when they react to achieve a more stable atomic structure. Molecules are formed when atoms
share electrons. Compounds are made of molecules that contain more than one kind of atom. All
compounds are composed of molecules, but not all molecules are compounds. For example, H2
is not a compound because it contains only one kind of atom.
Reference: 2.1
Level of Difficulty: Medium
95) Compare and contrast ionic vs. covalent chemical bonds.
Answer: Chemical bonding involves either donating/receiving electrons or sharing electrons
between atoms. In an ionic bond, atoms are held together by the opposite electrical charges
created by donating or receiving electrons. In a covalent bond, two atoms share electrons to
stabilize their outer electron orbitals without loss or gain of electrons. Most organic compounds
are held together by covalent bonds. Electrolytes are held together by ionic bonds.
Reference: 2.2
Level of Difficulty: Medium
96) Relate activation energy to concentration, temperature and catalysts.
Answer: Activation energy is the energy needed to break and make chemical bonds during a
chemical reaction. No chemical reaction can occur unless the reactant molecules collide with
each other Hard enough to break chemical bonds. The higher the temperature is, the faster
reactant molecules will be moving and the more likely they will bump into each other and react.
If the concentration of reactant molecules is high, the reactants are more likely to collide and
react. Catalysts are substances that make it more likely that reactant molecules will interact.
Catalysts are not permanently changed by the chemical reactions in which they participate. Many
catalysts in the body are large proteins. The enzymes hold reactants in ways that make it more
likely that the necessary molecular collision will occur, thus lowering activation energy.
Reference: 2.3
Level of Difficulty: Medium
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97) Explain the role of water in maintenance of body temperature.
Answer: Because water has such a high heat capacity, it can absorb and release large amounts of
heat with only a modest change in its own temperature, thus lessening the impact of changes in
environmental temperatures on the body. Also, because of the high heat of vaporization of water,
the evaporation of sweat acts as an important cooling mechanism.
Reference: 2.4
Level of Difficulty: Medium
98) Explain how the carbonic acid-bicarbonate buffer system works in healthy individuals.
Answer: Carbonic acid (H2CO3) is a weak acid. It can reversibly dissociate molecules into H+
ions and HCO3- ions. The dissociation could be written as H2CO3 <--> H+ + HCO3-. If too many
H+ ions are present in the body, the reaction will move toward the left to absorb the excess. If too
few H+ ions are present, the reaction will move toward the right to correct the imbalance.
Reference: 2.4
Level of Difficulty: Medium
99) Describe the three major types of lipids found in the body.
Answer: The most abundant type of lipid in the body is the triglyceride, which is made of 3 fatty
acids joined to one glycerol molecule. Fatty acids are long chains of hydrocarbons. If there are
no double bonds between those carbons, the fatty acid is saturated. If there is one double bond,
the fatty acid is monounsaturated. Fatty acids with many double bonds are polyunsaturated.
Another kind of lipid is the steroid, which composed of molecules in which carbons are joined
together in a particular 4 ring structure. Some steroids are hormones; others are important in cell
membrane structure. The cell membrane is mostly composed of a bilayer of phospholipids. The
phospholipids have 2 hydrocarbon tails that are hydrophobic and a phospholipid head that is
hydrophilic. The bilayer arranges the tails of the two layers together and creates a barrier
between the cell and its environment.
Reference: 2.7
Level of Difficulty: Medium
100) Compare and contrast the structures of DNA and RNA.
Answer: DNA and RNA are both formed from small units known as nucleotides. DNA
nucleotides contain a phosphate group, deoxyribose, and a nitrogenous base (adenine, thymine,
guanine, or cytosine). RNA nucleotides contain a phosphate group, ribose, and a nitrogenous
base (adenine, uracil, guanine, or cytosine). DNA molecules are double-stranded with
nucleotides joined by complementary base pairing (A-T and C-G). RNA molecules are single
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stranded. They are much shorter than DNA molecules since they are formed from a part of a
DNA molecule.
Reference: 2.9
Level of Difficulty: Medium
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