1.
An oxygen atom has eight protons. (a) Sketch in the arrangement of electrons around the nucleus of the oxygen atom in the following diagram. (b) How many more electrons will it take to fill the outermost energy level?

2.
What is the following type of decomposition reaction called?
A–B–C–D + H2O → A–B–C–H + HO–D
3.
The subatomic particle with the least mass (a) carries a negative charge, (b) carries a positive charge, (c) plays no part in the atom’s chemical reactions, (d) is found only in the nucleus.
4.
Isotopes of an element differ from each other in the number of (a) protons in the nucleus, (b) neutrons in the nucleus, (c) electrons in the outer shells, (d) a, b, and c are all correct.
5.
The number and arrangement of electrons in an atom’s outer energy level determines the atom’s (a) atomic weight, (b) atomic number, (c) molecular weight, (d) chemical properties.
6.
All organic compounds in the human body contain all of the following elements except (a) hydrogen, (b) oxygen, (c) carbon, (d) calcium, (e) both a and d.
7.
A substance containing atoms of different elements that are bonded together is called a(n) (a) molecule, (b) compound, (c) mixture, (d) isotope, (e) solution.
8.
All the chemical reactions that occur in the human body are collectively referred to as (a) anabolism, (b) catabolism, (c) metabolism, (d) homeostasis.
9.
Which of the following chemical equations illustrates a typical decomposition reaction? * (a) A + B → AB * (b) AB + CD → AD + CB * (c) 2A2 + B2 → 2A2B * (d) AB → A + B
10.
The speed, or rate, of a chemical reaction is influenced by (a) the presence of catalysts, (b) the temperature, (c) the concentration of the reactants, (d) a, b, and c are all correct.
11.
A pH of 7.8 in the human body typifies a condition referred to as (a) acidosis, (b) alkalosis, (c) dehydration, (d) homeostasis.
12.
A(n) _____ is a solute that dissociates to release hydrogen ions, and a(n) _____ is a solute that removes hydrogen ions from solution.
(a) base, acid, (b) salt, base, (c) acid, salt, (d) acid, base.
13.
Special catalytic molecules called _____ control chemical reactions in the human body. (a) enzymes, (b) cytozymes, (c) cofactors, (d) activators, (e) cytochromes.
14.
Which of the following is not a function of a protein? (a) support, (b) transport, (c) metabolic regulation, (d) storage of genetic information, (e) movement.
15.
Complementary base pairing in DNA includes the pairs (a) adenine–uracil and cytosine–guanine, (b) adenine–thymine and cytosine–guanine, (c) adenine–guanine and cytosine–thymine, (d) guanine–uracil and cytosine–thymine.
16.
What are the three subatomic particles in atoms?
17.
What four major classes of organic compounds are found in the body?
18.
List three important functions of triglycerides (neutral fats) in the body.
19.
List seven major functions performed by proteins.
20.
* (a) What three basic components make up a nucleotide of DNA? * (b) What three basic components make up a nucleotide of RNA?
21.
What three components are required to create the high-energy compound ATP?
LEVEL 2 Reviewing Concepts
22.
If a polypeptide contains 10 peptide bonds, how many amino acids does it contain? (a) 9, (b) 10, (c) 11, (d) 12.
23.
A dehydration synthesis reaction between glycerol and a single fatty acid would yield a(n) (a) micelle, (b) omega-3 fatty acid, (c) triglyceride, (d) monoglyceride, (e) diglyceride.
24.
Explain how enzymes function in chemical reactions.
25.
What is a salt? How does a salt differ from an acid or a base?
26.
Explain the differences among nonpolar covalent bonds, polar covalent bonds, and ionic bonds.
27.
In an exergonic reaction, (a) large molecules are broken down into smaller ones, (b) small molecules are assembled into larger ones, (c) molecules are rearranged to form new molecules, (d) molecules move from reactants to products and back, (e) energy is released during the reaction.
28.
The hydrogen bonding that occurs in water is responsible for all of the following, except (a) the high boiling point of water, (b) the low freezing point of water, (c) the ability of water to dissolve nonpolar substances, (d) the ability of water to dissolve inorganic salts, (e) the surface tension of water.
29.
A sample that contains an organic molecule has the following constituents: carbon, hydrogen, oxygen, nitrogen, and phosphorus. Is the molecule more likely to be a carbohydrate, a lipid, a protein, or a nucleic acid?
LEVEL 3 Critical Thinking and Clinical Applications
30.
An atom of the element calcium has 20 protons and 20 neutrons. Determine the following information about calcium: (a) number of electrons, (b) atomic number, (c) atomic weight, (d) number of electrons in each energy level.
31.
A certain reaction pathway consists of four steps. How would decreasing the amount of enzyme that catalyzes the second step affect the amount of product produced at the end of the pathway?
32.
An important buffer system in the human body involves carbon dioxide (CO2) and bicarbonate ion (HCO3–) in the reversible reaction
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3−
If a person becomes excited and exhales large amounts of CO2, how will the pH of the person’s body be affected?
ANSWERS
1. * a.

Oxygen atom * b. Two more electrons can fit into the outermost energy level of an oxygen atom.
2.
hydrolysis
3.
a
4.
b
5.
d
6.
d
7.
b
8.
c
9.
d
10.
d
11.
b
12.
d
13.
a
14.
d
15.
b
16.
protons, neutrons, and electrons
17.
carbohydrates, lipids, proteins, and nucleic acids
18.
Triglycerides (1) provide a significant energy reserve, (2) serve as insulation and thus act in heat conservation, and (3) protect organs by cushioning them.
19.
(1) support (structural proteins); (2) movement (contractile proteins); (3) transport (transport proteins); (4) buffering; (5) metabolic regulation; (6) coordination and control (hormones and neurotransmitters); and (7) defense (antibodies)
20.
(a) DNA: deoxyribose, phosphate, and nitrogenous bases (A, T, C, G); (b) RNA: ribose, phosphate, and nitrogenous bases (A, U, C, G)
21.
(1) adenosine, (2) phosphate groups, and (3) appropriate enzymes
Level 2 Reviewing Concepts
22.
c
23.
d
24.
Enzymes are specialized protein catalysts that lower the activation energy for chemical reactions. Enzymes speed up chemical reactions but are not used up or changed in the process.
25.
A salt is an ionic compound consisting of any cations other than hydrogen ions and any anions other than hydroxide ions. Acids dissociate and release hydrogen ions, while bases remove hydrogen ions from solution (usually by releasing hydroxide ions).
26.
Nonpolar covalent bonds have an equal sharing of electrons. Polar covalent bonds have an unequal sharing of electrons. Ionic bonds result from the loss or gain of electrons.
27.
e
28.
c
29.
The molecule is a nucleic acid. Carbohydrates and lipids do not contain nitrogen. Although both proteins and nucleic acids contain nitrogen, only nucleic acids normally contain phosphorus.
Level 3 Critical Thinking and Clinical Applications
30.
(a) number of electrons = 20; (b) atomic number = 20; (c) atomic weight = 40; (d) 2 electrons in first shell, 8 in second shell, 8 in third shell, and 2 in outer shell.
31.
Decreasing the amount of enzyme at the second step would slow down the remaining steps of the pathway because less substrate would be available for the next two steps. The net result would be a decrease in the amount of product.
32.
If a person exhales large amounts of CO2, the level of H+ in the blood will decrease. A decrease in the amount of H+ will cause the pH to increase.