Chapter 2

Question 1

acid

Answer 1

A molecule that releases a proton when dissolved in water;
this dissociation generates hydronium (H3O+) ions, thereby
lowering the pH.

Question 2

amino acid

Answer 2

Small organic molecule containing both an amino group
and a carboxyl group; it serves as the building block of
proteins.

Question 3

atom

Answer 3

The smallest particle of an element that still retains its
distinctive chemical properties; consists of a positively
charged nucleus surrounded by a cloud of negatively
charged electrons.

Question 4

atomic weight

Answer 4

The mass of an atom relative to the mass of a hydrogen
atom; equal to the number of protons plus the number of
neutrons that the atom contains

Question 5

ATP

Answer 5

Activated carrier that serves as the principal carrier of
energy in cells; a nucleoside triphosphate composed of
adenine, ribose, and three phosphate groups. (See Figure
2–26.)

Question 6

Avogadro´s number

Answer 6

The number of molecules in a mole, the quantity of
a substance equal to its molecular weight in grams;
6.0221409 × 10^23

Question 7

base

Answer 7

Molecule that accepts a proton when dissolved in water;
also used to refer to the nitrogen-containing purines or
pyrimidines in DNA and RNA

Question 8

buffer

Answer 8

Mixture of weak acids and bases that maintains the pH of a

solution by releasing and taking up protons.

Question 9

chemical bond

Answer 9

A sharing or transfer of electrons that holds two atoms

together. (See also covalent bond and noncovalent
bond. )

Question 10

chemical group

Answer 10

A combination of atoms, such as a hydroxyl group (–OH) or
an amino group (–NH2), with distinct chemical and physical
properties that influence the behavior of the molecule in
which it resides

Question 11

condensation reaction

Answer 11

Chemical reaction in which a covalent bond is formed
between two molecules as water is expelled; used to build
polymers, such as proteins, polysaccharides, and nucleic
acids.

Question 12

conformation

Answer 12

Precise, three-dimensional shape of a protein or other
macromolecule, based on the spatial location of its atoms
in relation to one another.

Question 13

covalent bond

Answer 13

Stable chemical link between two atoms produced by

sharing one or more pairs of electrons

Question 14

DNA

Answer 14

Double-stranded polynucleotide formed from two separate
chains of covalently linked deoxyribonucleotide units.
It serves as the cell’s store of genetic information that is
transmitted from generation to generation

Question 15

electron

Answer 15

Negatively charged subatomic particle that occupies space

around an atomic nucleus (e–)

Question 16

electronegativity

Answer 16

The tendency of an atom to attract electrons

Question 17

electrostatic attraction

Answer 17

Force that draws together oppositely charged atoms.
Examples include ionic bonds and the attractions between
molecules containing polar covalent bonds

Question 18

fatty acid

Answer 18

Molecule that consists of a
carboxylic acid attached to
a long hydrocarbon chain.
Used as a major source of energy during metabolism and as
a starting point for the synthesis of phospholipids

Question 19

hydrogen bond

Answer 19

A weak noncovalent interaction
between a positively charged
hydrogen atom in one molecule
and a negatively charged atom,
such as nitrogen or oxygen, in another; hydrogen bonds are
key to the structure and properties of water

Question 20

hydrolysis

Answer 20

Chemical reaction that involves cleavage of a covalent
bond with the accompanying consumption of water (its –H
being added to one product of the cleavage and its –OH to
the other); the reverse of a condensation reaction.

Question 21

hydronium ion

Answer 21

The form taken by a proton (H+) in aqueous solution.

Question 22

hydrophilic

Answer 22

Molecule or part of a molecule that readily forms hydrogen
bonds with water, allowing it to readily dissolve; literally,
“water loving.”

Question 23

hydrophobic

Answer 23

Nonpolar, uncharged molecule or part of a molecule
that forms no hydrogen bonds with water molecules and
therefore does not dissolve; literally, “water fearing.”

Question 24

hydrophobic force

Answer 24

A noncovalent interaction that forces together the
hydrophobic portions of dissolved molecules to minimize
their disruption of the hydrogen-bonded network of water;
causes membrane phospholipids to self-assemble into a
bilayer and helps to fold proteins into a compact, globular
shape

Question 25

inorganic

Answer 25

Not composed of carbon atoms.

Question 26

ion

Answer 26

An atom carrying an electrical charge, either positive or

negative

Question 27

ionic bond

Answer 27

Interaction formed when one atom donates electrons to
another; this transfer of electrons causes both atoms to
become electrically charged.

Question 28

lipid

Answer 28

An organic molecule that is insoluble in water but dissolves
readily in nonpolar organic solvents; typically contains
long hydrocarbon chains or multiple rings. One class, the
phospholipids, forms the structural basis for biological
membranes

Question 29

lipid bilayer

Answer 29

Thin pair of closely juxtaposed sheets, composed mainly of
phospholipid molecules, that forms the structural basis for
all cell membranes

Question 30

molecular weight

Answer 30

Sum of the atomic weights of the atoms in a molecule; as

a ratio of molecular masses, it is a number without units.

Question 31

molecule

Answer 31

Group of atoms joined together by covalent bonds.

Question 32

noncovalent bond

Answer 32

Chemical association that does not involve the sharing
of electrons; singly they are relatively weak, but they can
sum together to produce strong, highly specific interactions
between molecules. Examples are hydrogen bonds and van
der Waals attractions.

Question 33

nucleotide

Answer 33

Basic building block of the nucleic ac

Question 34

organic molecule

Answer 34

Chemical compound that contains carbon and hydrogen

Question 35

pH scale

Answer 35

Concentration of hydrogen ions in a solution, expressed
as a logarithm. An acidic solution with pH 3 will contain
10–3 M hydrogen ions

Question 36

polar

Answer 36

In chemistry, describes a molecule or bond in which

electrons are distributed unevenly.

Question 37

polymer

Answer 37

Long molecule made by covalently linking multiple identical

or similar subunits (monomers)

Question 38

proton

Answer 38

Positively charged particle found in the nucleus of every

atom; also, another name for a hydrogen ion (H+).

Question 39

RNA

Answer 39

Molecule produced by the transcription of DNA; usually
single-stranded, it is a polynucleotide composed of
covalently linked ribonucleotide subunits. Serves a variety
of informational, structural, catalytic, and regulatory
functions in cells.

Question 40

subunit

Answer 40

A monomer that forms part of a larger molecule, such as an
amino acid residue in a protein or a nucleotide residue in
a nucleic acid. Can also refer to a complete molecule that
forms part of a larger molecule. Many proteins, for example,
are composed of multiple polypeptide chains, each of which
is called a protein subunit

Question 41

sugar

Answer 41

A substance made of carbon, hydrogen, and oxygen with
the general formula (CH2O)n. A carbohydrate or saccharide.
The “sugar” of everyday use is sucrose, a sweet-tasting
disaccharide made of glucose and fructose

Question 42

van der Waals attraction

Answer 42

Weak noncovalent interaction, due to fluctuating electrical
charges, that comes into play between two atoms within a
short distance of each other