1

Question 1

_____ is made of combinations of _____—substances such as hydrogen or carbon that cannot be broken down or interconverted by chemical means.

Answer 1

Matter
Elements

Question 2

The smallest particle of an element that still retains its distinctive
chemical properties is an _____.

Answer 2

Atom

Question 3

The characteristics of substances other than pure elements—including the materials from which living cells are made—depend on which atoms they contain and the way that these
atoms are linked together in groups to form______.

Answer 3

Molecules

Question 4

Each ____ has at its center a dense, positively charged nucleus, which
is surrounded at some distance by a cloud of negatively charged _____, held in orbit by______ to the nucleus.

Answer 4

Atom
Electron
electrostatic attraction

Question 5

The ____ consists of two kinds of subatomic particles: ________,
which are positively charged, and ______, which are electrically neutral.

Answer 5

Nucleus
Protons
Neutrons

Question 6

The ______ of an element is determined by the number of protons
present in its atom’s nucleus. An atom of ______ has a nucleus composed of a single proton; so hydrogen, with an atomic number of 1, is the ______.

Answer 6

Atomic number
Hydrogen
Lightest element

Question 7

The _____ carried by each proton is exactly______and______
to the charge carried by a single electron.

Answer 7

Electric charge
equal and opposite

Question 8

the number of ___________ surrounding the nucleus is therefore _______ to the number of positively charged protons that the nucleus contains; thus the number of______ in an atom also equals the atomic number.

Answer 8

negatively charged electrons

Equal
electrons

Question 9

_______ have essentially the same ___ as protons.

Answer 9

Neutrons
Mass

Question 10

an element can
exist in several physically distinguishable but chemically identical forms, called _______, each having a different number of neutrons but the same number of protons.

Answer 10

isotopes

Question 11

The number of electrons in an
atom is equal to the number of protons, so that the atom has no____.

Answer 11

net charge

Question 12

_______ of almost all the elements occur naturally, including some that are unstable—and thus _______.

Answer 12

Multiple isotopes
radioactive

Question 13

The_________ of an atom, or the ___________ of a molecule,
is its mass relative to the mass of a __________.

Answer 13

atomic weight
molecular weight
hydrogen atom

Question 14

The mass of an atom or a molecule is generally specified in ______, one dalton being an atomic mass unit essentially equal to the mass of a hydrogen atom.

Answer 14

daltons

Question 15

An individual carbon atom is roughly_______ in diameter, so it would take about ______of them, laid out in a straight line, to span a ______.

Answer 15

0.2 nm
5 million
millimeter

Question 16

One proton or neutron weighs approximately_______.

Answer 16

1/(6 × 1023) gram.

Question 17

This huge number, called _________, allows us to relate everyday quantities of chemicals to numbers of individual atoms or molecules. If
a substance has a molecular weight of _______of the substance will
contain_______.

Answer 17

Avogadro’s number
X, X grams
6 × 1023 molecules

Question 18

The concept of_____ is used widely in chemistry as a way to represent the number of molecules that are available to participate in chemical reactions.

Answer 18

mole

Question 19

there is a strict limit to the number of electrons that can be accommodated in an orbit of a given type, a so-
called_________.

Answer 19

electron shell

Question 20

This electron exchange can be
achieved either by __________ from one atom to another or by _________ between two atoms. These two strategies generate the two types of ______ that can bind atoms strongly to one another

Answer 20

transferring electrons
sharing electrons
chemical bonds

Question 21

an ________ is formed when electrons are donated by one atom to another

Answer 21

ionic bond

Question 22

a ________ is formed when two atoms share a pair of electrons

Answer 22

covalent bond

Question 23

Atoms can attain a more
stable arrangement of electrons in their_______ by interacting with one another.

Answer 23

outermost shell

Question 24

The number of protons in
an atom determines its ______.

Answer 24

atomic number

Question 25

An atom consists of a nucleus surrounded by an _______.

Answer 25

electron cloud

Question 26

A ______ is a cluster of atoms held together by ______, in which electrons are_____ rather than transferred between atoms.

Answer 26

molecule covalent bonds shared

Question 27

The________ form a cloud of negative charge that is densest between the two positively charged nuclei.

Answer 27

shared electrons

Question 28

The attractive and repulsive forces are precisely in balance when these nuclei are separated by a characteristic distance, called the______.

Answer 28

bond length

Question 29

Most covalent bonds involve the sharing of two electrons, one donated by each participating atom; these are called_______.

Answer 29

single bonds

Question 30

________are shorter and stronger than single bonds and have a characteristic effect on the geometry of molecules containing them.

Answer 30

Double bonds

Question 31

A _______ between two atoms generally allows the rotation of one part of a molecule relative to the other around the bond axis.

Answer 31

single covalent bond

Question 32

A _________prevents such rotation, producing a more rigid and _____________ of atoms.

Answer 32

double bond less flexible arrangement

Question 33

Covalent bonds in which the electrons are shared unequally in this way are known as________.

Answer 33

polar covalent bonds

Question 34

A_______ (in the electrical sense) is one in which the positive charge is concentrated toward one atom in the molecule (the positive pole) and the negative charge is concentrated toward another atom (the negative pole).

Answer 34

polar structure

Question 35

The tendency of an atom to attract electrons is called its_______, a property that was first described by the chemist_______.

Answer 35

electronegativity Linus Pauling

Question 36

________ is measured by the amount of energy that must be supplied to break the bond, usually expressed in units of either______ or_______.

Answer 36

Bond strength kilocalories per mole (kcal/mole) kilojoules per mole (kJ/mole)

Question 37

A _______ is the amount of energy needed to raise the temperature of ________. Thus, if 1 kilocalorie of energy must be supplied to break 6 × 1023 bonds of a specific type (that is, 1 mole of these bonds), then the strength of that bond is _______.

Answer 37

kilocalorie 1 liter of water by 1°C 1 kcal/mole

Question 38

________ is equal to about 4.2 kJ, which is the unit of energy universally employed by physical scientists and, increasingly, by cell biologists as well.

Answer 38

One kilocalorie

Question 39

covalent bonds are normally broken only during specific chemical reactions that are carefully controlled by highly specialized protein catalysts called_______.

Answer 39

enzymes

Question 40

The resulting bonds, called _____, are usually formed between atoms that can attain a completely filled outer shell most easily by _______ electrons to—or ______ electrons from—another atom, rather than by sharing them.

Answer 40

ionic bonds donating accepting

Question 41

Positive ions are called ______ and negative ions are called ______.

Answer 41

cations anions

Question 42

In aqueous solution, ionic bonds are ________ than the covalent bonds that hold atoms together in molecules.

Answer 42

10–100 times weaker

Question 43

the electrical attraction between them can establish a weak bond called a_______. These bonds are ______ than covalent bonds and are easily broken by random thermal motions.

Answer 43

hydrogen bond much weaker

Question 44

______ are not limited to water. In general, a hydrogen bond can form whenever a positively charged H atom held in one molecule by a polar covalent linkage comes close to a negatively charged atom— typically an oxygen or a nitrogen—belonging to another molecule

Answer 44

Hydrogen bonds

Question 45

substances that contain polar bonds and can form hydrogen bonds also mix well with water. Such substances are termed _________, meaning that they are ________. A large proportion of the molecules in the aqueous environment of a cell fall into this category, including sugars, DNA, RNA, and a majority of proteins.

Answer 45

hydrophilic “water-loving”

Question 46

________molecules, by contrast, are uncharged and form few or no hydrogen bonds, and they do not dissolve in water.

Answer 46

Hydrophobic (“water-fearing”)

Question 47

________ are individually quite weak, their energies can sum to create an effective force between two molecules.

Answer 47

noncovalent bonds

Question 48

What are the noncovalent bonds

Answer 48

hydrogen bonds Electrostatic attractions van der Waals attraction hydrophobic force

Question 49

_______ are strongest when the atoms involved are fully charged, as are Na+ and Cl– ions. But a ________ can occur between molecules that contain polar covalent bonds.

Answer 49

Electrostatic attractions weaker electrostatic attraction

Question 50

__________, comes into play when any two atoms approach each other closely. These nonspecific interactions spring from fluctuations in the distribution of electrons in every atom, which can generate a transient attraction when the atoms are in very close proximity. These weak attractions occur in all types of molecules, even those that are nonpolar and cannot form ionic or hydrogen bonds.

Answer 50

van der Waals attraction

Question 51

a _______ is generated by a pushing of nonpolar surfaces out of the hydrogen-bonded water network, where they would otherwise physically interfere with the highly favorable interactions between water molecules.

Answer 51

hydrophobic force

Question 52

Hydrophobic forces play an important part in promoting molecular interactions—in particular, in building _______, which are constructed largely from _____ with long hydrocarbon tails.

Answer 52

cell membranes lipid molecules

Question 53

Substances that release protons when they dissolve in water, thus forming H3O+, are termed ______. Molecules that accept protons when dissolved in water are called ______.

Answer 53

acids bases

Question 54

The interior of a cell is kept close to neutral by the presence of _______: mixtures of weak acids and bases that will adjust proton concentrations around pH 7 by releasing protons (acids) or taking them up (bases) when ever the pH changes.

Answer 54

buffers

Question 55

______ is outstanding among all the elements in its ability to form large molecules.

Answer 55

Carbon

Question 56

carbon-containing compounds are called _______. By contrast, all other molecules, including water, are said to be ______.

Answer 56

organic molecules inorganic

Question 57

The small organic molecules of the cell are carbon compounds with molecular weights in the range _______ or so carbon atoms.

Answer 57

100–1000 that contain up to 30

Question 58

Some are used as ________ to construct the cell’s polymeric ________—its proteins, nucleic acids, and large polysaccharides.

Answer 58

monomer subunits macromolecules

Question 59

What are the four main families of small organic molecules in cells.

Answer 59

Sugars, fatty acids, amino acids, and nucleotides

Question 60

Sets of molecules with the same chemical formula but different structures are called _____, and mirror-image pairs of such molecules are called______.

Answer 60

isomers optical isomers

Question 61

_______ can be linked by covalent bonds—called ________—to form larger ________.

Answer 61

Monosaccharides glycosidic bonds carbohydrates

Question 62

________ linked together make a ______, such as sucrose, which is composed of a _____ and a _____ unit.

Answer 62

Two monosaccharides disaccharide glucose fructose

Question 63

Larger sugar polymers range from the _______ (trisaccharides, tetrasaccharides, and so on) up to giant _______, which can contain thousands of _________ (monomers).

Answer 63

oligosaccharides polysaccharides monosaccharide subunits

Question 64

A bond is formed between an –OH group on one sugar and an –OH group on another by a ________, in which a molecule of water is expelled as the bond is formed.

Answer 64

condensation reaction

Question 65

The bonds created by all of these condensation reactions can be broken by the reverse process of______, in which a molecule of water is consumed.

Answer 65

hydrolysis

Question 66

________, which synthesize larger molecules from smaller subunits, are energetically unfavorable;__________, which break down larger molecules into smaller subunits, are energetically favorable.

Answer 66

condensation reactions hydrolysis reactions

Question 67

The ________ has a central role as an energy source for cells. It is broken down to smaller molecules in a series of reactions, releasing energy that the cell can harness to do useful work.

Answer 67

monosaccharide glucose

Question 68

Cells use simple polysaccharides composed only of glucose units—principally ______ in animals and _____ in plants—as long-term stores of glucose, held in reserve for energy production.

Answer 68

glycogen starch

Question 69

The most abundant organic molecule on Earth—the _____ that forms plant cell walls—is a polysaccharide of glucose.

Answer 69

cellulose

Question 70

Another extraordinarily abundant organic substance, the ____ of insect exoskeletons and fungal cell walls, is also a polysaccharide.

Answer 70

chitin

Question 71

Smaller oligosaccharides can be covalently linked to proteins to form ______, or to lipids to form _____, which are both found in cell membranes.

Answer 71

glycoproteins glycolipids

Question 72

A ______ molecule, such as _____, has two chemically distinct regions. One is a long ________, which is hydrophobic and not very reactive chemically. The other is a _________, which behaves as an acid (carboxylic acid):

Answer 72

fatty acid palmitic acid Hydrocarbon chain Carboxyl group

Question 73

Molecules—such as fatty acids—that possess both hydrophobic and hydrophilic regions are termed _______.

Answer 73

amphipathic

Question 74

The hydrocarbon tail of palmitic acid is _______: it has _______ between its carbon atoms and contains the maximum possible number of hydrogens.

Answer 74

saturated no double bonds

Question 75

Some other fatty acids, such as oleic acid, have _________, with one or more double bonds along their length.

Answer 75

unsaturated tails

Question 76

Fatty acids have both ________ and _______ components.

Answer 76

hydrophobic and hydrophilic

Question 77

Fatty acids are stored in the _____ of many cells in the form of fat droplets composed of _______ compounds made of three fatty acid chains covalently joined to a ______.

Answer 77

cytoplasm triacylglycerol molecules glycerol molecule

Question 78

________ are the animal fats found in meat, butter, and cream, and the plant oils such as corn oil and olive oil.

Answer 78

Triacylglycerols

Question 79

______ are loosely defined as molecules that are insoluble in water but soluble in fat and organic solvents such as _______. They typically contain ________, as in the fatty acids, or multiple linked aromatic rings, as in the ______.

Answer 79

Lipids benzene long hydrocarbon chains steroids

Question 80

The most unique function of fatty acids is in the establishment of the _____, the structure that forms the basis for all cell membranes.

Answer 80

lipid bilayer

Question 81

_____ are small organic molecules with one defining property: they all possess a carboxylic acid group and an amino group, both attached to a ________ atom.

Answer 81

Amino acids central α-carbon

Question 82

Cells use amino acids to build _______—polymers made of amino acids, which are joined head-to-tail in a long chain that folds up into a three-dimensional structure that is unique to each type of protein.

Answer 82

proteins

Question 83

The covalent bond between two adjacent amino acids in a protein chain is called a ______, and the resulting chain of amino acids is therefore also known as a ________.

Answer 83

peptide bond polypeptide

Question 84

Sugars Are both Energy Sources and Subunits of _______

Answer 84

Polysaccharides

Question 85

Fatty Acid Chains Are Components of _________.

Answer 85

Cell Membranes

Question 86

Amino Acids Are the Subunits of ________.

Answer 86

Proteins

Question 87

Nucleotides Are the Subunits of ___ and ___.

Answer 87

DNA and RNA

Question 88

DNA and RNA are built from subunits called ________.

Answer 88

nucleotides

Question 89

Nucleotides consist of a ________-containing ring compound linked to a ________ that has one or more ________ groups attached to it.

Answer 89

Nitrogen five-carbon sugar phosphate

Question 90

The sugar can be either ribose or deoxyribose. Nucleotides containing ribose are known as ________, and those containing deoxyribose are known as _________.

Answer 90

ribonucleotides deoxyribonucleotides

Question 91

There is a strong family resemblance between the different nucleotide bases. Cytosine (C), thymine (T), and uracil (U) are called _______, because they all derive from a six-membered pyrimidine ring; guanine (G) and adenine (A) are _______, which bear a second, A five-membered ring fused to the six-membered ring.

Answer 91

pyrimidines purines

Question 92

A base plus its sugar (without any phosphate group attached) is called a ________.

Answer 92

nucleoside

Question 93

the _________ known as ____________, or ____, participates in the ______ in hundreds of metabolic reactions.

Answer 93

ribonucleoside triphosphate adenosine triphosphate ATP transfer of energy

Question 94

_____ is formed through reactions that are driven by the energy released from the break down of foodstuffs. Its three phosphates are linked in series by two ______________.

Answer 94

ATP phosphoanhydride bonds

Question 95

Rupture of these phosphate bonds by hydrolysis releases large amounts of useful energy, also known as _________.

Answer 95

free energy

Question 96

Nucleotides also have a fundamental role in the storage and retrieval of biological information. They serve as ________ for the construction of ________—long polymers in which nucleotide subunits are linked by the formation of covalent __________ between the phosphate group attached to the sugar of one nucleotide and a hydroxyl group on the sugar of the next nucleotide.

Answer 96

building blocks nucleic acids phosphodiester bonds

Question 97

Polysaccharides, proteins, and nucleic acids are made from _________.

Answer 97

monomeric subunits