Chapter 2: "The Chemical Bases Of Life"

Question 0

Inorganic compounds:

Answer 0

Small, simple substances.

Question 1

The chemistry and physics of the molecules that constitute living things is called:

Answer 1

Molecular biology.

Question 2

Organic compounds:

Answer 2

carbon-containing compounds that are generally large and complex.

Question 3

Electron:

Answer 3

Is a particle that carries a unit of negative electric charge.

Question 4

Proton:

Answer 4

Carries a unit of positive charge.

Question 5

Neutron:

Answer 5

Is an uncharged particle. In an electrically neutral atom, the number of electrons is equal to the number of protons.

Question 6

Clustered together, protons and neutrons compose the:

Answer 6

Atomic nucleus.

Question 7

Every element has a fi xed number of protons in the atomic nucleus, known as the_________.

Answer 7

Atomic number.

Question 8

Oxygen:

Answer 8

Required for cellular respiration; present in most organic compounds; component of water.

Question 9

Carbon:

Answer 9

Forms backbone of organic molecules; each car-bon atom can form four bonds with other atoms.

Question 10

Hydrogen:

Answer 10

Present in most organic compounds; component of water; hydrogen ion (H+) is involved in some energy transfers

Question 11

Nitrogen:

Answer 11

Component of proteins and nucleic acids; component of chlorophyll in plants.

Question 12

Calcium:

Answer 12

Structural component of bones and teeth; cal-cium ion (Ca2+) is important in muscle contrac-tion, conduction of nerve impulses, and blood clotting; associated with plant cell wall.

Question 13

Phosphorus:

Answer 13

Component of nucleic acids and of phospholipids in membranes; important in energy transfer reac-tions; structural component of bone.

Question 14

Potassium:

Answer 14

Potassium ion (K+) is a principal positive ion (cat-ion) in interstitial (tissue) fl uid of animals; impor-tant in nerve function; aff ects muscle contraction; controls opening of stomata in plants.

Question 15

Sulfur:

Answer 15

Component of most proteins.

Question 16

Sodium:

Answer 16

Sodium ion (Na+) is a principal positive ion (cat-ion) in interstitial (tissue) fl uid of animals; impor-tant in fl uid balance; essential for conduction of nerve impulses; important in photosynthesis in plants.

Question 17

Magnesium:

Answer 17

Needed in blood and other tissues of animals; ac-tivates many enzymes; component of chlorophyll in plants.

Question 18

Chlorine:

Answer 18

Chloride ion (Cl−) is principal negative ion (anion) in interstitial (tissue) fl uid of animals; important in water balance; essential for photosynthesis.

Question 19

Iron:

Answer 19

Component of hemoglobin in animals; activates certain enzymes.

Question 20

The periodic table:

Answer 20

Is a chart of the elements arranged in order by atomic number.

Question 21

atomic mass unit (amu):

Answer 21

One (amu) is equal to the approximate mass of a single proton or a single neutron. Protons and neutrons make up almost all the mass of an atom. Th e mass of a single electron is only about 1/1800 the mass of a proton or neutron.

Question 22

Most elements consist of a mixture of atoms with different numbers of neutrons and thus different masses. Such atoms are called:

Answer 22

Isotopes.

Question 23

Isotopes of the same element have the same number of ____and____; only the number of ______ varies.

Answer 23

protons and electrons. neutrons.

Question 24

some isotopes are unstable and tend to break down, or decay, to a more stable isotope (usually becoming a diff erent element); such_______ emit radiation when they decay.

Answer 24

Radioisotopes.

Question 25

Radioactive decay can be detected by a method known as:

Answer 25

Autoradiography.

Question 26

Electrons move through characteristic regions of 3-D space, called_____. Each_____ contains a maximum of ___ electrons.

Answer 26

orbitals.orbital, 2.

Question 27

it is impossible to know an electron's position at any given time, orbitals are most accurately depicted as:

Answer 27

Electron clouds.

Question 28

Th e energy of an electron depends on the orbital it occupies. Electrons in orbitals with similar energies, said to be at the same principal energy level make up an:

Answer 28

Electron Shell.

Question 29

Th e most energetic electrons, known as valence electrons, are said to occupy the:

Answer 29

Valence shell.

Question 30

The________ is represented as the outermost concentric ring in a Bohr model.

Answer 30

Valence Shell.

Question 31

An ____ can move to an orbital farther from the nucleus by receiving more energy, or it can give up energy and sink to a lower energy level in an orbital nearer the nucleus.

Answer 31

Electron.

Question 32

The chemical behavior of an atom is determined primarily by the number and arrangement of its:

Answer 32

Valence electrons.

Question 33

T he valence shell of hydrogen or helium is full (stable) when it contains 2 electrons. The valence shell of any other atom is full when it contains:

Answer 33

8 electrons.

Question 34

Elements in the same vertical column (belonging to the same group) of the periodic table have similar chemical properties because:

Answer 34

Their valence shells have similar tendencies to lose, gain, or share electrons.

Question 35

A chemical compound:

Answer 35

Consists of atoms of two or more different elements combined in a fixed ratio.

Question 36

Two or more atoms may become joined very strongly to form a stable particle called a:

Answer 36

Molecule.

Question 37

A _____ is a shorthand expression that describes the chemical composition of a substance.

Answer 37

Chemical formula.

Question 38

In the simplest formula (also known as an empirical formula):

Answer 38

The subscripts give the smallest whole-number ratios for the atoms present in a compound.

Question 39

An example of the simplest formula for hydrazine is:

Answer 39

NH2, indicating a 1:2 ratio of nitrogen to hydrogen.

Question 40

A molecular formula is:

Answer 40

The subscripts indicate the actual numbers of each type of atom per molecule. Th e molecular for-mula for hydrazine is N2H4, which indicates that each molecule of hydrazine consists of two atoms of nitrogen and four atoms of hydrogen.

Question 41

The structural formula:

Answer 41

Shows not only the types and numbers of atoms in a molecule but also their arrangement.

Question 42

An example of the structural formula for water is .

Answer 42

H-O-H

Question 43

The molecular mass of a compound is the sum of the atomic masses of the component atoms of a single molecule; thus, the molecular mass of water, H2O, is:

Answer 43

(hydrogen: 2 × 1 amu) + (oxygen: 1 × 16 amu), or 18 amu.

Question 44

The amount of an element or compound whose mass in grams is equivalent to its atomic or molecular mass is:

Answer 44

1 mole (mol).

Question 45

1 mol of any substance always has exactly the same number of units, whether those units are:

Answer 45

Small atoms or large molecules.

Question 46

The very large number of units in a mole, 6.02 × 10^23, is known as:

Answer 46

Avogadro's number.

Question 47

Atoms can be held together by forces of att raction called:

Answer 47

Chemical bonds.

Question 48

Bond energy:

Answer 48

Is the energy necessary to break a chemical bond.

Question 49

Covalent bonds:

Answer 49

Involve the sharing of electrons between atoms in a way that results in each atom having a fi lled valence shell.

Question 50

Atoms can also be linked by covalent bonds to form molecules; the resulting compound is a:

Answer 50

Covalent compound.

Question 51

When one pair of electrons is shared between two atoms, the covalent bond is called a:

Answer 51

Single covalent bond.

Question 52

When two pairs of electrons are shared in this way, the covalent bond is called a:

Answer 52

Double covalent bond.

Question 53

A triple covalent bond is formed when:

Answer 53

Three pairs of electrons are shared between two atoms.

Question 54

When an atom forms covalent bonds with other atoms, the orbitals in the valence shell may become rearranged in a process known as:

Answer 54

Orbital hybridization.

Question 55

Electronegativity:

Answer 55

Is a measure of an atom's att raction for shared electrons in chemical bonds.

Question 56

When covalently bonded atoms have similar electronegativities, the electrons are shared equally and the co-valent bond is described as:

Answer 56

Nonpolar.

Question 57

A covalent bond between atoms that differ in electronegativity is called a:

Answer 57

Polar covalent bond.

Question 58

A polar molecule:

Answer 58

Has one end with a partial positive charge and another end with a partial negative charge.

Question 59

positively charged ions are termed:

Answer 59

Cations.

Question 60

valence electrons tend to gain electrons from other atoms and become negatively charged:

Answer 60

Anions.

Question 61

Cations and anions are involved in energy transformations within the cell such as:

Answer 61

The transmission of nerve impulses, muscle contraction, and many other biological processes.

Question 62

An_______ forms as a consequence of the att-raction between the positive charge of a cation and the negative charge of an anion

Answer 62

Ionic bond.

Question 63

Ionic compound:

Answer 63

Is a substance consisting of anions and cations bonded by their opposite charges.

Question 64

As a liquid it is capable of dissolving many substances, particularly those that are polar or ionic, because of the polarity of water molecules. The localized partial positive charge (on the hy-drogen atoms) and partial negative charge (on the oxygen atom) on each water molecule attract and surround the anions and cations, respectively, on the surface of an ionic solid.

Answer 64

H2O ( Water)

Question 65

Hydration:

Answer 65

In solution, each cation and anion of the ionic compound is surrounded by oppositely charged ends of the water molecules.

Question 66

Van der Waals interactions:

Answer 66

A region with a temporary excess of electrons will have a weak negative charge, whereas one with an electron defi cit will have a weak positive charge. Adjacent molecules may interact in regions of slight opposite charge.

Question 67

oxidation–reduction, or:

Answer 67

Redox reaction.

Question 68

Oxidation:

Answer 68

Is a chemical process in which an atom, ion, or molecule loses one or more electrons.

Question 69

Reduction:

Answer 69

is a chemical process in which an atom, ion, or molecule gains one or more electrons.

Question 70

Cohesion:

Answer 70

Water molecules have a strong tendency to stick to one another.This is due to the hydrogen bonds among the molecules.

Question 71

Capillary action:

Answer 71

which is the tendency of water to move in narrow tubes, even against the force of gravity.

Question 72

Substances that interact readily with water are_______. Examples include table sugar (sucrose, a polar compound) and table salt

Answer 72

Hydrophilic (“water-loving”).

Question 73

Many_______substances found in living things are especially important because of their ability to form associations or structures that are not disrupted.

Answer 73

Hydrophobic (“water-fearing”).

Question 74

The degree of a solution's acidity is generally expressed in terms of______, defined as the negative logarithm (base 10) of the hydrogen ion concentration (expressed in moles per liter):

Answer 74

pH.

Question 75

Acid:

Answer 75

Is a substance that dissociates in solution to yield hydrogen ions (H+) and anions.

Question 76

Base:

Answer 76

Is defined as a proton acceptor. Most bases are sub-stances that dissociate to yield a hydroxide ion (OH−) and a cation when dissolved in water.

Question 77

Buffer:

Answer 77

Is a substance or combination of substances that resists changes in pH when an acid or base is added.