Chapter 2: "The Chemical Bases Of Life" Flashcards
Inorganic compounds:
Small, simple substances.
The chemistry and physics of the molecules that constitute living things is called:
Molecular biology.
Organic compounds:
carbon-containing compounds that are generally large and complex.
Electron:
Is a particle that carries a unit of negative electric charge.
Proton:
Carries a unit of positive charge.
Neutron:
Is an uncharged particle. In an electrically neutral atom, the number of electrons is equal to the number of protons.
Clustered together, protons and neutrons compose the:
Atomic nucleus.
Every element has a fi xed number of protons in the atomic nucleus, known as the_________.
Atomic number.
Oxygen:
Required for cellular respiration; present in most organic compounds; component of water.
Carbon:
Forms backbone of organic molecules; each car-bon atom can form four bonds with other atoms.
Hydrogen:
Present in most organic compounds; component of water; hydrogen ion (H+) is involved in some energy transfers
Nitrogen:
Component of proteins and nucleic acids; component of chlorophyll in plants.
Calcium:
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.
Phosphorus:
Component of nucleic acids and of phospholipids in membranes; important in energy transfer reac-tions; structural component of bone.
Potassium:
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.
Sulfur:
Component of most proteins.
Sodium:
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.
Magnesium:
Needed in blood and other tissues of animals; ac-tivates many enzymes; component of chlorophyll in plants.
Chlorine:
Chloride ion (Cl−) is principal negative ion (anion) in interstitial (tissue) fl uid of animals; important in water balance; essential for photosynthesis.
Iron:
Component of hemoglobin in animals; activates certain enzymes.
The periodic table:
Is a chart of the elements arranged in order by atomic number.
atomic mass unit (amu):
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.
Most elements consist of a mixture of atoms with different numbers of neutrons and thus different masses. Such atoms are called:
Isotopes.
Isotopes of the same element have the same number of ____and____; only the number of ______ varies.
protons and electrons. neutrons.
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.
Radioisotopes.
Radioactive decay can be detected by a method known as:
Autoradiography.
Electrons move through characteristic regions of 3-D space, called_____. Each_____ contains a maximum of ___ electrons.
orbitals.orbital, 2.
it is impossible to know an electron’s position at any given time, orbitals are most accurately depicted as:
Electron clouds.
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:
Electron Shell.
Th e most energetic electrons, known as valence electrons, are said to occupy the:
Valence shell.
The________ is represented as the outermost concentric ring in a Bohr model.
Valence Shell.
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.
Electron.
The chemical behavior of an atom is determined primarily by the number and arrangement of its:
Valence electrons.
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:
8 electrons.
Elements in the same vertical column (belonging to the same group) of the periodic table have similar chemical properties because:
Their valence shells have similar tendencies to lose, gain, or share electrons.
A chemical compound:
Consists of atoms of two or more different elements combined in a fixed ratio.
Two or more atoms may become joined very strongly to form a stable particle called a:
Molecule.
A _____ is a shorthand expression that describes the chemical composition of a substance.
Chemical formula.
In the simplest formula (also known as an empirical formula):
The subscripts give the smallest whole-number ratios for the atoms present in a compound.
An example of the simplest formula for hydrazine is:
NH2, indicating a 1:2 ratio of nitrogen to hydrogen.
A molecular formula is:
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.
The structural formula:
Shows not only the types and numbers of atoms in a molecule but also their arrangement.
An example of the structural formula for water is .
H-O-H
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:
(hydrogen: 2 × 1 amu) + (oxygen: 1 × 16 amu), or 18 amu.
The amount of an element or compound whose mass in grams is equivalent to its atomic or molecular mass is:
1 mole (mol).
1 mol of any substance always has exactly the same number of units, whether those units are:
Small atoms or large molecules.
The very large number of units in a mole, 6.02 × 10^23, is known as:
Avogadro’s number.
Atoms can be held together by forces of att raction called:
Chemical bonds.
Bond energy:
Is the energy necessary to break a chemical bond.
Covalent bonds:
Involve the sharing of electrons between atoms in a way that results in each atom having a fi lled valence shell.
Atoms can also be linked by covalent bonds to form molecules; the resulting compound is a:
Covalent compound.
When one pair of electrons is shared between two atoms, the covalent bond is called a:
Single covalent bond.
When two pairs of electrons are shared in this way, the covalent bond is called a:
Double covalent bond.
A triple covalent bond is formed when:
Three pairs of electrons are shared between two atoms.
When an atom forms covalent bonds with other atoms, the orbitals in the valence shell may become rearranged in a process known as:
Orbital hybridization.
Electronegativity:
Is a measure of an atom’s att raction for shared electrons in chemical bonds.
When covalently bonded atoms have similar electronegativities, the electrons are shared equally and the co-valent bond is described as:
Nonpolar.
A covalent bond between atoms that differ in electronegativity is called a:
Polar covalent bond.
A polar molecule:
Has one end with a partial positive charge and another end with a partial negative charge.
positively charged ions are termed:
Cations.
valence electrons tend to gain electrons from other atoms and become negatively charged:
Anions.
Cations and anions are involved in energy transformations within the cell such as:
The transmission of nerve impulses, muscle contraction, and many other biological processes.
An_______ forms as a consequence of the att-raction between the positive charge of a cation and the negative charge of an anion
Ionic bond.
Ionic compound:
Is a substance consisting of anions and cations bonded by their opposite charges.
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.
H2O ( Water)
Hydration:
In solution, each cation and anion of the ionic compound is surrounded by oppositely charged ends of the water molecules.
Van der Waals interactions:
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.
oxidation–reduction, or:
Redox reaction.
Oxidation:
Is a chemical process in which an atom, ion, or molecule loses one or more electrons.
Reduction:
is a chemical process in which an atom, ion, or molecule gains one or more electrons.
Cohesion:
Water molecules have a strong tendency to stick to one another.This is due to the hydrogen bonds among the molecules.
Capillary action:
which is the tendency of water to move in narrow tubes, even against the force of gravity.
Substances that interact readily with water are_______. Examples include table sugar (sucrose, a polar compound) and table salt
Hydrophilic (“water-loving”).
Many_______substances found in living things are especially important because of their ability to form associations or structures that are not disrupted.
Hydrophobic (“water-fearing”).
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):
pH.
Acid:
Is a substance that dissociates in solution to yield hydrogen ions (H+) and anions.
Base:
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.
Buffer:
Is a substance or combination of substances that resists changes in pH when an acid or base is added.
