atom
basic unit of matter
proton
positively charged subatomic particle
electron
negatively charged subatomic particle; gives an element its chemical properties
neutron
subatomic particle that has the same mass as a proton but no electric charge
nucleus
the positively charged center of an atom
orbital
a region of space around the nucleus of an atom where an electron is likely to be found
ion
atom that has a positive or negative charge
atomic mass
mass of an atom expressed in atomic mass units
atomic number
number of protons in the nucleus of an atom
isotope
atoms of the same element that have different numbers of neutrons
radioisotope
isotope that has an unstable nucleus and undergoes radioactive decay
compound
substance formed by chemical union of two or more elements in definite proportions
molecule
smallest unit of most compounds
ionic bond
bond formed when one or more electrons are transferred from one atom to another
covalent bond
a bond formed when atoms share one or more pairs of electrons
reactant
element or compound that enters into a chemical reaction
substrate
reactant of an enzyme-catalyzed reaction
product
a chemical substance formed as a result of a chemical reaction
potential energy
stored energy
kinetic energy
energy of motion
activation energy
minimum amount of energy required to start a chemical reaction
decomposition reaction
reaction in which one compound breaks into at least two products
catabolism
breakdown of more complex substances into simpler ones
synthesis reaction
reaction in which two or more substances combine to form a single compound
anabolism
synthesizing a complex molecule from simpler compounds
exchange reaction
reaction in which molecules are exchanged to create new products; AB + CD ---> AD + CB
reversible reaction
chemical reaction in which the prodcuts re-form the original reactants
equilibrium reaction
reaction that is reversible and the rates of the forward and reverse reactions are equal
nutrient
chemical needed for the maintenance, growth, and development of the body
metabolite
any chemical produced by metabolism
mixture
two or more substances that are physically mixed together but not chemically combined
solution
homogeneous mixture of two or more substances
solute
the dissolved substance in a solution
solvent
the substance in which a solute is dissolved to form a solution
suspension
mixture of water and nondissolved materials whcih can be separated with filtration or settling
electrolyte
a substance when dissolved in water conducts electric current
salt
compound that conducts electricity when dissolved in water; created from the reaction of an acid and a base
inorganic compound
any compound that does not contain carbon-carbon bonds
organic compound
compound that contains carbon bonded to hydrogen and is found in living things
acid
compound that forms hydrogen ions (H+) in solution
base
compound that produces hydroxide ions (OH+) in solution
neutralization
a chemical reaction in which an acid and a base interact to form a salt
hydrogen ion
positively charged atom of hydrogen (H+)
hydroxide ion
negatively charged ion made of oxygen and hydrogen (OH-)
pH scale
measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14
enzyme
specialized proteins that speed up chemical reactions
catalyst
substance that initiates or accelerates a chemical reaction without itself being affected
RNA
single-stranded nucleic acid involved in protein synthesis
DNA
double-stranded molecule that contains the genetic code
glycogen
polysaccharide that stores glucose in animals
glucose
sugar that is the major source of energy for the body's cells
monosaccharide
single sugar molecule
polysaccharide
large carbohydrate made of chains of monosaccharide molecules
glycerol
with fatty acids, make up the building blocks of lipids
fatty acid
with glycerol, make up the building blocks of lipids
nucleotide
building block of a nucleic acid
amino acid
basic building blocks of protein molecules
ATP
provides the energy for all cellular work; product of cellular respiration
active site
the site on an enzyme that attaches to a substrate
denaturation
a structural change in a protein that results in a loss of its biological properties
macromolecule
very large complex molecule
polymer
large molecule formed when many smaller molecules bond together
monomer
small molecular unit that is the building block of a larger molecule
nucleic acid
macromolecule made up of subunits called nucleotides
lipid
organic compound made mainly from carbon and hydrogen atoms; includes fats, oils, and waxes
protein
organic compound that is made of one or more chains of amino acids and that is a principal component of all cells
carbohydrate
organic compound used by cells to store and release energy
buffer
an ionic compound that resists changes in its pH