Term | Definition |
matter | anything that occupies space and has mass |
mass | a measure of the amount of matter in an object; a fundamental property of an object that is not affected by the forces that oct on the object, such as the gravitational force |
element | a substance that cannot be separated or broken down into simpler substances by chemical means; all atoms of an element have the same atomic number |
atom | the smallest unit of an element that maintains the chemical properties of that element |
nucleus | an atom's central region, which is made up of protons and neutrons |
atomic number | number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element |
mass number | sum of the number of protons and neutrons in the nucleus of an atom |
electron | a subatomic particle that has a negative charge |
orbital | a region in an atom where there is a high probability of finding electrons |
isotope | an atom that has the same number of protons (or the same atomic number) as other atoms of the same element do but that has a different number of neutrons (and thus a different atomic mass) |
compound | a substance made up of atoms of two or more different elements joined by chemical bonds |
chemical bond | the attractive force that holds atoms or ions together |
covalent bond | a bond formed when atoms share one or more pairs of electrons |
molecule | a group of atoms that are held together by chemical forces; a molecule is the smallest unit of matter that can exist by itself and retain all of a substance's chemical properties |
ion | an atom, radical, or molecule that has gained or lost one or more electrons and has a negative or positive charge |
ionic bond | the attractive force between oppositely charged ions, which form when electrons are transferred from one atom to another |
energy | capacity to do work |
chemical reaction | the process by which one or more substances change to produce one or more different substances |
reactant | a substance that participates in a chemical reaction |
product | a substance that forms in a chemical reaction |
metabolism | the sum of all chemical processes that occur in an organism |
activation energy | the minimum amount of energy required to start a chemical reaction |
catalysis | the acceleration of a chemical reaction by a catalyst |
enzyme | a molecule, either protein or RNA, that acts as a catalyst in biochemical reactions |
redox reaction | a reaction in which electrons are transferred between atoms; also known as an oxidation-reduction reaction |
oxidation reaction | a chemical reaction in which a reactant loses one or more electrons such that the reactant becomes more positive in charge |
reduction reaction | a chemical change in which electrons are gained, either by the removal of oxygen, the addition of hydrogen, or the addition of electrons |
polar | describes a molecule in which the positive and negative charges are separated |
hydrogen bond | the intermolecular force occurring when a hydrogen atom that is bonded to a highly electronegative atom of one molecule is attracted to two unshared electrons of another molecule |
coheshion | the force that holds molecules of a single material together |
adhesion | the attractive force between two bodies of different substances that are in contact with each other |
capillarity | the attraction between molecules that results in the rise of a liquid in small tubes |
solution | a homogeneous mixture throughout which two or more substances are uniformly dispersed |
solute | in a solution, the substance that dissolves in the solvent |
solvent | in a solution, the substance in which the solute dissolves |
concentration | the amount of a particular substance in a given quantity of a mixture, solution, or ore |
saturated solution | a solution that cannot dissolve any more solute under the given conditions |
aqueous solution | a solution in which water is the solvent |
hydroxide ion | the the OH- ion |
hydronium ion | an ion consisting of a proton combined with a molecule of water; H3O+ |
acid | any compound that increases the number of hydronium ions when dissolved in water; acids turn blue litmus paper red and react with bases and some metals to form salts |
base | any compound that increases the number of hydroxide ions when dissolved in water; bases turn red litmus paper blue and react with acids to form salts |
ph scale | a range of values that are used to express the acidity or alkalinity (basicity) of a system; each whole number on the scale indicates a tenfold change in acidity; a pH of 7 is neutral, a pH of less than 7 is acidic, and a pH of greater than 7 is basic |
buffer | a solution made from a weak acid and its conjugate base that neutralizes small amounts of acids or bases added to it |
organic compound | a covalently bonded compound that contains carbon, excluding carbonates and oxides |
functional group | the portion of a molecule that is active in a chemical reaction and that determines the properties of many organic compounds |
monomer | a simple molecule that can combine with other like or unlike molecules to make a polymer |
polymer | a large molecule that is formed by more than five monomers, or small units |
macromolecule | a very large organic molecule, usually a polymer, composed of hundreds or thousands of atoms |
condensation reaction | a chemical reaction in which two or more molecules combine to produce water or another simple molecule |
hydrolysis | a chemical reaction between water and another substance to form two or more new substances; a reaction between water and a salt to create an acid or a base |
ATP | adenosine triphosphate, an organic molecule that acts as the main energy source for cell processes; composed of a nitrogenous base, a sugar, and three phosphate groups |
carbohydrate | a class of molecules that includes sugars, starches, and fiber; contains carbon, hydrogen, and oxygen |
monosaccharide | a simple sugar that is the basic subunit of a carbohydrate |
disaccharide | a sugar formed from two monosaccharides |
polysaccharide | one of the carbohydrates made up of long chains of simple sugars; polysaccharides include starch, cellulose, and glycogen |
protein | an organic compound that is made of one or more chains of amino acids and that is a principal component of all cells |
amino acid | a compound of a class of simple organic compounds that contain a carboxyl group and an amino group and that combine to form proteins |
peptide bond | the chemical bond that forms between the carboxyl group of one amino acid and the amino group of another amino acid |
polypeptide | a long chain of several amino acids |
enzyme | a molecule, either protein or RNA, that acts as a catalyst in biochemical reactions |
substrate | a part, substance, or element that lies beneath and supports another part, substance, or element; the reactant in reactions catalyzed by enzymes |
active site | on an enzyme, the site that attaches to a substrate |
lipid | a fat molecule or a molecule that has similar properties; examples include oils, waxes, and steroids |
fatty acid | an organic acid that is contained in lipids, such as fats or oils |
triglyceride | a lipid made of three fatty acid molecules and one glycerol molecule |
phospholipid | a lipid that contains phosphorus and that is a structural component in cell membranes |
wax | a type of structural lipid consisting of a long fatty-acid chain that is joined to a long alcohol chain |
steroid | a type of lipid that consists of four carbon rings to which various functional groups are attached and that usually has a physiological action |
nucleic acid | an organic compound, either RNA or DNA, whose molecules are made up of one or two chains of nucleotides and carry genetic information |
DNA | deoxyribonucleic acid, the material that contains the information that determines inherited characteristics |
RNA | ribonucleic acid, a natural polymer that is present in all living cells and that plays a role in protein synthesis |
nucleotide | in a nucleic-acid chain, a subunit that consists of a sugar, a phosphate, and a nitrogenous base |