atom
basic unit of matter
nucleus
the center of the atom which contains the protons and neutrons; in cells, structure that contains the cell's genetic material (DNA) and controls the cell's activities
electron
negatively charged particle; located outside the atomic nucleus
element
substance consisting entirely of one type of atom
isotope
atom of an element that has a number of neutrons different from that of other atoms of the same element
compound
substance formed by the chemical combination of two or more elements in definite proportions
ionic bond
bond formed when one or more electrons are transferred from one atom to another
ions
atom that has a positive or negative charge
covalent bond
bond formed by the sharing of electrons between atoms
molecule
smallest unit of most compounds
van der Waals forces
a slight attraction that develops between the oppositely charged regions of nearby molecules
cohesion
attraction between molecules of the same substance
adhesion
attraction between molecules of different substances; in plants, attraction between unlike molecules
mixture
material composed of two or more elements or compounds that are physically mixed together but not chemically combined
solution
mixture of two or more substances in which the molecules of the substances are evenly distributed
solute
substance that is dissolved in a solvent to make a solution
solvent
substance in which a solute is dissolved to form a solution
suspension
mixture of water and nondissolved materials
pH scale
measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14
acid
compound that forms hydrogen ions (H+) in solution
base
compound that produces hydroxide ions (OH+) in solution
buffer
weak acid or base that can react with strong acids or bases to help prevent sharp, sudden changes in pH
monomer
small unit that can join together with other small units to form polymers
polymer
large compound formed from combinations of many monomers
carbohydrate
compound made up of carbon, hydrogen, and oxygen atoms; major source of energy for the human body
monosaccharide
single sugar molecule
polysaccharide
large macromolecule formed from monosaccharides
lipid
macromolecule made mainly from carbon and hydrogen atoms; includes fats, oils, and waxes
nucleic acid
macromolecule containing hydrogen, oxygen, nitrogen, carbon, and phosphorus
nucleotide
monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base
ribonucleic acid (RNA)
single-stranded nucleic acid that contains the sugar ribose
deoxyribonucleic acid (DNA)
nucleic acid that contains the sugar deoxyribose
protein
macromolecule that contains carbon, hydrogen, oxygen, and nitrogen; needed by the body for growth and repair and to make up enzymes
amino acid
compound with an amino group (?NH2) on one end and a carboxyl group (?COOH) on the other end
chemical reaction
process that changes one set of chemicals into another set of chemicals
reactant
element or compound that enters into a chemical reaction
product
element or compound produced by a chemical reaction
activation energy
energy needed to get a reaction started
catalyst
substance that speeds up the rate of a chemical reaction
enzyme
protein that acts as a biological catalyst
substrate
reactant of an enzyme-catalyzed reaction