acid
any substance that forms hydrogen ions (H+) in water and has a pH below 7.
atom
(physics and chemistry) the smallest component of an element having the chemical properties of the element
base
any substance that forms hydroxide ions (OH-) in water and has a pH above 7
compound
(chemistry) a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight
covalent bond
a chemical bond that involves sharing a pair of electrons between atoms in a molecule
element
any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter
ion
atom that has a positive or negative charge
ionic bond
a chemical bond in which there is a transfer of electrons; one atom loses an electron to form a positive ion and the other atom gains to electron to form a negative ion
isotope
one of two or more atoms with the same atomic number but with different numbers of neutrons
metabolism
set of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes
mixture
combination of substances in which individual components retain their own properties
molecule
two or more atoms held together by covalent bonds
nucleus
positively charged center of an atom composed of neutrons and positively charged protons, and surrounded by negatively charged electrons
pH
a value that indicated the acidity or alkalinity of a solution on a scale of 0-14, based on the proportion of H+ ions.
solution
a homogeneous mixture of two or more substances
diffusion
process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated
dynamic equilibrium
result of diffusion where there is continuous movement of particles but no overall change in concentration
hydrogen bond
weak chemical bond formed by the attraction of positively charged hydrogen atoms to other negatively charged atoms
polar molecule
molecule with an unequal distribution of charge, resulting in the molecule having a positive end and a negative end
amino acid
basic building blocks of protein molecules
carbohydrate
organic compound used by cells to store and release energy; composed of carbon, hydrogen, and oxygen
enzyme
any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactions
lipid
large organic compounds made mostly of carbon and hydrogen with a small amount of oxygen; examples are fats, oils, waxes, and steroids; are insoluble in water and used by cells for energy storage, insulation, and protective coatings, such as in membranes
nucleic acid
a macromolecule, either RNA or DNA, whose molecules are made up of one or two chains of nucleotides and carry genetic information
nucleotide
basic building block of nucleic acid formed from a simple sugar, a phosphate group, and a nitrogenous base.
peptide bond
the primary linkage of all protein structures
polymer
large molecule formed when many smaller molecules bond together
protein
macromolecule that contains carbon, hydrogen, oxygen, and nitrogen; needed by the body for growth and repair and to make up enzymes