Chapter 4 Vocabulary
Chemical basis of Life
Biology
Chemistry: the study of matter.
Matter: anything that occupies space and has mass – the physical “stuff” of the universe.
Element: makes up all matter. A pure substance that cannot be broken down into other substances by
chemical means.
Trace elements: elements that make up less than 0.01% of your body mass but still essential to your health. (I,
Fe, Cu, F, Mn, Se)
Essential element: elements essential for life. N, O, H, and C make up about 96% of living matter in your body.
Ca, P, K, and S make up the other 4%.
Atom: smallest possible particle of an element. Each element is made up of a single kind of atom. Each atom is
made up of subatomic particles.
Subatomic particles: particles that make up an atom consisting of protons(nucleus and + charge), neutron
(nucleus and neutral charge) and electrons (electron cloud and – charge).
Nucleus: center of the atom that holds the protons and neutrons.
Electron cloud: orbitals surrounding the nucleus of an atom that hold the electrons.
Electron orbital or shell/energy levels: area within the electron cloud that holds the electrons.
Compound: a substance containing 2 or more elements that are chemically combined in a fixed ratio.
Atomic number: the number of protons an individual element has. Identifies the element. No 2 elements have
the same atomic number.
Isotope: elements that have the same number of protons but different number of neutrons. (ex: C-12, C-13,
C-14).
Radioactive isotope: isotope in which the nucleus decays (breaks down ) over time, giving off radiation in the
form of matter and energy. Used in research and medicine.
Periodic table: A table in which the chemical elements are arranged in order of increasing atomic number.
Elements with similar properties are arranged in the same column (called a group), and elements with the
same number of electron shells are arranged in the same row (called a period).
Chemical bond: a mutual attraction between two atoms resulting from a redistribution of their outer
electrons.
Valence electrons: the electrons found in the outer energy level.
Ionic bond: a chemical bond that occurs when an atom transfers an electron to another atom. Atoms either
gain or lose electrons in the formation of a compound.
Ion: any charged atomic formed by gaining or losing electrons.
Covalent bond: a chemical bond that forms when 2 atoms share electrons.
Molecule: 2 or more atoms held together by a covalent bond.
Polar molecule: a molecule in which opposite ends have opposite electric charges. (Ex: water)
Hydrogen bond: chemical bond formed by a weak attraction between a hydrogen atom of one molecule and a
slightly negative atom within another molecule.
Chemical formula: tells you the number and types of atoms in a molecule.
Structural formula: indicates how atoms in a molecule are linked by bonds. How the molecule is arranged.
Chemical reaction: a process in which one or more substances are changed into others. Remember
matter is neither created nor destroyed; only rearranged. May be endothermic/endergonic (requires
energy) or exothermic/exergonic (gives off energy).
Reactants: the starting materials for a chemical reaction.
Products: the ending materials of a chemical reaction.
Thermal energy: total amount of energy associated with the random movement of atoms and molecules in a
sample of matter.
Temperature: measure of the average energy of random motion of the particles in a substance.
Metabolism: All of the chemical reactions that occur in an organism.
Density: amount of matter in a given volume. High density substances have more tightly packed atoms than
low density substances. D=m/v (broken heart)
Mixture: a substance consisting of two or more substances mixed together without any chemical bonding
between them.
Solution: a uniform mixture of 2 or more substances.
Solvent: the substance that dissolves the other substance and is present in the greater amount.
Solute: the substance that is dissolved and is present in a lesser amount.
Aqueous solution: a solution where the solvent is water. Water is the main solvent inside cells, blood, plant
sap, and many solutions necessary for life.
Acid: when a chemical compound contributes additional H+ (hydronium) ions in an aqueous solution.
Base: when a chemical compound removes H+ ions in an aqueous solution. Usually have an excess of OH(hydroxide) ions.
pH scale: describes how acidic or basic (alkaline) a solution is. Ranges from 0 (most acidic) to 14 (most basic or
alkaline). Each pH unit represents a tenfold change in the concentration of H + ions. Solutions that have equal
concentrations of H+ and OH- ions are said to be neutral which is a pH of 7.To neutralize an acid you need to
add a base.
Buffer: substances that cause a solution to resist changes in pH. Biological molecules are very sensitive to pH
changes therefore many biological fluids contain buffers. A buffer works by accepting H+ ions when levels rise
and donating H+ when their levels fall. Helps maintain homeostasis.
Adhesion: a type of attraction that occurs between unlike molecules.
Cohesion: the tendency of molecules of the same kind to stick to one another.
Atomic mass unit (amu): unit of measure that describes the mass of subatomic particles.