(See related pages)
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| absolute (Kelvin) temperature scale | Zero on the Kelvin scale is absolute zero or -273.15°C, the lowest possible temperature (See page(s) 181) |
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| acid | a substance that releases hydrogen ions, H+, usually in aqueous solution (See page(s) 246) |
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| acid anhydride | a compound, typically an oxide of a nonmetallic element, that reacts with water to generate an acid (See page(s) 253) |
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| acid deposition | the process by which acid is deposited through precipitation, fog, or air-borne particles (See page(s) 251) |
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| acid neutralizing capacity (ANC) | the capacity of a lake to resist change in pH when acids are added to it (See page(s) 267) |
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| acid precipitation | (see acid deposition ) |
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| acid rain | (see acid deposition ) |
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| acidic solution | an aqueous solution in which the H+ ion concentration is greater than the OH- concentration; a solution with a pH less than 7.0 (See page(s) 248) |
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| activation energy | the energy necessary to initiate a chemical reaction (See page(s) 163) |
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| active (receptor) site | the region of an enzyme molecule where the catalytic activity occurs (See page(s) 406, 491) |
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| addition polymerization | a process in which monomeric molecules combine to form a polymer without the elimination of any atoms (See page(s) 367) |
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| aerosol | a form of liquid in which the droplets are so small that they stay suspended in the air rather than settling (See page(s) 31) |
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| alkali | a term applied to some bases (See page(s) 247) |
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| allotropes | two forms of the same element that differ in their molecular or crystal structure and hence in their properties (See page(s) 49) |
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| alpha particle | a particle given off during radioactive decay consisting of 2 protons and 2 neutrons; it has a mass of 4 amu and a charge of +2 (See page(s) 300) |
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| amine | a basic organic compound with the generic formula RNH2 (See page(s) 375) |
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| aminFo acid | a compound containing a carboxylic acid group (—COOH), a basic amino group (—NH2), and a characteristic R group; amino acids polymerize to form proteins (See page(s) 375, 489) |
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| amino acid residues | amino acids that have been incorporated into a peptide chain (See page(s) 454) |
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| amniocentesis | the procedure in which a sample of the amniotic fluid is withdrawn from the mother's uterus and tested (See page(s) 498) |
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| ampere | a unit of electrical current (See page(s) 331) |
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| anabolic steroid | a compound that promotes muscle growth but can have serious negative side effects (See page(s) 417) |
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| androgens | male sex hormones (See page(s) 413) |
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| anion | a negatively charged ion (See page(s) 213) |
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| anode | the electrode at which oxidation occurs (See page(s) 329) |
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| antagonist | a molecule that occupies the active site of an enzyme but exhibits no activity (See page(s) 416) |
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| antibody | a protective biological agent generated by the body in response to infection (See page(s) 496) |
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| aqueous solutions | solutions in which water is the solvent (See page(s) 202) |
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| aquifer | a large natural underground reservoir (See page(s) 201) |
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| atmospheric pressure | the force with which the atmosphere presses down on a given surface area (See page(s) 13) |
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| atom | the smallest unit of an element that can exist as a stable independent entity (See page(s) 19) |
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| atomic mass | the mass of an atom expressed relative to a value of exactly 12 for carbon-12 (See page(s) 118 , 120) |
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| atomic mass unit (amu) | a unit used to express the mass of individual atoms and molecules, equal to 1.66 X 10-24 g (See page(s) 118) |
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| atomic number | the number of protons in an atomic nucleus, equal to the number of electrons in an electrically neutral atom (See page(s) 50) |
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| atomic weight | (see atomic mass ) |
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| Avogadro's number | the number of objects in one mole, 6.02 X 1023 (See page(s) 120) |
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| basal metabolism rate (BMR) | the number of Calories necessary to support basic body functions (See page(s) 461) |
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| base | a substance that releases hydroxide ions, OH-, usually in aqueous solution (See page(s) 246) |
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| basic solution | an aqueous solution in which the OH- concentration is greater than the H+ concentration; a solution with a pH greater than 7.0 (See page(s) 248) |
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| beta particle | an electron released during radioactive decay; it has a mass of 1/1838 amu and an electrical charge of -1 (See page(s) 300) |
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| biomass | materials produced by biological processes (See page(s) 176) |
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| biotechnology | technology based on the manipulation and alteration of biological materials, especially genetic material (See page(s) 496) |
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| bond energy | the amount of energy that must be absorbed to break a specific chemical bond, usually expressed in kJ/mole of bonds (See page(s) 158) |
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| breeder reactor | a fission reactor that converts U-238 to fissionable Pu-239 while generating energy (See page(s) 299) |
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| calibration graph | a graph of the absorbances versus the concentrations of several solutions of known concentration (See page(s) 231) |
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| calorie | the amount of heat necessary to raise the temperature of exactly 1 gram of water by 1 degree Celsius; 4.184 J (See page(s) 151) |
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| Calorie | the amount of heat necessary to raise the temperature of exactly 1 kilogram of water by 1 degree Celsius; 1000 cal; used in nutri-tion (See page(s) 152, 436) |
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| carbohydrate | a compound containing carbon, hydrogen, and oxygen, the latter two in the same 2:1 atom ratio as found in water (See page(s) 443) |
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| carbon cycle | the cyclic process by which carbon and its compounds circulate through the animal, vegetable, and mineral kingdoms (See page(s) 115) |
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| carboxylic acid | an acidic organic compound with the general formula RCOOH (See page(s) 374, 401) |
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| catalyst | a chemical substance that participates in a chemical reaction and influences its speed without undergoing permanent change (See page(s) 81, 370) |
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| cathode | the electrode at which reduction occurs (See page(s) 329) |
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| cation | a positively charged ion (See page(s) 213) |
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| Chapman cycle | the set of four related reactions that represents the natural steady-state formation and destruction of ozone in the strato-sphere (See page(s) 71) |
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| Chargaff's rules | the generalization that, in DNA from all species, the percent of adenosine equals the percent thymine and the percent guanine equals the percent cytosine (See page(s) 484) |
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| chemical change | (see chemical reaction ) |
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| chemical equation | a representation of a chemical reaction using chemical symbols and formulas (See page(s) 23) |
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| chemical formula | a representation of the elementary composition of a chemical compound (See page(s) 20) |
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| chemical reaction | a process in which substances described as reactants are transformed into different substances called products (See page(s) 23) |
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| chemical symbols | one- or two-letter symbols that represent the chemical elements (See page(s) 16) |
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| chiral isomers | two forms of a compound, with the same formula and the same number and elementary identity of atoms, whose molecules are nonidentical mirror images of each other; also known as optical isomers (See page(s) 408) |
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| chlorination | disinfection of water supplies with chlorine gas, sodium hypochlorite, or calcium hypochlorite (See page(s) 223) |
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| chlorofluorocarbon | a compound com-posed of the elements chlorine, fluo-rine, and carbon (See page(s) 48, 78) |
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| chromosomes | thread-like strands with-in cell nuclei that are the repository of genetic information in the form of DNA molecules (See page(s) 480) |
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| clone | an identical copy of a molecule, cell, or organism (See page(s) 494) |
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| codon | a sequence of three nitrogen-containing bases in a DNA molec-ule that encodes for a specific amino acid during protein synthesis (See page(s) 490) |
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| coenzyme | a substance, generally consisting of small molecules, working in conjunction with an enzyme to enhance the enzyme's activity (See page(s) 464) |
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| combustion, | burning; the rapid combination of oxygen with a flammable material, accompanied by the evolution of heat energy (See page(s) 23, 154) |
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| complementary bases | the DNA base pairs: adenine with thymine and guanine with cytosine (See page(s) 485) |
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| compound | a pure substance made up of two or more elements in a fixed, characteristic chemical combination and composition (See page(s) 18) |
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| concentration | the ratio of amount of substance (solute) to amount of water (solvent or solution) (See page(s) 205) |
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| condensation polymerization | a pro-cess in which monomeric molecules combine to form polymers by the elimination of small molecules such as H2O (See page(s) 373) |
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| conservation of energy, law of (first law of thermodynamics) | energy is neither created nor destroyed; the energy of the universe is con-stant (See page(s) 152) |
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| conservation of matter and mass, law of | in a chemical reaction, matter and mass are conserved; the mass of the reactants converted equals the mass of products formed (See page(s) 24) |
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| copolymer | a polymer consisting of two or more different monomeric units (See page(s) 373) |
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| covalent bond | a chemical bond created when two bonded atoms share electrons (See page(s) 54) |
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| covalent compound | a compound consisting of molecules that are in turn made up of covalently bonded atoms; a molecular compound (See page(s) 218) |
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| cracking | breaking down of large molecules in petroleum into smaller ones in the gasoline range (See page(s) 172) |
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| current | the rate at which electrons flow; measured in amperes (See page(s) 331) |
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| daughter | the isotope formed by the radioactive decay of the "parent" isotope (See page(s) 301) |
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| density | mass per unit volume; usually expressed in grams per cubic centimeter or grams per milliliter (See page(s) 211) |
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| deoxyribonucleic acid (DNA) | the compound constituting the genetic material of all living things (See page(s) 481) |
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| desalination | any process that removes ions from salty water, such as sea or brackish waters (See page(s) 237) |
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| dipeptide | a compound composed of two amino acid units (See page(s) 455) |
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| distillation | a purification or separation process in which a solution is heated to the boiling point and the vapors are condensed and collected (See page(s) 169, 237) |
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| DNA fingerprinting | the technique of DNA matching that can be used to identify the individual source of a DNA sample (See page(s) 500) |
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| DNA probes | relatively short segments of single-stranded DNA used to specifically bind to other DNA (See page(s) 496) |
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| double bond | a covalent bond consisting of two pairs of electrons shared between two bonded atoms (See page(s) 57) |
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| double helix | description of the molec-ular structure of deoxyribonucleic acid (DNA) (See page(s) 484) |
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| efficiency | the fraction of heat energy that is converted to work in a power plant (See page(s) 181) |
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| electrochemical cell (battery) | a device that converts the energy released in a spontaneous chemical reaction into electrical energy (See page(s) 329) |
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| electrode | an electrical conductor that serves as the site of a chemical reaction in an electrochemical or electrolytic cell (See page(s) 329) |
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| electrolysis | the electrical decomposition of a compound into its constituent elements (See page(s) 346) |
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| electrolyte | a solution that conducts electricity or a compound that conducts electricity when melted or dissolved in water (See page(s) 213) |
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| electrolytic cell | a device in which applied electrical energy is used to bring about a nonspontaneous reaction (See page(s) 329) |
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| electromagnetic spectrum | the entire range of radiant energy, including X ray, gamma, ultraviolet, visible, infrared, microwave, and radio wave radiation (See page(s) 60) |
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| electron | a subatomic particle with a mass of 1/1838 amu and a charge of -1 unit that is of great importance in atomic structure and chemical reactivity (See page(s) 50) |
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| electronegativity | a measure of the attraction of an atom for the electrons that constitute its covalent bond (See page(s) 208) |
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| electrophoresis | a method of separating molecules based on their rate of movement in an electric field; the speed at which a molecule travels depends on its size (mass) and electric charge (See page(s) 500) |
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| element | a substance that cannot be broken down into simpler stuff by any chemical means (See page(s) 15) |
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| endothermic | absorbing heat (See page(s) 157) |
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| energy | the capacity to do work (See page(s) 151) |
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| entropy | a measure of randomness in position or energy (See page(s) 184) |
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| enzyme | a biochemical catalyst; a protein that influences the rate and direction of a chemical reaction (See page(s) 491) |
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| essential amino acid | an amino acid that cannot be synthesized by the body and must be supplied in the diet (See page(s) 456) |
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| essential fatty acid | a fatty acid that cannot be synthesized by the body and must be supplied in the diet (See page(s) 450) |
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| ester | an organic compound with the general formula RCOOR¢; formed by the condensation reaction of a carboxylic acid and an alcohol (See page(s) 374) |
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| estrogens | female sex hormones (See page(s) 413) |
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| exothermic | releasing heat (See page(s) 154) |
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| exposure | the amount of a substance encountered (See page(s) 9) |
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| fat | a triglyceride; a compound made from fatty acids and glycerol (See page(s) 446) |
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| fatty acid | an acidic compound with a long hydrocarbon chain; a component of fats and oils (See page(s) 446) |
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| first law of thermodynamics (law of conservation of energy) | energy is neither created nor destroyed; the energy of the universe is constant (See page(s) 152) |
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| fission (nuclear) | a reaction in which a large atomic nucleus, such as uranium-235, splits when struck by a neutron to form two smaller fragments, and releases neutrons and large quantities of energy (See page(s) 288) |
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| fraction | a component separated from bulk crude oil (petroleum) by fractional distillation based on the fraction's boiling point (See page(s) 169) |
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| free radical | an unstable chemical species with an unpaired elec-tron (See page(s) 76) |
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| frequency | in wave motion, the number of waves passing a fixed point in one second (See page(s) 58) |
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| fuel cell | a cell in which a fuel such as hydrogen is allowed to react with oxygen under controlled conditions and the chemical energy is converted to electricity (See page(s) 334) |
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| functional groups | groupings of atoms that confer characteristic properties on the molecule and the compound (See page(s) 373, 401) |
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| galvanic cell | a device that converts the energy released in a spontaneous chemical reaction into electrical energy (See page(s) 329) |
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| gamma rays | short-wavelength, high-energy electromagnetic radiation released during radioactive de-cay (See page(s) 160, 301) |
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| gas chromatography (GC) | an analytical method that uses the differential absorption of components in a mixture carried by a gas as they move down a packed column; a detector indicates the emergence of each component from the mixture as it leaves the column (See page(s) 233) |
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| gene therapy | the introduction of normal genes into patients lacking them (See page(s) 499) |
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| generic drug | a drug that is equivalent to a pioneer drug but not able to be marketed until the patent protection of the pioneer drug runs out (20 years) (See page(s) 424) |
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| genetic engineering | the manipulation and alteration of genetic material (DNA) for a wide variety of purposes (See page(s) 495) |
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| global greenhouse effect | the return of 84% of the energy radiated from the surface of the Earth (See page(s) 103) |
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| green chemistry | designing chemical products and processes that reduce or eliminate the use and/or generation of hazardous sub-stances (See page(s) 30) |
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| greenhouse effect | the process by which atmospheric gases such as CO2, CH4, and H2O trap and return a major portion of the heat (infrared radiation) radiated by the Earth (See page(s) 103) |
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| greenhouse factor | a number that represents the relative contribution of a compound to global warm-ing (See page(s) 126) |
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| green revolution | the development of high-yield grains through genetic modification (See page(s) 470) |
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| groundwater | water pumped from wells that have been drilled into aquifers (See page(s) 201) |
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| half-life | the time required for the level of radioactivity to fall to one-half its initial value (See page(s) 307) |
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| hard water | water containing a significant concentration of magnesium or calcium ions (See page(s) 225) |
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| heat | the form of energy that flows from a hotter to a colder body (See page(s) 151) |
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| heat of combustion | the quantity of heat released when a fuel is burned; variously expressed in cal/g, cal/ mole, J/g, or J/mole (See page(s) 156) |
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| heavy metal | a member of a rather ill-defined group of metallic elements with high densities and large atomic masses (See page(s) 228) |
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| high-density lipoprotein (HDL) | a combination of lipid and protein that transports cholesterol from dead or dying cells back to the liver; the HDL's density depends on the ratio of lipid to protein (See page(s) 452) |
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| high-level nuclear waste (HLW) | waste typically from spent fuel taken from commercial nuclear reactors and from nuclear weapons production (See page(s) 309) |
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| hormones | substances produced by the body's endocrine glands that can have a wide range of physiological functions, including serving as "chemical messengers" (See page(s) 403) |
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| human genome | the totality of human genetic information (See page(s) 507) |
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| Human Genome Project | an international effort to map all the genes in the human organism and determine the DNA base sequence (See page(s) 507) |
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| hybrid car | an automobile that uses a gasoline engine and an electric motor in combination as an alternative method of propulsion (See page(s) 343) |
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| hydrocarbon | a compound of hydrogen and carbon (See page(s) 26, 168) |
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| hydrogen bond | a relatively weak electrostatic attraction between a hydrogen atom bearing a net positive charge and lone pair electrons on a nitrogen, oxygen, or fluorine atom bearing a net negative charge; hydrogen bonds exist between some molecules and within some large molecules (See page(s) 209) |
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| hydronium ion | the H3O+ ion responsible for acidic properties in solution (See page(s) 246) |
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| infrared radiation | heat radiation; the region of the electromagnetic spectrum adjacent to the red end of the visible spectrum and characterized by wavelengths longer than red light (See page(s) 60) |
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| interferons | naturally occurring protein-based molecules that provide protection against viruses (See page(s) 495) |
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| ion | an electrically charged atom or a group of covalently bonded atoms; can be positive (cation) or negative (anion) (See page(s) 213) |
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| ion exchange | a process in which ions are interchanged, usually between a solution and a solid (See page(s) 228) |
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| ionic bond | a chemical bond created by the electrostatic attraction between oppositely charged ions (See page(s) 213) |
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| ionic compound | a compound consisting of positively and negatively charged ions (See page(s) 213) |
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| isomers | different compounds with the same formula and the same number and kinds of atoms; isomers differ in molecular structure, that is, the way in which the constituent atoms are arranged (See page(s) 172, 398) |
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| isotopes | two (or more) forms of the same element whose atoms differ in number of neutrons and therefore in mass number and atomic mass (See page(s) 53) |
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| joule | a unit of energy corresponding to kg×m2/s2 (See page(s) 62, 151) |
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| Kelvin scale | the absolute temperature scale whose zero corresponds to -273.15°C, the lowest possible temperature (See page(s) 181) |
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| kilocalorie, kcal | an energy unit equal to 103 calories or 1 nutritional Calorie (Cal) (See page(s) 460) |
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| lethal dose-50 | the minimum dose required to kill 50% of test animals (See page(s) 421) |
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| Lewis structure | a representation of molecular structure based on the octet rule that uses dots to represent electrons (See page(s) 54) |
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| lipids | fats, oils, and related compounds (See page(s) 446) |
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| liter, L | a unit of volume; 1 L = 103 mL (See page(s) 205) |
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| low-density lipoprotein (LDL) | a com-bination of lipid and protein that transports cholesterol from the liver to peripheral tissues; the LDL's density depends on the ratio of lipid to protein (See page(s) 452) |
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| low-level radioactive waste (LLW) | nuclear waste contaminated with relatively small quantities of radioactive materials; other than high-level nuclear waste (See page(s) 314) |
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| macrominerals | minerals such as calcium, phosphorus, chlorine, potassium, sulfur, sodium, and magnesium, necessary for life. The adult Recommended Daily Allowances for macrominerals is from one to two grams (See page(s) 465) |
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| macromolecule | a molecule with large molecular size and a high molar mass; term often applied to polymers (See page(s) 363) |
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| macronutrients | the major classes of compounds required for nutrition: carbohydrates, fats, and proteins (See page(s) 438) |
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| malnutrition | a condition caused by a diet lacking in the proper mix of nutrients, even though enough Calo-ries are eaten daily (See page(s) 438) |
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| mass | a measure of the quantity of matter in a body, often expressed in grams or kilograms, and measured by weighing the object with a balance (See page(s) 19) |
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| mass number | the sum of the number of protons and the number of neutrons in any atomic nucleus (See page(s) 53, 289) |
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| maximum contaminant level (MCL) | the legal limit of a contaminant, expressed in ppm or ppb (See page(s) 221) |
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| maximum contaminant level goal (MCLG) | the level, in ppm or ppb, at which a person weighing 70 kg (154 lb) could drink 2 L of water containing the contaminant every day for 70 years without suffering any ill effects (See page(s) 221) |
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| mesosphere | the region of the atmo-sphere above an altitude of 50 kilometers (See page(s) 13) |
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| microminerals | the microminerals are zinc, copper, iron, and fluorine (See page(s) 465) |
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| microwave radiation | electromagnetic radiation with relatively long wavelengths, low frequencies, and low-energy photons; stimulates molecular rotations; used in microwave ovens and in radar (See page(s) 114) |
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| millirem (mrem) | one thousandth of a rem (See page(s) 305) |
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| minerals | in general, inorganic chemical substances; more specifically, the inorganic chemical substances required for healthy nutrition and body function; classified as macro-minerals, microminerals, and trace minerals (See page(s) 465) |
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| mixture | a physical combination of two or more substances (elements or compounds) present in variable amounts (See page(s) 15) |
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| molar mass | the mass of one Avo-gadro's number (1 mole) of atoms, molecules, or whatever particles are specified; usually expressed in grams (See page(s) 121) |
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| molarity, M | the number of moles of solute present in 1 L of solution (See page(s) 206) |
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| mole | one Avogadro's number of anything; 6.02 X 1023 atoms, molecules, electrons, etc. (See page(s) 121) |
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| molecular compound | a compound consisting of molecules; a covalent compound (See page(s) 218) |
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| molecular mass | the mass of a molecule expressed relative to a value of exactly 12 for carbon-12 (See page(s) 121) |
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| molecular pharming | the practice of using domesticated animals to produce drugs and other medically significant substances (See page(s) 505) |
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| molecularweight | (see molecular mass ) |
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| molecule | a combination of a fixed number of atoms, held together by chemical bonds in a certain geometric arrangement (See page(s) 20) |
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| monomer | a small molecule that combines with other monomers to yield a polymer (See page(s) 363) |
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| monounsaturated | having one carbon-carbon double bond per molecule; usually applied to fats or fatty acids (See page(s) 447) |
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| n-type semiconductor | a material that will not normally conduct electricity well, but will do so under certain conditions through the movement of electrons (See page(s) 350) |
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| neutral solution | an aqueous solution containing equal concentrations of H+ and OH- ions; a solution with a pH of 7.0 (See page(s) 249) |
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| neutralization | the chemical reaction of an acid and a base (See page(s) 247) |
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| neutron | a subatomic particle with a mass of 1 amu and no electrical charge (See page(s) 50) |
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| nitrogen balance | a condition in which the body excretes as much nitrogen as it ingests (See page(s) 456) |
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| nonelectrolyte | a substance that does not conduct electricity, either melted or in solution (See page(s) 212) |
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| nonspontaneous | a process that will not occur by itself, but only if energy is supplied from some external source (See page(s) 184) |
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| nuclear transfer | the use of a very thin, hollow needle to remove a cell's nucleus to transfer it to an unfertilized egg from which the nucleus has been removed (See page(s) 506) |
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| nucleotide | the repeating unit of DNA, consisting of a nitrogen-containing base, a deoxyribose sugar, and a phosphate group (See page(s) 482) |
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| nucleus (atomic) | the center of an atom (See page(s) 50) |
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| octet rule | a generalization that, in most stable molecules, all atoms except hydrogen will share in eight outer electrons (See page(s) 55) |
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| oils | triglycerides that are liquid at room temperature (See page(s) 446) |
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| optical isomers | (see chiral isomers ) |
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| osmosis | the natural tendency for a solvent to move through a membrane from a region of higher solvent concentration to a region of lower solvent concentration (See page(s) 237) |
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| outer electrons | the electrons in the outer energy level of an atom; the outer electrons are chiefly responsible for the chemical properties of that particular element (See page(s) 51) |
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| oxidation | a process in which an atom, ion, or molecule loses one or more electrons (See page(s) 329) |
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| oxygenated gasoline | gasoline blend-ed with oxygen-containing compounds such as MTBE, ethanol, or methanol (See page(s) 174) |
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| p-type semiconductor | a material that will not normally conduct electricity well, but will do so under certain conditions through the movement of positively charged "holes" (See page(s) 350) |
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| parent | the isotope undergoing radio-active decay (See page(s) 301) |
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| parts per million (ppm) | a measure of concentration that can be expressed in units of mass or in numbers of atoms, molecules, and/or ions (See page(s) 6) |
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| peptide bond | the molecular linkage bonding amino acid residues in proteins and monomers in nylon (See page(s) 375) |
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| periodic table | an organization of the elements in order of increasing atomic number and grouped according to similar chemical properties and similar electron arrangements (See page(s) 16) |
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| pH | a number, typically between 0 and 14, that indicates the acidity of a solution; also, the negative logarithm of the hydrogen ion concentration when the concentration is expressed as moles of H+ ion per liter of solution; pH = -log(MH+) (See page(s) 249, App. 3) |
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| phenyl group | a common molecular fragment based on a hexagon of six carbon atoms (the benzene ring); —C6H5 (See page(s) 369) |
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| photon | a "particle" of radiant energy (See page(s) 62) |
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| photosynthesis | the process by which green plants use sunlight to power the conversion of carbon dioxide and water into sugars, such as glucose, plus oxygen (See page(s) 100) |
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| photovoltaic cell | a device that converts radiant energy into electricity (See page(s) 349) |
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| pioneer drug | the first version of a drug to be marketed under a brand name (See page(s) 424) |
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| Planck's constant | the proportionality constant relating the energy of a photon to the frequency of radiation; 6.63 X 10-34 J×s (See page(s) 62) |
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| plasmid | a ring of bacterial DNA; used as a vector for introducing new genes in recombinant DNA research and technology (See page(s) 494) |
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| polar covalent bond | a covalent bond in which the electrons are not equally shared but displaced toward the more electronegative atom (See page(s) 208) |
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| polyamide | a polymer formed by the condensation reaction of amino acids (in which case the polyamide is a protein) or of diacids and diamines (in which case the poly-amide is nylon) (See page(s) 375) |
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| polyatomic ion | a group of covalently bonded atoms bearing a positive or negative electrical charge (See page(s) 215) |
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| polyester | a polymer formed by the condensation reaction of diacid and dialcohol monomers (See page(s) 374) |
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| polymer | a substance consisting of long macromolecular chains (See page(s) 363) |
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| polymerase chain reaction (PCR) | a technique for rapidly making many copies of a DNA segment (See page(s) 496) |
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| polyunsaturated | having more than one carbon-carbon double bond per molecule; usually applied to fats and oils (See page(s) 447) |
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| potable | water fit for human consumption (See page(s) 223) |
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| potential energy | on a molecular scale, the energy related to the positions of atoms and molecules (See page(s) 54) |
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| prescription drugs | drugs that could be habit forming, toxic, or unsafe for use except under medical supervision (See page(s) 420) |
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| primary structure | the identity and sequence of the amino acid residues present in a protein molecule (See page(s) 491) |
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| primers | single-stranded nucleotides that bracket and identify the section of DNA to be copied in the polymerase chain reaction (See page(s) 496) |
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| products | the substances formed from reactants as a result of a chemical reaction (See page(s) 23) |
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| prostaglandins | a group of hormonelike compounds produced by the body where they cause a variety of responses including fever, swelling, and pain; inhibited by aspirin (See page(s) 403) |
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| proteins | polymers made up of various amino acids as the monomeric units; essential components of the body and the diet (See page(s) 453, 489) |
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| proton | a subatomic particle with a mass of 1 amu and a charge of +1 (See page(s) 50) |
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| quantized | separated into discrete energy levels, as, for example, the electronic energy levels in an atom (See page(s) 62) |
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| racemic mixture | a mixture consisting of equal amounts of each optical isomer (See page(s) 409) |
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| radiation absorbed dose (rad) | the absorption of 0.01 joule of radiant energy per kilogram of tissue (See page(s) 304) |
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| radioactivity | the phenomenon in which certain unstable atomic nuclei emit radiation and thereby undergo nuclear transformation (See page(s) 300) |
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| reactants | the starting materials in a chemical reaction that are transformed into products during the reaction (See page(s) 23) |
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| receptor site | a site on a cell or molecule where a hormone or other biologically active molecule can bind (See page(s) 406) |
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| recombinant DNA | DNA that has incorporated into it DNA from another organism (See page(s) 494) |
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| reduction | a process in which an atom, ion, or molecule gains one or more electrons (See page(s) 329) |
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| reformulated gasolines (RFG) | oxygenated gasolines that contain a lower percentage of certain volatile hydrocarbons (See page(s) 175) |
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| rem (roentgen equivalent mammal) | a unit of radiation, rem = number of rads X Q, a quality factor characteristic of the type of radiation (See page(s) 304) |
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| replication | the process by which copies of DNA are made (See page(s) 486) |
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| resonance | possible structures of a molecule for which more than one Lewis structure can be written, differing by the arrangement of valence electrons but having the same arrangement of atomic nu-clei (See page(s) 57) |
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| reverse osmosis | a process for water purification in which water is forced through a membrane, and ions and other contaminants are filtered out (See page(s) 237) |
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| risk assessment | the process of analyzing and balancing the risks and benefits associated with some particular course of action (See page(s) 9) |
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| saturated | having only carbon-carbon single bonds; usually applied to fats and oils (See page(s) 447) |
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| scientific notation | a system for writing numbers as the product of a number, usually with one digit to the left of the decimal point, and 10 raised to the appropriate power or exponent, for example, 6.02 X 1023 (See page(s) 10) |
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| second law of thermodynamics | it is impossible to completely convert heat into work without making some other changes in the universe; heat will not of itself flow from a colder to a hotter body; the entropy of the universe is increasing (See page(s) 184) |
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| secondary structure | helices, parallel chains, and other localized structural features in the overall structure of a protein molecule (See page(s) 491) |
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| semiconductors | materials that do not normally conduct electricity well but will do so under certain conditions (See page(s) 349) |
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| Sievert, Sv | a unit of radiation dosage equal to 100 rem (See page(s) 304) |
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| significant figures | the number of numerals that correctly represents the accuracy with which an experimental quantity is known (See page(s) 39) |
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| singlebond | a covalent bond consisting of one pair of electrons shared between two bonded atoms (See page(s) 54) |
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| softwater | water that contains low concentrations of magnesium, calcium, or iron ions (See page(s) 225) |
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| solute | a component that dissolves in a solvent to form a solution (See page(s) 202) |
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| solution | a homogenous mixture at the atomic, molecular, and/or ionic level, consisting of a solute (or solutes) dissolved in a solvent (See page(s) 202) |
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| solvent | in a solution, the component present in the largest concentration, usually the liquid component in which the solute dissolves (See page(s) 202) |
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| source reduction | decreasing the amount of plastic waste generated by reducing the quantity of plastics produced and used (See page(s) 380, 385) |
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| specific heat | the quantity of heat energy that must be absorbed to increase the temperature of 1 gram of a substance by 1°Celsius (See page(s) 211) |
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| spectrophotometer | an instrument in which light of a desired wavelength is passed through a sample into a detector where the light is converted into an electrical signal (See page(s) 230) |
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| spent fuel | material remaining in fuel rods after they have been removed from a nuclear reactor (See page(s) 299, 310) |
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| spontaneous | a process that can occur by itself, though it may be necessary to initiate the reaction (See page(s) 184) |
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| steady state | a condition in which a dynamic system is in balance so that there is no net change in the concentration of the major participants in the reactions (See page(s) 71) |
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| steroids | a class of ubiquitous and diverse organic compounds that contain three six-membered carbon rings and one five-membered ring (See page(s) 410) |
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| storage battery | batteries that store electrical energy, such as a lead-acid storage battery (See page(s) 333) |
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| stratosphere | the region of the atmo-sphere between 15 and 50 kilometers above sea level; location of the ozone layer (See page(s) 13) |
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| substrate | the species on which an enzyme acts (See page(s) 491) |
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| surface water | lakes, rivers, and reservoirs (See page(s) 201) |
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| temperature | a property that determines the direction of heat flow; when two bodies are in contact, heat always flows from the object at the higher temperature to that at the lower temperature (See page(s) 151) |
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| tertiary structure | the overall three-dimensional structure of a protein molecule (See page(s) 491) |
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| tetrahedron | a regular figure with four identical sides, each one an equilateral triangle; the four corners of the tetrahedron correspond to the locus of the four electron pairs (bonding and/or nonbonding) around an atom that obeys the octet rule (See page(s) 107) |
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| thermal energy | energy characterized by the random motion of molecules (See page(s) 183) |
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| thermoplastic | polymers that tend to be flexible and can be melted and shaped (See page(s) 366) |
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| titration | the reaction of a reagent with a measured volume of a solution of known concentration (See page(s) 226) |
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| toxicity | the intrinsic hazard of a substance (See page(s) 9) |
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| trace minerals | dietary minerals generally needed in microgram quantities; iodine, selenium, vanadium, chro-mium, manganese, cobalt, nickel, molybdenum, and tin (See page(s) 465) |
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| transgenic organism | an organism hav-ing the genes of more than one species (See page(s) 503) |
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| triglyceride | an ester composed of three fatty acids and glycerol; fats and oils are typically triglycerides (See page(s) 446) |
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| triple bond | a covalent bond consisting of three pairs of electrons shared between two bonded atoms (See page(s) 57) |
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| troposphere | the part of the atmo-sphere that lies on the surface of the Earth (See page(s) 12) |
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| ultraviolet | the region of the electromagnetic spectrum adjacent to the violet end of the visible spectrum and characterized by wavelengths shorter than violet light (See page(s) 60) |
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| undernourishment | a condition in which the daily intake of food is insufficient to supply the body's energy requirements (See page(s) 438) |
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| unsaturated | having at least one carbon-carbon double bond per molecule; often applied to fats and oils (See page(s) 447) |
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| vaccine | a biological agent that produces or increases immunity to a particular disease (See page(s) 496) |
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| vector | a molecular or cellular component, for example a plasmid, used to import foreign DNA into a host cell (See page(s) 494) |
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| virus | a biochemical species consisting of nucleic acid and protein that can be replicated in a host cell, where it often causes disease (See page(s) 495) |
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| vitamins | organic compounds that serve a variety of functions essential to life, often by promoting metabolic processes (See page(s) 464) |
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| volt | a unit of electrical potential (See page(s) 329) |
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| voltage | a measure of difference in electrical potential (See page(s) 329) |
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| wavelength | in wave motion, the distance between successive peaks (See page(s) 58) |
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| weight | a measure of the attraction of gravity on an object, proportional to mass (See page(s) 19) |
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| work | work is done when movement occurs against a restraining force; equal to the force multiplied by the distance over which the motion occurs (See page(s) 151) |
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| X ray | electromagnetic radiation with short wavelengths, high frequencies, and high-energy photons; used in medical diagnosis and therapy, and in determining crystal structures; can damage biological tissue (See page(s) 60) |
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| X-ray diffraction | a procedure for determining crystal and molecular structure by interpreting the pattern formed when X rays are scattered by the constituent atoms (See page(s) 484) |
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| zeolite | a claylike mineral made up of aluminum, silicon, and oxygen; often used as a water softener or catalyst (See page(s) 228) |