| A | B |
|---|
| Adenine | A nitrogen-containing base found in nucleic acids, ATP, NAD, and other compounds. |
| Alpha helix | A prevalent type of secondary protein structure. |
| Amino acid | Organic compounds containing both NH2 and COOH groups. Proteins are polymers of amino acids. |
| Beta pleated sheet | Type of protein secondary structure; results from hydrogen bonding between polypeptide regions running antiparallel to each other. |
| Carbohydrates | Organic compounds containing carbon, hydrogen, and oxygen in the ratio 1:2:1. Common examples are sugars, starch, and cellulose. |
| Cellulose | A straight-chain polymer of glucose molecules, used by plants as a structural supporting material. |
| Chemical evolution | The theory that life originated through the chemical transformation of inanimate substances. |
| Complementary base pairing | The AT (or AU), TA (or UA), CG, and GC pairing of bases in double-stranded DNA, in transcription, and between tRNA and mRNA. |
| Condensation reaction | A reaction in which two molecules become connected by a covalent bond and a molecule of water is released. (AH + BOH → AB + H2O.) |
| Cytosine | A nitrogen-containing base found in DNA and RNA. |
| Denaturation | Loss of activity of an enzyme or nucleic acid molecule as a result of structural changes induced by heat or other means. |
| Deoxyribose | A five-carbon sugar found in nucleotides and DNA. |
| Dissacharide | A carbohydrate made up of two monosaccharides (simple sugars). |
| Disulfide bridge | The covalent bond between twosulfur atoms (–S—S–) linking to molecules or remote parts of the same molecule. |
| DNA | Deoxyribonucleic acid. The fundamental hereditary material of all living organisms. In eukaryotes, stored primarily in the cell nucleus. A nucleic acid using deoxyribose rather than ribose. |
| Double helix | In DNA, the natural, right-handed coil configuration of two complementary, antiparallel strands. |
| Ester linkage | A condensation (water-releasing) reaction in which the carboxyl group of a fatty acid reacts with the hydroxyl group of an alcohol. Lipids are formed in this way. |
| Fat | A triglyceride that is solid at room temperature. |
| Fatty acid | A molecule with a long hydrocarbon tail and a carboxyl group at the other end. Found in many lipids. |
| Functional group | A characteristic combination of atoms that contribute specific properties when attached to larger molecules. |
| Glucose | The most common monosaccharide; the monomer of the polysaccharides starch, glycogen, and cellulose. |
| Glycerol | A three-carbon alcohol with three hydroxyl groups; a component of phospholipids and triglycerides. |
| Glycogen | An energy storage polysaccharide found in animals and fungi; a branched-chain polymer of glucose, similar to starch. |
| Glycosidic linkage | Bond between carbohydrate (sugar) molecules through an intervening oxygen atom (–O–). |
| Guanine | A nitrogen-containing base found in DNA, RNA, and GTP. |
| Hexose | A sugar containing six carbon atoms. |
| Hydrolysis | A chemical reaction that breaks a bond by inserting the components of water: AB + H2O → AH + BOH. |
| Isomers | Molecules consisting of the same numbers and kinds of atoms, but differing in the bonding patterns by which the atoms are held together. |
| Lipids | Substances in a cell which are easily extracted by organic solvents; fats, oils, waxes, steroids, and other large organic molecules, including those which, with proteins, make up the cell membranes. |
| Macromolecule | A giant polymeric molecule. The macromolecules are proteins, polysaccharides, and nucleic acids. |
| Monomer | A small molecule, two or more of which can be combined to form oligomers (consisting of a few monomers) or polymers (consisting of many monomers). |
| Monosaccharide | A simple sugar. Oligosaccharides and polysaccharides are made up of monosaccharides. |
| Nucleic acid | A long-chain alternating polymer of deoxyribose or ribose and phosphate groups, with nitrogenous bases—adenine, thymine, uracil, guanine, or cytosine (A, T, U, G, or C)—as side chains. DNA and RNA are nucleic acids. |
| Nucleotide | The basic chemical unit in a nucleic acid. A nucleotide in RNA consists of one of four nitrogenous bases linked to ribose, which in turn is linked to phosphate. In DNA, deoxyribose is present instead of ribose. |
| Oil | A triglyceride that is liquid at room temperature. |
| Oligosaccharide | A polymer containing a small number of monosaccharides. |
| Pentose | A sugar containing five carbon atoms. |
| Peptide linkage | The bond between amino acids in a protein. Formed between a carboxyl group and amino group (CO—NH–) with the loss of water molecules. |
| Phosphodiester linkage | The connection in a nucleic acid strand, formed by linking two nucleotides. |
| Phospholipids | Lipids containing a phosphate group; important constituents of cellular membranes. |
| Polymer | A large molecule made up of similar or identical subunits called monomers. |
| Polysaccharide | A macromolecule composed of many monosaccharides (simple sugars). Common examples are cellulose and starch. |
| Primary structure | The specific sequence of amino acids in a protein. |
| Protein | One of the most fundamental building substances of living organisms. A long-chain polymer of amino acids with twenty different common side chains. Occurs with its polymer chain extended in fibrous proteins, or coiled into a compact macromolecule in enzymes and other globular proteins. |
| Purine | One of the types of nitrogenous bases. The purines adenine and guanine are found in nucleic acids. |
| Pyrimidine | A type of nitrogenous base. The pyrimidines cytosine, thymine, and uracil are found in nucleic acids. |
| Quaternary structure | The specific three dimensional arrangement of protein subunits. |
| R group | The distinguishing group of atoms of a particular amino acid. |
| Ribose | A five-carbon sugar in nucleotides and RNA. |
| RNA | Ribonucleic acid. An often single stranded nucleic acid whose nucleotides use ribose rather than deoxyribose and in which the base uracil replaces thymine found in DNA. Serves as genome from some viruses. |
| Saturated fatty acid | A fatty acid usually containing from 12 to 18 carbon atoms and no double bonds. |
| Secondary structure | Of a protein, localized regularities of structure, such as the alpha-helix and the beta-pleated sheet. |
| Starch | A polymer of glucose; used by plants to store energy. |
| Structural isomers | Molecules made up of the same kinds and numbers of atoms, in which the atoms are bonded differently. |
| Teritary structure | In reference to a protein, the relative locations in three-dimensional space of all the atoms in the molecule. The overall shape of a protein. |
| Thymine | A nitrogen-containing base found in DNA. |
| Triglyceride | A simple lipid in which three fatty acids are combined with one molecule of glycerol. |
| Unsaturated hydrocarbon | A compound containing only carbon and hydrogen atoms, with one or more pairs of carbon atoms that are connected by double bonds. |
| Uracil | A pyrimidine base found in nucleotides of RNA. |
| Vitamins | Organic compounds that an organism cannot synthesize, but nevertheless requires in small quantity for normal growth and metabolism. |
