| A | B |
|---|
| alpha helix | spiral shape constituting one form of the secondary structure of proteins, arising from a specific hydrogen-bonding structure |
| amino acid | organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of proteins |
| antiparallel | opposite arrangement of the sugar-phosphate backbones in a DNA double helix |
| beta pleated sheet | econdary structure of proteins in which the polypeptide chain folds back and forth |
| carbohydrate | sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides) |
| catalyst | chemical agent that changes the rate of a reaction without being consumed by the reaction |
| cellulose | structural polysaccharide of cell walls, consisting of glucose monomers joined by β-1, 4-glycosidic linkages |
| chaperonin | protein molecule that assists the proper folding of other proteins |
| chitin | structural polysaccharide of an amino sugar found in many fungi and in the exoskeletons of all arthropods |
| cholesterol | steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids |
| condensation reaction | reaction in which two molecules become covalently bonded to each other through the loss of a small molecule, usually water |
| dehydration reaction | chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule |
| denaturation | a process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive |
| deoxyribonucleic acid (DNA) | double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell’s proteins |
| deoxyribose | sugar component of DNA, having one less hydroxyl group than ribose, the sugar component of RNA |
| disaccharide | double sugar, consisting of two monosaccharides joined by dehydration synthesis |
| disulfide bridge | strong covalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer |
| double helix | form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape |
| fat (triacylglycerol) | biological compound consisting of three fatty acids linked to one glycerol molecule |
| fatty acid | long carbon chain carboxylic acid |
| gene | iscrete unit of hereditary information consisting of a specific nucleotide sequence |
| glycogen | extensively branched glucose storage polysaccharide found in the liver and muscle of animals |
| glycosidic linkage | covalent bond formed between two monosaccharides by a dehydration reaction |
| hydrolysis | chemical process that lyses, or splits, molecules by the addition of water |
| hydrophobic interaction | type of weak chemical bond formed when molecules that do not mix with water coalesce to exclude the water |
| lipid | One of a family of compounds, including fats, phospholipids, and steroids, that are insoluble in water |
| macromolecule | giant molecule formed by the joining of smaller molecules, usually by a condensation reaction |
| monomer | subunit that serves as the building block of a polymer |
| monosaccharide | simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides |
| nucleic acid | polymer (polynucleotide) consisting of many nucleotide monomers |
| nucleotide | building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group |
| peptide bond | covalent bond between two amino acid units, formed by a dehydration reaction |
| phospholipid | molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail |
| polymer | long molecule consisting of many similar or identical monomers linked together |
| polynucleotide | polymer consisting of many nucleotide monomers |
| polypeptide | polymer (chain) of many amino acids linked together by peptide bonds |
| polysaccharide | polymer of up to over a thousand monosaccharides, formed by dehydration reactions |
| primary structure | level of protein structure referring to the specific sequence of amino acids |
| protein | three-dimensional biological polymer constructed from a set of 20 different monomers called amino acids |
| purine | double ringed nitrogenous bases; Adenine (A) and guanine (G) |
| pyrimidine | single ringed nitrogenous bases, cytosine (C), thymine (T), and uracil (U) |
| quaternary structure | particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide |
| ribonucleic acid (RNA) | nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U) |
| ribose | sugar component of RNA |
| saturated fatty acid | fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms |
| secondary structure | repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bond formation between peptide linkages |
| starch | storage polysaccharide in plants consisting entirely of glucose. |
| steroid | lipid characterized by a carbon skeleton consisting of four rings with various functional groups attached |
| tertiary structure | due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges |
| triacylglycerol | Three fatty acids linked to one glycerol molecule |
| unsaturated fatty acid | fatty acid possessing one or more double bonds between the carbons in the hydrocarbon tail |
| X-ray crystallography | diffraction of an X-ray beam by the individual atoms of a molecule to study the three-dimensional structure of the molecule |
