10 Генетическая инженерия (1160079), страница 11
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Configurational isomerscannot be interconverted without breakingone or more covalent bonds.conformation: The spatial arrangementof substituent groups that are free to assume different positions in space, withoutbreaking any bonds, because of the freedom of bond rotation.conformation, /?: See p conformation.conjugate acid-base pair: A protondonor and its corresponding deprotonatedspecies; for example, acetic acid (donor)and acetate (acceptor).conjugate redox pair: An electron donorand its corresponding electron acceptorform; for example, Cu" (donor) and Cu2+(acceptor), or NADH (donor) and NAD+(acceptor).conjugated protein: A protein containing one or more prosthetic groups.consensus sequence: A DNA or aminoacid sequence consisting of the residuesthat occur most commonly at each position within a set of similar sequences.conservative substitution: Replacementof an amino acid residue in a polypeptideby another residue with similar properties; for example, substitution of Glu byAsp.G-4Glossaryconstitutive enzymes: Enzymes required at all times by a cell and presentat some constant level; for example, manyenzymes of the central metabolic pathways.
Sometimes called "housekeepingenzymes."corticosteroids: Steroid hormonesformed by the adrenal cortex.cosmid: A cloning vector, used for cloninglarge DNA fragments; generally containssegments derived from bacteriophages andvarious plasmids.cotransport: The simultaneous transport,by a single transporter, of two solutesacross a membrane. See antiport, symport.coupled reactions: Two chemical reactions that have a common intermediateand thus a means of energy transfer fromone to the other.covalent bond: A chemical bond thatinvolves sharing of electron pairs.cristae: Infoldings of the inner mitochondrial membrane.cyclic AMP (cAMP): A second messengerwithin cells; its formation by adenylatecyclase is stimulated by certain hormonesor other molecular signals.cyclic electron flow: In chloroplasts, thelight-induced flow of electrons originatingfrom and returning to photosystem I.cyclic photophosphorylation: ATP synthesis driven by cyclic electron flowthrough photosystem I.cytochromes: Heme proteins serving aselectron carriers in respiration, photosynthesis, and other oxidation-reduction reactions.cytokinesis: The final separation ofdaughter cells following mitosis.cytoplasm: The portion of a cell's contents outside the nucleus but within theplasma membrane; includes organellessuch as mitochondria.cytoskeleton: The filamentous networkproviding structure and organization tothe cytoplasm; includes actin filaments,microtubules, and intermediate filaments.cytosol: The continuous aqueous phase ofthe cytoplasm, with its dissolved solutes;excludes the organelles such as mitochondria.dalton: The weight of a single hydrogenatom (1.66 x 10 ~24 g).dark reactions: See carbon fixation reactions.de novo pathway: Pathway for synthesisof a biomolecule, such as a nucleotide,from simple precursors; as distinct from asalvage pathway.deamination: The enzymatic removal ofamino groups from biomolecules such asamino acids or nucleotides.degenerate code: A code in which a single element in one language is specifiedby more than one element in a secondlanguage.dehydrogenases: Enzymes catalyzingthe removal of pairs of hydrogen atomsfrom their substrates.deletion mutation: A mutation resultingfrom the deletion of one or more nucleotides from a gene or chromosome.denaturation: Partial or complete unfolding of the specific native conformationof a polypeptide chain, protein, or nucleicacid.denatured protein: A protein that haslost its native conformation by exposure toa destabilizing agent such as heat or detergent.deoxyribonucleic acid: See DNA.deoxyribonucleotides: Nucleotides containing 2-deoxy-D-ribose as the pentosecomponent.desaturases: Enzymes that catalyze theintroduction of double bonds into the hydrocarbon portion of fatty acids.desolvation: In aqueous solution, therelease of bound water surrounding asolute.dextrorotatory isomer: A stereoisomerthat rotates the plane of plane-polarizedlight clockwise.diabetes mellitus: A metabolic diseaseresulting from insulin deficiency; characterized by a failure in glucose transportfrom the blood into cells at normal glucoseconcentrations.dialysis: Removal of small moleculesfrom a solution of a macromolecule, byallowing them to diffuse through a semipermeable membrane into water.differential centrifugation: Separationof cell organelles or other particles of different size by their different rates of sedimentation in a centrifugal field.differentiation: Specialization of cellstructure and function during embryonicgrowth and development.diffusion: The net movement of molecules in the direction of lower concentration.digestion: Enzymatic hydrolysis of majornutrients in the gastrointestinal system toyield their simpler components.diploid: Having two sets of genetic information; describing a cell with two chromosomes of each type.dipole: A molecule having both positiveand negative charges.diprotic acid: An acid having two dissociable protons.disaccharide: A carbohydrate consistingof two covalently joined monosaccharideunits.dissociation constant: (1) An equilibrium constant {Kd) for the dissociation ofa complex of two or more biomoleculesinto its components; for example, dissociation of a substrate from an enzyme.(2) The dissociation constant (Ka) of anacid, describing its dissociation into itsconjugate base and a proton.disulfide bridge: A covalent cross linkbetween two polypeptide chains formed bya cystine residue (two Cys residues).DNA (deoxyribonucleic acid): A polynucleotide having a specific sequence ofdeoxyribonucleotide units covalently joinedthrough 3',5'-phosphodiester bonds; servesas the carrier of genetic information.DNA chimera: A DNA containing geneticinformation derived from two differentspecies.DNA cloning: See cloning.DNA library: A random collection ofcloned DNA fragments that includes all ormost of the genome of a given organism;also called a genomic library.DNA ligase: An enzyme that creates aphosphodiester bond between the 3' endof one DNA segment and the 5' end ofanother.DNA looping: The interaction of proteinsbound at distant sites on a DNA moleculeso that the intervening DNA forms a loop.DNA polymerase: An enzyme that catalyzes template-dependent synthesis ofDNA from its deoxyribonucleoside5'-triphosphate precursors.DNA replicase system: The entire complex of enzymes and specialized proteinsrequired in biological DNA replication.DNA supercoiling: The coiling of DNAupon itself, generally as a result of bending, underwinding, or overwinding of theDNA helix.DNA transposition: See transposition.domain: A distinct structural unit of apolypeptide; domains may have separatefunctions and may fold as independent,compact units.double helix: The natural coiled conformation of two complementary, antiparallelDNA chains.Glossarydouble-reciprocal plot: A plot of 1/VOversus 1/[S], which allows a more accuratedetermination of Vmax and Km than a plotof Vo versus [S]; also called the Lineweaver-Burk plot.3E0'i See standard reduction potential.E.
coli (Escherichia coli): A commonbacterium found in the small intestine ofvertebrates; the most well-studied organism.electrochemical gradient: The sum ofthe gradients of concentration and of electric charge of an ion across a membrane;the driving force for oxidative phosphorylation and photophosphorylation.electrochemical potential: The energyrequired to maintain a separation ofcharge and of concentration across amembrane.electrogenic: Contributing to an electrical potential across a membrane.electron acceptor: A substance that receives electrons in an oxidation—reductionreaction.electron carrier: A protein, such as aflavoprotein or a cytochrome, that can reversibly gain and lose electrons; functionsin the transfer of electrons from organicnutrients to oxygen or some other terminal acceptor.electron donor: A substance that donates electrons in an oxidation-reductionreaction.electron transfer: Movement of electronsfrom substrates to oxygen via the carriersof the respiratory (electron transfer) chain.electrophile: An electron-deficient groupwith a strong tendency to accept electronsfrom an electron-rich group (nucleophile).electrophoresis: Movement of chargedsolutes in response to an electrical field;often used to separate mixtures of ions,proteins, or nucleic acids.elongation factors: Specific proteins required in the elongation of polypeptidechains by ribosomes.eluate: The effluent from a chromatographic column.enantiomers: Stereoisomers that arenonsuperimposable mirror images of eachother.end-product inhibition: See feedbackinhibition.endergonic reaction: A chemical reaction that consumes energy (that is, forwhich AG is positive).endocrine glands: Groups of cells specialized to synthesize hormones and secrete them into the blood to regulate othertypes of cells.endocytosis: The uptake of extracellularmaterial by its inclusion within a vesicle(endosome) formed by an invagination ofthe plasma membrane.endonuclease: An enzyme that hydrolyzes the interior phosphodiester bonds ofa nucleic acid; that is, it acts at pointsother than the terminal bonds.endoplasmic reticulum: An extensivesystem of double membranes in the cytoplasm of eukaryotic cells; it encloses secretory channels and is often studdedwith ribosomes (rough endoplasmic reticulum).endothermic reaction: A chemical reaction that takes up heat (that is, for whichAH is positive).energy charge: The fractional degree towhich the ATP/ADP/AMP system is filledwith high-energy phosphate groups.energy coupling: The transfer of energyfrom one process to another.enhancers: DNA sequences that facilitatethe expression of a given gene; may belocated a few hundred, or even thousand,base pairs away from the gene.enthalpy (H): The heat content of a system.enthalpy change (AH): For a reaction, isapproximately equal to the difference between the energy used to break bonds andthe energy gained by the formation of newones.entropy (S): The extent of randomness ordisorder in a system.enzyme: A biomolecule, either protein orRNA, that catalyzes a specific chemicalreaction.
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