10 Генетическая инженерия (1160079), страница 13
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The protein component aloneis an apolipoprotein.low-energy phosphate compound: Aphosphorylated compound with a relatively small standard free energy of hydrolysis.lyases: Enzymes that catalyze the removal of a group from a molecule to forma double bond, or the addition of a groupto a double bond.lymphocytes: A subclass of leukocytesinvolved in the immune response. B lymphocytes synthesize and secrete antibodies; T lymphocytes either play a regulatory role in immunity or kill foreign andvirus-infected cells.lysis: Destruction of a cell's plasma membrane or of a bacterial cell wall, releasingthe cellular contents and killing the cell.lysogeny: One of two outcomes of the infection of a host cell by a temperatephage.
It occurs when the phage genomebecomes repressed and is replicated aspart of the host DNA; infrequently it maybe induced, and the phage particles soproduced cause the host cell to lyse.lysosome: A membrane-bounded organelle in the cytoplasm of eukaryotic cells; itcontains many hydrolytic enzymes andserves as a degrading and recycling centerfor unneeded components.macromolecule: A molecule having amolecular weight in the range of a fewthousand to many millions.mass-action ratio: For the reaction aA +[C]c [D]dbBcC + dD, the ratio:matrix: The aqueous contents of a cell ororganelle (the mitochondrion, for example)with dissolved solutes.meiosis: A type of cell division in whichdiploid cells give rise to haploid cells destined to become gametes.membrane transport: Movement of apolar solute across a membrane via a specific membrane protein (a transporter).messenger RNA (mRNA): A class ofRNA molecules, each of which is complementary to one strand of DNA; carries thegenetic message from the chromosome tothe ribosomes.metabolism: The entire set of enzymecatalyzed transformations of organic molecules in living cells; the sum of anabolismand catabolism.metabolite: A chemical intermediate inthe enzyme-catalyzed reactions of metabolism.metalloprotein: A protein having ametal ion as its prosthetic group.metamerism: Division of the body intosegments; in insects, for example.micelle: An aggregate of amphipathicmolecules in water, with the nonpolar portions in the interior and the polar portions at the exterior surface, exposed towater.Michaelis-Menten constant (Km): Thesubstrate concentration at which an enzyme-catalyzed reaction proceeds at onehalf its maximum velocity.Michaelis-Menten equation: The equation describing the hyperbolic dependenceof the initial reaction velocity, Vo, on substrate concentration, [S], in many enzymecatalyzed reactions: Vo = max.G-9Michaelis-Menten kinetics: A kineticpattern in which the initial rate of anenzyme-catalyzed reaction exhibits a hyperbolic dependence on substrate concentration.microbodies: Cytoplasmic, membranebounded vesicles containing peroxideforming and peroxide-destroying enzymes;include lysosomes, peroxisomes, and glyoxysomes.microfilaments: Thin filaments composed of actin, found in the cytoplasm ofeukaryotic cells; serve in structure andmovement.microsomes: Membranous vesiclesformed by fragmentation of the endoplasmic reticulum of eukaryotic cells; recovered by differential centrifugation.microtubules: Thin tubules assembledfrom two types of globular tubulin subunits; present in cilia, flagella, centrosomes, and other contractile or motilestructures.mitochondrion: Membrane-bounded organelle in the cytoplasm of eukaryotes;contains the enzyme systems required forthe citric acid cycle, fatty acid oxidation,electron transfer, and oxidative phosphorylation.mitosis: The multistep process in eukaryotic cells that results in the replication ofchromosomes and cell division.mixed-function oxidases (oxygenases):Enzymes, often flavoproteins, that usemolecular oxygen (O2) to simultaneouslyoxidize a substrate and a cosubstrate(commonly NADH or NADPH).modulator: A metabolite that, whenbound to the allosteric site of an enzyme,alters its kinetic characteristics.molar solution: One mole of solute dissolved in water to give a total volume of1,000 mL.mole: One gram molecular weight of acompound.
See Avogadro's number.monoclonal antibodies: Antibodies produced by a cloned hybridoma cell, whichtherefore are identical and directedagainst the same epitope of the antigen.monolayer: A single layer of orientedlipid molecules.monoprotic acid: An acid having onlyone dissociable proton.monosaccharide: A carbohydrate consisting of a single sugar unit.mRNA: See messenger RNA.mucopolysaccharide: An older name fora glycosaminoglycan.multienzyme system: A group of relatedenzymes participating in a given metabolic pathway.G-10Glossarymutarotation: The change in specific rotation of a pyranose or furanose sugar orglycoside accompanying the equilibrationof its a- and /3-anomeric forms.mutases: Enzymes that catalyze thetransposition of functional groups.mutation: An inheritable change in thenucleotide sequence of a chromosome.myofibril: A unit of thick and thin filaments of muscle fibers.myosin: A contractile protein; the majorcomponent of the thick filaments of muscle and other actin-myosin systems.NAD, NADP (nicotinamide adeninedinucleotide, nicotinamide adeninedinucleotide phosphate): Nicotinamide-containing coenzymes functioning ascarriers of hydrogen atoms and electronsin some oxidation—reduction reactions.native conformation: The biologicallyactive conformation of a macromolecule.negative cooperativity: A phenomenonof some multisubunit enzymes or proteinsin which binding of a ligand or substrateto one subunit impairs binding to anothersubunit.negative feedback: Regulation of a biochemical pathway achieved when a reaction product inhibits an earlier step in thepathway.neuron: A cell of nervous tissue specialized for transmission of a nerve impulse.neurotransmitter: A low molecularweight compound (usually containing nitrogen) secreted from the terminal of aneuron and bound by a specific receptorin the next neuron; serves to transmit anerve impulse.nicotinamide adenine dinucleotide,nicotinamide adenine dinucleotidephosphate: See NAD, NADP.ninhydrin reaction: A color reactiongiven by amino acids and peptides onheating with ninhydrin; widely used fortheir detection and estimation.nitrogen cycle: The cycling of variousforms of biologically available nitrogenthrough the plant, animal, and microbialworlds, and through the atmosphere andgeosphere.nitrogen fixation: Conversion of atmospheric nitrogen (N2) into a reduced, biologically available form by nitrogen-fixingorganisms.nitrogenase complex: A system of enzymes capable of reducing atmosphericnitrogen to ammonia in the presence ofATP.noncompetitive inhibition: A type ofenzyme inhibition not reversed by increasing the substrate concentration.noncyclic electron flow: The lightinduced flow of electrons from water toNADP+ in oxygen-evolving photosynthesis; it involves both photosystems I and II.nonessential amino acids: Amino acidsthat can be made by humans and othervertebrates from simpler precursors, andare thus not required in the diet.nonheme iron proteins: Proteins, usually acting in oxidation-reduction reactions, containing iron but no porphyringroups.nonpolar: Hydrophobic; describing molecules or groups that are poorly soluble inwater.nonsense codon: A codon that does notspecify an amino acid, but signals the termination of a polypeptide chain.nonsense mutation: A mutation thatresults in the premature termination of apolypeptide chain.nonsense suppressor: A mutation, usually in the gene for a tRNA, that causesan amino acid to be inserted into a polypeptide in response to a terminationcodon.nucleases: Enzymes that hydrolyze theinternucleotide (phosphodiester) linkagesof nucleic acids.nucleic acids: Biologically occurring polynucleotides in which the nucleotide residues are linked in a specific sequence byphosphodiester bonds; DNA and RNA.nucleoid: In bacteria, the nuclear zonethat contains the chromosome but has nosurrounding membrane.nucleolus: A densely staining structurein the nucleus of eukaryotic cells; involvedin rRNA synthesis and ribosome formation.nucleophile: An electron-rich group witha strong tendency to donate electrons toan electron-deficient nucleus (electrophile);the entering reactant in a bimolecularsubstitution reaction.nucleoplasm: The portion of a cell's contents enclosed by the nuclear membrane;also called the nuclear matrix.nucleoside: A compound consisting of apurine or pyrimidine base covalentlylinked to a pentose.nucleoside diphosphate kinase: Anenzyme that catalyzes the transfer of theterminal phosphate of a nucleoside5'-triphosphate to a nucleoside 5'-diphosphate.nucleoside diphosphate sugar: A coenzymelike carrier of a sugar molecule, functioning in the enzymatic synthesis of polysaccharides and sugar derivatives.nucleoside monophosphate kinase: Anenzyme that catalyzes the transfer of theterminal phosphate of ATP to a nucleoside5'-monophosphate.nucleosome: Structural unit for packaging chromatin; consists of a DNA strandwound around a hi stone core.nucleotide: A nucleoside phosphorylatedat one of its pentose hydroxyl groups.nucleus: In eukaryotes, a membranebounded organelle that contains chromosomes.oligomer: A short polymer, usually ofamino acids, sugars, or nucleotides; thedefinition of "short" is somewhat arbitrary, but usually less than 50 subunits.oligomeric protein: A multisubunit protein having two or more identical polypeptide chains.oligonucleotide: A short polymer of nucleotides (usually less than 50).oligopeptide: A few amino acids joinedby peptide bonds.oligosaccharide: Several monosaccharidegroups joined by glycosidic bonds.oncogene: A cancer-causing gene; any ofseveral mutant genes that cause cells toexhibit rapid, uncontrolled proliferation.See also proto-oncogene.open reading frame: A group of contiguous nonoverlapping nucleotide codons in aDNA or RNA molecule that do not includea termination codon.open system: A system that exchangesmatter and energy with its surroundings.See also system.operator: A region of DNA that interactswith a repressor protein to control theexpression of a gene or group of genes.operon: A unit of genetic expression consisting of one or more related genes andthe operator and promoter sequences thatregulate their transcription.optical activity: The capacity of a substance to rotate the plane of plane-polarized light.optimum pH: The characteristic pH atwhich an enzyme has maximal catalyticactivity.organelles: Membrane-bounded structures found in eukaryotic cells; containGlossaryenzymes and other components requiredfor specialized cell functions.origin: The nucleotide sequence or site inDNA where DNA replication is initiated.osmosis: Bulk flow of water through asemipermeable membrane into anotheraqueous compartment containing solute ata higher concentration.osmotic pressure: Pressure generated bythe osmotic flow of water through a semipermeable membrane into an aqueouscompartment containing solute at ahigher concentration.oxidation: The loss of electrons from acompound.oxidation, p: See /3 oxidation.oxidation-reduction reaction: A reaction in which electrons are transferredfrom a donor to an acceptor molecule; alsocalled a redox reaction.oxidative phosphorylation: The enzymatic phosphorylation of ADP to ATP coupled to electron transfer from a substrateto molecular oxygen.oxidizing agent (oxidant): The acceptorof electrons in an oxidation—reduction reaction.oxygen debt: The extra oxygen (abovethe normal resting level) consumed in therecovery period after strenuous physicalexertion.oxygenases: Enzymes that catalyze reactions in which oxygen is introduced intoan acceptor molecule.palindrome: A segment of duplex DNAin which the base sequences of the twostrands exhibit twofold rotational symmetry about an axis.paradigm: In biochemistry, an experimental model or example.partition coefficient: A constant thatexpresses the ratio in which a given solute will be partitioned or distributed between two given immiscible liquids atequilibrium.pathogenic: Disease-causing.pentose: A simple sugar with a backbonecontaining five carbon atoms.pentose phosphate pathway: A pathway that serves to interconvert hexosesand pentoses and is a source of reducingequivalents and pentoses for biosyntheticprocesses; present in most organisms.
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