A graph showing the ef-fect of different wavelengths of radiation,usually light,on a given process. It is oftensimilar to the absorption spectrum of the sub-stance that absorbs the radiation and cantherefore be helpful in identifying that sub-stance. For ...[繼續(xù)閱讀]

    Symbol: Ea The mini-mum energy a particle,molecule,etc.,must acquire before it can react; i.e. theenergy required to initiate a reaction regard-less of whether the reaction is exothermic orendothermic. Activation energy is often rep-resented as an energy ...[繼續(xù)閱讀]

    The region of an enzymemolecule that combines with and acts on thesubstrate. It consists of amino acids arrangedin a configuration specific to a particular sub-strate or type of substrate. Binding of an in-hibiting compound elsewhere on the enzymemolecule...[繼續(xù)閱讀]

    The transport of moleculesor ions across a cell membrane against a concen-tration gradient,with the expenditure of energy:it is probably an attribute of all cells. Anythingthat interferes with the provision of energy willinterfere with active transport. T...[繼續(xù)閱讀]

    A protein complex found inmuscle,formed between molecules of actinand myosin present in adjacent thick and thinmuscle filaments. These actomyosin com-plexes are involved in the process of musclecontraction; their formation is important inthe concerted mec...[繼續(xù)閱讀]

    1 . The extent to which an or-ganism,or a physiological or structural char-acteristic of an organism,is suited to a par-ticular environment. Organisms that have be-come highly adapted to one environment arethen often not so adaptable as less specializedor...[繼續(xù)閱讀]

    Anenzyme that is produced by a cell only in thepresence of its substrate. Compare constitu-tive enzyme.細胞只在其底物存在時才能產(chǎn)生的 一種酶。比較196頁constitutive enzyme。...[繼續(xù)閱讀]

    The gradual formationthrough evolution of a number of different va-rieties or species from a common ancestor,each adapted to a different ecological niche.A classic example of adaptive radiation is il-lustrated by Darwins finches. See alsoDarwins finches.從...[繼續(xù)閱讀]

    In lateral organs,such as a leaf,the upper surface,i.e. the side facing to-wards the main axis. Adaxial is synonymouswith ventral when the latter term is being ap-plied to lateral organs. Compare abaxial.側(cè)生器官(如葉片)上表面與植物的主軸相對。當adaxial用來描述側(cè)生器官時與...[繼續(xù)閱讀]

    A nitrogenous base found in DNAand RNA. It is also a constituent of certaincoenzymes,e.g. NAD and FAD,and whencombined with the sugar ribose it forms thenucleoside adenosine found in AMP,ADP,and ATP. Adenine has a purine ring struc-ture. See illustration ...[繼續(xù)閱讀]