六级辅导：英语六级阅读(03)
<p> <span word="NASA">NASA</span>-<span word="Funded">Funded</span> <span word="Research">Research</span> <span word="Discovers">Discovers</span> <span word="Life">Life</span> <span word="Built">Built</span> <span word="With">With</span> <span word="Toxic">Toxic</span> <span word="Chemical">Chemical</span></p><p> <span word="NASA">NASA</span>-<span word="funded">funded</span> <span word="astrobiology">astrobiology</span> <span word="research">research</span> <span word="has">has</span> <span word="changed">changed</span> <span word="the">the</span> <span word="fundamental">fundamental</span> <span word="knowledge">knowledge</span> <span word="about">about</span> <span word="what">what</span> <span word="comprises">comprises</span> <span word="all">all</span> <span word="known">known</span> <span word="life">life</span> <span word="on">on</span> <span word="Earth">Earth</span>.</p><p> <span word="Researchers">Researchers</span> <span word="conducting">conducting</span> <span word="tests">tests</span> <span word="in">in</span> <span word="the">the</span> <span word="harsh">harsh</span> <span word="environment">environment</span> <span word="of">of</span> <span word="Mono">Mono</span> <span word="Lake">Lake</span> <span word="in">in</span> <span word="California">California</span> <span word="have">have</span> <span word="discovered">discovered</span> <span word="the">the</span> <span word="first">first</span> <span word="known">known</span> <span word="microorganism">microorganism</span> <span word="on">on</span> <span word="Earth">Earth</span> <span word="able">able</span> <span word="to">to</span> <span word="thrive">thrive</span> <span word="and">and</span> <span word="reproduce">reproduce</span> <span word="using">using</span> <span word="the">the</span> <span word="toxic">toxic</span> <span word="chemical">chemical</span> <span word="arsenic">arsenic</span>. <span word="The">The</span> <span word="microorganism">microorganism</span> <span word="substitutes">substitutes</span> <span word="arsenic">arsenic</span> <span word="for">for</span> <span word="phosphorus">phosphorus</span> <span word="in">in</span> <span word="its">its</span> <span word="cell">cell</span> <span word="components">components</span>.</p><p> <span word="The">The</span> <span word="definition">definition</span> <span word="of">of</span> <span word="life">life</span> <span word="has">has</span> <span word="just">just</span> <span word="expanded">expanded</span>, <span word="said">said</span> <span word="Ed">Ed</span> <span word="Weiler">Weiler</span>, <span word="NASAs">NASAs</span> <span word="associate">associate</span> <span word="administrator">administrator</span> <span word="for">for</span> <span word="the">the</span> <span word="Science">Science</span> <span word="Mission">Mission</span> <span word="Directorate">Directorate</span> <span word="at">at</span> <span word="the">the</span> <span word="agencys">agencys</span> <span word="Headquarters">Headquarters</span> <span word="in">in</span> <span word="Washington">Washington</span>. <span word="As">As</span> <span word="we">we</span> <span word="pursue">pursue</span> <span word="our">our</span> <span word="efforts">efforts</span> <span word="to">to</span> <span word="seek">seek</span> <span word="signs">signs</span> <span word="of">of</span> <span word="life">life</span> <span word="in">in</span> <span word="the">the</span> <span word="solar">solar</span> <span word="system">system</span>, <span word="we">we</span> <span word="have">have</span> <span word="to">to</span> <span word="think">think</span> <span word="more">more</span> <span word="broadly">broadly</span>, <span word="more">more</span> <span word="diversely">diversely</span> <span word="and">and</span> <span word="consider">consider</span> <span word="life">life</span> <span word="as">as</span> <span word="we">we</span> <span word="do">do</span> <span word="not">not</span> <span word="know">know</span> <span word="it">it</span>.</p><p> <span word="This">This</span> <span word="finding">finding</span> <span word="of">of</span> <span word="an">an</span> <span word="alternative">alternative</span> <span word="biochemistry">biochemistry</span> <span word="makeup">makeup</span> <span word="will">will</span> <span word="alter">alter</span> <span word="biology">biology</span> <span word="textbooks">textbooks</span> <span word="and">and</span> <span word="expand">expand</span> <span word="the">the</span> <span word="scope">scope</span> <span word="of">of</span> <span word="the">the</span> <span word="search">search</span> <span word="for">for</span> <span word="life">life</span> <span word="beyond">beyond</span> <span word="Earth">Earth</span>. <span word="The">The</span> <span word="research">research</span> <span word="is">is</span> <span word="published">published</span> <span word="in">in</span> <span word="this">this</span> <span word="weeks">weeks</span> <span word="edition">edition</span> <span word="of">of</span> <span word="Science">Science</span> <span word="Express">Express</span>.</p><p> <span word="Carbon">Carbon</span>, <span word="hydrogen">hydrogen</span>, <span word="nitrogen">nitrogen</span>, <span word="oxygen">oxygen</span>, <span word="phosphorus">phosphorus</span> <span word="and">and</span> <span word="sulfur">sulfur</span> <span word="are">are</span> <span word="the">the</span> <span word="six">six</span> <span word="basic">basic</span> <span word="building">building</span> <span word="blocks">blocks</span> <span word="of">of</span> <span word="all">all</span> <span word="known">known</span> <span word="forms">forms</span> <span word="of">of</span> <span word="life">life</span> <span word="on">on</span> <span word="Earth">Earth</span>. <span word="Phosphorus">Phosphorus</span> <span word="is">is</span> <span word="part">part</span> <span word="of">of</span> <span word="the">the</span> <span word="chemical">chemical</span> <span word="backbone">backbone</span> <span word="of">of</span> <span word="DNA">DNA</span> <span word="and">and</span> <span word="RNA">RNA</span>, <span word="the">the</span> <span word="structures">structures</span> <span word="that">that</span> <span word="carry">carry</span> <span word="genetic">genetic</span> <span word="instructions">instructions</span> <span word="for">for</span> <span word="life">life</span>, <span word="and">and</span> <span word="is">is</span> <span word="considered">considered</span> <span word="an">an</span> <span word="essential">essential</span> <span word="element">element</span> <span word="for">for</span> <span word="all">all</span> <span word="living">living</span> <span word="cells">cells</span>.</p><p> <span word="Phosphorus">Phosphorus</span> <span word="is">is</span> <span word="a">a</span> <span word="central">central</span> <span word="component">component</span> <span word="of">of</span> <span word="the">the</span> <span word="energy">energy</span>-<span word="carrying">carrying</span> <span word="molecule">molecule</span> <span word="in">in</span> <span word="all">all</span> <span word="cells">cells</span> <span word="and">and</span> <span word="also">also</span> <span word="the">the</span> <span word="phospholipids">phospholipids</span> <span word="that">that</span> <span word="form">form</span> <span word="all">all</span> <span word="cell">cell</span> <span word="membranes">membranes</span>. <span word="Arsenic">Arsenic</span>, <span word="which">which</span> <span word="is">is</span> <span word="chemically">chemically</span> <span word="similar">similar</span> <span word="to">to</span> <span word="phosphorus">phosphorus</span>, <span word="is">is</span> <span word="poisonous">poisonous</span> <span word="for">for</span> <span word="most">most</span> <span word="life">life</span> <span word="on">on</span> <span word="Earth">Earth</span>. <span word="Arsenic">Arsenic</span> <span word="disrupts">disrupts</span> <span word="metabolic">metabolic</span> <span word="pathways">pathways</span> <span word="because">because</span> <span word="chemically">chemically</span> <span word="it">it</span> <span word="behaves">behaves</span> <span word="similarly">similarly</span> <span word="to">to</span> <span word="phosphate">phosphate</span>.</p>
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