Life on earth
BY Alonso RicARdo And JAck W. szostAk
f
Fresh clues hint at how the first living organisms arose from inanimate matter
E
very living cell, even the simplest bacterium, teems with mo-lecular contraptions that would be the envy of any nanotech-nologist. As they incessantly shake or spin or crawl around
the cell, these machines cut, paste and copy genetic molecules, shut-tle nutrients around or turn them into energy, build and repair cellu-lar membranes, relay mechanical, chemical or electrical messages—n othe list goes on and on, and new discoveries add to it all the time. It is virtually impossible to imagine how a cell’s machines, which are mostly protein-based catalysts called enzymes, could have formed spontaneously as life first arose from nonliving matter around 3.7 billion years ago. To be sure, under the right conditions some build-ing blocks of proteins, the amino acids, form easily from simpler chemicals, as Stanley L. Miller and Harold C. Urey of the University of Chicago discovered in pioneering experiments in the 1950s. But Key conceptS
■
Researchers have found a way that the genetic molecule RNA could have formed from chemi-gigoing from there to proteins and enzymes is a different matter. A cell’s protein-making process involves complex enzymes pull-ing apart the strands of DNA’s double helix to extract the informa-tion contained in genes (the blueprints for the proteins) and translate it into the finished product. Thus, explaining how life began entails a serious paradox: it seems that it takes proteins—as well as the in-formation now stored in DNA—to make proteins.
cals present on the early earth.On the other hand, the paradox would disappear if the first organ-isms did not require proteins at all. Recent experiments suggest it ■
Other studies have supported the hypothesis that primitive would have been possible for genetic molecules similar to DNA or to cells containing molecules its close relative RNA to form spontaneously. And because these mol-similar to RNA could assemble ecules can curl up in different shapes and act as rudimentary catalysts, spontaneously, reproduce and they may have become able to copy themselves—to reproduce—with-evolve, giving rise to all life. out the need for proteins. The earliest forms of life could have been ■
Scientists are now aiming at simple membranes made of fatty acids—also structures known to creating fully self-replicating artificial organisms in the lab-oriform spontaneously—that envelope
BY Alonso RicARdo And JAck W. szostAk
f
Fresh clues hint at how the first living organisms arose from inanimate matter
E
very living cell, even the simplest bacterium, teems with mo-lecular contraptions that would be the envy of any nanotech-nologist. As they incessantly shake or spin or crawl around
the cell, these machines cut, paste and copy genetic molecules, shut-tle nutrients around or turn them into energy, build and repair cellu-lar membranes, relay mechanical, chemical or electrical messages—n othe list goes on and on, and new discoveries add to it all the time. It is virtually impossible to imagine how a cell’s machines, which are mostly protein-based catalysts called enzymes, could have formed spontaneously as life first arose from nonliving matter around 3.7 billion years ago. To be sure, under the right conditions some build-ing blocks of proteins, the amino acids, form easily from simpler chemicals, as Stanley L. Miller and Harold C. Urey of the University of Chicago discovered in pioneering experiments in the 1950s. But Key conceptS
■
Researchers have found a way that the genetic molecule RNA could have formed from chemi-gigoing from there to proteins and enzymes is a different matter. A cell’s protein-making process involves complex enzymes pull-ing apart the strands of DNA’s double helix to extract the informa-tion contained in genes (the blueprints for the proteins) and translate it into the finished product. Thus, explaining how life began entails a serious paradox: it seems that it takes proteins—as well as the in-formation now stored in DNA—to make proteins.
cals present on the early earth.On the other hand, the paradox would disappear if the first organ-isms did not require proteins at all. Recent experiments suggest it ■
Other studies have supported the hypothesis that primitive would have been possible for genetic molecules similar to DNA or to cells containing molecules its close relative RNA to form spontaneously. And because these mol-similar to RNA could assemble ecules can curl up in different shapes and act as rudimentary catalysts, spontaneously, reproduce and they may have become able to copy themselves—to reproduce—with-evolve, giving rise to all life. out the need for proteins. The earliest forms of life could have been ■
Scientists are now aiming at simple membranes made of fatty acids—also structures known to creating fully self-replicating artificial organisms in the lab-oriform spontaneously—that envelope
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第1个回答 2014-03-15
第2个回答 2014-03-15
My hero is jclsncosmlxajojis
第3个回答 2014-03-15
考英语作弊吧？^_^追问
家庭作业
追答噢，忘了今天星期六
追问对啊。。。
追答几年级了
追问废话。我这上面不是写着高一的嘛。。
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