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can life only arise from carbon based molecules ? on Mon Aug 24, 2009 3:33 pm
Can life only arise from carbon based molecules ?
http://www.google.com.br/search?hl=pt-BR&source=hp&q=can+life+only+arise+from+carbon+based+molecules+%3F&btnG=Pesquisa+Google&meta=&aq=f&oq=
http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry
The Alternatives to Carbon-Based Life
Silicon is the element most like carbon (it is directly beneath carbon on the periodic table), a fact picked up by more than one science fiction writer. But the silicon-silicon bond is extremely weak, and will fall apart in contact with water, for instance. A more likely possibility is an silicon-oxygen backbone to the molecule. The oxygen-silicon bond is strong, it is what defines sand, and a range of compounds based on this system, silicones, are manufactured in this world. Whether they could encompass the complexity required for life is impossible to say, but I would not rule it out. The problem with a silicon-oxygen world is; what is the driving force? Carbon based life can be divided between oxidizers (animals burn food to produce carbon dioxide) and reducers (plants use carbon dioxide in photosynthesis). Silicon based life does not have this potential, and would presumably more closely resemble fungi. While there may be lifeforms that eat the silica-fungi, they would be 'low energy' lifeforms, without the strength to move around.
Non carbon based life
http://www.google.com.br/search?q=non+carbon+based+life&btnG=Pesquisar&hl=pt-BR&sa=2
http://en.wikipedia.org/wiki/Carbon-based_life
http://www.physicsforums.com/showthread.php?t=67954
http://www.google.com.br/search?hl=pt-BR&source=hp&q=can+life+only+arise+from+carbon+based+molecules+%3F&btnG=Pesquisa+Google&meta=&aq=f&oq=
http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry
Perhaps the least unusual "alternative" biochemistry would be one with differing chirality of its biomolecules. In known Earth-based life, amino acids are almost universally of the L form and sugars are of the D form. Molecules of opposite chirality have identical chemical properties to their mirrored forms, so life that used D amino acids and/or L sugars may be possible.
It is somewhat questionable, however, whether this is even a truly alternative biochemistry. While it is certainly an alternative biostereochemistry, that molecules that are overwhelmingly found in one enantiomer can often be found in another in different (and often more primitive) organisms, such as members of Archea, make it an open topic whether an alternative biostereochemistry is really "alternative".
Scientists have speculated about the pros and cons of using atoms other than carbon to form the molecular structures necessary for life, but no one has proposed a theory employing such atoms to form all the molecular machinery necessary for life. Since humans are carbon-based beings and have never encountered any life that exists outside the earth’s environment, excluding the possibility of all other elements may be considered carbon chauvinism.
It is somewhat questionable, however, whether this is even a truly alternative biochemistry. While it is certainly an alternative biostereochemistry, that molecules that are overwhelmingly found in one enantiomer can often be found in another in different (and often more primitive) organisms, such as members of Archea, make it an open topic whether an alternative biostereochemistry is really "alternative".
Scientists have speculated about the pros and cons of using atoms other than carbon to form the molecular structures necessary for life, but no one has proposed a theory employing such atoms to form all the molecular machinery necessary for life. Since humans are carbon-based beings and have never encountered any life that exists outside the earth’s environment, excluding the possibility of all other elements may be considered carbon chauvinism.
The Alternatives to Carbon-Based Life
Silicon is the element most like carbon (it is directly beneath carbon on the periodic table), a fact picked up by more than one science fiction writer. But the silicon-silicon bond is extremely weak, and will fall apart in contact with water, for instance. A more likely possibility is an silicon-oxygen backbone to the molecule. The oxygen-silicon bond is strong, it is what defines sand, and a range of compounds based on this system, silicones, are manufactured in this world. Whether they could encompass the complexity required for life is impossible to say, but I would not rule it out. The problem with a silicon-oxygen world is; what is the driving force? Carbon based life can be divided between oxidizers (animals burn food to produce carbon dioxide) and reducers (plants use carbon dioxide in photosynthesis). Silicon based life does not have this potential, and would presumably more closely resemble fungi. While there may be lifeforms that eat the silica-fungi, they would be 'low energy' lifeforms, without the strength to move around.
Non carbon based life
http://www.google.com.br/search?q=non+carbon+based+life&btnG=Pesquisar&hl=pt-BR&sa=2
http://en.wikipedia.org/wiki/Carbon-based_life
http://www.physicsforums.com/showthread.php?t=67954
Last edited by elshamah888 on Sun Jan 03, 2010 3:46 am; edited 1 time in total
