The Limits of Organic Life in Planetary Systems (2007) / Chapter Skim
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7 Life Detection and Biomarkers
7 Life Detection and Biomarkers
Pages 80-83
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From page 80... ...
In chemical processes, left- and right-handed molecules are generally formed in equal amounts, unless chiral reagents, catalysts, or surfaces are present to introduce a bias. Also, some organisms may synthesize the same chiral compound in different enantiomeric forms (e.g., bacterial peptide toxins)
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From page 81... ...
Moreover, biotic processes display an enantiomeric excess; e.g., left-handed amino acids and right-handed sugars almost exclusively predominate in living systems. Carbon atoms bearing four different substituents are said to be chiral centers.
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From page 82... ...
However, the data on enantiomeric excess are also consistent with a biotic origin, The larger asteroids may have stayed clement inside for several hundreds of millions of years, raising the possibility that life, or some borderline form, emerged there. This would be the case if the Murchison meteorite originated in an asteroid (or a comet)
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From page 83... ...
Vertical height is proportional to the change in free energy (G)
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