Saat penelitian ilmiah sudah begitu jauh orang Islam disini yang dungu-dungu
kayak anjing masih saja bersedia melahap bualan orang Arab primitif yang bilang
allah yang tidak berbukti ada itu menciptakan Adam ari tanah liat - kayak
tukang kendi begitu.
Harga diri, itulah yang tidak mereka miliki.
Web address:
http://www.sciencedaily.com/releases/2012/12/
121212130709.htm
Was Life Inevitable? New Paper Pieces Together Metabolism's Beginnings
--
Carbon fixing and other chemical sub-processes that together constitute
metabolism each comprise dozens of steps; some are quick and easy turnkey
reactions with simple molecules, others require highly specific chemical
helpers, or catalysts. The parts of metabolism that guide carbon fixation
through its unstable intermediate stages fall into the latter category,
requiring help. But these seemingly unlikely reactions are remarkably
consistent across all living systems. (Credit: © amenic181 / Fotolia)
__
Dec. 12, 2012 Describing how living organisms emerged from Earth's abiotic
chemistry has remained a conundrum for scientists, in part because any credible
explanation for such a complex process must draw from fields spanning the
reaches of science.
A new synthesis by two Santa Fe Institute researchers offers a coherent picture
of how metabolism, and thus all life, arose. The study, published December 12,
2012, in the journal Physical Biology, offers new insights into how the complex
chemistry of metabolism cobbled itself together, the likelihood of life
emerging and evolving as it did on Earth, and the chances of finding life
elsewhere.
"We're trying to bring knowledge across disciplines into a unified whole that
fits the essentials of metabolism development," says co-author Eric Smith, a
Santa Fe Institute External Professor.
Creating life from scratch requires two abilities: fixing carbon and making
more of yourself. The first, essentially hitching carbon atoms together to make
living matter, is a remarkably difficult feat. Carbon dioxide (CO2), of which
Earth has plenty, is a stable molecule; the bonds are tough to break, and a
chemical system can only turn carbon into biologically useful compounds by way
of some wildly unstable in-between stages.
As hard as it is to do, fixing carbon is necessary for life. A carbon
molecule's ability to bond stably with up to four atoms makes it phenomenally
versatile, and its abundance makes it suitable as a backbone for trillions of
compounds. Once an organized chemical system can harness and manipulate carbon,
it can expand and innovate in countless ways.
In other words, carbon fixation is the centerpiece of metabolism -- the basic
process by which cells take in chemicals from their environments and build them
into products they need to live. It's also the link between the geochemistry of
Earth and the biochemistry of life.
In a paper earlier this year, Smith and Santa Fe Institute Omidyar Fellow
Rogier Braakman mapped the most primitive forms of carbon fixation onto major,
early branching points in the tree of life (PLoS Computational Biology, April
18, 2012). Now, the two researchers have drawn from geochemistry, biochemistry,
evolution, and ecology to detail the likeliest means by which molecules lurched
their way from rocks to cells.
Their 62-page "Logic of Metabolism" paper presents a new, coherent picture of
how this complex system fits together.
What started as wonky geochemical mechanisms were sequentially replaced and
fortified by biological ones, the authors believe. "Think of life like an onion
emerging in layers, where each layer functions as a feedback mechanism that
stabilizes and improves the ability to fix carbon," says Braakman.
Carbon fixing and other chemical sub-processes that together constitute
metabolism each comprise dozens of steps; some are quick and easy turnkey
reactions with simple molecules, others require highly specific chemical
helpers, or catalysts.
The parts of metabolism that guide carbon fixation through its unstable
intermediate stages fall into the latter category, requiring help. But these
seemingly unlikely reactions are remarkably consistent across all living
systems. In fact, says Braakman, their ubiquity and the difficulty with which
they are forged make them the chemical constraints within which all living
systems operate -- in a sense, the scaffolding for the tree of life.
It's these dependable regularities of hierarchy and modularity, amid the
panoply of reactions comprising metabolism, that stabilize the system and
enable its complexity.
Braakman and Smith describe specific features of metabolism and sub-divide
helper metabolites by their functions. For example, vitamin B9, a complex
molecule in the 'cofactor' class, facilitates the (otherwise unstable)
incorporation of one-carbon compounds into metabolism.
In mapping the chemical pathways to life's emergence, the researchers touch on
a more existential question: How likely was it for life to have developed at
all? Extraordinarily so, says Braakman. "Metabolism appears to be an 'attractor
state' within organic chemistry, where it was likely to be selected regardless
of earlier stages of chemical evolution" in the chaotic, high-energy conditions
of prebiotic Earth, he says.
Can it happen elsewhere? Possibly, even probably, he says. Rocky planets
usually have cores chemically similar to ours, so if a planet is volcanically
(and perhaps tectonically) active and has an ocean, it will probably have
hydrothermal vents that spew chemicals, creating the potential conditions for
life, Braakman says. In fact, the physics of star and planet formation make the
chances of such conditions pretty reasonable.
Smith cautions, however, that we still have much to learn about the chemical
and physical conditions that might lead to life-like organization, but he hopes
their paper will at least "lead to experimental questions that focus more
directly on the key functions that link metabolism to geochemistry."
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Story Source:
The above story is reprinted from materials provided by Santa Fe Institute.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal References:
Rogier Braakman, Eric Smith. The compositional and evolutionary logic of
metabolism. Physical Biology, 2013; 10 (1): 011001 DOI:
10.1088/1478-3975/10/1/011001
Rogier Braakman, Eric Smith. The Emergence and Early Evolution of
Biological Carbon-Fixation. PLoS Computational Biology, 2012; 8 (4): e1002455
DOI: 10.1371/journal.pcbi.1002455
Need to cite this story in your essay, paper, or report? Use one of the
following formats:
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MLA
Santa Fe Institute (2012, December 12). Was life inevitable? New paper pieces
together metabolism's beginnings. ScienceDaily. Retrieved December 13, 2012,
from http://www.sciencedaily.com /releases/2012/12/121212130709.htm
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of
ScienceDaily or its staff.
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