Life With Small Molecules
Nobel Laureate Christian de Duve has called for "a rejection of improbabilities so incommensurably high that they can only be called miracles, phenomena that fall outside the scope of scientific inquiry." DNA, RNA, proteins and other elaborate large molecules must then be set aside as participants in the origin of life. Inanimate nature provides us with a variety of mixtures of small molecules, whose behavior is governed by scientific laws, rather than by human intervention.
Fortunately, an alternative group of theories that can employ these materials has existed for decades. The theories employ a thermodynamic rather than a genetic definition of life, under a scheme put forth by Carl Sagan in the Encyclopedia Britannica: A localized region which increases in order (decreases in entropy) through cycles driven by an energy flow would be considered alive. This small-molecule approach is rooted in the ideas of the Soviet biologist Alexander Oparin, and current notable spokesmen include de Duve, Freeman Dyson of the Institute for Advanced Study, Stuart Kauffman of the Santa Fe Institute, Doron Lancet of the Weizmann Institute, Harold Morowitz of George Mason University and the independent researcher G¿nter W¿chtersh¿user. I estimate that about a third of the chemists involved in the study of the origin of life subscribe to theories based on this idea. Origin-of-life proposals of this type differ in specific details; here I will try to list five common requirements (and add some ideas of my own).
(1) A boundary is needed to separate life from non-life. Life is distinguished by its great degree of organization, yet the second law of thermodynamics requires that the universe move in a direction in which disorder, or entropy, increases. A loophole, however, allows entropy to decrease in a limited area, provided that a greater increase occurs outside the area. When living cells grow and multiply, they convert chemical energy or radiation to heat at the same time. The released heat increases the entropy of the environment, compensating for the decrease in living systems. The boundary maintains this division of the world into pockets of life and the nonliving environment in which they must sustain themselves.
Today, sophisticated double-layered cell membranes, made of chemicals classified as lipids, separate living cells from their environment. When life began, some natural feature probably served the same purpose. David W. Deamer of the University of California, Santa Cruz, has observed membrane-like structures in meteorites. Other proposals have suggested natural boundaries not used by life today, such as iron sulfide membranes, mineral surfaces (in which electrostatic interactions segregate selected molecules from their environment), small ponds and aerosols.
(2) An energy source is needed to drive the organization process. We consume carbohydrates and fats, and combine them with oxygen that we inhale, to keep ourselves alive. Microorganisms are more versatile, and can use minerals in place of the food or the oxygen. In either case, the transformations that are involved are called redox reactions. They involve the transfer of electrons from an electron rich (or reduced) substance to an electron poor (or oxidized) one. Plants can capture solar energy directly, and adapt it for the functions of life. Other forms of energy are used by cells in specialized circumstances--for example, differences in acidity on opposite sides of a membrane. Yet others, such as radioactivity and abrupt temperature differences, might be used by life elsewhere in the universe. Here I will consider redox reactions as the energy source.
(3) A coupling mechanism must link the release of energy to the organization process that produces and sustains life. The release of energy does not necessarily produce a useful result. Chemical energy is released when gasoline is burned within the cylinders of my automobile, but the vehicle will not move unless that energy is used to turn the wheels. A mechanical connection, or coupling, is required. Each day, in our own cells, each of us degrades pounds of a nucleotide called ATP. The energy released by this favorable reaction serves to drive processes that are less favorable but necessary for our biochemistry. Linkage is achieved when the reactions share a common intermediate, and the process is speeded up by the intervention of an enzyme. One assumption of the small-molecule approach is that coupled reactions and primitive catalysts sufficient to get life started exist in nature.
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11 Comments
Add CommentHomeopatics as an Energy Network -
Reply | Report Abuse | Link to thisOne can conjecture that as in the human body just one germ can produce a large colony, also really
small quantities of homeopatic moleclules "reproduce" to larger amounts in cells and tissues (energy networks).
May be only just for small times but enough to induce health
benefits.
hope to hear your opinions
Marco Magagnini, Ph.D - Milan
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Edited by Marco Maga at 12/03/2007 11:05 AM
Do you see prions, which are arguably heritable material in the absence of nucleic acids, as supporting the theory of metabolism first?
Reply | Report Abuse | Link to thisThis is my opinion of life:
Reply | Report Abuse | Link to thisOur universe is like a rugby ball and v r just a dot moving across it from the starting point of the Big Bang n now it's moving towards the end of the universe at an accelerating pace (Dark forces). There is an evidence of the accelerating Dark Forces by some of the scientists' observation: the Milky Way Galaxy is getting apart from the nearest galaxy (Andromeda) at an increasing distance. But im not that agree wif this comment. The reason of our galaxy is getting further apart wif the other galaxy may be due to differences in masses. The Andromeda Galaxy may has a higher mass than our Milky Way n since both of the galaxy is moving in the vacuum condition, it will result in an increasing interval of distance.
(Assume there's a multiverse)
When the galaxies is moving toward the end of the universe, everything will move faster n faster in the vacuum condition n results in the speed of greater than light. When this occurs, an extremely high gravitivity forces created and then everything will move in a slow pace n crushed into a single point like a melting pot. Wat will happen next? A massive blackhole will be created n everything like our galaxy will be sucked into it and causes a new Big Bang in the other dimension of universe. There it goes, everything starts again in the new dimension of universe! If this is true, life is just like a cycle. We will bcome ourselves again for infinitive times!
My conclusion is: Life is not simply created for no reason so as the Big bang theory. Everything is not simply pop out or exist for no reason! If those DNA n RNA theories of origin of life r used to prove the creation of life, it may make sense. But it's still not enuf evidences to prove "why u r you, not me?" "why i am myself, not u?"... There's no such answer yet till now on the scientific aspect. If u r not convinced wif the above statement, be optimistic. If u r given life for being u now, there will be another time that u will be given life again to become other things else!
prions are know to assume the beta amyloid structure.......and they are NOT SELF Replicated.When there is pressure with normal proteins...the normal ones turn into the amyloid form.(Thats not what you call self..is it?)
Reply | Report Abuse | Link to thisI consider them as malformed proteins that did not get eliminated because of their ability to convert normal proteins to amyloid form.
Life's Manifest
Reply | Report Abuse | Link to thisRecapitulation of some earlier notes on
The Drive, Nature And Purpose Of Life: Scientific Comprehension
http://www.physforum.com/index.php?showtopic=14988&st=195&#entry330517
A. Uniqueness Of science among human artifacts
ALL aspects of our culture are, of course, anthropoartifacts, including science. Yet among those artifacts science has a distinct uniqueness for us.
During the recent several centuries in the course of human history humans have been developing science at an accelerating rate as a provider of convincing, ever closer approaching, approximate models of the real world.
B. The drive and nature of life
The drive of life and of its evolution is to enhance the functionality and survivability of the genes, in order to maintain and enhance Earth-biosphere's temporary constrained energy storage and to maintain it BIO as long as possible.
It is the genes, life's prime strata organisms, that evolve, and the evolution of genomes, the 2nd stratum of life, and of the 3rd life stratum cellular organisms, is an interenhancing consequence of their genes' evolution.
C. The nature of life
Earth Life: 1. a format of temporarily constrained energy, retained in temporary constrained genetic energy packages in forms of genes, genomes and organisms 2. a real virtual affair that pops in and out of existence in its matrix, which is the energy constrained in Earth's biosphere.
Earth organism: a temporary self-replicable constrained-energy genetic system that supports and maintains Earth's biosphere by maintenance of genes.
Gene: a primal Earth's organism. (1st stratum organism)
Genome: a multigenes organism consisting of a cooperative commune of its member genes. (2nd stratum organism)
Cellular organisms: mono- or multi-celled earth organisms. (3rd stratum organism)
D. Update of underlying life sciences conception is thus feasible
- First were independent individual genes, Earth's primal organisms.
- Genes aggregated cooperatively into genomes, multigenes organisms, with genomes' organs.
- Simultaneously or consequently genomes evolved protective and functional membranes, organs.
- Then followed cellular organisms, with a variety of outer-cell membrane shapes and
functionalities.
This conception is a scientific, NOT TECHNOLOGICAL, life-science innovation.
It is tomorrow's comprehension of life and of its evolution.
IT IS FRAUGHT WITH INTRIGUING DARWINIAN EVOLUTION IMPLICATIONS.
IT IS FRAUGHT WITH INTRIGUING TECHNOLOGICAL DEVELOPMENTS POTENTIALS.
E. The purpose of OUR, human, life
The purpose of OUR life and its promotion is ours to formulate and set. It derives solely from our cognition.
Suggesting,
Dov Henis
http://blog.360.yahoo.com/blog-P81pQcU1dLBbHgtjQjxG_Q--?cq=1
Very informative article when it comes down to understanding the way proteins are a functional unit in life.
Reply | Report Abuse | Link to thisSo far the best alternative hypothesis I've read on the topic of life's origins.
Reply | Report Abuse | Link to thisI have a suggestion for testing this hypothesis with experiments: it is probably safe to assume that our planet has been on a 24 hour cycle due to it's rotation and the distance from the sun probably hasn't changed much; the sun probably contributed to numerous UV or heat induced reactions on the Earth's surface. Most living things on this planet adhere to the 24 (+variation) hour cycle, the circadian rhythm (with the exception of some cyanobacteria and deep sea species, not sure about this). there are probably many slow-acting reactions, i.e., those with roughly a 24 hour cycle that can be tested in the lab for a cyclical pattern. In fact, they do not have to be 24 hours to test the stated hypothesis given that any cycle can lead to the development of an organized pattern. Given that this state of the planet's environment probably hasn't changed drastically (e.g., from a 100 hour day), it is probable that the earliest cycles were 24 hour based.
comments welcome.
MEch
-origin of life huh, i don't know but writing and assignment on this really helped me out to grasp the concepts of the requirements of life and the difference between "small molecules" that might have started life or "RNA first". Long article but got a point across....
Reply | Report Abuse | Link to thisI wonder how the history of the Solar System and the Earth/Moon pair could colour our understanding of this process.
Reply | Report Abuse | Link to thisI would expect the frequent, violent tides of hot water during the early life of the Earth,when the Moon was very close and the Earth was cool enough for water to condense and accumulate, would provide an vigorous environment for rapid evolution and distribution of the chemical building blocks for 'life'. But would the level of complexity that could develop at that time be constrained by these same conditions.
The latest theories seem to suggest that both the large, influential moon and the water arrived on the Earth by impact. What are the chances of this happening in such a way and at such a time that they were not absorbed or distributed, but remained localised enough to have the observed impact on the Earth.
Could the resulting conditions and their impact on 'life' be so rare as to be almost unique?
How would life have developed without the mixing & distribution possible in a large body of well-stirred, hot, volitile liquid? Could it have survived an "extinction-event" meteor impact, for example?
Unbelievable! Origin Of Life Pre-Metabolism?
Reply | Report Abuse | Link to thisThe Wheel has Just Been Reinvented!
Read All About It!
What Came First in the Origin of Life? New Study Contradicts the 'Metabolism First' Hypothesis
http://www.sciencedaily.com/releases/2010/01/100108101433.htm
Dov Henis
(Comments From The 22nd Century)
Updated Life's Manifest May 2009
http://www.the-scientist.com/community/posts/list/140/122.page#2321
28Dec09 Implications Of E=Total[m(1 + D)]
http://www.the-scientist.com/community/posts/list/184.page#4587
Cosmic Evolution Simplified
http://www.the-scientist.com/community/posts/list/240/122.page#4427
PS: Just reflect about sleep and chirality... DH
I am surprised that this research has not yet attracted a mass of religious zealots who are horrified that humans are trying to take over God's primary feat - the creation of life. This hubris can result in nothing less than what happened to those who constructed the Tower of Babel, stuff like that. Anyway, I hope I live to see my fellow humans achieve this goal. For now, I carry a card in my wallet that says: I am an atheist. In case for accident call a doctor
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