Changing the Paradigm
Systems of the type I have described usually have been classified under the heading "metabolism first," which implies that they do not contain a mechanism for heredity. In other words, they contain no obvious molecule or structure that allows the information stored in them (their heredity) to be duplicated and passed on to their descendants. However a collection of small items holds the same information as a list that describes the items. For example, my wife gives me a shopping list for the supermarket; the collection of grocery items that I return with contains the same information as the list. Doron Lancet has given the name "compositional genome" to heredity stored in small molecules, rather than a list such as DNA or RNA.
The small molecule approach to the origin of life makes several demands upon nature (a compartment, an external energy supply, a driver reaction coupled to that supply, and the existence of a chemical network that contains that reaction). These requirements are general in nature, however, and are immensely more probable than the elaborate multi-step pathways needed to form a molecule that can function as a replicator.
Over the years, many theoretical papers have advanced particular metabolism first schemes, but relatively little experimental work has been presented in support of them. In those cases where experiments have been published, they have usually served to demonstrate the plausibility of individual steps in a proposed cycle. The greatest amount of new data has perhaps come from G¿nter W¿chtersh¿user and his colleagues at the Technische Universit¿t M¿nchen. They have demonstrated portions of a cycle involving the combination and separation of amino acids, in the presence of metal sulfide catalysts. The energetic driving force for the transformations is supplied by the oxidation of carbon monoxide to carbon dioxide. They have not yet demonstrated the operation of a complete cycle or its ability to sustain itself and undergo further evolution. A "smoking gun" experiment displaying those three features is needed to establish the validity of the small molecule approach.
The principal initial task is the identification of candidate driver reactions--small molecule transformations (A to B in the example before) that are coupled to an abundant external energy source (such as the oxidation of carbon monoxide or a mineral). Once a plausible driver reaction has been identified, there should be no need to specify the rest of the system in advance. The selected components (including the energy source) plus a mixture of other small molecules normally produced by natural processes (and likely to have been abundant on the early Earth) could be combined in a suitable reaction vessel. If an evolving network were established, we would expect the concentration of the participants in the network to increase and alter with time. New catalysts that increased the rate of key reactions might appear, while irrelevant materials would decrease in quantity. The reactor would need an input device to allow replenishment of the energy supply and raw materials, and an outlet to permit the removal of waste products and chemicals that were not part of the network.
In such experiments, failures would be easily identified. The energy might be dissipated without producing any significant changes in the concentrations of the other chemicals or the chemicals might simply be converted to a tar, which would clog the apparatus. A success might demonstrate the initial steps on the road to life. These steps need not duplicate those that took place on the early Earth. It is more important that the general principle be demonstrated and made available for further investigation. Many potential paths to life may exist, with the choice dictated by the local environment.
An understanding of the initial steps leading to life would not reveal the specific events that led to the familiar DNA-RNA-protein-based organisms of today. However, because we know that evolution does not anticipate future events, we can presume that nucleotides first appeared in metabolism to serve some other purpose, perhaps as catalysts or as containers for the storage of chemical energy (the nucleotide ATP still serves this function today). Some chance event or circumstance may have led to the connection of nucleotides to form RNA. The most obvious function of RNA today is to serve as a structural element that assists in the formation of bonds between amino acids in the synthesis of proteins. The first RNAs may have served the same purpose, but without any preference for specific amino acids. Many further steps in evolution would be needed to "invent" the elaborate mechanisms for replication and specific protein synthesis that we observe in life today.
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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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