De oerknal... Bevestigd!

[praha]

Oorspronkelijk geplaatst door ElFlamencoLoco

...........Vragen als "wat heeft de oerknal veroorzaakt?" zijn dus totaal zinloos. De oerknal is het enige fenomeen waarvan het onduidelijk is of er wel een oorzaak van aan de basis lag. Alle andere fenomenen ná de oerknal kunnen we perfect duiden, zelfs die tijdens de allereerste nanoseconden erna.

dat heb je zéér mooi geschets...

Misschien dat hier de ondefinieerbare, onbegrijpbare Instantie kan geplaatst worden die gelovigen doorgaans God noemen? En dan krijgt het epitheton "Schepper" opnieuw een heel actuele betekenis, die de wetenschap geenszins uitsluit en door de wetenschap evenmin uit te sluiten is. (Uiteraard ook niet te bewijzen.)

dit vindt ik toch wel steeds het toppunt hoor...
mij niet gelaten want ik noem mezelf geen atheïst ...
ik vraag me alleen af waarom heb je nog een 'iets' meer nodig als de quantumfysica ( in veronderstelling ) je perfect het antwoord geeft op dat 'niets' ?

[ronnydecoster]

De gedachten dat een intelligente Ontwerper het universum tot bestaan heeft gebracht is in overeenstemming met wat sommige geleerden de "big-bang-theorie" (theorie van de oerexplosie) voor het ontstaan van het heelal noemen. De laaste jaren heeft deze theorie de overhand gekregen op de "steady-state"-theorie, op grond waarvan men beweert dat het universum eeuwig heeft bestaan en dus zonder begin is. Maar wij behoeven ons niet te verlaten op het drijfzand van de moderne wetenschappelijke theorieën om te bewijzen dat er een Schepper is. De Schepper zelf maakt namelijk duidelijk wie en wat hij is: Dit heeft Jehovah gezegd .... Ik zelf heb de aarde gemaakt en heb zelfs de mens daaop geschapen. Ik --- mijn eigen handen hebben de hemelen uitgespannen en aan heel het heerleger ervan heb ik bevel gegeven. (Jes.45:11-12). De bewijzen dat hij de Schepper is, kunnen in oneinding veel dingen die wij om ons heen zien, waargenomen en bewonderd worden.

Zoals hoe de mens geschapen is: Ongetwijfeld hebben wij allemaal wel eens de kleine vingertjes van de baby gestreeld --- zo zacht, zo prachtig van vorm, zo fijn--- veel verfijnder dan de klauwen van een dier! En ongetwijfeld hebben wij erover nagedacht hoe het kleine leventje van die baby begon doordat een eicel van de moeder, ter grootte van een speldepunt, werd verenigd met een zaadcel van de vader, veel te klein om het met het blote oog gezien te worden. Ja , wij hebben allemaal een klein begin gehad, als een eicel die zich deelde en deelde, en zich steeds maar bleef delen, totdat uiteindelijk de meer dan 10.000.000.000.000 cellen waaruit een volwassen mens bestaat, "wisten" wanneer ze moesten ophouden met delen.
Groet Ronny

[ronnydecoster]

Als er geen Schepper is, moet het leven vanzelf zijn begonnen. Vele denken dit. Maar wordt deze zienwijze door toenemende kennis ondersteund?

In de oudheid zagen de Egytenaren plotseling scarabeeën of mestkevers uit de grond te voorschijn komen, en zij geloofde dat deze kevers uit zichzelf waren ontstaan. De Encyclopedia Americana vermeldt: Vaak werden enorme mestkevers op de modderbanken langs de rivier de Nijl aangetroffen en dit gaf ondersteuning aan het geloof in spontane generatie (Deel 24, blz 336, uitgave van 1977�*. Maar wat was er in werkelijkheid gebeurd? De wijfjes van deze keversoort hadden mest tot een balletje gerold, er eitjes in gelegd en ze begraven. De eitjes waren uitgekomen, de larven hadden zich gevoed met de mest en waren later als kevers te voorschijn gekomen. Alles welbeschouwd was het dus geen spontane generatie.
De Griekse filosofen onderwezen spontane generatie van het leven, dat wil zeggen levende organismen zouden vanzelf uit onbezielde stof ontstaan. In de Vijfde eeuw V.G.T. stelden zowel Anaxagoras als Empédocles hier geloof in. Een eeuw later meende Arisroteles dat wormen en slakken door rottingsprocessen werden voortgebracht. Nog tot in de zeventiende eeuw G.T. werd door wetenschapsmensen als Francis Bacon en William Harvey spontane generatie onderwezen.
In die zelfde eeuw toon de Redi echter aan dat maden alleen in vlees verschenen nadat door vliegen eitjes op dat vlees gelegd. Bacteriën werden ontdekt, en ze werden begroet als een bewijs van spontane generatie totdat in de achttiende eeuw Spallanzani aantoonde dat ze ontkiemden uit sporen. Een eeuw later werd de kwestie door de onderzoekingen van Pasteur definitief beslist. Hij bewees dat leven slechts uit leven afkomstig is. Wetenschapmensen aanvaarden die zienswijze nu, maar vele houden vol dat zo'n twee- tot drieduizend miljoen jaar geleden wel spontaan is ontstaan.

Groet Ronny

[lantjes]

Oorspronkelijk geplaatst door ronnydecoster

Als er geen Schepper is, moet het leven vanzelf zijn begonnen. Vele denken dit. Maar wordt deze zienwijze door toenemende kennis ondersteund?

In de oudheid zagen de Egytenaren plotseling scarabeeën of mestkevers uit de grond te voorschijn komen, en zij geloofde dat deze kevers uit zichzelf waren ontstaan. De Encyclopedia Americana vermeldt: Vaak werden enorme mestkevers op de modderbanken langs de rivier de Nijl aangetroffen en dit gaf ondersteuning aan het geloof in spontane generatie (Deel 24, blz 336, uitgave van 1977�*. Maar wat was er in werkelijkheid gebeurd? De wijfjes van deze keversoort hadden mest tot een balletje gerold, er eitjes in gelegd en ze begraven. De eitjes waren uitgekomen, de larven hadden zich gevoed met de mest en waren later als kevers te voorschijn gekomen. Alles welbeschouwd was het dus geen spontane generatie.
De Griekse filosofen onderwezen spontane generatie van het leven, dat wil zeggen levende organismen zouden vanzelf uit onbezielde stof ontstaan. In de Vijfde eeuw V.G.T. stelden zowel Anaxagoras als Empédocles hier geloof in. Een eeuw later meende Arisroteles dat wormen en slakken door rottingsprocessen werden voortgebracht. Nog tot in de zeventiende eeuw G.T. werd door wetenschapsmensen als Francis Bacon en William Harvey spontane generatie onderwezen.
In die zelfde eeuw toon de Redi echter aan dat maden alleen in vlees verschenen nadat door vliegen eitjes op dat vlees gelegd. Bacteriën werden ontdekt, en ze werden begroet als een bewijs van spontane generatie totdat in de achttiende eeuw Spallanzani aantoonde dat ze ontkiemden uit sporen. Een eeuw later werd de kwestie door de onderzoekingen van Pasteur definitief beslist. Hij bewees dat leven slechts uit leven afkomstig is. Wetenschapmensen aanvaarden die zienswijze nu, maar vele houden vol dat zo'n twee- tot drieduizend miljoen jaar geleden wel spontaan is ontstaan.

Groet Ronny

Het juiste mengsel chemische elementen, H, O², .... een streepje bliksem en hopla, eencelligen op termijn , reeds op laboschaal bewezen....

[ronnydecoster]

Oorspronkelijk geplaatst door lantjes

Het juiste mengsel chemische elementen, H, O², .... een streepje bliksem en hopla, eencelligen op termijn , reeds op laboschaal bewezen....

Het is een gewaagde veronderstelling dat de primitieve atmosfeer van de aarde de noodzakelijke gassen zou hebben bevat, en dan bovendien nog in de juiste verhouding , om de hele keten van reacties te doen beginnen. Er is geen bewijs waardoor dit wordt ondersteund.

Groet Ronny

[Judokus]

Oorspronkelijk geplaatst door lantjes

Het juiste mengsel chemische elementen, H, O², .... een streepje bliksem en hopla, eencelligen op termijn , reeds op laboschaal bewezen....

Is dat echt? Wil je me een link naar die publicatie eens bezorgen, ik wil dat graag eens lezen.

[Nynorsk]

@ the pinguin:

*knuf*

jeminee.

[lantjes]

Oorspronkelijk geplaatst door Judokus

Is dat echt? Wil je me een link naar die publicatie eens bezorgen, ik wil dat graag eens lezen.

'k heb daar ondertussen enkele jaren geleden op de BBC (horizon?) eens een reportage over gezien....dat wordt even zoeken.

Het was in een gesloten omgeving met de elementen dewelke men denkt aanwezig te zijn geweest in het prille begin van het leven op aarde. Daar voegde men electriciteit aan toe en men kreeg verbindingen die de basis vormen voor "leven".

'k zoek dit eens op....

[ronnydecoster]

De wetenschappelijke methode, is als volgt : Observeer wat er gebeurt ; vorm op basis van deze waarnemingen een theorie met betrekking tot waarnemingen een theorie door verdere waarnemingen en door experimenten en kijk of de op de theorie gebaseerde voorspellingen uitkomen. Wordt deze methode door evolutionisten toegepast?
Astronoom Robert Jastrow zegt: Tot hun verdriet komen geleerder niet tot een bevredigend antwoord, omdat de chemici er nooit in zijn geslaagd het experiment van moeder natuur : leven scheppen uit niet-levende materie, te herhalen. De natuurwettenschap weet niet hoe het is gebeurd. --- Machine en intellect (1982), blz 24.
De evolutionist Loren Eiseley gaf toe : Na de theoloog te hebben berist omdat hij zich op mythen en wonderen verlaat, bevond de wettenschap zich in de weinig benijdenswaardige positie een eigen mythologie te moeten creëren : namelijk de veronderstelling dat gebeurtenissen waarvan na lang proberen niet bewezen kon worden dat ze thans plaatsvinden, wel in het oerverleden hadden plaatsgevonden. --- The Immense Journey (New York, 1957). blz 199.
De natuurkundige H.S. Lipson zei: De enige aanvaardbare verklaring is schepping . Ik weet dat dit voor natuurkundige een gruwel is, zoals het dat voor mij ook is, maar wij moeten een theorie die ons niet bevalt, niet verwerpen wanneer ze door experimenten wordt gestaafd. --- Physics Bulletin, 1980, deel 31, blz 138.
Groet Ronny

[lantjes]

Oorspronkelijk geplaatst door Judokus

Is dat echt? Wil je me een link naar die publicatie eens bezorgen, ik wil dat graag eens lezen.

al snel iets gevonden

Miller-Urey experiment


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The Miller-Urey experiment attempts to recreate the chemical conditions of the primitive Earth in the laboratory, and synthesized some of the building blocks of life.


The Miller-Urey experiment (or Urey-Miller experiment) was an experiment that simulated hypothetical conditions present on the early Earth and tested for the occurrence of chemical evolution (the Oparin and Haldane hypothesis stated that conditions on the primitive Earth favored chemical reactions that synthesized organic compounds from inorganic precursors; the Miller-Urey tested this hypothesis). The experiment is considered to be the classic experiment on the origin of life. It was conducted in 1953 by Stanley L. Miller and Harold C. Urey at the University of Chicago.
Contents

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• <LI class=toclevel-1>1 Experiment and interpretation <LI class=toclevel-1>2 Other experiments <LI class=toclevel-1>3 Earth's early atmosphere <LI class=toclevel-1>4 Recent related studies <LI class=toclevel-1>5 See also
• 6 References

//
[edit]

Experiment and interpretation


The experiment


The experiment used water (H2O), methane (CH4), ammonia (NH3) and hydrogen (H2). The chemicals were all sealed inside a sterile array of glass tubes and flasks connected together in a loop, with one flask half-full of liquid water and another flask containing a pair of electrodes. The liquid water was heated to induce evaporation, sparks were fired through the atmosphere and water vapor to simulate lightning, and then the atmosphere was cooled again so that the water could condense and trickle back into the first flask in a continuous cycle.
At the end of one week of continuous operation, Miller and Urey observed that as much as 10-15% of the carbon within the system was now in the form of organic compounds. Two percent of the carbon had formed amino acids, including 13 of the 21 that are used to make proteins in living cells, with glycine as the most abundant. However, there are two forms of amino acids, referred to as left-handed and right-handed amino acids. Only left-handed amino acids are found in living organisms, with the exception of some exotic marine life and the cell walls of bacteria, but the Miller-Urey experiment, and all subsequent experiments, succeeded in creating right- and left-handed amino acids in roughly a 50/50 ratio.
The molecules produced were simple organic molecules, far from a complete living biochemical system, but the experiment established that the hypothetical processes could produce some building blocks of life without requiring life to synthesize them first.
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Other experiments

This experiment inspired many experiments in a similar vein. In 1961, Joan Oró found that amino acids could be made from hydrogen cyanide (HCN) and ammonia in a water solution. He also found that his experiment produced a large amount of the nucleotide base adenine. Experiments conducted later showed that the other RNA and DNA bases could be obtained through simulated prebiotic chemistry with a reducing atmosphere.
There were similar (electric discharge) experiments on the origin of life prior to or contemporaneous with Miller-Urey. An article in The New York Times, March 8, 1953, page E9, titled "Looking Back Two Billion Years" describes the work of Wollman [sic] (William) M. MacNevin at Ohio State University. (The Miller Science paper was not published until May 1953.) MacNevin was passing 100,000 volt sparks through methane and water vapor and produced "resinous solids" that were "too complex for analysis." The article describes other early earth experiments being done by MacNevin. It is not clear if he ever published any of these results in the primary scientific literature.
[edit]

Earth's early atmosphere

There have been a number of objections to the implications derived from these experiments. Scientists believe that Earth's original atmosphere might contain less of the reducing molecules as was thought at the time of Miller-Urey experiment:
Originally it was thought that the primitive secondary atmosphere contained mostly NH3 and CH4. However, it is likely that most of the atmospheric carbon was CO2 with perhaps some CO and the nitrogen mostly N2. The reasons for this are (a) volcanic gas has more CO2, CO and N2 than CH4 and NH3 and (b) UV radiation destroys NH3 and CH4 so that these molecules would have been short-lived. UV light photolyses H2O to H· and ·OH radicals. These then attack methane, giving eventually CO2 and releasing H2 which would be lost into space. In practice gas mixtures containing CO, CO2, N2, etc. give much the same products as those containing CH4 and NH3 so long as there is no O2. The H atoms come mostly from water vapor. In fact, in order to generate aromatic amino acids under primitive earth conditions it is necessary to use less hydrogen-rich gaseous mixtures. Most of the natural amino acids, hydroxyacids, purines, pyrimidines, and sugars have been produced in variants of the Miller experiment.[1] More recent results may question these conclusions. The University of Waterloo and University of Colorado conducted simulations in 2005 that indicated that the early atmosphere of Earth could have contained up to 40 percent hydrogen---implying a much more hospitable environment for the formation of prebiotic organic molecules. The escape of hydrogen from Earth's atmosphere into space may have occurred at only one percent of the rate previously believed based on revised estimates of the upper atmosphere's temperature.[2] One of the authors, Prof. Owen Toon notes: "In this new scenario, organics can be produced efficiently in the early atmosphere, leading us back to the organic-rich soup-in-the-ocean concept... I think this study makes the experiments by Miller and others relevant again." Outgassing calculations using a chondritic model for the early earth, (Washington University, September 2005) complement the Waterloo/Colorado results in re-establishing the importance of the Miller-Urey experiment.[3]
Although lightning storms are thought to have been very common in the primordial atmosphere, they are not thought to have been as common as the amount of electricity used by the Miller-Urey experiment implied. These factors suggest that much lower concentrations of biochemicals would have been produced on Earth than was originally predicted (although the time scale would be 100 million years instead of a week). Similar experiments, both with different sources of energy and with different mixtures of gases, have resulted in amino and hydroxy acids being produced; it is likely that at least some organic compounds would have been generated on the early Earth.
However, when oxygen gas is added to this mixture, no organic molecules are formed. Opponents of Miller-Urey hypothesis seized upon recent research that shows the presence of uranium in sediments dated to 3.7 Ga and indicates it was transported in solution by oxygenated water (otherwise it would have precipitated out) (Rosing & Frei 2004). These opponents argue that this presence of oxygen precludes the formation of prebiotic molecules via a Miller-Urey-like scenario, attempting to invalidate the hypothesis of abiogenesis. However, the authors of the paper are arguing that this presence of oxygen merely evidences the existence of photosynthetic organisms 3.7 Ga ago (a value about 200 Ma earlier than current values[4]), a conclusion which while pushing back the time frame in which Miller-Urey reactions and abiogenesis could potentially have occurred, would not preclude them. Though there is somewhat controversial evidence for very small (less than 0.1%) amounts of oxygen in the atmosphere almost as old as Earth's oldest rocks the authors are not in any way arguing for the existence of a strongly oxygen containing atmosphere occurring any earlier than previously thought, and they state: ". . . In fact most evidence suggests that oxygenic photosynthesis was present during time periods from which there is evidence for a non-oxygenic atmosphere".
Conditions similar to those of the Miller-Urey experiments are present in other regions of the solar system, often substituting ultraviolet light for lightning as the driving force for chemical reactions. On September 28, 1969, the Murchison meteorite that fell near Murchison, Victoria, Australia was found to contain over 90 different amino acids, nineteen of which are found in Earth life. Comets and other icy outer-solar-system bodies are thought to contain large amounts of complex carbon compounds (such as tholins) formed by these processes, in some cases so much so that the surfaces of these bodies are turned dark red or as black as asphalt. The early Earth was bombarded heavily by comets, possibly providing a large supply of complex organic molecules along with the water and other volatiles they contributed. (This could also imply an origin of life outside of Earth, which then migrated here. See: Panspermia)
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Recent related studies

During recent years, studies have been made of the amino acid composition of the products of "old" areas in "old" genes, defined as those that are found to be common to organisms from several widely separated species, assumed to share only the last universal ancestor (LUA) of all extant species. These studies found that the products of these areas are enriched in those amino acids that are also most readily produced in the Miller-Urey experiment. This suggests that the original genetic code was based on a smaller number of amino acids -- only those available in prebiotic nature -- than the current one. (Brooks et al. 2002).

[lantjes]

en voor de liefhebbers :

THE ORIGIN OF LIFE




About 4.8 Gigayears (Giga = 109) B.P. (= before present) a huge but very thin cloud of dust and gas condensed under the influence of gravitation into a large ball of gas (the sun) surrounded by smaller lumps of denser matter (planets). Heat was released by the gravitational collapse and also by the radioactivity of some elements present in the original dust. This heat raised the temperature of the planets, including Earth, far above their present values.

Elemental Composition of the Universe & Earth

Atoms per 100,000

Element Universe Earth Crust Life

H 92,700 120 2,900 60,600

He 7,200 <0.1 <0.1 0

O 50 48,900 60,400 26,700

Ne 20 <0.1 <0.1 0

N 15 0.3 7 2,400

C 8 99 55 10,700

Si 2.3 14,000 20,500 <1

Mg 2.1 12,500 1,800 11

Fe 1.4 18,900 1,900 <1

The universe consists mostly of H plus He. The heavier elements together comprise about 0.1% of the total. Planets such as the earth are composed of trace impurities in the universe which have concentrated at one point. The Earth is mostly Fe, Mg, Si, and O, with the other elements contributing 5% of the total. Life originated as a result of chemical reactions occurring (largely) in the atmosphere followed by reactions in the primeval oceans and lakes.

The Lithosphere of the Earth

The lithosphere consists of the core, the mantle and the crust. The crust consists mostly of the silicates of Fe, Al, Ca, Mg, Na, and K. The mantle is mostly Fe and Mg silicate with a small amount of Fe and heavy metal sulfides. The core is mostly a molten mixture of Fe and Ni.

The Primitive Hydrosphere

Most of the present ocean water (possible up to 90%) derives from outgassing by volcanic activity, hot springs, etc. the primitive earth thus had much less surface water. During the first few hundred million years of the Earth's existence, the water was in the form of stream, condensing later as the Earth cooled off.



Ancient Atmospheres

Primary Atmosphere

Originally Earth had an atmosphere mostly of H2 plus He. However, the mass of the Earth was too small to hold these light gases and they were lost into space.

Secondary Atmosphere

The Earth then accumulated a secondary atmosphere, due partly to outgassing from volcanoes, and partly to the reaction of condensing water vapor (formed as the Earth cooled) with minerals such as nitrides (hence NH3), carbides (hence CH4, CO, etc.) and sulfides (hence H2S). There was no free oxygen (any free O2 would have reacted with P, Si and metals such as molten iron to give minerals e.g. iron oxides, silicates, phosphates, etc.).

Volcanic Outgassing

Volcanic activity was much greater on the hotter primitive Earth. Volcanic gas consists mostly of steam (95%) and variable amounts of CO2, N2, SO2, H2S, S, HCl, B2O3, and smaller quantities of H2, CH4, SO3, NH3 and HF but no O2. Carbon dioxide is always the second major component (up to 4%).

Tertiary Atmosphere

The present atmosphere is of biological origin. Reactive gases such as NH3, CH4, etc., have been consumed. The inert components (N2, traces of Ar, Xe, etc.) remained unchanged and large amounts of oxygen have been produced by photosynthesis. This change did not occur until the evolution of the O2 evolving variant of photosynthesis, first seen in the cyanobacteria, about 2.5 Gyr B.P. The O2 content of the atmosphere reached 1% about 800 Myr B.P. and 10% about 400 Myr B.P. Today it is about 20%.

Evidence for the increase in O2 content of the atmosphere comes partly from the finding that rocks of different ages are oxidized to different extents. Thus rocks of age 1,800-2,500 Myr are found to contain UO2, FeS, ZnS and PbS and FeO, all of which are unstable in the presence of even small amouts of O2. Later rocks contain mostly Fe3+ rather than Fe2+, and more oxidized ores of U, Zn and Pb etc.



Time Scale for Origin of Planets and Life

Millions of Years Ago What Happened

20,000 Big Bang
4,600 Origin of planets and Sun

4,400 Earth cools enough for water to condense

3,500 Origin of life - probably thermophiles

3,000 Anaerobic photosynthetic bacteria

2,500 Cyanobacteria - oxygen appears

1,500 Eukaryotes (primitive algae)

1,000 Multicellular organisms

600 First skeletons & easily recognizable fossils

2 Homo erectus

0.2 Homo sapiens

0.006 Sumerians invent civilization

0.002 Roman Empire civilizes Europe

0.0004 British Empire civilizes World

0.00004 DNA double helix discovered

0.000004 you enrolled at SIU

0.0000004 you signed up for Micr425

Atmospheric Reactions

The primitive (secondary) atmosphere contained N2, H2O (vapor), NH3, H2S, CO and CO2. These reacted to give such small organic molecules as HCN and HCHO:

2CH4 + N2 ===> 2HCN +3H2

CO + NH3 ===> HCN +H2O

The HCN and HCHO continued to react and further products were formed e.g. in the atmosphere:

HCHO + NH3 ===> H2N-CH2OH ===> HN=CH2 + H2O
HN=CH2 + HCN ===> H2NCH2CN

In the primeval ocean:

H2NCH2-CN + 2H2O ===> H2NCH2COOH + NH3

This sequence of reactions (the Strecker synthesis) has formed glycine, the simplest amino acid. More complex reactions form more complex amino acids from other substrates. Replacement of NH3 with H2O vapor in the above reactions gives hydroxy acids (e.g. lactic acid) instead of amino acids.

These atmospheric reactions need a source of energy to drive them. On the primeval Earth there were a variety of possible energy sources.



Relative Energy Source of Energy

1000 a) Sunlight. 98% of sunlight photons are visible and of insufficient energy to promote chemical reactions. Of the ultraviolet-photons (<300 nm wavelength) only about 1% (those <200nm) would be highly effective. Today most of the ultraviolet is screened out by the ozone (O3) layer. In primeval times there was no ozone and UV rays penetrated freely.

100 b) Electric discharges (corona discharges, lightning).

70 c) Natural radioactivity. Most of the high energy radiation (i.e. more energetic than UV) comes from the interior of the earth. Uranium-238 and -235 and Thorium-232 give off alpha and gamma radiation. Potassium 40 is a gamma and beta emitter only. 4000 Myr ago there was about 4 times the amount of Uranium-238 and the overall radioactivity was perhaps three times the present level.

25 d) Shock waves in the atmosphere (from thunder and meteorite impact).

5 e) Solar wind.

5 f) Volcanic heat. Important locally.

g) Cosmic rays.


The relative energy is per unit surface area of the earth per year. (Ultraviolet is set to 1000). It is important to realize that molecular O2 would have destroyed the products of primitive atmospheric reactions. As regards the origin of life O2 is a highly toxic molecule whereas HCN, H2S, CO, and HCHO are life promoting.

The Miller Experiment

The theory of the origin of life was put forward by the Russian biochemist Alexandr Oparin in the 1920's. In the 1950's, Miller mimicked the primitive Earth atmospheric reactions. A mixture of methane, ammonia and water vapor was subjected to a high voltage discharge (to simulate lightning). Organic compounds were formed and dissolved in a flask of water, where further reaction is possible. There are many variants of this experiment (different gas compositions, different energy sources, etc.). As long as oxygen is excluded the results are similar. First aldehydes (e.g. HCHO, CH3CHO) and cyanides (HCN, NC-CN) are formed and later a large variety of organic compounds, mostly acids. Note that genuine biological compounds are formed together with isomers which are not found in living cells. For example, sarcosine and beta-alanine are both isomers of alanine. About 15% of the methane is converted to soluble organic molecules and quite a lot more is converted to un-analysable organic tar. Typical products are:

Molecule Name Relative Yield

H-COOH formic acid 1000

H2N-CH2-COOH glycine 275

HO-CH2-COOH glycolic acid 240

H2N-CH(CH3)-COOH alanine 150

HO-CH(CH3)-COOH lactic acid 135

H2N-CH2CH2-COOH beta-alanine 65

CH3-COOH acetic acid 65

CH3-CH2-COOH propionic acid 55

CH3-NH-CH2-COOH sarcosine 20

HOOC-CH2CH2-COOH succinic acid 17

H2N-CO-NH2 urea 9

HOOC-CH2CH2CH(NH2)-COOH glutamic acid 2.5

HOOC-CH2CH(NH2)-COOH aspartic acid 1.7



Originally it was thought that the primitive secondary atmosphere contained mostly NH3 and CH4. However, it is likely that most of the atmospheric carbon was CO2 with perhaps some CO and the nitrogen mostly N2. The reasons for this are (a) volcanic gas has more CO2, CO and N2 than CH4 and NH3 and (b) UV radiation destroys NH3 and CH4 so that these molecules would have been short-lived. UV light photolyses H2O to H· and ·OH radicals. These then attack methane, giving eventually CO2 and releasing H2 which would be lost into space.

In practice gas mixtures containing CO, CO2, N2, etc. give much the same products as those containing CH4 and NH3 so long as there is no O2. The H atoms come mostly from water vapor. In fact, in order to generate aromatic amino acids under primitive earth conditions it is necessary to use less hydrogen-rich gaseous mixtures. Most of the natural amino acids, hydroxyacids, purines, pyrimidines, and sugars have been produced in variants of the Miller experiment.

Some differences worth noting are:

a) Sulfur. Electric discharge results in the formation of ammonium thiocyanate from gas mixtures containing H2S. The production of cysteine and other sulfur containing compounds has been achieved using beta radiation.
b) Aromatic amino acids. Mixtures must be less rich in hydrogen to give aromatic instead of saturated compounds.

c) Catalysts. The presence of silica, quartz, or sand during heating of gas mixtures greatly increases the yield of more complex amino acids, including aromatics.

Phosphorus

One of the major problems of pre-biotic chemistry is how phosphorus could have entered into reactions. There is plenty of phosphorus available, but it is found as insoluble phosphate minerals.

a) Phosphates of Ca and other divalent metals are very insoluble, hence most of the phosphorus would precipitate as Ca phosphate derivatives e.g. fluoro-apatite Ca10(PO4)6F2

b) Most phosphorus experiments have used high concentrations of pyrophosphate or polyphosphoric acid and are therefore geologically implausible.

Synthesis and Destruction

Note that the same energy sources that produce organic molecules are also very effective at destroying them. Accumulation of organic material therefore requires removal of products from the reaction region - hence the imitation primeval ocean in the Miller experiment. Water shields molecules from UV and electric discharges. The survival of organic molecules on the primitive earth would have depended on their escape from UV radiation etc either by dissolution in seas or lakes or by adsorption to minerals. Organic molecules formed in the upper regions of the atmosphere would mostly have been destroyed again very quickly. Note that organic acids and in particular amino acids are ionic and therefore nonvolatile. Consequently once synthesized and safely in aqueous solution there is little tendency for such molecules to return to the atmosphere. The intermediates, such as aldehydes and cyanides are not only reactive but also volatile. Consequently these molecules do not accumulate as final products.



Primitive Earth Syntheses

a) Amino Acids e.g. Serine
Glycolaldehyde is formed from formaldehyde in the atmosphere and reacts by the Strecker reaction:

HCHO + HCHO ===> HOCH2CHO (glycolaldehyde)

HOCH2CHO + NH3 ===> HOCH2CH(OH)NH2

HOCH2CH(OH)NH2 ===> HOCH2CH=NH + H2O

HOCH2CH=NH + HCN ===> HOCH2CH(NH2)-CN

Hydrolysis of the cyanide group occurs in the primeval ocean:

HOCH2CH(NH2)-CN + 2H2O ===> HOCH2CH(NH2)-COOH + NH3

Overall we get:

2HCHO + HCN + H2O ===> HOCH2CH(NH2)COOH

b) Synthesis of Sugars

Glucose = C6H12O6 = (CH2O)6 Formaldehyde = CH2O

Even today photochemical formation of HCHO occurs in the atmosphere and can be detected in rain. Condensation of formaldehyde under mildly alkaline conditions produces a vast variety of polymeric materials - the Formose reaction. Isomers of (CH2O)5 and (CH2O)6 are most frequent with tetramers and heptamers in smaller amounts. Most common biological sugars such as ribose, glucose etc. are found as products of the formose reaction, together with a wide range of isomers and derivatives.

c) Synthesis of Purines Adenine = C5H5N5 = (HCN)5



Adenine is a pentamer of hydrogen cyanide. Adenine is manufactured industrially in Japan by heat-polymerizing HCN. On the primitive earth a tetramer of HCN probably formed by successive condensations. This then rearranged under the influence of ultraviolet light to form one ring. A fifth HCN then condensed with this precursor to form the second ring. When HCN is heated in solution with NH3 a black tar is formed together with adenine as the major soluble aromatic product. The thermal mechanism shown below is probably slightly different from the UV promoted pathway. Note that ammonia is needed as a catalyst. It takes part in the reaction but an equal number of ammonia molecules are released as are incorporated. Smaller amounts of guanine and other purine derivatives are also formed.



Extraterrestrial Biomolecules

a) Interstellar space. Radio frequency spectroscopy has found H2O, NH3, and organic molecules in interstellar dust clouds, i.e. in the type of material from which the solar system condensed. Representative molecules are HCHO, CO, HCN, HCOOH, CH3OH, HCHS (thioformaldehyde), CH3CN, HCC-CN (cyanoacetylene). In addition many ions and radicals are found e.g. OH, CH+, and CN. Silicon monoxide (SiO), which is not stable on Earth, and tiny grains of Silica are also found.

Note that interstellar dust clouds have a density about 10-14 of the Earth's atmosphere (at sea level). Two points of importance:

1) Interstellar concentrations of organic molecules are very low, consequently reactive molecules and unstable molecular fragments collide extremely rarely and so can survive

2) Interstellar space is heavily irradiated by UV which tends to produce radicals/ions from molecules. Thus complex molecules tend to be destroyed unless they are shaded by a large enough accumulation of interstellar dust.

b) Meteorites. There are two major classes - stony meteorites and metallic (iron) meteorites. The stony meteorites contain mostly silicates of Mg and Fe. A sub-class of these, the carbonaceous chondrites, contain in addition from 0.2 to 5% carbon, 1.8 to 6.7% sulfur and 0.1 to 22% water. Hydrocarbons, fatty acids, malonic acid, succinic acid, fumaric acid and amino acids have been found. The amino acids are a racemic D, L mixture and contain non-protein amino acids. These organic compounds are therefore probably extraterrestrial in origin.

c) Panspermia. Panspermia is the theory that the earth was seeded with primitive life forms from other planets where life actually arose. This merely puts the origin of life backwards to another earth-like planet. It might be possible for very small, radiation resistant spores to travel around the universe under light pressure or for contamination by space travel to occur.

Polymerization and the Primitive Soup

The molecules formed above would dissolve in the primeval ocean, so forming the "primitive soup." Estimates suggest that the primeval oceans may have contained as much as 5-10% organic materials. Other estimates are much lower and suggest that organic material was concentrated by evaporation in tidal basins or in inland lakes etc.

Polymerization to give biological macromolecules usually requires the removal of H2O. Clearly, H2O was in excess in the oceans and removal of H2O from molecules was therefore unfavorable. This leads to a requirement for condensing agents which withdraw water. Several possible primeval condensing agents have been proposed:

a) Cyanides including HCN itself and derivatives such as cyanogen (NC-CN), hydrogen cyanate (HCNO) and cyanoacetylene (HCºC-CN).

Consider the reaction: A-OH + H-B ===> A-B + HO

This can be pulled over by reaction with a cyanide derivative R-CN:

A-OH + R-CºN ===> A-O-C=NH ===> A-B + H2N-CO-R
|
R + B-H

b) Condensing agents derived from phosphate. Inorganic polyphosphates would have been present in primeval times (formed by volcanic heat from phosphates for example). Polyphosphates can react with many organic molecules to give organic phosphates. Amino acids give two possible products. Acyl phosphates have the phosphate group attached to the carboxyl group of the amino acid (NH2CHRCO-OPO3H2) Phosphoramidates have it attached to the amino group of the amino acid (H2O3P-NH-CHR-COOH).

Gentle heating or irradiation will then give polypeptides. Modern life uses acyl phosphate derivatives during protein synthesis. However, laboratory synthesis of DNA uses phosphoramidates. Analogous reactions can give AMP from adenine and polynucleotides can then form by polymerization.

c) Clay and apatite minerals. Absorption of monomers to catalytic minerals promotes many reactions. Montmorillonite clay will condense aminoacids to form polypeptides up to 200 residues long. Note that whereas biological proteins are bonded using only the alpha-NH2 and alpha-COOH groups of amino acids these "primeval polypeptides" contain substantial numbers of bonds involving side chain residues.

d) Dry heat. Proteinoids can be formed by heating amino acid mixtures at around 150°C for a few hours. Dry heat would have occurred when pools left behind by a changing coastline evaporated, or near volcanoes. These primeval proteinoids contain up to 250 amino acids and can be partially digested by some proteolytic enzymes. Several enzymatic activities have been detected in thermal proteinoids, although not anywhere near as efficient as modern enzymes. Such activities include esterase (versus nitrophenyl acetate) which shows Michaelis-Menten kinetics and a pH optimum, and only occurs if histidine residues are present. Proteinoids containing heme can be made by including heme in the mixture before heating and exhibit peroxidase activity. Zinc containing proteinoids show ATPase activity.


Enzyme Activities of Proteinoids

Reaction Special Characteristics Substrate

esterase histidine p-nitrophenyl-phosphate

ATPase Zn2+ ATP

amination and Cu2+ alpha-ketoglutarate

deamination ´glutamate

peroxidase and heme, basic proteinoids H2O2 and H-donors e.g.

catalase hydroquinone, NADH

decarboxylation basic proteinoids oxaloacetate

acidic proteinoids pyruvate

Informational Macromolecules

Biological information is passed on by template-specific polymerization of nucleotides. A mixture of polyphosphate, purine and pyrimidines will produce random nucleic acid chains if ribose or deoxyribose is included. One problem, not yet solved is that life uses 3', 5' linked nucleic acid whereas primeval type syntheses give RNA molecules with a mixture of linkages, but mostly 2', 5'. (Deoxyribose has no 2'-OH so cannot give 2', 5' links).

When an RNA template is incubated with a mixture of nucleotides, plus a primeval condensing agent, a conplementary piece of RNA is synthesized. This nonenzymatic reaction is catalyzed by lead ions, with an error rate of about 1 wrong base in 10. With zinc ions, a great improvement is seen and lengths of up to 40 bases are produce with an error rate of about 1 in 200. All modern day RNA and DNA polymerases contain zinc. If a 3', 5' linked RNA template is used about 75% of the newly formed RNA is 3', 5' linked. However, this does not surmount the problem that the original formation of RNA type polymers favors the non-biological 2', 5' linkage very heavily. It is thought that RNA probably provided the first informational molecule and that DNA is a later invention designed to store information in a more stable and more accurate form.

The appearance of informational macromolecules has given rise to three alternative theories:

a) Life without nucleic acids. Primitive proteins coalesced into vesicles. Nucleic acids were incorporated as a genetic apparatus later.
b) Naked genes. Primitive RNA replicated alone, later a protein coat was added.

c) Both the protein and RNA were included when the first vesicles formed i.e. neither of the two extreme theories is correct.

Asymmetry

Life uses only L-amino acids to make proteins and mostly D-sugars. Primeval mixtures were racemic. Proteins could form from D-amino acids just as well as from L-amino acids. What is important is that a stable protein structure (in particular alpha-helices, beta-sheets) requires amino acids all of one configuration NOT a mixture. Although assymetry was therefore required, the choice of L- over D- for amino acids (and vice versa for sugars) was most likely quite arbitrary. Once the choice had been made, life was committed to the chosen isomer.



Coacervates, Proteinoid Microspheres & Liposomes

Oparin, who first outlined the theory of the chemical origin of life, worked on coacervates. Coacervation is a process occurring in aqueous solutions of highly hydrated polymers. Two phases separate spontaneously and one of these may consist of hollow, polymer-rich, microscopic droplets suspended in the surrounding medium. Gums are anionic polysaccharides from plants and bind well to positive or neutral proteins. Protein plus polysaccharide or RNA will often form coacervates and enzymes can be trapped inside the droplets when they form.


Composition and Size of Coacervate Droplets

Materials diam (mM) mass (picog) % polymer in droplets

Albumin plus Gum 3 to 6 5 to12 20 to 35

Histone plus Gum 3 to 7 3 to 20 8 to 15

Histone plus RNA 1 to 15 2 to 100 4 to 50

For example, when Oparin made coacervates with NADH dehydrogenase trapped inside they would catalyse the reduction of methyl red by NADH. The substrates diffused in and the products diffused out. Coacervates with glycogen phosphorylase trapped inside convert glucose-1-phosphate (from the aqueous medium) into starch (=glycogen) which accumulates inside the coacervate droplets. The starch merges with the wall of the droplet which therefore increases in size and eventually divides into two. This continues until the enzyme is too dilute to produce further growth by making starch. If both glycogen phosphorylase and amylase are trapped inside the same vesicle, starch is made by the glycogen phosphorylase and degraded to maltose by the amylase. The net result is a steady state in which no growth of the droplet occurs but glucose-1-phosphate is converted to maltose.







If hot solutions of thermal proteinoids are cooled under the correct conditions they produce microspheres, about 2 microns in diameter. These are sometimes hollow and have outer membranes of protein. Basic (i.e. positively charged) proteinoids selectively associate with RNA. When protein/RNA microspheres are incubated with amino acid adenylates they produce short polypeptide chains i.e. they act like primeval ribosomes.

Similar experiments can be done with vesicles made of lipids. When liposomes are made with lipids whose fatty acids are 10-12 carbons long they are leaky to small proteins and oligonucleotides. If the fatty acids are 14 carbons long they will allow small molecules (nucleotides etc) in or out, but small proteins and oligonucleotides cannot cross. When the fatty acids are 16-18 carbons long, the liposomes are impermeable even to small solutes. Polynucleotide phosphorylase can be trapped in liposomes. When lipids with C14 chains were used, and ATP was added it crossed the membrane. The enzyme converted it into oligonucleotides which were trapped inside the vesicle.

[ronnydecoster]

Als ruwe, stenen werktuigen getuigen van een ontwerper, getuigen dan ingewikkelde levensvormen niet veel grotere kracht van het bestaan van een wijze en machtige Schepper?

Als er in de bergen een steenlawine voortkomt, verwachten we beneden een ordeloze berg stenen en rotsblokken aan te treffen. We zouden onze ogen niet geloven als alle stenen in de vorm van een prachtige rotswoning tot rust zouden komen, want een woning vereist ontwerp en doelgerichte arbeid. En zonder ontwerper geen ontwerp, zonder intelligente werker geen doelgerichte arbeid. Dit komt overeen met de bijbelse verklaring in Hebreeën 3:4: Elk huis wordt door iemand gebouwd.

Een geleerde graaft in aarde puin en vindt dan een ronde, langwerpige steen, glad van uiterlijk, met een groef die het midden van de steen omcirkelt. Hij twijfelt er niet aan dat dit een werktuig is van een primitieve mens. Hij is er van overtuigd dat deze steen met een leren riem aan een stok bevestigd heeft gezeten en als hamer of wapens is gebruikt. Of hij vindt een platte steen met een scherpe rand en hij is er zeker van dat dit een mes of schrapper is geweest, gemaakt door iemand uit het Stenen Tijdperk. Of een klein stukje scherp vuursteen in de vorm van een pijlpunt overtuigt hem ervan dat dit werd bewerkt door een mens om als punt van zijn speer te dienen. Zulke doelgericht ontworpen dingen zijn, aldus deze geleerde, geen produkt van een toevallige samenloop van omstandigheden.

Het werk getuigt van een werker. Deze gereedschappen en wapens zijn ruw van vorm en daarom worden hun maskers als primitief beschouwd, want apen maken geen werktuigen en die van de moderne mens zijn veel ingenieuzer van ontwerp. Dus plaatsen de geleerden de mensen die zulke werktuigen vervaardigen, in een stenen tijdperk, en speculeren ze dat hun verschijning en hersencapiciteit ongeveer tussen die van apen en de moderne mens in moet hebben gelegen. Vandaar dat ze hen voorstellen als voorovergebogen, harige wezens met een laag voorhoofd. Hun scheppingen getuigen van meer ontwerp en doelgerichtheid dan een stok die een aap misschien ergens heeft gevonden, maar zijn toch veel minder dan werktuigen die de moderne mens weet te scheppen. De geleerden zien de werker afgespiegeld in zijn werk en beoordelen zijn kwaliteiten naar zijn werken.
Groet Ronny

[ronnydecoster]

Gaat het echter om het overvloedige plante- en dierenleven op aarde, dan verlaten de meesten geleerden hun standpunt van een ontwerp van een ontwerper getuigt Toch zijn de eenvoudigste organismen veel en veel ingewikkelder dan ruwe stenen werktuigen. Ja, zelfs de eencellige protozoën kunnen niet als eenvoudig worden beschouwd. Want in hun ene cel is het vermogen aanwezig om alle lichaamsfuncties te verrichten die bij gewervelde dieren door diverse organen worden verricht. Evolutionaire geleerden stellen echter met klem dat een dergelijk ingewikkeld organisme geen ontwerper heeft gehad, maar eenvoudig door toeval tot bestaan is gekomen. In vergelijking echter met het spontane ontstaan van een protozo, is het veel aannemelijker dat ruwe stenen werktuigen zijn gevorm tijdens een steenlawine of in een woeste bergbeek, terwijl zelfs de vorming van een rotswoning uit een steenlawine in vergelijking ermee een voor de hand liggende zaak is.

Hoe komt het toch dat veel intelligente mensen wanneer het gaat om de meest ingewikkelde scheppingen in het heelal, hun logische regel dat doelgericht ontwerp de eigenschappen van een intelligente maker weerspiegelen, niet meer toepassen? Emotioneel vooroordeel? De bijbel is het met hun regel eens, maar zij schuwen de bijbelse consequentie ervan: Zijn onzichtbare hoedanigheden worden van de schepping der wereld af duidelijk gezien, omdat ze worden waargenomen door middel van de dingen die gemaakt zijn, ja, zijn eeuwige kracht en Godheid (Rom.1:20). Zij zouden het ontstaan van een ruw, stenen werktuig nooit aan het toeval willen toeschrijven, maar omarmen datzelfde toeval wel zonder meer als de schepper van niet alleen ééncellige diertjes, maar van alle levensvormen op aarde, de mens incluis! Zij weigeren in deze wonderen de hand van de grote Ontwerper van het universum te zien.
Groet Ronny