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The first cell

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The first cell

Postby thank.darwin » Wed Feb 16, 2005 1:41 am

How did the first cell come to be? Did a phospholipids bilayer come first and then the other makings of a cell? How did those lipids first get to the planet? I know the answer to these questions - I want to start a conversation about it. Here is some back round information for those who wish to participate but don't know what this is about - A cell membrane is made up of phospholipids that have positively charged heads and hydrophobic tails that face in ward; the heads face outwards. A cell membrane helps keep things out such as viruses and poisons but it still has to take in things such as food and nutrients and flush out access waste. Polar molecules and large molecules have a hard time getting through the membrane but small non-polar molecules can get past the membrane through simple diffusion. In the early sixties biophysicist Alec Bangham of the Animal Physiology Institute in Cambridge, England, made a discovery about lipids - they can put themselves together; When he placed lipids from egg yolks in water they arranged themselves into double layered circles the size of a cell - these lipid bubbles are known as liposomes. David Deamer did an experiment were he took lipids and some DNA (with a intense fluorescent green dye attached) and placed them in a test tube and added a little water and when he discovered that the DNA ended up in the liposomes. Polycyclic aromatic hydrocarbons (PAH) might have supplied the first cells with energy- when PAH's is exposed to light it can give off an electron and that could have supplied the cell with energy (That's what chlorophyll does for plants). Deamer also took liposomes loaded with polymerase and put them into a beaker with two other molecules - a nucleotide and protease. They placed a dye in also that could slip through the liposomes and would attach to RNA. They discovered that the liposomes let the nucleotide in and the polymerase assembled it into RNA. So what is your opinion? Could have a cell survived without a cell membrane? Did the membrane come after the first cell? Did the first cell seek refuge in something other than a liposome? What do you think?
Information taken from (First Cell, by Carl Zimmer, Discover vol. 16 No. 11/ November 1995/ Biology and Medicine)
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Postby kthakore » Thu Feb 24, 2005 12:06 am

there is a current theory that lor cells might have developed when an organic asteroids collied in to earth. This is supported by the fact that earth' s development wasn't hott enought to create carbon out of bnuclear reactions. Affter nemerous reactions, the carbon allowed for long structures of molecules. As random reactions occured, some molecules or interactions of molecules ( think early lipids membrane and nucleuses) "survived longer", due to the fact that coplex reactions were able to reproduce the same molecules or interations of molecules, out of raw materials. This after eons evolved in the life we know.
A SPARK IS ALL THAT IS NEEDED
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Postby thank.darwin » Thu Feb 24, 2005 12:50 am

Thank-you for posting :D Will anyone else put their opinion out there?
No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
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Postby t4k9 » Thu Feb 24, 2005 2:17 am

Recently, I started learning how cell works. Hence im a newbie at this and i have alot of questions. u asked how did the first cell come about? im not too sure. but i would like to know, how did the first dna come about? it seemed to me that dna is loaded with codes of instructions on how amino acids are sequenced, hence the code for making proteins. and, for the first cell to evolve, don't we need protein? but, protein comes from dna instructions, which is inside a cell? to me, this is like a chick and egg question. but, we know that the egg came first, since there were dinosore eggs way b4 chicken :wink: , anyways, that's besides the point.
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Postby mith » Thu Feb 24, 2005 5:33 am

Gizoogle for the stanley-urey experiment
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Postby thank.darwin » Thu Feb 24, 2005 1:23 pm

What is that mithrilhack?
No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
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Postby thank.darwin » Thu Feb 24, 2005 1:25 pm

To answer your question t4k9, polymerase could have been able to assemble the early forms of RNA... I don't know exactly how the first DNA could have come about?
No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
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Postby Poison » Thu Feb 24, 2005 7:09 pm

mithrilhack wrote:Gizoogle for the stanley-urey experiment


I think so. try to find some info about that. I think it really can explain. you can find it in all books about evolution i guess.
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Postby Poison » Thu Feb 24, 2005 7:13 pm

Have a look at this . I think I've found something:
http://www.chem.duke.edu/~jds/cruise_ch ... iller.html
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Postby mith » Thu Feb 24, 2005 8:39 pm

go to gizoogle.com and search for stanley-urey experiment. Sorry if I wasn't clearer before.
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Postby thank.darwin » Fri Feb 25, 2005 4:04 pm

Thank-you mithrilhack...
No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
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Postby clarence » Thu May 05, 2005 10:59 am

Hey thank.darwin,

Here are some hypotheses I know about the first cell's origin.

1. Panspermia, which says life came from someplace other than earth. This hypothesis, however, still does not answer how the first life arose.

2. Proteinoid microspheres (Fox 1960, 1984; Fox and Dose 1977; Fox et al. 1995; Pappelis and Fox 1995): This hypothesis gives a plausible account of how some replicating structures, which might well be called alive, could have arisen. Its main difficulty is explaining how modern cells arose from the microspheres.

3. Clay crystals (Cairn-Smith 1985): This says that the first replicators were crystals in clay. Though they do not have a metabolism or respond to the environment, these crystals carry information and reproduce. Again, there is no known mechanism for moving from clay to DNA.

4. Emerging hypercycles: This proposes a gradual origin of the first life, roughly in the following stages: (1) a primordial soup of simple organic compounds. This seems to be almost inevitable; (2) nucleoproteins, somewhat like modern tRNA (de Duve 1995a) or peptide nucleic acid (Nelson et al. 2000), and semicatalytic; (3) hypercycles, or pockets of primitive biochemical pathways that include some approximate self-replication; (4) cellular hypercycles, in which more complex hypercycles are enclosed in a primitive membrane; (5) first simple cell. Complexity hypothesis suggests that the self-organization is not improbable. This view of abiogenesis is the current front-runner.

5. The iron-sulfur world (Russell and Hall 1997; Wächtershäuser 2000): It has been found that all the steps for the conversion of carbon monoxide into peptides can occur at high temperature and pressure, catalyzed by iron and nickel sulfides. Such conditions exist around submarine hydrothermal vents. Iron sulfide precipitates could have served as precursors of cell walls as well as catalysts (Martin and Russell 2003).

6. Polymerization on sheltered organophilic surfaces (Smith et al. 1999): The first self-replicating molecules may have formed within tiny indentations of silica-rich surfaces so that the surrounding rock was its first cell wall.
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