How did the first cell develop?

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How did the first cell develop?
« on: 24/05/2011 11:30:02 »
@TykeJ asked the Naked Scientists:
How did the first cell develop?

What do you think?
« Last Edit: 24/05/2011 11:30:02 by _system »


Offline granpa

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How did the first cell develop?
« Reply #1 on: 24/05/2011 18:26:11 »
first life or first cell?


Offline CliffordK

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How did the first cell develop?
« Reply #2 on: 25/05/2011 23:59:22 »
first life or first cell?
I would think it would be the same thing.
The first life would have been a unicellular prokaryote. 

I compare life to the Rubik's Cube.

When I first got my cube.
I was quick to solve one side.
Then discovered that solving one side was pointless unless the first row below it was also solved.
Then fiddling around, within a day or two I got it solved, perhaps in a large part with random movements.
The next time it took me a half a day or so, again with a lot of random movements.
Then, I sat down to try to figure out what was happening, and learned successive patterns that were sufficient to get it down to a couple of minutes.
Later I learned that there were two basic approaches to solving the cube.  Top-->Bottom-->Middle  &  Top-->Middle-->Bottom.  I tried to learn the top-->bottom-->middle approach, but never got very comfortable with it.

Anyway, back to life.  There is some speculation on whether life formed on Earth, or was transported to Earth via asteroids and supernova remnants.  The only way we'll know the true answer to that is if we find life that developed independently on another planet or solar system and compare the DNA and protein structures.

Nonetheless, life would have had to develop SOMEWHERE.

Likely some of the basic hydrocarbons spontaneously formed.  Amino acids & etc.  Catalysts help reactions, but they will also spontaneously occur down an energy gradient, and sometimes even up an energy gradient. 

Perhaps prion-like proteins formed that could self-catalyze their own formation.

If long-chain hydrocarbons existed, especially with polar heads and tails they would have spontaneously formed micelles. 

And, if some of the cellular machinery also existed and was spontaneously captured in a micelle, it would have formed the basis for a cell.  Over time, these micelles likely would have spontaneously ruptured, reformed, and perhaps even merged.

Over time, the micelles that were more cell like were favored. 

DNA, RNA, & Protein transcription would have given some sense of "memory" for structures to the cell.

Things like error correction mechanisms in DNA transcription would have come much later.

Likely the early cells would have just absorbed "energy" from the environment, for example consuming long-chain hydrocarbons to produce CO2.  But, sporadic energy reserves, and perhaps elevated CO2 levels would have favored those cells that developed crude methods for photosynthesis, or capturing of geothermal energy.  But, if CO2 levels plummeted, the more cannibalistic cells would have been favored, and eventually a balance would be reached.

4 billion years or so for evolution is a very long time.

If two life forms developed independently, it is quite possible that the most competitive one literally chewed up the other, and it it couldn't form the basic life functions of energy capture and replication fast enough, the second form would have just died off.

Yes, there is a lot of hand waving in the arguments.

It is believed that Eukaryotes developed over a billion years later than the Prokaryotes, and that at least the mitochondria eukaryote organelle developed from a captured prokaryote.  There are, however, many similarities between eukaryotes and prokaryotes including the basic DNA structure.

Prokaryotes developed methods called plasmids to share DNA.  Perhaps viruses and phages developed from plasmids gone rogue.