Originally posted by sascha
So, after all you said, how do you explain that synthesizing a living cell has never been achieved?
Simple: Cells are not simple. They are a complex network of intricatly interacting components far beyond our understanding of them. But all of that complexity comes almost entirely from those four molecules. The DNA and RNA part is relatively simple, the lIpid part is easy...its the proteins that are a pain in the bum to figure out. They are complex, varied, and can do almost anything.
After all, with self-assembling membranes and DNA replicating through RNA, it should be standard procedure...
Leaving out "how it all came together in the first place" is not a good basis, because then the rest of the talk is like building the first floor of a house on a floating foundation.
See, these two points are related. I left out the 'How it all came together' because we don't know, and yet the 'How it all came together' holds the key to why we can't synthesis cells in vitro. It is unreasonable to believe that a cell as complex as the types we see today are anything like what they were like when this game of life started, so trying to synthesis an 'end product' cell using natural processes is ludicrous. We would need a test tube the size of the earth, and 3 billion years. Not a small flask and 3 years in a lab.
Instead of talking about 'living' cells you prefer to call them 'functional cells', assuming that by replicating cells are performing all of what cells can do. But then that leaves out the essential element of what makes an organism into an organism -- as opposed to a mere heap of tumorous luxuration.
What is that essential element?
I left it out because I have no idea what else a cell does other than keep itself alive (maintaining itself in a state viable to replicate) long enough to leave as many offspring as it can, thus perpetuating the functional procedure that was bred into it via evolution. If cells do anything more than that, please tell me.
You give a little clue in saying "given the right components / environment" but then close down again in saying "The cell just happens to provide all of those elements". From what you say, making it sound so easy, the synthesis of living cells should pose no problems. And yet in practice it does, even enormous ones.
Oh, my words have nothing to do with the synthesis of living cells, my words only relate to the amazing specificity that cells no posses in their functionality.
The right environment/components thing is shown by processes such as PCR. By simply mixing the Nucleotides (A, C, T and G), a DNA template, two primers (one for each direction) and Taq POlymerase, the Template is replicated exponentially. This process of DNA replication does not require some special 'Life force' or anything like that to occur, it just occurs. BUT, if there was no DNA, no Nucleotides, no Polymerase or no primers, then it wouldn't occur. Cells ensure that all of those parts are present inside it, because if they weren't, the cell would not be able to replicate, and then it would never make it this far... The only reason we see what we do, is because it happened (somehow), and it works. If it didn't work, we wouldn't see it. (and don't)
Now, as for the synthesis of lIving cells, I think this misses the point on many levels, and hopefully now you will see why I think this. Based on the fact that early 'life' would not have been cells like we now know them, something like PCR is most likely the first form of life.
It is unlikely, but possible that the first 'life form' (or, to say something less controversial, the first replicating molecule was an RNA molecule of a sequence that folded up into an RNA Polymerase type molecule. The molecule could then be duplicated by simple complementary nucleotide addition, and then when there were many copies of itself, it could even catalyse this process. And say this RNA molecule was at the bottom of the ocean, near a Hydrothermal vent, and the vent pushed it up where it was cooler and could flow down to the ground again away from the vent, but as it approaches the ground, the current would pull it back into the vent again, sucking it in, then blowing it up. In this way you get a hot/cold cycling process, much like PCR.
This is all entirely fictionally made up from the top of my head, but this is a reasonably valid hypothesis for something along the lines of how replicating molecules may have started. And from there, you ahve replication, heredity, and differential fitness: You have evolution. Things will onyl get more and more impressive.
