Re: Let's be more exact.
- From: "Perplexed in Peoria" <jimmenegay@xxxxxxxxxxxxx>
- Date: Wed, 20 Apr 2005 01:10:41 -0400 (EDT)
<TomHendricks474@xxxxxx> wrote in message news:d43tc2$1k6o$1@xxxxxxxxxxxxxxxxxxxxxx
> More questions:
> 1. How do you get your replicators?
They grow on the surface of a mineral. See Wachtershauser's papers.
> There are problems with
> every scenario. What are the ones with your scenario, and how do
> you suggest they were solved.
The big ones are where do the reducing equivalents come from, and where
does the energy come from. In Wachtershauser's view, both energy and
reducing equivalents come from pyrite formation. In my view, the
carbon source is CO, so both problems are smaller. Still problems,
though, so pyrite may still be a good solution.
> 2. What is the replicator made of?
Lipids.
> where does that come from?
They form (autotrophically) on the mineral.
> Why would an RNA replicator or any replicator need protein?
There are no free-floating RNA "replicators" in my theory.
An RNA world organism doesn't exactly "need" protein. But, once one
such organism invents protein, it quickly finds uses for the material
and thus gains a selective advantage.
> How did RNA and protein come together?
I sketched an answer. Amino acid pathways were developed as a sideline
to carbon fixation pathways. These pathways made use of tRNAs. Some
uses of amino-acylated tRNAs involved peptide bond formation (including
some of the steps in purine biosynthesis - look it up!). Eventually a
mutation occurred in a ribosome which caused it to act as a protein
synthesis machine rather than as a transcriptase.
> Give answers to the problems of cataytic loops.
The catalytic loops that I think were important in the origin of life
did not involve RNA.
> Where is the energy to form the RNA coming from.
Ultimately either from a strong source of reducing power, or from a
photoactivated weak source of reducing power. This energy is converted
into phosphate bond energy by a mechanism involving a PMF, just as
it is today.
> Is it endless or a one time energy.
Obviously, we need a continuing source of energy.
> There's a catch 22 here, Usually molecules need energy to escape
> being destroyed by energy (need metabolism to avoid sun UV damage,
> or thermal sterilization or etc.) There are problems with every
> energy source. Which one did you choose and how do you overcome the
> problems to lightning, thermal sterilization, chemical string of
> events, etc.
You make an important point here. Energy must be "directed into productive
channels" if it is to be useful to life. See Wachtershauser's discussion
in "Groundworks" regarding the requirements that the energy source must
satisfy.
In my theory and Wachtershauser's the original energy source is a
source of reducing power, and it is "directed" to the portion of the
molecules that "need" it by the self-organizing properties of membranes
and the fact that the part of the molecule to be reduced is exactly the
part of the molecule that is in contact with the energy source.
> 3. If the replicator A has A1 daughter replicator, and A1-A2 and so forth
> how do you keep the chain from breaking once. Does it have fluke
> luck on every replication. Luck+Luck+Luck+ Luck for millions of years
> or until luck leads to many replicants who magically have all the food
> they need to replicate more without a single break.
My "autocatalytic cycles" are auto-productive. That is, every trip around
the cycle (assuming no slip-ups) produces additional molecules of the
"replicator". So, it can afford a few slip-ups. It is exactly the same
situation as with reproducing organisms. Do you realize that you are the
product of "Luck+Luck+Luck+Luck for millions of years" - you are descended
from a line of organisms which successfully reproduced themselves without
fail for millions of years?
> 4. Same problem with '5 steps of the magical chemical wand' scenarios.
> How is it that every step is foolproof and not once does any aspect of
> the steps NOT work.
How is it, Tom, that in the line of descent leading to you, every step
was foolproof?
AFAIK, no one claims an OOL scenario in which every step is foolproof.
Before you have a reproducing organism, you deal with errors by starting
again from scratch. You assume that you get a lot of tries, so that
sooner or later you get it right. But once you have reproduction, then
every step doesn't need to be foolproof. In fact, mis-steps can become
a creative engine.
> The usual out here is to depend on the massive amount of time
> it took - but that presents problems too. When and how long did you have.
Several hundred million years, a little over 3 thousand million years
ago. I don't see why you think that everyone but yourself is confused on
this point.
> 5. Look at the Moon facing us. See how it was bombarded? How does your
> scenario fare with that bombardment striking earth?
No differently than any other scenario. If you get hit by a meteorite, you
die. If there are too many meteorites, then everyone dies, and life has
to start from scratch.
> 6. When did this happen on earth?
The first lipid world organisms? 3.? gya. The origin of translation?
Many hundred million years later.
> what was the temp range?
Something around 100-200C, I would guess, for the original lipid world
organisms. Range doesn't apply - this happened too far below the surface
for day/night and summer/winter to have any effect.
> Atmosphere.
A few days ago I would have said something like 1 atm of CO2 and 0.8 atm
of N2. Now, if Pavlov et al are correct, I would say 0.2 atm CO2, 0.3 atm
CO, 0.1 atm H2, and 0.7 atm N2. But it doesn't matter all that much for
the original lipid world organisms. Where it makes a difference is in how
soon these organisms can free themselves from a mineral surface near the vents.
> When did the seas form?
4.2 gya, IIRC. Well before the first lipid-world organisms.
> Was it a wet/dry cycle or all in water.
All in water, or in wet soil, except perhaps when the time comes to develop
high-energy phosphates.
> IF all in water that presents real problems too.
What problems?
> 7. Why is a replicator an advantage for anything except fulfilling "Darwinian
> Destiny"?
Because replicators can "survive by proxy" far longer than non-reproducing
molecules can survive. Unless those non-reproducing molecules are completely
inert and completely sheltered.
> 8. Cell? where and how and when.
Depends on what you mean by "cell":
- Lipid membranes from day 1.
- Closed vesicles as "spores" not too long after.
- Closed vesicles throughout the organism life cycle late in the lipid
world.
- Cells in the modern sense (the good stuff is inside!) probably not until
after the invention of protein synthesis - that is, many hundred
million years after the first lipid-membrane organism.
.
- References:
- Let's be more exact.
- From: TomHendricks474
- Let's be more exact.
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