blah blah blah.... 3.8 billion years.... nitrogen.... blah blah... basically two chemists figured out that earth's early atmosphere had been a reducing (electron-adding) environment, in which organic compounds could have formed from simple molecules. The energy came form lightning and intense UV radiation (no ozone remember?). then stanley miller did that experiment where amino acids and other organic compounds were formed. hmm... they apparently also found "complex, oily hydrocarbons"...
bloody murder! "4.5 billion year old chonodrite (something from space) collected in southern austrualia in 1969 contained more than 80 amino acids" :-O modern life only uses 20 or so amino acids! (I had to learn them all... tryptophan, phenylalanine, etc.. not that I remember them anymore) "remarkably the proportions of these amino acids are similar to those produced by the miller-urey experiment"
and it says they can't possibly be contaminants from earth (the amino acids in the thing) for some chemistry reasons i don't get.
now abiotic synthesis of polymers:
"researchers have produced amino acid polymers by dripping solutions of amino acids onto hot sand, clay, or rock. The polymers formed spontaneously without the help of enzymes or ribosomes" "such molecules might have acted as weak catalysts for a variety of reactions on early earth"
protobionts:
"while miller-urey-type experiments have yielded some of the nitrogenous bases of DNA and RNA, they have not produced anything like nucleotides"
ALTHOUGH... They have! I read a ... scientific american?... article that said they had created self-replicating RNA in a lab... exclusively with the environment of old earth, and without cheating (using RNA to start with and then making it self-replicating or something like that)
"necessary conditions may have been met by protobionts, agregates of abiotically produced molecules surrounded by a membrane... structure" they "exhibit some of the properties assosiated with life including simple reproduction and metabolism as well as maintenance of internal chemical environment different from that of their surroundings"
"lab experiments demonstrate that protobionts could have formed spontaneously from abiotically produced organic compuonds. for example, small membrane-bounded droplets called liposomes can form when lipids or other organic molecules are added to water. (figure 26.4)" (shows a liposome "giving birth" to smaller liposomes, and another one having simple metabolism.)
..... "much like the lipid bilayer of a plasma membrane [...] some liposomes store energy in the form of a membrane potential, a voltage across the surface. such liposomes can discharge the volage in nerve cell-like fashion, such excitability is a characteristic of all life"
if some things come together, like the amino acids and polymers getting inside the liposome "then those droplets could have selectively taken up organic molecules from their environment"
RNA world:
first genetic material- probably RNA.
two people found RNA (which plays a central role in protein synthesis) can also carry out a number of enzyme-like catalytic functions. They called 'em ribozymes. they can make complementary pieces of RNA, if they're supplied with nucleotide building blocks. others can remove segments of themselves (self splicing introns), or can act on diff. molecules such as tRNA.
"natual selection on the molecular level has been observed operating on RNA populations in the laboratory. Unlike double-stranded DNA," "RNA molecules assume a variety of 3-D shapes" ..."the molecules thus have both a genotpe and a phenotype" "RNA molecules with certain base sequences are more stable and replicate faster and with fewer errors"
blah blah blah, families of closely related RNA, "occasionally a copying error will result in a molecule that folds into a shape that is even more stable or more adept at self-replication than the ancestral sequence."
blah blah suggested that " rna molecules may have been short virus-like sequences and these sequenes were aided in their replication by random amino acid polymers that had rudimentary catalytic capabilities", and that may have happened in protobionts.
ugh. there's more but i don't feel like typing it all out.
I'm guessing it says something about from then on, with the help of natural selection, RNA could have lost an oxygen atom and become DNA, and then ta-da you have your first cells.
there, plenty of evidence that it could have happened.
