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Author Topic:   Homochirality question
SiniSha
Inactive Member


Message 1 of 7 (199733)
04-16-2005 9:01 AM


I've been lurking for some time now, and decided to join in with this question.
Life as we know it is dependent on homochirality. I was wondering:
Why aren't there life forms based on opposing homochirality (D-AAs)(of course they would have to have their own evolutionary path)?
Chance for getting both homochiralities(HC) is not that much higher than getting just one.
How would life based on one HC outcompete life based on the other HC?
I mean, they aren't even competing for the same nutrients.
P.S. I'm not sure my question is clear, because English is not my native language, so if it turns out it's not clear, I'll try to clarify it.

Replies to this message:
 Message 3 by jar, posted 04-16-2005 7:12 PM SiniSha has not replied
 Message 4 by Coragyps, posted 04-16-2005 7:45 PM SiniSha has replied

  
SiniSha
Inactive Member


Message 5 of 7 (199901)
04-17-2005 1:41 PM
Reply to: Message 4 by Coragyps
04-16-2005 7:45 PM


quote:
My thoughts on why we're all made of L-amino acids and D-sugars is that it was "luck" - the very early almost-life forms with L-amino acids got a small head start and "ate" the D-forms. Polypeptides (chains of amino acids) with both chiralities would be much more disordered - by which I mean only that they would have a much tougher time forming the neat little coils and pleats we see in homochiral proteins - and would probably lose out in any self-catalytic games that would lead to more of themselves
You didn't quite understand my question. I was not asking why isn't our biochemistry based on both L- and D-AAs, but why are there no life forms based on D-AAs.
Also, why and how would L-based early life forms "eat" D-forms? Are racemases evolutionary old enzymes?
quote:
I'll bet a nickel that sugars are D because amino acids are L, or perhaps vice versa.
I hope they are, because I hate the idea of a frozen accident, but I hate the idea of two frozen accidents twice as much

This message is a reply to:
 Message 4 by Coragyps, posted 04-16-2005 7:45 PM Coragyps has replied

Replies to this message:
 Message 6 by Coragyps, posted 04-17-2005 2:24 PM SiniSha has not replied
 Message 7 by Brad McFall, posted 04-17-2005 5:27 PM SiniSha has not replied

  
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