my group did a small project regarding this topic. did some reading of it last time. Most of the reasons are traced back to the origin of life. Like the aa that first existed on earth (which come from the outer space) consist of more L than D. This come from the examination of meteorite from the outer space.

The other is that it’s due to the magnetic field (or radiation or something like that) that formed during the formation of a star (which could be earth) is more supportive for the formation of L-aa.

And some others which are beyond my level of understanding..

The following are the links that we used for the project:

http://www.ast.cam.ac.uk/AAO/local/www/ … ality.html

http://ourworld.compuserve.com/homepage … estion.htm

http://www.rae.org/revev6.html

http://www.madsci.org/posts/archives/ma … .Bc.r.html

I think the answer resembles the answer to the question; why in most countries people drive on the right side of the road? Why not both? Why not on the left?
Well, it couldn’t have been both because they’d bump into each other.
And yes, it could be the left side like in Britain, but the reasons for it are historical – it just happened this way…

Hi,

The reason is ‘assymetry of fundamental particles due to the non-conservation of parity of the universe.’ Non-conservation of parity means that different laws apply to a hypothetical mirror image of our universe.

(watever that means….but sounds really cool…)

Reference: Physical Chemistry by P.W. Atkins.

I read the link about the murchison asteroid and it seems legit, why have I never heard of it before? Is there some controversy regarding it?

i just adding this for fun.. my group mates come up with our own theory regarding this last time.

During early earth, there exist two different forms of organisms: one is the D-aa organisms, the other is the L-aa organisms.. they have different metabolic and genetic pathway, etc.. then one day something happen to the earth that killed all the D-aa (probably a very huge meteorite that hit the earth or sudden extreme change in the earth environment). Eventually, only left L-aa organisms which continue to grow, reproduce and proliferate..

Again.. it’s just for funsake:p.

n btw, i have heard of some microbes can actually utilise D-aa.. such that D-aa is added to the media for differential selection..

Hm… your theory has flaus: How come the meteorite wiped out ALL the D-organisms and left L-organisms. Does that mean that L-organisms were "better"? If it’s like that, then how?

well.. that is only a part of the "story" 😛 . The details of the story was thought out by my group mates..

In the early earth, (a much earlier time when there was still no knowledge of it nowadays) the earth environment was divided into two hemispheres. The northern hemisphere is supportive of L-organism growth only and the southern is supportive of D-organisms only. This was due to the differences in genetic and metabolic mechanism between the two.
Neither one can survive in the other’s environment. Thus, there was little transfer of gene between the two…

As for the meteor, it happened to hit the southern part and create such a huge impact that it annihilated all the D-organisms and most of the L-organisms.. The L-organisms that managed to adapt to the changes in earth environment (due to the meteorite impact) survived and the rest died.

I just thought of this:
*Perhaps the surviving L-organisms could be what the scientist called the LUCA (Last Common Universal Ancestor)*

haha.. i think it has become more like a story… 😆

Fitness is one of the very important thing in this part.
See ; was all the things happened simultaneously or not ? this also matters.
And i don’t think that there is a huge difference in the environmental conditions on both the hemispheres. 😯
( May be I’m wrong) ❗

Hi hrushikesh,

Heres a brand new reason for the old problem – Why more L than D in biology ?

Link:
➡ http://www.newscientist.com/article/mg18925404.400

Chk it out ppl. 8)

hi cytochrome! 😀

that’s an interesting article! can you find the full text of the article?

followed yr link but it’s only a summary of the article. did a search but din find the full text.. wuld like to noe more about it 😀

well, basically the article in New Scientist say that water protect the L-amino acid.
three quarter of water consist of ortho h2o, a slightly magnetic molecules and
one quarter non-magnetic para h2o.
this weak force causes the L amino acid to be slightly magnetic meaning it interact more readily with magnetic ortho h2o
therefore L amino acid is more stable