Homochirality and Racemic mixtues (Chemistry)

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Homochirality and Racemic mixtues (Chemistry)

Postby AtheistKiwi » Mon May 30, 2011 8:55 pm

In a You Tube discussion on a video about Intelligent Design, a user brought up (as evidence for ID) "Homochirality and Racemic mixtues", which appear to be two obscure chemistry theory that are beyond my knowledge. I am not able to work out if these are serious, or ID crap.
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Re: Homochirality and Racemic mixtues (Chemistry)

Postby fastthumbs » Tue Jul 26, 2011 7:30 am

AtheistKiwi wrote:In a You Tube discussion on a video about Intelligent Design, a user brought up (as evidence for ID) "Homochirality and Racemic mixtues", which appear to be two obscure chemistry theory that are beyond my knowledge. I am not able to work out if these are serious, or ID crap.


In organic chemistry, this is quite common and is not at all an obscure chemistry theory.

Many organic (containing carbon) compounds have various geometric forms which is referred to as chirality. A compound is chiralic when it is not superimposable upon its mirror image due to containing an asymmetric carbon atom. Take cyclohexane... it has two different geometries... a "boat" and "chair" geometric form. Homochiriality means that there is only a single geometric form present... In biological systems, an enzyme uses one form of a compound to build a particular structure because the enzyme can only attached to a specific geomtry. Think of it this way - you have a peg board with only round holes (enzyme). The compound used has two shapes (say squares and round) - so only the round version of the compound is used.

Racemic mixtures, or racemates basically means a true 1:1 mixture of chirality types, which under polarized light, shows no change due to rotation of the light source (IIRC)

How either of this supports ID, I have no freaking clue. Odds are the ID supporter has a poor understanding of organic chemistry or is just parroting some other ID talking head that has poor understanding of organic chemistry (ID crap as you put it).
Last edited by fastthumbs on Tue Jul 26, 2011 7:45 am, edited 2 times in total.
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Re: Homochirality and Racemic mixtues (Chemistry)

Postby eimerian » Wed Jul 27, 2011 12:43 pm

fastthumbs wrote:How either of this supports ID, I have no freaking clue.


The argument goes something like:

1) Almost all amino acids used by life on earth are left-handed.
2) Right-handed amino acids are rarely produced in nature. In fact, some of them are even toxic.
3) If amino acids are created by chemical reactions you end up with an racemic blend of left- and right-handed amino acids.
4) Therefore if life emerged from random chemical reactions, how is it possible that life uses only one kind of amino acids? This points to a designer.


Of course this is wrong for many reasons...
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Postby fastthumbs » Wed Jul 27, 2011 5:07 pm

What a bad arguement!

Different chiralities have different chemical properties (even if the enantiomer had similiar bulk properties - solubility, melting point, etc. it's not relevant - all but the simplest of biologically relevant molecules are asymmetric, inter-molecular interactions would have been between asymmetric participants, each no more likely to confuse their partner with its enantiomer than with any other molecule). Any molecule complex enough to have heritable variation would certainly have been complex enough to be asymmetric. To such molecules, discrimination between enantiomers wouldn't have been any more of a problem than discriminating between other possible reactants. So in the primordial soup, certain chiralities would be "more fit" for replicating then their enantiomer counterparts (most counterparts I'd speculate had 0 fitness), thus life on Earth favored the use of D-sugars and L-amino acids.

It's likely the IDiot has a poor chemistry understanding, counter with this: The words pacer and recap are palindromes, but most readers have no more trouble telling them apart than telling either from caper.
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Postby eimerian » Thu Jul 28, 2011 8:45 am

Being a good skeptic and all I am concerned that I may have commited the straw man fallacy when I gave such a superficial explanation of the argument.

So here is a link to a creationist making his case:
http://creation.com/origin-of-life-the-chirality-problem
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