Monday, January 19, 2009
All That's Left is left
I came across yet another evolution problem. There are two orientations of amino acids; left and right. They are mirror images of each other. It would be very difficult for life to exist if there was a mixture of these because the two types would be incorporated randomly into a protein resulting in a protein with different properties that would not be able to do its job. With a few exceptions, all the amino acids on earth are left-handed. The question is why? Each has an equal probability of occurring. What got rid of virtually all of the right-handed amino acids so that life could occur? A very real possibility is the existence of a creator. Are there other explanations that I don't know about?
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Is this an an example of Chirality? Louis Pasteur first noticed that sodium ammonium nitrate cystals (paratartrate crystals) crystals existed in two orientations, but that biological sources of the crystals only existed in one orientation.
ReplyDelete"To Pasteur this discovery had a deeper meaning. He proposed that asymmetrical molecules were indicative of living processes. In the broadest sense, he was correct. We know today that all of the proteins of higher animals are made up of only those amino acids that exist in the left-hand form. The mirror image right-hand amino acids are not used by human or animal cells. Likewise, our cells burn only the right-handed form of sugar, not the left-handed form that can be made in the test tube. It was the discovery of asymmetry of organic molecules that provided Pasteur with the "inescapable forward moving logic" that enchained him as he began his studies on alcoholic fermentation."
Yes, this is an example of Chirality. I have heard of some bacteria that have right-handed amino acids but I don't know of anything else. Do you know of any reason why left-handed amino acids predominate?
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