Tuesday, April 22, 2008

Handedness (Chirality)


Twenty types of amino acids make up proteins. They come in mixed amounts of mirror images in nature. (It is called "chirality," pronounced ki-RAL-ity). This is a picture of one type of biological amino acid, alanine. The amino acids are made of atoms (carbon, oxygen, nitrogen, hydrogen). In biological life, only one of these "hands," the left one, is found. This is one of the first puzzles of origin of life. John Lennox (in his book, God's Undertaker) discusses the probability of just one protein of one hundred amino acids (an average number for proteins) forming by chance in the way it has. It would be 1 in 2^100, or 1 in 10^30 (a 1 with 30 zeroes after it). The number of seconds in universe so far (if it is about 13-14 billion years old) is less than 10^18, which gives you an idea of size of the numbers. The base 2 stands for the left or right hand of the amino acid that could be included in that protein by chance.

This number does not factor in that there are hundreds of types of amino acids found in nature, but only 20 types in biological life. It also does not start to evaluate whether the amino acids make a protein which can be used in nature. Living proteins have shapes which give them their ability to act, just like toasters and coffee machines have different shapes for different jobs.

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