Monday, December 20, 2010

Protein Folding

There are hundreds, if not thousands, of metabolic processes occurring in each of the trillions of cells in your body at this very moment. Each of those processes requires the work of a team of specialized proteins, and each of those proteins must have a particular shape in order to perform its assigned task.

Examples of Protein Shapes
 If a particular protein fails to achieve the proper shape when it is formed the fitness of the cell will suffer and thereby hangs an interesting problem. Given that the universe of possible configurations that a protein could adopt is vastly greater than the number of seconds since the earth formed, how is it that just these highly specific shapes have been discovered for each of the myriad proteins in the cell by natural selection? Biologists tell us that the shape of a protein is a function of the sequence of amino acids that make the protein up, much like beads make up a necklace, but how, out of all the possible sequences that there are, did just the right sequence arise?

Cornelius Hunter offers an interesting discussion on the problem at Darwin's God. He writes:
But [the protein] works just fine only because a very special amino acid sequence was specified. That amino acid sequence is just as astronomically rare as the three dimensional structure that the unfolded protein was able to find. So from where did this amino acid sequence come?

The string of amino acids that make up a protein comes from the cell’s translating machine called the ribosome. The ribosome takes as input a string of nucleotides and produces as output a string of amino acids. The translation is done according to the genetic code.

And from where did the string of nucleotides come? It came from the DNA. A massive protein copying machine slides along an opened section of DNA and copies a gene.

And from where did the DNA gene come? According to evolution it evolved, but it is here that we find another entropy barrier. Just as the folding protein is confronted with an astronomical number of structures, so too the DNA gene is confronted with its own nightmare of choices. But that is where the similarities end.
DNA is a code. It's information. At bottom is the question of where information comes from. Can it be produced by chance and blind forces, or does it require intention and intelligence? We have never experienced information such as a code being produced apart from a mind, and yet despite the complete lack of empirical warrant the naturalist takes an enormous leap of faith and chooses to believe, without any evidence, that not only are such wonders possible but that they actually happened in the origin of living things.

Then the naturalist, having committed himself to the belief that unthinking nature is capable of such miracles, the equivalent of believing that a computer program could be produced by a random symbol generator, criticizes those who are skeptical as being superstitious and unscientific for thinking that the existence of information is evidence of the existence of an intelligent mind. Pretty funny, I think.