The last chapter dealt with the
synthesis of adenine, but it was not a complete analysis in that even if the enzymes
required to create adenine existed, they would have no way to power the chemical reactions
that they facilitate. These enzymes would be like a gas powered car with no gas, or a
solar powered car with no sun and no battery.
The last chapter presented the argument that the concentration of
adenine in the primitive ocean was very dilute; therefore, any proposed form of life that
uses RNA and DNA to replicate must be able to synthesize adenine. The same argument is
even more compelling with ATP. The concentration of ATP cannot exceed that of adenine
because adenine is needed to make ATP. Unlike adenine, ATP contains high energy bonds.
This means that ATP would have a very short lifetime. ATP would undoubtably decay to AMP
in a matter of days. So the concentration of ATP in the primitive ocean or in a localized
soup would have been negligible.
Figure 14.1: ATP has Two High Energy Bonds
ATP stands for adenine triphosphate. Figure 14.1 shows that ATP is
composed of one adenine molecule, one ribose molecule, and 3 phosphate groups. The high
energy bonds are located between the phosphate groups.
All living things use ATP for energy. This suggests that the capability
to synthesize ATP arose before the common ancestor diverged to create all the branches in
the tree of life. Both nucleotide biosynthesis and ATP synthesis were required before life
could emerge. Life that has to wait several hundred thousand years to replicate is not a
reasonable model for the first living cell. Not only is such an organism replicating too
slowly to evolve in the time allotted, but it certainly would not replicate at all as it
would be destroyed before it acquired the necessary chemicals. The first living organism
must have been able to synthesize both nucleic acids and ATP.
Figure 14.2: The Tree of Life
In figure 14.2, ATP synthesis is shown coincidently with adenine
synthesis. On purely theoretical grounds, the two processes must have evolved at the same
time. It is one of the many chicken or the egg paradoxes that plague origin of life
theories.
The creation of a chemical like adenine from the chemicals readily
available of the primitive earth would result in a decrease in entropy. So this cannot
happen unless an energy source is used to drive the chemical reaction. Plenty of energy
sources were available on the primitive earth, but unless some system is in place that can
use these energy sources to drive a chemical reaction, the energy sources are of no value.
Life knows how to use energy sources to drive chemical reactions. That is life can take
the energy stored in a chemical like ATP, and use this energy to synthesize another
chemical, like adenine (the enzymes that create adenine actually require 5 ATP molecules
to drive the process). How can life possibly make ATP if the concentration of adenine is
so low that the first living cell only comes into contact with an adenine molecule every
hundred years or so? The model is only plausible if both capabilities emerge at the same
time. The implication is that the knowledge calculated in the last
chapter is too small. For the system to function, the enzymes in the last chapter also
need ATP. Thus, the total system must include the enzymes required to make adenine, as
well as the additional enzymes required to make ATP.
Life creates ATP by a process called oxidation. Oxidation will be the
subject of the next section.
next: Oxidation
home: Intelligent Design and the origin of life
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