Prebiotic Evolution: ATP Energy

ATP Synthase

ATP synthase is an incredible enzyme. It is the smallest rotary motor in the world. The protons moved across the cell membrane by the electron donor/acceptor/dehydrogenase complex (figure 14.6) serve as the energy source for ATP synthase.

   ATP synthase lets these proteins flow back to the other side of the cell membrane, and this powers a small rotary motor imbedded inside the membrane and causes it to spin. The spinning portion called the rotor has a stalk attached to it. The stalk is not straight but rather curved. Because other peptide chains surround the stalk, as the stalk spins, it forces these surrounding proteins to move. This allows these surrounding proteins to create ATP from ADP.

   ATP synthase was one of the first enzymes because it is absolutely necessary for many of the organisms that are thought to have existed on the primitive earth. All of the bacteria that oxidize non-organic chemicals to obtain energy use ATP synthase to make ATP.

   The enzyme is composed of 8 distinct peptide chains. If any one of the chains is missing, the enzyme does not function. So ATP synthase is an irreducibly complex system. The subunits, their amino acid number, information and knowledge are shown in table 14.2. The operation of ATP synthase is illustrated in figure 14.9. The table and the figure together explain why this was not the first protein to synthesize ATP. If a system involving ATP synthase is required for the origin of life, then it will never get off the ground. The protein is too complex and contains too much knowledge.


Table 14.2: Information and Knowledge in ATP Synthase

   This table assumes that the knowledge per amino acid is similar to that of G3PD. Thus, column 3 obtains molecular knowledge by multiplying the number of amino acids by 3.16 (primordial soup), and column 4 obtains molecular knowledge (genetic code) by multiplying the number of amino acids by 0.57. The last row is the sum of each column.

   For this table to be correct all of the subunits must evolve independently, and this probably did not happen, because the sequence of the alpha chain is very similar to the beta chain. One of these two chains, probably evolved by gene duplication. Therefore information theory can still assign a number of bits, but these bits can no longer be related back to a probability because the knowledge is redundant.

   To solve this issue, assume that the alpha chain is redundant knowledge and that it should not be included in the molecular knowledge calculation. This results in a molecular knowledge of 4904 bits (soup) and 885 bits (genetic code).

   The chance of this protein evolving does not depend on whether or not the genetic code is in place. It is just too complex. The odds with the genetic code are given as follows: 1 in 2⁸⁸⁵ or 1 in chance in 2.5x10²⁶⁶ tries. Even without the math a closer inspection of figure 14.9, explains why the odds are so poor. ATP synthase is a single protein, and its very existence implies design.


Figure 14.9: ATP Synthase




Conclusion:

The examples offered in this book are representative of the challenges that life faced at or immediately after its origin. Other systems of enzymes found in life are shared by bacteria and higher animals. For example, photosynthesis is carried out in both bacteria and in plants. The conclusion is that many if not most of these genes had to emerge right at the base of the tree of life. For purely logistic reasons, many of these genes were required by the first living organisms.

   Any system of chemicals that does not know how to live is not a living organism, and this means that self replicating molecules only exist in text books. They will never be found in the lab, because the second law forbids their existence. In the end, there is no escape from the inevitable conclusion. The first living cell needed to emerge all at once, and chemical evolution cannot explain such a miracle.

   On final idea needs to be considered. Many astronomers have suggested that the vast number of stars coupled with the extreme age of the universe can explain the origin of life. But these scientists never support their claims with statistics. They do not even bother with a single mathematical calculation. They state as a fact that life must exist on other planets because of the size and age of the universe. The next chapter will explore this claim.

References:

1) Watson et al. Molecular Biology of the Gene, 5th edition, Cold Spring Harbor, 2004.
2) Stryer, Biochemistry, Freeman and Company, 1988.
3) Madigan et al., Brock Biology of Microorganisms, ninth edition,, Prentice Hall, 2000.
4) Hutcheon et al., "Energy-driven subunit rotation at the interface between subunit a and the c oligomer in the Fo sector of Escherichia coli ATP synthase," PNAS, vol 99.
5) Zhou et al.,"Subunit rotation in Escherichia coli FoF1-ATP synthase during oxidative phosphorylation," PNAS, vol 94, 1997.


Intelligent Design and the Origin of Life