The Minimum Requirements for Life

One assignment I received during a graduate course in microbiology was to find a candidate for the first living cell. The first cell would have needed to metabolize and replicate. We (the other graduate students and I) began by looking for the simplest possible living cell. We narrowed it down to the archaeon and viruses. Simple viruses only need about 10 000 base pairs but we disqualified them because they absolutely must have another cell to be able to reproduce. Some archaeon need only 30 000 base pairs in their DNA molecule and so the archaeon became our candidate for the simplest life form and possibly a relative of the first living cell on earth. The largest human DNA molecule by contrast has 220 million base pairs. Then we gathered a list of everything the cell needed to be able to be considered a living thing. Now, I'm going from memory here so forgive me if I omit something or get numbers wrong. Here is what the simplest living things needs to be a living thing;

- a minimum of 30 000 base pairs in the correct order with phosphate and sugars to provide the backbone

- a minimum of 12 proteins with the amino acids in the correct order

- a number of molecules of ATP

- a number of molecules of NADPH

- a semi-permeable cell wall that completely engulfs these substances

There were other things on the list but I forget them. If any one of these components was missing or a tiny percentage of the nucleotides or amino acids are out of order, the cell would not be able to function and there would be no life. It was astounding to me how complex the simplest living cell was. I cannot imagine this set of circumstances happening by chance. First of all, where did all these components come from? The experiment of Miller and Urey in 1953 has been more or less discarded as a viable example of the early earth's environment. Even if there were amino acids, what is the probability of them lining up in the correct order for not one but 12 different proteins. It's been a while since I've taken statistics but the probability of the amino acids of just one protein lining up in the correct order is so infinitesimally small, it is hardly worth considering, let alone a DNA molecule of 30 000 base pairs. It is not logical for the first cell to have happened by chance. There must be another explanation. I have read of a theory that postulates that the components for the first cell were "seeded" on earth by meteorites. I find this unlikely also. What is the probability of all these components being in close enough proximity to each other and then engulfed by a semi-permeable cell wall? What kind of environment could have formed these components somewhere out in space? How could these components have remained viable in the harsh environment of space and the traumatic trip to earth? I have yet to see a reasonable model for the first living cell. This aspect of the origin of life debate pulls me toward the intelligent design side.