SERACHING FOR THE ORIGIN OF LIFE
ANOTHER LIFE STARTER?
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Question from Chapter 4
What is RNA, and could it have been formed by natural process and go on to make living cells?
What is RNA?
RNA is shorthand for "RiboNucleic Acid". It has this name because it contains a molecule name ribose (a type of sugar), and was first found in the nucleus of cells. It has since been found in other places in the cell, including the cell's protein making factories, which are called ribosomes.
Why would RNA arise before proteins?
Even when a collection of pure left handed amino acids is available, they must be joined in an ordered sequence to make useful proteins. In living cells proteins are made in structures called ribosomes that use information carried on RNA molecules to put the amino acids in the correct order for each protein.
Could RNA and the information it carries arise spontaneously?
RNA has three components:
1 - ribose, a type of sugar,
2 - a base,
3 - a phosphate.
The phosphate is the same as inorganic phosphate that forms by natural process in the environment, whilst bases and sugars have been made separately in experiments similar to Miller's amino acid experiment. One of the RNA bases, adenine, has been made from the lethal gas hydrogen cyanide, which some evolutionists claim existed in the "primitive earth" atmosphere. Sugars can be made by irradiation of simple gas molecules, although sparking the mixture does not work. Therefore, it would seem that RNA could be made by natural processes.
The Handy Problem Again
Like amino acids, sugars are also chiral, i.e. they come in right and left handed forms, and a mixture of both forms is always produced by "primitive earth" experiments. The results of all sugar producing experiments can be summarised as:
Matter + Energy + Time NP® Mixed Left &Right Sugars
However, living cells only use right handed sugars.
This means to make RNA, as is found in living cells, there must be a way of producing pure right handed molecules, or at least separating out the right handed molecules from a mixture of right and left handed sugars.
All experiments to date have shown the only way to produce 100% right handed sugars is to use scientists' brains to apply Outside Information, which is not a Natural Property of the system. The formula for producing a pure solution of right handed sugars is:
Matter + Energy + Time OI® 100% RH Sugars
Therefore, the same type of problem occurs for making RNA for living cells by natural processes as occurs for making amino acids into proteins for living cells. RNA cannot have arisen spontaneously due to Natural Properties of the Universe because the Ribose of RNA is exclusively right handed - a situation which does not occur spontaneously.
Other RNA Problems
In living cells RNA is a relatively short lived molecule. Outside a cell, RNA simply dissolved in water, it tends to quickly fall apart. This is a problem for a theory that claims life evolved from chemicals dissolved in a primitive ocean. Steven Brenner, a chemist at the University of Florida, Gainesville, points out that biological molecules do not function well on their own in water. Molecules essential for living cells to function, i.e. DNA, RNA and proteins, consist of long chains of smaller molecules, and water tends to spit up the bonds that join the small molecules together. Brenner claims, "The structure of RNA screams, 'I did not arise in water!'" He goes on to explain that "in about four out of five cases, synthetic organic chemists will avoid using water as a solvent." (Ref. Nature, vol. 436, p1084, 25 Aug 2005)
RNA has a more complex structure than proteins, which consist of strings of amino acid molecules. RNA consists of chains of molecules called Nucleotides, of which ribose is only one part. Each Nucleotide consists of three parts - a phosphate (P), a ribose sugar, and a base.
RNA molecules are made by linking the ribose and phosphate molecules leaving the bases projecting out from the ribose.
There are four different bases and the information carried on the RNA molecule is determined by the sequence of bases along the length of the RNA chain. The bases are adenine, uracil, cytosine and guanine, which are abbreviated to A, U, G and C. Therefore, coded information on RNA can be written as sequences of letters, e.g. AUUGCGCAUGCA, etc.
Why does the sequence of bases in RNA matter?
Information carried on RNA is used to determine the sequence of amino acids in proteins. The sequence of the amino acids determines the structure of the protein, which determines how it will function. Some proteins must be formed into very precise shapes in order to carry out their function. Let's look at an example associated with left and right handed amino acids.
Dead Sardine Problem
We obtain amino acids in our diet from eating proteins in food that used to be alive. Therefore, the amino acids are all left handed, but as we saw in the a previous section, after death, natural processes cause the exclusively left handed amino acids of living cells undergo racemisation and start turning into a mixture of left and right amino acids. Amino acids racemise quite slowly, but heat and other food processing treatments speed up the process. Therefore, when you eat some preserved protein food, e.g. canned sardines, you eat a small number of right handed acids.
Any right handed amino acids you eat are no use to your body and can be dangerous in large amounts. Therefore, the body has a way of getting rid of right handed amino acids. An enzyme named D-Amino Acid Oxidase (DAAO) breaks them down and the breakdown products are eliminated by the kidneys.
Precise Protein Structures
The enzyme DAAO breaks down the right handed amino acids, but leaves the left handed ones alone, i.e. it must be able to distinguish between the right and left handed amino acids. DAAO can do this because it has a very precise shape, which fits the right handed amino acids. The precise shape of the enzyme is determined by the sequence of amino acids that form it.
Remember what we have said about separating right and left handed molecules. In every known case the separation has only been achieved by the deliberate activities of creative, intelligent scientists setting up a system that distinguishes between left and right handed molecules. What does this suggest about the origin of D-Amino Acid Oxidase?
If amino acids are not put together in the right order, the resulting protein will not function properly and may be completely useless. Therefore, the protein factories in living cells, the ribosomes, must have the correct information for each protein they are going to make. In living cells that information is brought to the ribosome by an RNA molecule, called messenger RNA.
This brings us to another serious problem for a naturalistic explanation of the origin of life. Where did the information needed to make functional proteins originate?
Messenger RNA is only a "go-between". It does not create the information it carries. It gets it from another larger, more complex molecule named Deoxyribonucleic Acid or DNA. DNA also contains a Ribose sugar, but the sugar has less oxygen, hence its name Deoxy-ribose.
Like RNA it consists of chains of nucleotides (sugar, phosphate, base) with the information being coded in the sequence of bases. In cells, DNA is the archive of information for all the RNA, and hence, proteins in the body. If DNA is the source of information for making RNA and proteins, could DNA be the first molecule?
DNA in living cells is made with exclusively right handed sugar molecules, so we have the same problem as we had with making RNA by naturalistic process, i.e. natural processes always make left/right mixtures. Neither RNA nor DNA could have evolved spontaneously.
However, the biggest problem is where does DNA get its information from?
Even if the components of DNA could be made by natural processes, could natural processes put information onto DNA?
This vital question is the topic of Chapter 6.
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