Origin of Life

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Origin of Life
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In order to more clearly understand the problems
surrounding the origin of life a determination of
the chemical compounds involved must be made. A
brief review of chemistry is necessary.
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As was pointed out earlier in the textbook all
living organisms are made up of proteins which in
turn are made up of amino acids in a particular
order.
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The model shows that the structure of the
compound is centered around a carbon atom. The
chemical compound making up the R Group
determines the type and name of the resultant
amino acid.
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Think CriticallySince any compound with the
proper valence can attach at the R Group site how
many different amino acids do you estimate are
possible?
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It is estimated that there are more than 2,000
different amino acids.What percentage of these
are considered to be biologic?
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Further examination of the amino acid model
reveals that the position of the amino and
carboxyl groups can be switched. This means that
the shape of the amino acid can be changed even
though the chemical equation remains the same.
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.If the shape of the amino acid changes then the
shape of the protein changes. This means that
two proteins are possible even though they have
the same chemical equation.
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It is now apparent that the shape of the amino
acid is not only controlled by the R Group but
also the relative positions of the amino and
carboxyl groups to a line drawn through the R
Group and the Hydrogen atom.
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Chemical Compounds That Have the Same Chemical
Formula But Differ in Structure Are Called
Isomers. The Two That Are Involved In the
Quest For The Origin of Life Are Sugars and Amino
Acids. They Are Called Optical Isomers..
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Right Handed Left Handed
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Right handed and left handed molecules occur
naturally in EQUAL NUMBERS.
But a problem exists because Living organisms use
only ONE OR THE OTHER of these molecules.
Amino Acids Are All Left Handed Sugars Are All
Right Handed.
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If only ONE of the wrong handed molecules gets
into the chain of either amino acids or sugars
the result is a non-biologic compound.
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Think Critically
If a Right Handed Amino acid gets into a chain of
Left Handed amino acids why isnt the resulting
protein useful biologically?
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Think Critically

• Right Handed sugars are connected to the bases in
  the DNA. What happens when a Left Handed sugar
  connects to a base?

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The DNA is unable to coil up successfully.
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Think CriticallyWhat is the likelihood of a
primordial soup containing only biologic amino
acids? What do the L and D type molecules and
the great number of possible amino acids have any
effect on the origin of life concept? Support
your answer.
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