Origin of Life

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.

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.

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.

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?

It is estimated that there are more than 2,000 different

amino acids.What percentage of these are

considered to be biologic?

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.

.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.

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.

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.”.

Right Handed Left Handed

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.

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.

Think Critically

If a Right Handed Amino acid gets into a chain of Left Handed amino acids why isn’t the resulting protein useful biologically?

Think Critically

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

to a base?

The DNA is unable to coil

up successfully.

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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