Self And The Phenomenon Of Life: A Biologist Examines Life From Molecules To Humanity

Self and the Beginning of Life 35

“9x6” b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity

In 1969, a meteorite made up of carbonaceous chondrites landed
in Murchison, Victoria, in Australia. Carbonaceous chondrites origi-
nated from matter that existed in the planet-forming gas of the early
solar system. This is one of the most studied space rocks because it is
unequivocally recorded and is free of contamination. A total of 14,000
specific organic compounds, including more than 70 amino acids (such
as glycine, alanine, and glutamic acid), have been identified.^13 Polyols,
the polyhydroxylated compounds including sugars and other carbo-
hydrates that can form backbones of nucleic acids and components of
cell membrane, are indigenous to the meteorite.^14 In addition, xanthine
(a  precursor of guanine) and uracil (a pyrimidine component of RNA)
have been detected.^15 See Table 3.5 for comparative abundance of
organic compounds in the Murchison meteorite.

Table 3.5. Organic Compounds

in Murchison Meteorite

Amino acids ++

Carboxylic acids +++

Dicarboxylic acids ++

Hydroxy acids ++

Sulfonic acids ++++

Basic N-heterocyclics +

Purines & pyrimidines +

Pyridine carboxylic acids +

Amides ++

Amines ++

Alcohols ++

Aldehydes & ketones ++

Aliphatic hydrocarbons ++

Aromatic hydrocarbons ++

Sugar alcohols & acids ++

Phosphoric acid +

Note: ++++>1000 ppm, +++>100 ppm,

++>10 ppm, +>1 ppm

(ppm = parts per million)

[See Note 25; permission Royal Soc.]