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problem of globalisation

By | October 2013
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Chemical Evolution Theory of Life’s Origins
1. the synthesis and accumulation of small organic molecule
s, or monomers, such as
amino acids and nucleotides.

Production of glycine (an amino acid)
3 HCN + 2 H
2
O
energy
−→
C
2
H
5
O
2
N + CN
2
H
2
.

Production of adenine (a base):
5 HCN

C
5
H
5
N
5
,

Production of ribose (a sugar):
5 h
2
CO

C
5
H
10
O
5
.
2. the joining of these monomers into polymers, including pr oteins and nucleic acids.
Bernal showed that clay-like materials could serve as sites
for polymerization.
3. the concentration of these molecules into droplets, call
ed protobionts, that had
chemical characteristics different from their surroundin
gs. This relies heavily on
the formation of a semi-permeable membrane, one that allows
only certain
materials to flow one way or the other through it. Droplet form ation requires a
liquid with a large surface tension, such as water. Membrane formation naturally
occurs if phospholipids are present.
4. The origin of heredity, or a means of relatively error-fre e reproduction. It is widely,
but not universally, believed that RNA-like molecules were
the first self-replicators
— the RNA world hypothesis. They may have been preceded by ino rganic
self-replicators.
Lattimer, AST 248, Lecture 13 – p.1/20
Acquisition of Organic Material and Water

In the standard model of the formatio of the solar system, vol atile materials are
concentrated in the outer solar system. Although there is as much carbon as
nearly all other heavy elements combined in the Sun and the bu lk of the solar
nebula, the high temperatures in the inner solar system have lead to fractional
amounts of C of
10

3
of the average.

Ices are similarly much more abundant in the outer solar syst em.

Meteorite and comet impacts could deliver much of the Earth’ s volatile material,
especially C and H
2
O. At present-day rates, a billion years is needed to deliver...
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