LEC 24 Regulating Protein Synthesis -- Eukaryotes - ORIGIN...

ORIGIN OF CELLULARITY AND CELLULAR
DIVERSITY

Last impact heating
~3500
Geological stratigraphy,
together with radioactive
dating, show the
sequence of events in
the history of the Earth.
Note the entry for
“cyanobacteria” and
“stromatolites” only one
billion years after the
formation of the Earth.
But what came before them?
And how did cells become
more complicated 1.5 B
years later?

Chemical experiments, initiated by Stanley Miller and Harold Urey,
Showed that some biochemicals could be formed naturally
(but not all--where did the rest come from?)
Life starts with chemistry

Protobionts vs. surface layers
What is important about a cell?
How would you start, if you wanted to make
a model of a cell?
Hypothesis:
Metabolism (energy, reproduction) needs a
way of concentrating intermediates.

Cells

Adsorptive surfaces

Protobionts: a step
toward living cells?
In 1957, Sidney Fox demonstrated that dry mixtures of amino acids
could be encouraged to polymerize upon exposure to moderate heat.
When the resulting polypeptides, or proteinoids, were dissolved in hot
water and the solution allowed to cool, they formed small spherical
shells about 2 μ m in diameter—microspheres. Under appropriate
conditions, microspheres will bud new spheres at their surfaces.

Tiny compartments in mineral structures can shelter simple
molecules, while mineral surfaces can provide the scaffolding
on which those molecules assemble and grow. Beyond