Transcript sop - in a secure place with other

Surface Ocean
Processes
The Genesis of Life?
Step 1: Creating Amino Acids

The first step in the emergence of life would require simple
organic compounds that are the building blocks of life. The
1953 Miller-Urey experiment in showed some of these building
blocks could be easily formed in a mixture of water, methane
and ammonia when this mixture was exposed to an energy
source
NH3 + 2CH4 + 2H2O + energy ⇒ C2H5O2N + 5H2
Glycine looses mixed in the ocean
Right Hand Side H is looking to attach
to something else as is the “reactive”
H atom
Dilute Monomers
If the mixture of these monomers (single
carbon atoms) is too dilute in the oceans
the entire process will fail.
This next step must be taken:
Polymer Formation
 First step towards cells
 Note that Glycine is also found in the tails
of Comets  did comet delivery seed the
earth with building blocks of life?
 Mechanisms that concentrate the
monomers would aid in polymer formation
Clay Theory

The only practical mechanism for concentration is evaporation that is driven
by some agent. for evaporation. In this case, there are two clear
possibilities:

evaporate the surface water from small concentrations of ocean
water.
Inland tidal pool could evaporate under the intense sun in a couple
of weeks or so. The tidal mud would be come highly concentrated in
monomers that were originally in the ocean. The silicate surfaces
that compose this mud are known to be good catalysts for polymer
formation.
Four billion years ago the moon was substantially closer to the Earth
than it is now. That means that tides of a few thousand feet high
were not that unusual! Those large tides could have easily formed
relatively large inland, shallow lakes, which are prone to rapid
evaporation so that the monomers would settle into the clays that
formed the lake bottom.



heat the surface water
Deep Sea Thermal Concentration



Experiments starting in 1997 showed that amino acids and peptides
could form in the presence of carbon monoxide and hydrogen sulfide
with iron sulfide and nickel sulfide as catalysts under conditions of high
temperature and pressure, such as those found in a deep sea thermal
vent.
The successful experiments required temperatures of about 100 C and
moderate pressures, although one stage required 250 C and a pressure
equivalent to that found under 7 kilometers of rock. These conditions do
occur and therefore hydrothermal facilitation of protein synthesis (e.g.
polymer formation) could well have occurred in that environment.
In fact, this environment is more natural place for this chemistry to occur
and perhaps Step 2 is entirely driven by this deep sea process and
nothing relevant is happening on the surface. Over time this formed
polymers could drift up to the surface. Immersion in a liquid medium is
very important for further processes to occur since the liquid medium
both protects these large molecules from disruption by ultraviolet light
(remember, there is no ozone layer yet) and it serves as a transport and
interaction medium.
Step 3: Discovering a Genetic Code

Big Question
We don’t know but there are plenty of ideas …
DNA Formation




In our framework, it is now useful to think of the next set of steps
in terms of the idea of evolutionary advantage. For instance, its
clear that those polymers that can reproduce themselves have a
strong evolutionary advantage over those that can't because
those that can't die and those that can live.
Organic polymers in high concentration can separate out from
the liquid medium as individual droplets. These may be the first
proto-cells
Long chain moleules (e.g. peptides) can potentially act as a
primitive membrane for that proto-cell to control the flow of
nutrients/proteins to the proto-cell.
This exchange process continues, by Trial and Error until the
"right" combination is achieved (e.g. DNA).
Time

The fossil record shows that the first primitive
cells/bacteria capable of reproduction, known as bluegreen algae appear at least 2.8 BYA with some good
evidence for formations as old as 3.5 BY. In this
sense we know that it took at least one billion years to
evolve from atmospheric chemistry to blue green
algae via the oceanic pathway. Perhaps then, all you
need is time and a reasonable stable environment
(like the oceans) to exist for a billion years or so.
Multiplying Populations and the Need for
Resources



Eat each other? Fermentation process is
inefficient
Process another element H2S – from
volcanoes, metabolize the sulfur 
anaerobic photosynthesis which produces
glucose
Problem – not enough H2S to sustain growing
population
Aerobic Photosynthesis



Substitute H20 for H2S  requires 1/3 more
energy so use UV photons at ocean surface as
the energy input. Bacteria have to evolve this
capability
There is no shortage of H20 so bacteria that
develop this capability evolutionary advantage.
The fossil record indicates that it takes about 500
million years from the appearance of the first
blue-green algae engaging in anaerobic
photosynthesis (cyno) bacteria that are able to
use water producing oxygen as a waste product..