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: http://zebu.uoregon.edu/internet/l3a.html
Дата изменения: Tue Nov 26 21:49:58 1996
Дата индексирования: Mon Oct 1 22:03:52 2012
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Поисковые слова: arp 220
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Moving Towards Life
How did chemisty
and oceans produce this?
Cells Today:
- concentration of monomers and enzymes and proteins which
act as an energy source
- O and OH are removed (hydration)
- monomers join together to make polymers
4 Billion years ago:
- NO cells
- need to concentrate monomers together to facilitate polymer
formatoin
Step 2: Concentrate the Monomers:
- Local Evaporation (clays) --> Tides ?
- heat from expelled lava (St. Helens)
- tidal pools (bigger tides)
- freezing of water
Energy Sources:
- lightning (Jupiter)
- heat
- UV
All of the above are quite inefficient compared to enzymes
Clays --> Silicate Surfaces --> acts as a catalyst
Peptide chains of around 100 amino acids can be found today
Does the reaction on the silicate surfaces favor L amino acids?
Step 3: BIG, Unknown Next Step --> need to organize a system
capable of self-replication (e.g. DNA)
- Organic polymers in high concentration seperate out from
liquid medium as individual droplets --> proto-cells
- long chain molecules can act as a membrane
EVOLTUIONARY ADVANTAGE: Polymers that could reproduce themselves will
survive
- Trial and Error until "right" combination is acheived (DNA)
- every living organism on the earth has DNA
- Fossil Record indicates that single celled life first emerged
3.5 billion years ago
- Therefore it took one billion years to go from atmospheric
chemistry to blue green algaes via the oceanic pathway
- All you need is time?
Now we have a multiplying population of bacteria (prokaryotes) that
has to eat to survive:
What to eat?
- First feed off other organic molecules
via fermentation
- fermentation is very inefficient, releases little energy
- Big problem --> the food supply is running out
EVOLTUIONARY ADVANTAGE: Bacteria that could process plentiful UV light
and INorganic molecules will survive
-
are most plentiful molecules
dissolved in the oceans
-
requires least amount of energy to
break apart
- early blue green algae therefore metabolized
giving off sulfur as a waste product --> stinky anerobic photosynthesis
- Important --> photosynthesis evolved from a need for the bacteria
to be able to feed themselves and multiply
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