Moving Towards Life

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Дата изменения: Tue Nov 26 21:49:58 1996
Дата индексирования: Mon Oct 1 22:03:52 2012
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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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