Origin of life

From:http://www.mediafire.com/?jfijmimctnd

Life didn’t have to start with modern chemicals!

The pre-biotic environment contained many simple fatty acids.

Under a range of pH they SPONTANEOUSLY

form stable vesicles.

And they are permeable to small organic molecules…

…meaning no complex proteins are required to get stuff in.

When a vesicle encounters free fatty acids in solution, it will incorporate them.

Eating and growth are driven purely by thermodynamics.

When a vesicle grows it adopts a tubular branched shape…

Surface area grows faster than volume.

…which is easily divided by mechanical forces (waves, currents, rocks…)

During mechanical division, none of the contents of the vesicle are lost.

So far, with naturally occurring simple fatty acids,

we have a vesicle that can spontaneously grow and divide.

So what about the genetic material.

Again, modern nucleotides are too stable and require complex protein machinery to replicate.

The pre-biotic environment contained hundreds of types of different

nucleotides (not just DNA and RNA).

(All it took was 1 to self polymerize.)

Recent experiments have shown that some of these are capable

of spontaneous polymerization, such as Phosphoramidate DNA.

Monomers will base pair with a single stranded template and self ligate.

Hydrogen BondsBase Pair

Covalent BondLigation

They can also polymerize in solution, and spontaneously form new templates, or

extend existing templates.

No special sequences are required, it’s just chemistry.

So far we have lipid vesicles that can grow and divide,

and nucleotide polymers that can self replicate, all on their own.

But how does it become life?

Here’s how.

Our fatty acid vesicles are permeable to nucleotide

monomers, but not polymers.

Once spontaneous polymerization occurs within the vesicle, the

polymer is trapped.

Floating through the ocean, the polymer containing vesicles will encounter convection currents…

… such as those set up by hydrothermal vents.

(fatty acid vesicles are stable under near boiling conditions)

The high temperatures will separate the polymer strands and increase the

membrane’s permeability to monomers.

Once the temperature cools spontaneous polymerization can

occur. And the cycle repeats.

Here’s where it gets cool.

The polymer, due to surrounding ions, will increase the osmotic pressure within the

vesicle, stretching its membrane.

A vesicle with more polymer, through simple thermodynamics, will “steal” lipids

from a vesicle with less polymer.

This is the origin of competition.

They eat each other.

A vesicle that contains a polymer that can replicate faster,

will grow and divide faster,

eventually dominating the population.

-Monomers spontaneously polymerize and copy any template-Heat separates strands, increases membrane permeability to monomers-Polymer backbones attract ions increasing osmotic pressure-Pressure on the membrane drives its growth at the expense of nearby vesicles containing less polymer

Let’s Review: -Monomers diffuse into a fatty acid vesicle

-Mechanical forces cause vesicles to divide-Daughter vesicles inherit polymers from the parent vesicle-Polymer sequences that replicate faster will dominate the population…

Let’s Review: -Vesicles grow into tubular structures

Thus beginning evolution!

Early genomes were completely random and therefore contained

NO information.

It was their ability to spontaneously replicate, irrespective of sequence,

that drove growth and division of the fatty acid vesicles.

Any mutation that increases the rate of polymer replication

would be selected for.

And as I’ve shown before

Mutation +

Natural Selection=

Increased Information

Early beneficial mutations would include:

Change sequence to contain only the most common nucleotides.

Early beneficial mutations would include:

Don’t form secondary structures that block replication.

X

Early beneficial mutations would include:

Form sequences that are stable yet separate easily.

X

Early beneficial mutations would include:

Form secondary structures that show some enzymatic activity.

Just like RNA, early nucleotides could both store information and

function as enzymes.

Early polymer enzymes would:

Enhance replication

Early polymer enzymes would:

Use high energy molecules in the environment (near thermal vents)

to recharge monomers.

Early polymer enzymes would:

Synthesize lipids from other molecules in the environment.

Early polymer enzymes would:

Modify your lipids so they don’t leave your membrane.

And that’s it.

A simple 2 component system that SPONTANEOUSLY forms

in the pre-biotic environment…

…can eat, grow, contain information, replicate,

and EVOLVE…

…simply through thermodynamic, mechanical,

and electrical forces.