Abiotic Biotic Transition

on Hadean-Archean Earth

Outcrop of metamorphosed volcano-sedimentary rocks from Porpoise Cove, Canada.Abiotic Biotic Transition

Living cells are made of molecules! Modern cells fall into 3 categories (Domains):ArchaeaBacteriaEukarya

No matter which Domain a cell belongs to, it consists of 4 types of biomolecules:CarbohydratesLipidsProteinsNucleic acids

1) Small organic molecules were formed from even simpler inorganic molecules in the environment.

During the late Hadean Era (4.0 3.5 bya), Earth was very different than today!Atmosphere mostly CO2, CH4, NH3, N2, H2OIntense energy present lightning, geothermal, UV radiation

1) Small organic molecules were formed from even simpler inorganic molecules in the environment.The Miller Urey experiment, in 1953, first showed that small organic monomers could be formed by adding energyto simple inorganicmolecules, and mixing amino acid them in water!

nucleotidemid- to late-Hadean Era= about 400,000,000 years!

2) Then the monomers bonded together to form polymers Organic monomers can form chains, called polymers

Dehydration reaction:MonomerPolymeramino acidproteinnucleotidenucleic acidmonosaccharidepolysaccharideglycerol / fatty acid chainsfat molecules

2) Then the monomers bonded together to form polymersClay is a sediment with a regular, repeating layered mineral pattern

Has many industrial uses in absorbing & combining chemicals

Over time, volcanic ash often becomes clay in moist environments

2) Then the monomers bonded together to form polymers

What about hydrothermal vents as the setting for the origin of life?

Some researchers hypothesize that a reaction between S compounds could have provided the energy needed to produce organic carbon monomers. One product of this reaction is pyrite (also known as fool's gold). Organic monomers may also self-organize upon the surface of pyrite.

3) Next, the RNA polymers became able to copy themselves, and to be inherited

RNA

3) RNA polymers became able to copy themselves, and to be inherited

RNA likely preceded DNA

Nucleic acids hold chemical instructions for building proteins in cells

Any time a new cell is formed, the nucleic acid must be copied first!3) RNA polymers became able to copy themselves, and to be inheritedProteins are vital molecules in modern cellsEnzymes control chemical reactions, including DNA-RNAExperiments have shown RNA can replicate without help from enzymes ribozymesRNA World hypothesis

3) RNA polymers became able to copy themselves, and to be inheritedAll modern cells must be descended from other cellsFirst step is making a new copy of the directions Each new cell is an (almost) exact copy of its parent cellSuccessful cells are more likely to pass on the traits that make them successful!

4) Biomolecules became packaged into membranes made of lipids, which separated them from their watery environment.

All lipids share the characteristic of being hydrophobic.

Phospholipids have both a H-phobic and H-philic region!

Naturally and automatically assume a spherical shape when surrounded by water.4) Lipid membranes allow a cell to maintain homeostasis.All cells must be able to maintain a constant internal environment even as their external environment changes!

Stable internal environment allows complex chemistry to take place LIFE !!!!!!

Once homeostasis was in place, and genetic inheritance had begun,biological evolution by natural selection began, and has continued for about 3,500,000,000 years..........did you think it was done, just because todays organisms are here?