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How were the organic molecules (amino acids, nucleotides) that define life created?

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How were these assembled into macromolecules (proteins, nucleic acids)?

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How were these able to reproduce themselves?

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How were these assembled into a system separated from the surroundings?

4.5 billion years ago, Earth was a hostile place

         − severe volcanic and tectonic activity

             − intense ultraviolet energy from the sun

− no oxygen in the atmosphere

What were the four stages of early life formation?

1. Abiotic synthesis of small organic molecules (monomers) 

    2. Polymerization – joining of monomers into polymers

3. Packaging of these molecules into protobionts (membranes) that maintained distinct internal chemistry

4. System to store information and use it to guide synthesis

1. Nucleic Acids (Purines, Pyrimidines)
2. Amino acids and Protiens
3. Lipids and Phospholipids
4. Carbohydrates / Sugars

Primordial Soup consisted of

1. Water Vapour
2. Hydrogen
3. Methane
4. Ammonia
5. Carbon Dioxide

The primordial soup virtually did not have oxygen because no bacteria or living organism existed to turn C02 to 02.

What does the Oparin-Haldane theory propose?

Hydrothermal vents are heated water, which are rich in Hydrogen, Hydrogen Sulfide, CO2 and Nitrogen.

Gasses from the vents bubble up through chambers producing a geothermal gradient which provided the energy to generate lipids, proteins and nucleotides.

More than 500 meteorites hit earth every year, many of them are rich in organic molecules.

Nucleotides

Proteins

Carbohydrates

Charged layered structure of clay allows for molecular adhesion forces to bring monomers together

Clays can store potential energy which are then used in energy requiring polymerization reactions.

What is a protobiont?

Can they be spontaneously generated?

What are their properties?

group of abiotically produced organic molecules surrounded by a membrane → unique internal chemistry and concentration of molecules

Yes they can be spontaneously generated.

May be similar to liposome –lipid vesicle with lipid bilayer similar to cell membrane

• Selectively permeable

• Capable of simple reproduction and metabolism

RNA molecules can function as enzymes -> Known as Ribozymes

Catalytic properties due to folding = Specificity for Substrate

Early life may have lived in an RNA world

•DNA is better at information storage than RNA

•Chemically more stable

•Base uracil replaced with thymine –DNA repair

•Double-stranded –DNA repair

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•Proteins are better catalysts than RNA

•rate of catalysis 10-100 times greater

•Variety of proteins – 22 different amino acids into proteins BUT only combinations of 4 nucleotides in RNA

•Amino acids can interact chemically –bonding arrangements not possible between nucleotides

How did the early symbionts evolve?

Which symbiont did not survive?

Early protobionts used molecules present in the environment for growth and replication

•Heterotrophs (other-feeding) - organisms that obtain carbon from organic molecules–likely via anaerobic respiration and fermentation

•Produced CO2

•Autotrophs (self-feeding) emerged, which are organisms that obtain carbon from inorganic molecules (often CO2)

•Anoxygenic photosynthesis

•Evolution of oxygenic photosynthesis -cyanobacteria use water as electron donor – produce O2

Primordial heterotrophs did not survive the change in environment, and those that did evolved the capacity for aerobic respiration

Eukaryotes : Have membrane enclosed organelles

Prokaryotes : Lack membrane enclosed organelles

What is the modern classification of cells today based on?

What are the 3 domains of cell, 4 kingdoms of Eukarya? What are the two cell types?

3 Domains : Archaea, Bacteria, Eukarya

Cell types : Eukaryotes, Prokaryotes

4 Kingdoms : Fungi, Protists, Animalia, Plantae