- Chemical evolution
- Biological evolution
Primitive life forms:
spontaneously
Complex life: by the Creator
Pasteur’s experiment
1860’s
air
microbes
in trap
Oparin hypothesis
Alexander Oparin
• Organic compounds undergo a series of reactions leading to more and more complex
molecules
• Certain macro-molecules formed colloid aggregates, or 'coacervates'
• Coacervates were able to absorb and assimilate organic compounds from the
environment in a way reminiscent of metabolism
• They would have taken part in evolutionary processes, eventually leading to the first
life forms
Emergence of Life in 4 steps
0. Inorganic matter
1. Organic monomer
1. Abiotic synthesis of organic monomers
2. Abiotic synthesis of polymers
3. Origin of self-replicating molecules
2. polimer
4.Separation from the outer environment:-formation of pro-cells
4. Membrane enclosed compartment
1. Formation of organic monomers
- Miller’s experiment (1953)
CH4
Water vapor
Electrode
Stanley Miller
Organic compounds from inorganic materials:
amino acids, sugars, and nucleotide bases
Condenser
But no:
ribose, fatty acids with long carbon chain
peptide bond
Cooled
water
Hypotheses:
1. Primordial soup
2. Primordial pizza
3. Rain drops
H2O
Cooled water
containing organic
compounds
Sample of chemical analysis
2. Polymerisation
Asp + Glu
120 oC
polypeptides
Fox &Dose: peptide bond in vitro
3. Replication- The RNA world
ribozymes
Monomers
1
Formation of short RNA polymers
2
Replication
The RNA world– replication
Self-replication of RNA
Self-replicating RNA acts as template
on which polypeptide forms
Polypeptide
Polypeptide acts as primitive enzyme that
aids RNA replication
RNA
Evolution
of genetic coding
RNA
genetic info
RNA
RNA
ribozyme
genetic info
protein
enzyme
DNA
RNA
genetic info messenger
Protein
enzyme
4. The membrane
Spontaneous origin of two-layered phospholipid layers
membrane
RNA
Hydrophilous head
Hydrophobous tail
H2O
polypeptide
Early conditions for life
Organic compound from
inorganic materials:
(1) Chemosynthetic bacteria (4 billion years) - energy: H2S oxidation
(2) Anaerob photosynthesizing bacteria (3.8 billion years)
- light energy only for ATP.(not for photolysis)
- H for organic molecules: from H2S or from organic matter.
(3) Cyanobacteria:
- H2O: H resource (3.2 billion year): no O2 accumulation during 2 billion years
(only in the last 1.5 billion yrs): Fe2+bound the oxigen
- O2: for aerorespiration
-
- O2 – UV – O3. : protects dryland living beings
The monophyletic origin of Life
– Chirality
• Handedness: Some molecules exist in two versions based on the position of
the bond:one molecule is the mirror image of the other.
• Sugars: right-handed
• Aminoacids: left-handed
The monophyletic origin of Life
–The genetic code is universal