Where do your get
new:
•Humans?
•Dandelions?
•Shitake mushrooms?
•E.coli bacteria?
17th century recipe
21
Days
=
Spontaneous Generation!
glassstoragejar.net
broadwaytovegas.com
History of Earth
3.8 Billion YA
First life forms were much
simpler than today
• DNA to store information to make
proteins
• ATP to power cell metabolism
• Enzyme catalyzed reactions
• Lipid cell membranes studded with
functional proteins
Abiogenesis-
The problem of how life arose from non-life
Basic Requirements
1)Raw materials : H2O, CO2, Organics,
phosphates
2)Energy Source: Sunlight, lightening
3) Boundary to contain and organize
the components
4) Polymers-including catalysts
5) Mechanism for reproduction and heredity
Lets look at raw materials:
• Oparin’s hypothesis1927-Compounds
containing C, H, O, N were believed to have
been present in the primitive atmosphere
of Earth
• H O, H , NH
2
2
3
(ammonia) CH4 (methane)
CO2, N2
• These chemicals are not living!
Miller and Urey
•Miller and Urey in 1952 exposed a
mixture of gases resembling our
primordial atmosphere (H2, NH3,
CH4,H2O) to electricity for 1 week
•At end of the experiment, the chamber
was coated with a red-brown layer rich in
amino acids
•Caution: the experiment did not create
life. But: amino acids are considered the
building blocks of life...
http://www.ucsd.tv/miller-urey/
What is an amino acid?
Warm-up 10/6
Why was Stanley
Miller’s
experiment such
a big deal?
Other research:
• New evidence suggests that the
atmosphere may not have been the
composition that Miller worked with
• Juan Oro found that amino acids could be
made from hydrogen cyanide (HCN) and
ammonia (NH3) in a water solution- He
also made adenine- one of the bases in
RNA
• Many lab experiment “recipes” have
produced 20 AA found in organisms,
sugars, lipids, nucleotide bases
Organics from Space
• Murchison Meteorite found in
Australia in 1969 found to
contain amino acids
• Subsequent discoveries-
meteorites and comets- have
found a wide variety of
organic compounds-including
sugars (which are needed to
build nucleotides)
Abiogenesis-
The problem of how life arose from non-life
Basic Requirements
1)Raw materials : H2O, CO2, Organics,
phosphates
2)Energy Source: Sunlight, lightening
3) Boundary to contain and organize
the components
4) Polymers-including catalysts
5) Mechanism for reproduction and heredity
Lipid vesicles
• Spherical structures made of lipid
will form spontaneously in liquid
water
• They can grow by absorbing more
lipids or other vesicles Video link
• They can be split in two if they get
large enough
• (imagine a soap bubble)
Abiogenesis-
The problem of how life arose from non-life
Basic Requirements
1)Raw materials : H2O, CO2, Organics,
phosphates
2)Energy Source: Sunlight, lightening
3) Boundary to contain and organize
the components
4) Polymers-including catalysts
5) Mechanism for reproduction and heredity
Turning monomers into
polymers
• Simple nucleotides will form in
the presence of phosphates
• Lab experiments have made
polypeptides (chains of AA) by
dripping organic monomers on
hot clay. The clay acts as a
catalyst to link the monomers.
Clay could also act as a catalyst
to link nucleotides (Primitive
RNA)
Video Link
Abiogenesis-
The problem of how life arose from non-life
Basic Requirements
1)Raw materials : H2O, CO2, Organics,
phosphates
2)Energy Source: Sunlight, lightening
3) Boundary to contain and organize
the components
4) Polymers-including catalysts
5) Mechanism for reproduction and heredity
DNA needs proteins (as
catalysts) to replicate
But...
Proteins need DNA’s
instructions to be assembled
So...
Which
came
first?
RNA World hypothesis
That earlier forms of life may have relied on RNA to
store information and catalyze reactions
• RNA has unique properties
• Stores info
• Can catalyze its own
replication (warm/cold
cycles drive its
replication)
• Can act like an enzyme
to catalyze reactions (like
protein synthesis)
http://pages.uoregon.edu/bsl/astronomy/Restricted_Images/
Sequence of events:
• Putting the pieces together:
Lets explore one model of
how it may have happened...
Stages of life
1st stage: simple hydrocarbons via UV + other energy sources - these
molecules accumulated in oceans (supported by M-U experiment)
2nd stage: simple molecules bond to create organic macromolecules:
1.Amino acids >> proteins 2. Hydrocarbons + sugars >> lipids
3rd stage: macromolecules organized in larger bodies; coacervates
develop (i.e. the precursor of cells)
4th stage: Nucleic acids: self-replicating molecules appear >> control
reproductive process
5th stage: evolution + natural selection
6th stage: autotrophic bacteria appear
7th stage: cyano-bacteria generate O2 as by-product of
photosynthesis. Atmospheric oxygen increases
8th stage: Organisms evolve and use oxygen to extract energy from
chemicals
9th stage: heterotrophic bacteria
10th stage: some eaten bacteria not digested: endosymbionts
11th stage: eukaryotic cells
... Nth stage: multicellular organisms
Resources
http://www.as.utexas.edu/astronomy/education/fall08/scalo/
secure/309l_sep30_origin.pdf
http://www.mssl.ucl.ac.uk/~ipf/phas1512/IF_Lect06.pdf
http://www.astronomy.ohio-state.edu/~pogge/Ast141/
Unit3/Lect19_Origins.pdf