BIOA01H3 Lecture Notes - Lecture 2: Stanley Miller, Hydrogen Sulfide, Reducing Atmosphere
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Lecture 2 + 4 + 6 (Chapter 2)
ORIGINS OF LIFE
- There are 7 characteristics that all forms of life share:
1) DISPLAY ORDER, all forms of life consists of organized cells.
2) HARNESS AND UTILIZE ENERGY, all forms of life acquires
energy from the environment and uses it to maintain their
3) REPRODUCE, all organisms have the ability to make more of
their won kind.
4) RESPOND TO STIMULI, organisms can make adjustment to
their structures, function, and behaviour in response to changes
to the external environment.
5) MAINTAIN HOMEOSTASIS, organisms are able to regulate
their internal environment such that conditions remain relatively
6) SHOW GROWTH and DEVELOPMENT, all organisms increase
their size by increasing the size and/or number of cells.
7) EVOLVE, populations of living organisms change over the
course of generations to become better adapted to their
- Viruses are not considered a form of life because they lack the
cellular machinery to synthesize their own proteins. They have to
highjack the machinery and metabolism of a living cell in order to
1) All organisms are composed of one or more cell.
2) The cell is the smallest unit that has the properties of life.
3) Cells arise only from the growth and division of pre-existing
CONDITIONS ON PRIMORDIAL EARTH
- Bombardment of rock from still forming solar system and
extensive volcanic and seismic activity.
- Earth radiated some of its heat and surface layers cooled and
solidified into the rocks of the crust.
- Because of its size, Earth’s gravitational pull was strong enough to
hold an atmosphere around the planet.
- Primordial atmosphere contained an abundance of water vapour
from the evaporation of water at the surface, and large amount of
hydrogen sulphide (H2S), carbon dioxide (CO2), ammonia (NH3),
and methane (CH4), which are basic building blocks for formation
- Compounds were formed by reactions in the atmosphere and
- Organic molecules such as amino acids, sugar, and the nucleotide
bases that form DNA and RNA are essential to the formation of life
and could have been made in the absence of life (abiotic
- Early atmosphere was a reducing atmosphere because of the high
concentration of molecules such as hydrogen (H2), methane and
- Today’s atmosphere is an oxidizing atmosphere because of the
presence of O2 (strong oxidizing molecule).
THE MILLER-UREY EXPRIMENT
- Primordial atmosphere = lack of oxygen = no ozone (O3) layer to
block sun’s ultraviolet light.
- Ultraviolet light + lighting provided the energy that combined with
the reducing conditions present in the atmosphere
accumulation of the simple “building blocks” required for life.
- STANLEY MILLER, created a simulation of the reducing atmosphere.
Miller placed components of a reducing atmosphere (hydrogen,
methane, ammonia, and water vapour) in a closed apparatus and
exposed the gases to an energy source in the form of continuous
sparking electrodes. Water vapour was added at one part and
condensed back into water by cooling another part.
- MILLER found all sorts of organic compounds in the water,
including urea, amino acids and lactic, formic, and acetic acid.
15% of carbon in methane was converted to organic compound.
- When HCN and CH2O molecules were added to the simulated
atmosphere in Miller’s apparatus, all building blocks of complex
molecules were produced (amino acids, fatty acids, and the purine
and pyrimidine building blocks of nucleic acids, sugar such as
glyceraldehydes, ribose, glucose, and fructose, and phospholipids,
which forms the lipid bilayers of biological membrane.)
THE SYNTHESIS OF POLYMERS FROM MONOMERS
- Nucleic acids and proteins are not individually synthesized
molecules, called monomers. They are macromolecules, built up