Science, Technology and the Environment (SC NATS 1840A) –
Thursday, November 8 , 2012
READINGS 5.1 Life Chemistry Genetics
Life 1 – Origins & Chemistry
In the beginning…
Planets formed from same cloud of gas and dust as the Sun, about 4.6 billion years ago…
Being made of the same “stuff”, terrestrial planets were very similar to one another at first.
Earth has changed significantly. Current condition on Mars and Venus suggest what primordial
Earth may have been like.
Earth’s original atmosphere probably looked much like those of Venus and Mars today.
Gasses likely to have been present include: Carbon Dioxide (CO2), Nitrogen (N2), Water (H2O),
Methane, Ammonia, Hydrogen Sulfide, Hydrochloric Acid, Molecular Hydrogen
Origins of Life:
Accepted scientific view of our origins begins with conditions on the newly-formed planet Earth.
Early environment likely featured
An unpleasant atmosphere
High ultra-violet (UV) radiation from the Sun
Frequent lightning discharges
Is it plausible that life appeared under such conditions?
Chemical Basis of Life:
All known life forms are built up from organic molecules.
Many of these molecules are gigantic. Such macromolecules involve thousands of atoms and
come in four main types
Nucleic Acids (DNA, RNA)
Lipids (fats) All are polymers made up of chains of simpler molecules called monomers.
Composed of one more chains of amino acids. Folded into a unique shape.
Only 22 “standard” amino acids.
Tens of thousands of different proteins, each with a specific function. Classified into 7
1) Structural proteins – that provide more cell walls, ligament tissue (collagen), provides
structure to the organs
2) Contractile Proteins – Muscle, will change their shape, will enable muscle contraction
3) Storage proteins (for developing embryos) – Storage for newly developing embryos
4) Defensive Proteins – Antibodies, their job is to find threats to organisms
5) Transport Proteins – Haemoglobin
6) Signal Proteins
7) Enzymes (regulators)
Direct the manufacture of proteins.
Building blocks are nucleotides, which form a chain.
Sugar-Phosphate chain with nitrogenous base appendages
Only 5 distinct nitrogenous bases: A, G, C, T, U
Phosphate (PO4 -2) => 5-Carbon Sugar => Nitrogen-containing Organic Base
Two forms of nucleic acids exist in all living cells
Deoxyribonucleic Acid (DNA):
Two chains o