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Life in a Bottle
Lecture Eleven, Feb. 10, 2003
Course Project
• Topic of your choosing related to class.
• Proposal (1-2 pages) Feb. 14, 2003.
• Project background (3-5 pages) Mar. 28,
2003.
• Project (10 pages) April 25.
Pathfinder the Race to Mars
• 60 min video on web site.
• 1996 Mars Global
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Surveyor lunched to orbit
and map Mars.
Also Mars Pathfinder with
its small rover.
These followed failed
Mars Observer in 1993.
See Manyrovers_full.jpg
(note, this is a 7.4 MB
image)
The Doomsday Asteroid
• 60 min Video
•
about impact of
comet Shoemaker
Levy 9 with Jupiter
and present day
threat from
impacts.
Keck Telescope
infrared images of
collision.
Hubble Image of Impact Plum
Impact site itself just out of site beyond rim
Gamma Ray Bursts
• The Nova program
Death Stars discusses
Gamma Ray bursts.
These are the most
energetic explosions
since the Big Bang.
They have now been
detected billions of
light years from
Earth.
Simulation of collapse
of giant rotating star to
produce two gamma
ray jets.
New Horizons Mission to Pluto
The Kuiper belt: Frontier of Solar
System
Spacecraft will flyby Pluto and
then on to a Kuiper belit object.
See http://pluto.jhuapl.edu
Origin of Life According to
Michelangelo
Origin of life according to Mel Brooks. Real Media clip of
creation of life from Young Frankenstein
The Chemistry of Life
• Start with very simple chemicals such as
CO2, H2O, N2, NH3.
• Temperature and pressure allow liquid
H2O.
• Energy source: could be ultraviolet
radiation from Sun, Lightening, Chemical
reactions.
• Somehow produce the building blocks of
life.
Amino Acids: Building Blocks of Life
• Amino acids are chemical compounds with amine groups
•
(containing nitrogen, N) and weak acid groups (HO2C)
that can be linked together to form long chains called
proteins.
Example: Amino acid Alanine
H
H
N
H
C
O
C
O
Acid group
H
Amine group
H
C
H
H
Chemistry 101:
Note, 4 bonds
for C, 3 bonds
for N, 2 for O
and 1 for H
Two amino
acids
H
N
C
H
O
C
H
Acid
group
N
C
O
H
C
Amine
group
H
C
H
H
H
C
O
H
H
O
H
H
H
H
• The amine group of one amino acid can react
with the acid group of another to produce a
molecule of H2O and the joining of the two.
These
react
to
form
H2O
H
O
C
N
O
H
C
H
H
H
C
C
H
H
O
O
H
C
H
H
H
N
H
N
H
C
H
C
H
H2O + O
H
C
N
Two amino acids
H
C
O
H
C
H
H
C
O
H
H
H
H
C
H
H
One longer chain that still has an amine and an acid group
Proteins are Made of Amino Acids
• Amino acids have an amine group (N) and an
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acid group (CO2H)
Can bind amino acids together to produce long
molecules called proteins.
Proteins form the basis for life on Earth.
Earth life uses proteins made from 20 different
amino acids strung together in definite orders.
Where did the amino acids come from?
How were they put together in the correct
order?
Life made from 20 amino acids
Glycine
Valine
Alanine
Lysine
Note, carbons at ends of lines and hydrogens are not shown
Red is oxygen (acid) and blue is nitrogen (amine) group
A Protein
• To specify a unique protein you must specify which one
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•
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of the 20 amino acids occurs first, which amino acid
occurs 2nd and so on.
A protein may be thousands of amino acids long.
To specify the exact molecule one needs a long string of
thousands of numbers each of which goes from 1 to 20.
For example,
5-19-20-1-5-7-8-8-15-20-20-1-1-1-…
Example let 1 be Glycine, 2 be Alanie … So this protein
has amino acid #5 then #19, #20 and so on for
thousands of links in the long chain.
The Left Hand of God
• A given amino acid
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can come in two
mirror image forms.
Life on Earth only
uses the left handed
form.
We don’t understand
the origin of this
chirality (Greek word
for hand).
Origin of Life
• Where did the amino acids come from?
• How is the information stored to specify
the sequence for each complex protein?
• How is the information acted on to
synthesis the proteins?
• How do the complex proteins function to
form a living organism?
Life is Old
• Life arose about 3.8
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•
billion years ago.
Clear fossils in 3.5
billion year old rocks.
Problem, few older
rocks have survived.
Great bombardment
and very hostile
conditions 4 billion
years ago and earlier.
Isotopes and Age of Life
• A carbon atom has 6 electrons.
• Carbon nuclei therefore have six protons. They
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can also have either 6, 7 or 8 neutrons to make
isotopes of carbon 12C, 13C or 14C. The
superscript indicates the mass number A which
is the sum of the number of neutrons plus
protons.
Isotopes have the same number of protons but
different numbers of neutrons.
Natural Carbon is:
• 99% 12C and 1% 13C
• 14C is radioactive with a half life of about 5000
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years. Thus all primordial 14C has long since
decayed.
Most chemical reactions are the same for
different isotopes and will not change the ratio
of 12C to 13C.
Reactions important for life work very slightly
faster for 12C than for 13C because it is lighter
and so moves faster.
13C is change in isotope ratio
• 13C is very small change in ratio of 13C to 12C
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compared to the normal value of this ratio.
Carbon in living material today is slightly
depleted in 13C.
Interesting evidence that carbon in 3.8 billion
year old samples also show this slight depletion.
Suggests that life is at least 3.8 billion years old.
Note, we have no undisturbed rocks on earth
older than about 3.5 billion years old.
Origin of Amino Acids?
• Amino acids can be made
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from simple inorganic
chemicals such as CH4,
NH3, H2O…
But how was this done?
Were the original amino
acids extraterrestrial?
Amino acids are found in
some meteorites.
Allende Meteorite
Miller Experiment
• Stanley Miller, a graduate
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student of Harold Urey, in
1953 placed H2O, H2, NH3,
CH4 in a flask.
He constantly boiled and recondensed the H2O and
added an electrical
discharge for energy.
Spectacular results:
produced lots of amino
acids and other organic
compounds.
Miller Experiment
• Miller thought he was simulating a
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thunderstorm on the primitive Earth.
He put H2, NH3, CH4… in the exp.
because these had just been seen
(via spectroscopy) in the atmosphere
of Jupiter.
We now think early atmosphere was
CO2 and had no free hydrogen.
Without free hydrogen the
experiment does not work and few
amino acids are made.
Jupiter
Miller Experiment
• Suggests that amino acids are
easy to make under the right
conditions and may be
common through out the
Universe.
• Thus the building blocks of life
may be common!
• However, we don’t know where
the correct conditions
occurred. The lack of H2 on
the early Earth appears to be a
real problem.
• Perhaps amino acids were
made off the Earth in a site
with free hydrogen.
DNA the Memory of Life
• How does life store the considerable
information needed to specify a complex
protein?
• This information is encoded in molecules
of DNA.
• DNA is made from four base pairs:
adenine, thymine, guanine, and cytosine
on a double helix backbone.
The Four Base Pairs in DNA
• The molecule adenine
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(a) always pairs with
thymine (t) and
guanine (g) pairs with
cytosine (c).
The information in
DNA is stored in
which of the four
(a,c,g,t) occur at each
position along the
double helix.
DNA
• Double helix structure
• Genetic code in order of
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the four bases (a,c,g,t)
arranged along one of the
helix strands.
For example, start at the
bottom with the strand
starting to the left: a c t g
atgggtactt
Information in 2nd strand
is the same.
DNA can Replicate!
• Double helix “unzips” and
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then new base pairs are
added to each single stand
to make two identical copies
of the original DNA molecule.
This allows cells to divide
with full copies of the genetic
code in each cell.
The structure of DNA helps
explain reproduction.
DNA Codes for Proteins
• DNA is not a protein and it is not made of amino
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acids.
DNA codes for the synthesis of proteins. Thus
DNA stores the information needed to make a
complex protein.
Modern cells have complex machinery to read
the DNA information and assemble amino acids
to make proteins.
How did early life do this before the complex
machinery was evolved?
For next time
• Read chap. 4 of Jakosky about the earliest
life and read “Vital Dust", pages 1-23 in
course packet about origin of life.
• Think about your course project. Proposal
(1-2 pages) due Feb. 14, 2003.