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This lecture -
What is life? Outline:
What is life? What is alien life?
Is there life unlike Earth-life?
DNA and its actions
What is it about DNA that aids evolution?
What could non-DNA life be like?
How could DNA life be formed from inorganicsources?
Where on the Early Earth might this havehappened?
Thought Question
Is a definition of life necessary?
Who needs one?
NASA does!
Does Craig Venter?
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What do you need for life?
A membrane
Metabolic machinery
A chemistry set
An information system
A method of reproduction
The reverse what is death?
When metabolism ceases with no prospect
of restarting:- Brig Klyce
(Metabolism: processes that convert
materials and energy for lifes needs
metabolism creates waste products (energyand chemicals)
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From Koshland reading: Seven pillars (essential
principles) of life
1. Program: organized plan that describes
ingredients and their kinetics (workings)
2. Improvisation life cannot control all of
its surroundings must be able to change its
program (evolution)
3. Compartmentalization limit volume,keep some chemicals in, some out
4. Energy you need it!
5. Regeneration a metabolizing system is
composed of catalysts (enzymes) and
chemicals things have to be replaced and
rebuilt
6. Adaptability fast behavioral response as
contrasted to show evolution (improvisationabove)
7. Seclusion chemical systems isolated
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Paul Davies
Life metabolizes,
Life has complexity and organization
Life develops, reproduces, evolves
Life is autonomous
From Schrodinger:
Living matter evades the decay to
equilibrium, and life feeds on negative
entropy. Life does this through
metabolism, overtly by eating, drinking,
breathing, or the exchange of material,
which forms the root of the word from its
original Greek definition.
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Lynn Margulis
All life is cellular. Therefore a virus is not
alive.
Life is matter that chooses
Every cell on Earth uses the same operating
system: DNA makes RNA makes proteins
Evolutionists [Darwinists] definitions of life (a few)
Life is a self-sustained chemical system capable of undergoingDarwinian evolution (Joyce, 1994)
Life is a self-replicating, evolving system based on organic
chemistry (Pace, 2002)
System capable of evolution by natural selection (Sagan, 1970)
Material system that undergoes Darwinian evolution (C. McKay)
The minimal living system must be self-duplicating and
mutable, and it must have the capacity for hetero-catalysis for
bringing about chemical changes in the environment that
support the self-duplication function (Hartman)
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Summary - what is life - the
NASA version
Life reproduces or replicates
Life metabolizes
Life evolves
Is a virus alive?
Metabolism?
Evolution?
Reproduction?
Other properties?
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The Evolution of the first Earth
Life
One of Darwins tenets was that all
life came from a single source - there
was some first living cell.
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Characteristics of Earth Life1. Water is essential for active life
2. It is contained in a microenvironment (cell)
3. It is carbon based
a. Nucleic acids consisting of 4 nucleotides
b. Dual nucleic acid system: RNA and DNA
c. Proteins: 20 amino acids
d. Lipids with straight chains of methyl branched chains
e. Metabolic energetics use phosphate anhydrides, thioesters
f. Metabolism uses nucleophile-electrophile reactions with C=O
4. It replicates5. It evolves (mutation and other mechanisms
for acquiring genetic material, and naturalselection
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How can our kind of life be
defined?
Uses DNA
A specific genetic code
Only twenty (and the same twenty) amino
acids
Always cellular? NO! (PW)
Is a virus alive, or is it even Life as weknow it? - not cellular, some without DNA
DNA- one way, or the only way
to store information necessary forlife?
DNA is hugely
complex
How was it first
synthesized?
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DNA DNA is a double helix.
A bonds to T: C bonds to G
In man, the DNA molecule , iffully extended, would have atotal length of 1.7 metres. Ifyou unwrap all the DNA youhave in all your cells, youcould reach the moon ...6000
times!
DNA Replication DNA is opened by
enzymes (unzips)
Complementarynucleotides bondwith the oldstrands
2 strands created: is the old strand; is the newstrand.
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DNA
Is our form of DNA the first out of the gate,
or the best out of the gate - was there
survival of the fittest among early DNA
molecules?
How did we arrive at a unified genetic code
on Earth? - John Baross, UW, suspects thatviruses were the agent that unified a diverse
zoo
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DNA TRANSLATIONtRNA translates mRNA into proteins
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DNA TRANSCRIPTIONDNA- GIVES CODE TO mRNA
SUMMARY
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Comparison of DNA and RNA
RNA is single
stranded
RNA has uracil
instead of
thymine
A-U
DNA is double
stranded
DNA has
thymine instead
of uracil
A-T
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Origin of Life on Earth
When?
Where?
How?
How else could this process have
occurred on Earth andwhat else
might have resulted?
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Borate Minerals Stabilize Ribose
A. Ricardo, M. A. Carrigan, A. N. Olcott, S. A. Benner, Science302:1931, 2004.
So where did life begin on Earth(if it began on Earth)
Some warm little pond- Darwin
Hydrothermal vents
Bubbles in tide pools/intertidal
In clouds
Brine ponds
Coupled impact craters! (?)
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Why impact craters?
Making RNA the hardest step. Ribosesugars unstable at high temperatures.
Ribose can be made by serial evaporationsand decanting of borate mineral reactionswith water
Need a desert to do this - and much
chemical glassware - or impact craters in adesert
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Primordial soup or primordialzoo?
Much nonsense about low diversity of early
life.
Probably there was a zoo of different
membrane types, and different genetic
systems within them
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RNA life
Self catalyzing. RNA serves as information
system, and enzyme to catalyze self
reproduction.
Does it also need a membrane, or could
there have been naked RNA?
How did DNA take over?
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Varieties of alien life
Change nature of information storage
molecule
Change solvent within cell- ammonia
instead of water
Is there Life as we do not know it
presently on Earth - and how would weknow?
Water vs. Not Water. The boundary between
conventional weird and truly weird
In water at 5 < pH < 9, DNA still has a protonation state that
permits Watson-Crick pairing
Within this range, alternative nucleotides, alternative amino
acids in the encoded protein, alternative lipid-forming
components, alternative metabolisms, all established as
functional.
Above and below this range, alternative nucleic acid structures
can manage.
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Some Weird (compared to Earth life ) life
Life that does not require carbon
Life that does not require selected elements other than
carbon,nitrogen, phosphorus, and sulfur (RNA world),
Life that does notrequire certain metals such as Mg, Na, K,
Life that works without Darwinian evolution.
(The reason whyDarwinian is included in so many definitionsof life is because we believe that it is the only mechanism
available)
Life without matter?????? (naaa)
Surely life requires a boundary to satisfythermodynamic requirements, and such aboundary needs to be anchored to matter.
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