13-Origins of Life

8/4/2019 13-Origins of Life

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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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13-Origins of Life

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