Origin of life

An effort to blend biology, chemistry, and physics in the search to identify and understand the origin of life in the universe It’s a “ Journey Back In Time” … By Kalpana Stuti, Ritu,

ORIGIN OF LIFE

The facts…… hidden somewhere

The story….… unrevealed The truth… not known exactly

The path… untraced

An attempt to explore the way!!!

An effort to blend biology, chemistry, and

physics in the search to identify and

understand the origin of life in the universe It’s a “ Journey Back In Time” …

By Kalpana Stuti, Ritu, Gauri

Miranda House

ORIGIN OF LIFE

BIG BANG

Oceans Haldane soup

Reducing atmosphere(gases like

abiotic synthesis of organic compounds)

OPARIN-HALDANE THEORY

Haldane Soup

Simple Molecules

Complex Molecules (building blocks)

Aggregates (coacervates and microspheres)

Protocells( proprimitive stage before formation of true cell

Proto cells + nucleic acid = self replicating system

“CELL”

Microsphere

ENERGY YIELDING SYSTEM

• “Cell” Energy Yielding System

Ozone Formation (shielding effect)

• Atmosphere changed to oxidizing from reducing.

• Evolution of photosynthesis which is followed by respiration.

How Eukaryotic Cell Changed to

Multicellular Organism….

• Geological Evidence

• Precambrian Fossil Evidence

• Laboratory Evidence

GEOLOGICAL EVIDENCE

• Sedimentary rock in past 500 million years are silicate sands clay, quartz type

indicating oxidizing conditions.

• Ancient Precambrian sediments containing sands with reduced iron minerals found in Canada, Brazil, South Africa.

• Banded iron ore deposits with mixed oxidation states in Quinland, Russia, India and Australia

PRECAMBRIAN FOSSIL EVIDENCE

• Elso Barghoorn et al studied polished thin sections of silica rich cherts from Gunflint

region of Northern Minnesota and Southern Canada with optical and electron

microscope.

• Living organisms algae, fungi, microbes associated with banded iron ore cherts

indicates that they were probably laid down under reducing atmospheric conditions.

LABORATORY EVIDENCE

•

•A mixture of H4,NH3, H2, and water

was put into a flask and energized

by an electrical discharge apparatus

to represent ultraviolet radiation

•The products were allowed to

condense and collect in a lower flask

• After a week, Miller and Urey

found a dark brown scum had

collected in the lower flask and was

found to contain several types of

amino acids together with sugars,

tars, and various other unidentified

organic chemicals

How could polymer form in dilute aqueous solution when polymerization is a

dehydration process?

• Sidney Fox experiment – Fox found that dry amino acids heated to 160-210OC, forms polymers of molecular weight 300,000 provided mixture contains Aspartic Acid and Glutamic Acid Thermal

protenoids so formed, if washed with water, form microspheres of fairly uniform diameter of 20, 000Ao

• Cinder Cone Hypothesis - Protenoid material first polymerized on hot dry volcanic Cinder Cones and then it was leached into oceans by rains to form microspheres.

These became early segregated chemical systems and eventually led to protocells.

• They tend to concentrate some molecules in their

interior and this in an ability that most primitive

protocells would have acquired Behavior of

Coacervate shows how earlier protocells would have

achieved internal compositions that were different

from their surroundings and could have developed

certain amount of chemical evidences.

Coacervate droplets formed

by interaction between gelatin and gum arabic A I Oparin

PANSPERMIA THEORY

Organic compounds arrived from outer space

It states that hydrocarbons and other organic

molecules (molecules that organisms contain or that might lead to the genesis of life) have been found in

meteorites –

 It means that at least prebiotic chemistry that leads

to the primordial soup might be going on there

Evidences in support of this theory

• In 1969 , a meteorite landed in Australia that was 12% water and contained traces of 92 amino acids.

Inference- It points to not only the presence of organic compounds in outer space, but also the capacity of such compounds to reach earth.

• Fred Hoyle and Chandra Wickramasinghe have argued persistently since the 1970s that complex organic substances, and perhaps even primitive organisms, might have evolved

on the surface of comic dust grains in space and then been transported to the Earth's surface by comets and meteorites.

Where did life begin???

• There is an ongoing debate regarding the most probable site of life's origins.

• The prevailing paradigm - life began near the ocean's surface, bathed in sunlight.

• Current Research - life arose near deep hydrothermal vents which is still under investigation.

"Scientists have long suspected that life on Earth originated in the ocean and strong evidence now suggests that the earliest life on our planet occurred in the depths of the ocean in the absence of heat and light."

Pulse of the Planet, American Museum of Natural History

Miller and Urey found

Deep-sea Vents

• Their discovery in late 1970’s stretched our concept of the origin of life on earth.

• Can life exist and that too thousands of meters beneath the surface of sea in absence of sunlight?

• It raised the possibility that earlier vents supplied the energy and chemical precursors for origin of protobionts.

Exploring the deep ocean floor

View of the first

Such geothermal vents

are called smokers

This photograph shows a black smoker, but smokers can also be white, grey, or clear

depending on the material being ejected

Photograph by Dudley Foster from RISE

expedition

Vent Community

brachyuran crabs swim and scuttle among blood-red tube worms large and small Scientists are still trying to figure out how the

offspring of such organisms disperse over long stretches of

inhospitable seafloor to colonize widely separated vent systems.

Giant Clams

The size of deep-sea giant clams is evident from the

hands of a scientist holding them.

(Photograph by William R Normark, USGS.)

Giant Tube Worms: RIFTIA

• On the bottom of the ocean

around deep-sea hydrothermal

vents, there is a profusion of life

that thrives on the hydrogen

sulfide (H

2 S) gas released from the vents.and live inside hard,

shell-like protective tubes that

attach to the rocks

Giant tubeworms that live around hydrothermal vents

on the sea floor These creatures are about the size of your hand in shallower waters, but in the ocean's deep they have been found as big as eight feet long!

How they live….

• These creatures lack mouths, anuses, intestines and stomachs, and scientists were at a loss to explain how these were getting nutrients to survive and grow

• Their insides are lined with bacteria that oxidize the H

2 S, turning it into usable nutrients for the worms

• The bacteria, in turn, benefit from the relationship because the worms deliver blood containing hemoglobin which helps the bacteria to break down the sulfides

• They live in a symbiotic relationship with a bacteria that may hold clues as to how life on earth began billions of years ago.

BIOCHEMISTRY AT THE VENTS

bacteria

Energy released helps in fixing

CO2 into small organic molecules

So this cycle is the same metabolic pathway that is utilized by plants in photosynthesis takes inorganic carbon dioxide and

fixes it into organic compounds that are then food But, the

difference here, the critical difference, is that rather than using

sunlight, these animals and bacteria are completely independent of sunlight They utilize chemical energy to power that reaction

So, ever imagined a life out of toxic Hydrogen Sulphide?!

Released

from vents

Chemical of Life - Ammonia,

FeO

46% yield 15 min

Powdered Basalt 20% yield

Stable upto 800oC

THE BIG BANG First proposed by George Lemaître in 1927

Salient Features

infinitesimally small, infinitely hot,

infinitely dense singularity.

and cooled to the size and temperature

of our present Universe.

Timeline of the Big Bang

What happened after the

Time since

Big Bang T (K)

0.01s 1011K · The Universe expands rapidly,

scale is doubled every 0.02s

· it cools, T ~ 1/R

15s 3 x 109K · Temperature is below threshold

for creation of electron/positron pairs

· e+/ e- annihilate

· The Universe is "reheated"

about 35% by annihilation

3 min 109K Era of Nuclear Reactions

· Nuclei begin to hold together

Time since

Big Bang T (K)

3 &1/2 min 108K End of Nuclear Reactions

neutrons have been "used-up" forming 4He

Universe is now 90% H nuclei( p+)

Evidences for the Big Bang

proportional to their distance This is called

"Hubble's Law," named after Edwin Hubble

(1889-1953) who discovered this phenomenon in

1929

• The abundance of the "light elements" Hydrogen

and Helium found in the observable universe are thought to support the Big Bang model of origins

•Cosmic Background Radiation predicted by

Cosmologist George Gamov in 1948 and discovered

by Arno Penzias & Robert Wilson of Bell Labs in

1965

THE COMPETITORS …

FOR THE THEORY ON ORIGIN OF THE

UNIVERSE

• The Bubble Universe / Andre Linde's Self Creating Universe

• The Inflationary Theory (1981, Alan Guth )

• The Protouniverse (white hole theory)

• The Steady State Theory (late 1940’s )

• The Oscillating Universe Theory ( 1960’s -70’s )

• The Cosmos by Carl Sagan

• Text Book of Biology by Campbell

• The Scientific American

Nobody understands the origin of life If they say they do, they are probably trying to

fool you.

— Ken Nealson, 2002

THANK YOU