1. Primary Cell
Instructor: Prof. F. Moore
Presented by: Z. Mokhtarzadeh
May 2013

2. Origin of the Universe
13.7 billion years ago
The ―Big Bang‖ led to the
formation of the stars of the
―universe‖
Matter and energy very
rapidly distributed throughout
universe
Temperatures dropped
Light elements (hydrogen and
helium) were produced in the
first few minutes of the Big Bang
4.6 billion years ago
Planets of our solar system
were formed including our earth

3. A billion Year Old Earth
By 3.5 billion years ago, when the Earth was a billion years old, it had a thick
atmosphere composed of CO2, methane, water vapor and other volcanic gases
By human standards this early
atmosphere was very poisonous
It contained almost no oxygen
Today our atmosphere is 21% oxygen

4. A billion Year Old Earth
By 3.5 billion years ago, the Earth also had extensive oceans and seas of salt water,
which contained many dissolved elements, such as iron.

5. Earth ~3.5 billion years ago Life
arose, but how did this happen?

6. No Life 0.5-1 billion years Life
?
How did we get here?
4.5 billion years ago ~3.5 billion years ago

7. Early Ideas about Origins of Life
▪ Spontaneous generation - life arising from nonliving matter
▪ Belief in it goes back to ancient Greek philosophy
Examples:
▪ mud producing fish
▪ grain producing mice
▪ decaying meat producing maggots

8. Redi’s Experiment
▪ Effort to disprove spontaneous generation
▪ Decaying meat in uncovered control jars vs. covered experimental jars.
▪ Results: maggots and flies filled the open jars but not covered jars.
Showed only flies produce flies.

9. The common belief in spontaneous generation
was stopped dead in its tracks in 1862 by Louis
Pasteur with his famous demonstration that
nutrient fluids, sterilized and sealed against
contamination, could be kept indefinitely
without the generation of microbial or other
forms of life.
In a sense, Pasteur was almost too good. His
experiment made scientists reject the idea that
life could have arisen spontaneously at any
time under any circumstances.
Pasteur’s Experiment (mid-1800s)

10. Primordial Soup theory
A.I.oparin
J.B.S. Haldane
In 1920s Oparin, a Russian and Haldane, an Englishman,
independently developed a hypothesis that forced reconsideration
of spontaneous generation. They agreed that spontaneous
generation of life is not possible under present earth conditions
but suggested that the earth's surface and atmosphere were far
different during its first millions of years of existence at present.
Primordial conditions would favor spontaneous generation of life
rather than inhibiting it.

11. The composition of early atmosphere
A.I.oparin
J.B.S. Haldane
Earth‘s early atmosphere had a composition very different than today‘s
atmosphere
•No free O2
•More reducing than present atmosphere
•Initially thought to contain H2O, H2, CH4, NH3

12. "Primordial soup" theory
Oparin and Haldane thought that with the mix of gases in
the atmosphere and the energy from lightning strikes,
amino acids could spontaneously form in the oceans. This
idea is now known as "primordial soup“. Oparin
suggested that the organic compounds could have
undergone a series of reactions leading to more and more
complex molecules. He proposed that the molecules
formed colloid aggregates, or 'coacervates', in an aqueous
environment. The coacervates were able to absorb and
assimilate organic compounds from the environment .They
would have taken part in evolutionary processes,
eventually leading to the first lifeforms.
The Oparin-Haldane hypothesis was NOT widely accepted at first because of the weight of
evidence against spontaneous generation and the lack of an effective way to test the hypothesis.

13. Miller–Urey experiment
1950s: Stanley Miller & Harold Urey recreated the
assumed early atmosphere
Contained H2O, H2, CH4, NH3
Lacked free O2
Energy input in forms of heat
and electrical sparks
Mimic geothermal heat and
lightning

14. Results
▪ After a week 15 amino acids in the
mixture
▪ Other biologically important
molecules had been formed
including ethanoic acid, lactic acid
and urea
▪ Later similar experiments were
done using CO2 that produced
nucleotides.

15. 1) Uncertainty about the early atmosphere was really of that type. The environment
produced by Miller was more reducing than we now believe the earth‘s early
atmosphere to have been.
2) How to produce polymers (proteins, nucleic acids)? The gas-discharge experiments
only produce monomers (if conditions are right), but none produce the long chain
molecules that are the ultimate basis for life on the earth.
3) With oxygen we have ozone. The ozone layer blocks out a lot of ultra violet light. Ultra
violet light destroys ammonia. Ammonia was one of the gasses used in the
experiment. This creates a problem, does it not?
This scenario has recently been criticised for several reasons:

16. In 1986, the geophysicist Louis Lerman suggested that the key process that formed the chemicals needed
for life took place within bubbles of the ocean‘s surface.
Louise Lerman’s
bubble model

17. Chemical Evolution
▪ First cells may have originated by chemical evolution involving 4 steps:
1) Abiotic (Non-biological) synthesis of small organic molecules (monomers)
2) Monomers joined together to form polymers (proteins, nucleic acids)
3) origin of self-replicating molecules that eventually made inheritance possible
4) packaging these molecules into pre-cells, droplets of molecules with
membranes that maintained an internal chemistry

18. Polimerization
Joining of monomers into polymers such as protein and nucleic acids.
 This polymerization in living cells is catalyzed by enzymes
 Early polymerizations must have occurred without the aid of enzymes
 Is this possible?

19. Sidney W.Fox Experiment
In 1957 Sidney Fox demonstrated that dry
mixtures of amino acids could be encouraged to
polymerize upon exposure to moderate heat.
When the resulting polypeptides, or proteinoids,
were dissolved in hot water and the solution
allowed to cool, they formed small spherical
shells about 2 μm in diameter—microspheres.

20. Protocells
▪ Proteinaceous microspheres – contain proteins and lipids but no nucleic acids
▪ Maintain a localized environment separate from the surroundings
▪ Incapable of precise reproduction
▪ Exhibit some properties associated with life
▪ Metabolism
▪ Protocells would eventually pick up RNA and DNA, develop enzymatic capabilities and
membrane organization = primitive cell

21. RNA or proteins?
A raging debate among biologists who study
the origin of life concerns which organic
molecules came first, RNA or proteins. Which
of these arose first is a matter of debate
In all modern organisms, nucleic acids (DNA
and RNA) are necessary to build proteins, and
proteins are necessary to build nucleic acids -
so which came first, the nucleic acid or the
protein?

22. A Protein World
The ―protein-first‖ group argues that without enzymes (which are
proteins), nothing could replicate at all, heritable or not. The ―protein-
first‖ proponents argue that nucleotides, the individual units of nucleic
acids such as RNA, are too complex to have formed spontaneously.
While there is no doubt that simple proteins are easier to synthesize
from abiotic components than nucleotides, both can form in the
laboratory under the right conditions. Deciding which came first is a
chicken-and-egg paradox.

23. Iron-Sulfur World
▪ A ―metabolism first‖ scenario involves naturally
occurring iron sulfide (also called pyrite)
crystals. These crystals can catalyze both
oxidation-reduction reactions (producing
energy) and polymerizations of amino acids.
▪ Works especially well at high temperatures and
pressures, such as are found in deep ocean vents
called ―black smokers‖.
▪ An active self-sustaining metabolic system in the
absence of inheritance.

24. An RNA World
The ―RNA world‖ group feels that without a hereditary molecule, other molecules
could not have formed consistently. The ―RNA world‖ argument earned support
when Thomas Cech at the University of Colorado discovered ribozymes, RNA
molecules that can behave as enzymes, catalyzing their own assembly. Recent work
has shown that the RNA contained in ribosomes catalyzes the chemical reaction that
links amino acids to form proteins. that means that RNA can both store genetic
information and cause the chemical reactions necessary to copy itself. This
breakthrough tentatively solved the chicken and egg problem: nucleic acids (and
specifically, RNA) came first — and later on, life switched to DNA-based inheritance.

25. The first membranes, the first cells
▪ The creation of a cell required a cell
membrane. The evolution of the
plasma membrane was a momentous
event because it separated life from
non-life
▪ Lipids spontaneously form bilayer
‗vesicles‘
▪ These are spherical shells on a
molecular scale
▪ They can contain self-replicating
RNA strands

26. Lipids in Membranes
▪ In order to spontaneously form a lipid bilayer lipid must have
▪ Charges and polar bonds in the head region to interact with water
▪ Long fatty acid tails to interact with each other
▪ Amphipathic

27. Lipid Membrane
▪ The formation of the membrane performed 3 important tasks
▪ the products of the genetic material could be kept close by
▪ A cell membrane separates the internal environment from the external
environment and regulates the movement of materials into and out of the
cell.
▪ Chemical reactions became more efficient as reactants could collide more
frequently

28. A Likely Model
▪ Amino acids are formed
▪ See the Miller-Urey Experiment
▪ Lipid bilayers form
▪ These are observed to form spontaneously
▪ Self-replicating RNA strings arise
▪ This stage is uncertain, but plausible
▪ RNA is able to catalyse its own replication
▪ RNA strings merge with Lipid bilayers shells
▪ First cells form
▪ All the components are held together in one place
▪ Facilitates chemical processes
Spontaneous generation of omino acids,
simple carbohydrates, and lipid
precursors
Formation of self-
replicating RNA
Formation of
proteins
Formation of
lipid bubbles
Evolution of DNA
Evolution of DNA RNA Enzymes
Protocells
Living cells

29. Unfortunately, our understanding of the origin of life is incomplete.
Little is known about how the first cells originated. Current hypotheses
involve chemical evolution within bubbles, but there is no general
agreement about their composition, or about how the process occurred.
Note that while some of these steps have been demonstrated in a lab,
nobody has ever made a living cell in a lab.

30. Refrences
▪ Clas blomberg, 2007, phisycs of life: Elsevier, p. 351-354
▪ Freeman, Harrington, Sharp, Biological Science: Pearson, p. 99&102
▪ Peter H. Raven, George B. Johnson, Jonathan Losos, Susan, 2005, Biology: McGraw-
Hill, p64&66
▪ WilliamMartin, Michael J. Russell,2002, On the origins of cells: The Royal Society
▪ "Did life come from another world?" Scientific American 293, 64 - 71 (2005)
▪ Woodward, Robert J., Photo editor,1969, Our amazing world of Nature: its marvels
and mysteries
▪ K. Popper, 1990, Pyrite and the origin of life: Nature 344 p. 387
▪ Huber, C.; Wächtershäuser, G. (1998). "Peptides by activation of amino acids with
CO on (Ni,Fe)S surfaces: implications for the origin of life". Science 281

31. Refrences
 https:// www.emc.maricopa.edu
 https://en.wikipedia.org
▪ https:// www.evolution.berkeley.edu
▪ http://astro.berkeley.edu
▪ https:// www.biologie.uni-hamburg.de
▪ https:// www.simsoup.info
▪ https:// scienceandscientist.org
▪ https:// www.godandscience.org
▪ http://evolution.about.com
▪ http://www.esa.int

32. Thank
you
Look out into the universe and contemplate the
glory of God. Observe the stars, millions of them,
twinkling in the night sky, all with a message of
unity, part of the very nature of God.