Download How does organic life form?

How does organic life form?
Name:_________________________________________
Adapted from Quest University Canada
Part 1 – Place the three pictures of earth from oldest to youngest (most recent).
1. Tell me everything that you see happening in the three pictures that helped you put them in the correct order:
a. Oldest
b. Middle
c. Youngest (most recent)
2. Describe the environment in the volcanic earth.
3. Describe the environment in the ocean earth.
4. Which of these could have some life forms living on them? Why?
Part 2 – Atmospheric Compositions
1. Interpreting Graphs – Which gas is the most abundant in Earth’s atmosphere today? What percentage of that
gas may have been present in early volcanic earth?
2. Interpreting Graphs – Which gas was probably most abundant in the early volcanic earth’s atmosphere? Why?
3. Where do you think the water in today’s oceans probably come from?
Part 3 – A Flash of Insight
It was the fall of 1951. Twenty-one-year old Stanley had recently traveled from his native California to the University of
Chicago to pursue a graduate degree in chemistry. At a departmental seminar, his imagination was captured by the
presentation from a professor in his department, the Nobel Laureate Harold C. Urey.
“In the course of an extended study on the origin of the planets I have come to certain definite conclusions relative to
the early chemical conditions on the Earth and their bearing on the origin of life,” said Urey.
Stan listened intently while Urey continued to explain how the early Earth atmosphere was not as it is today.
“One sees that hydrogen (H2) was a prominent constituent of the primitive atmosphere and hence that methane (CH4)
was as well. Nitrogen was present as nitrogen gas (N2) at high temperatures but may have been present as ammonia
(NH3) or ammonium salt at low temperatures.”
Stan was riveted. Urey went on to suggest, as had the Russian biochemist Oparin before him, that organic molecules
(compounds containing carbon atoms) might have formed on the early Earth from inorganic gases. This was provocative
because it suggested that the molecules of life (which are organic) could be created by simple chemistry, and it could
explain how the building blocks of life were first created on our primitive lifeless planet.
“It seems to me that experimentation on the production of organic compounds from water (H2O) and methane (CH4) in
the presence of ultra-violet light of approximately the spectral distribution estimated for sunlight would be most
profitable. The investigation of possible effects of electric discharges on the reactions should also be tried since electric
storms in the [Earth’s early] atmosphere can be postulated reasonably.”
I know how to test this! Thought Stan again. Circumstances didn’t allow him to approach Urey immediately, but a few
months later, he asked Urey for the opportunity to test the idea that the conditions and atmosphere of early Earth were
sufficient to create organic molecules, the building blocks of life. Urey thought the project was “too risky” for a graduate
student since it was unlikely to yield interesting results in the time allowed to complete a PhD (after all, the process
might have occurred over millions of years on Earth). At Stan’s insistence, Urey gave him a year to experiment.
1. Propose an experimental design to test the hypothesis that organic molecules formed from inorganic ones
under the conditions prevalent on the early Earth. Provide as many details and drawings as possible.
Part 4 – Earth in a Bottle (Miller-Urey Experiment)
Stan designed the glassware apparatus shown. He first
sterilized all of his equipment to make sure there were no
living things inside of it. He then created a vacuum inside the
tubes to remove out our atmosphere and he inserted a
mixture of gases that simulated the atmosphere of early
Earth: hydrogen (H2), methane (CH4), and ammonia (NH3).
He filled the bottom flask with water and placed it over the
flame to heat it creating water vapor.
In the top flask, he carefully inserted two electrodes and
passed an electric current which created sparks.
Between the top and bottom flasks was a connecting tube
fitted with a condensation chamber that cooled any gases
present to turn them to liquid.
Stan also placed a valve to permit sampling of the cooled
liquid, after the condenser, to test the chemical composition.
After a few days, he noticed that the water inside the flask rapidly turned from clear, to yellow, to a darker shade of
brown. These color changes indicated the creation of novel chemicals inside his apparatus.
1. This apparatus was meant to simulate the conditions of the early Earth. Describe how each portion of the
apparatus mimics a component of the early Earth environment.
a. The flask of water being heated
b. The flask with the electric discharge
c. The condensation chamber
2. What cycle the runs today in our environment does this test mimic with the water?
3. What are amino acids the building blocks too?
4. What gas is missing that we require for life today?
5. If what is shown is the experimental set-up. What might constitute an appropriate control test?
6. What kind of data should Stanley measure and record in this experiment? What does he have to do to collect
this data?
7. What are the possible problems with this experimental design? How could he fix them?
8. Electric discharges simulate lightning, a source of energy to drive chemical reactions. What other sources of
energy (identify at least two) might have been present on the early Earth? If possible how might they have been
simulated in this experiment?
9. If some of life’s organic molecules are created in Stan’s experiment, what are the implications for the origins of
life? (Will this tell us how life arose on Earth?)
10. Summarize: Why is the Miller-Urey experiment important in understanding the formation of organic life?
Part 5 – Miller’s Claim to Fame
Stan Used chromatography to separate and identify each chemical in his apparatus. His experiment produced large
quantities of the organic molecules glycine, alanine, aspartic acid, and gamma-amino butyric acid (GABA). The first three
are amino acids used as building blocks to make proteins in ALL living organisms; GABA serves as a neurotransmitter in
animals to facilitate communication between nerve cells. Below is the chemical structure of these molecules:
Stan’s gamble has paid off and this finding made Stan famous. In short order, he was asked for interviews by
newspapers and radio shows and his results graced the cover of Time magazine. Few graduate students receive this
much attention. The idea that “life” could be created
from primordial ooze quickly gripped the public’s
imagination.
Several researchers reproduced and confirmed his
results. As the chemical detection methods improved,
Stan’s experiment was eventually shown to yield an
impressive array of amino acids (33 different ones,
including more than half of the 20 that are used by living
organisms to make protein), as well as other organic
molecules such as sugars, lactic acid, and the nitrogen
bases of nucleic acids (which build DNA and RNA).
1. Look at the chemical composition of the compounds that Stan originally discovered in his apparatus. Where
does each of the atoms that make up these molecules come from? Go back to part 4 and reread what was in
the early Earth atmosphere. Particularly where does the carbon, nitrogen, and oxygen in these molecules come
from?
2. Most proteins begin their protein sequence with the amino acid methionine. A diagram of
the chemical structure is shown to the right. Is methionine likely to be among the 33
different amino acids discovered in Stan’s flasks? Why or why not?
3. What do you think is the significance of the neurotransmitter GABA that was found?
*** see other side for more current information****
Part 6 – Issues with Miller-Urey
What if Urey got it wrong? Here’s a summary of some of the evidence that suggests that the atmosphere of early Earth
different from Urey’s proposed model:
1. Post the Miller-Urey experiment we are still lacking what important element for survival?
2. Life’s building blocks (which are organic molecules) are essential for the creation of the first life. If Stan’s
experimental conditions did not mirror those found on the surface of early Earth, is it possible they were found
elsewhere? Where might this be? Suggest at least two possibilities.
Part 7 – Macromolecule (Biomolecule) Mix-up
Follow the directions on the macromolecule mix-up to build the four main types of biomolecules. Don’t forget to paste
them on this sheet and have the waters you cut out pasted next to them. I have already pasted the single items in for
you below. No need to color.
1. Carbohydrate
a. Two glucose molecules
b. Remaining glucose molecules
2. Lipids
a. Triglyceride
b. Phospholipid
3. Protein
a. Two amino acids connected
b. Remaining amino acids connected
4. Nucleic Acids (just paste one of each – ignore other nucleic acid directions)
a. Adenine
b. Cytosine
c. Thymine
d. Guanine
Part 8 – Formation of a cell membrane
A cell needs lipids (fats), proteins, carbohydrates (sugars), and nucleic
acids (genetic info) for structure. Given the following information about
the phospholipid how can it be situated around the outside of the cell so
that only the parts that like water are touching water so it can act as a
barrier.
Important information:
Phosphate group head is:
-
Negatively charged (attracts positively charged items)
Polar (also means that it has a charge)
Hydrophilic (loves being near water)
Fatty Acid Lipid Tails are:
-
Non-charged (no charge not attracted to anything)
Non-Polar (also means that it has no charge)
Hydrophobic (hates being near water)
This space outside the cell represents the water based environment the cell exists in. Draw in the phospholipids
around the cell to form the cell membrane so that only the head touches water and the tails don’t have to touch
any water.
CELL
Water filled
Part 9 – So where is life?
First life is considered to be prokaryotic (simple and single celled):
Problem: These can’t produce oxygen… AHHHHHH
How do we know? Based on the iron content of the oceans!
QUESTION: What color does iron turn when it is exposed to oxygen
(aka rusting)?
By looking at the rocks of the ancient oceans we can tell that oxygen started
when the iron started rusting.
QUESTION: What could have caused the release of oxygen?
Below on the left is the organelle chloroplast that allows plants to run photosynthesis. On the right is a special bacteria
called cyanobacterium that can run its own photosynthesis. Now what can be formed in our atmosphere?
Part 10 – Still a mystery?
“Nobody knows how life got started. Most of the
evidence from that time was destroyed by impact and
erosion. Science works on the frontier of knowledge
and ignorance. We’re not afraid to admit what we don’t
know. There’s no shame in that. The only shame is to
pretend that we have all the answers. Maybe someone
watching this, will be the first to solve the mystery of
how life on Earth began.”
-Neil Tyson Degrasse