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Name: ________________________________________
Class: ________
Date: ________
Identifying Life and its Origins Through Spectroscopy
Introduction:
One area of study that has always intrigued
scientists is the question of where did life begin,
and not only where but how? Ancient
civilizations have explored this question through
studies in philosophy and religion and those
studies continue today. Now though, the
methods of science and observation allow us to
study origins of life in a standardized and clear
way. We now have an understanding of the
basic organic molecules that make life possible.
Through the work of organic chemists, these
compounds have been broken down and
analyzed to the scale of their molecular and
even atomic structure. Because of this,
scientists have been able to pinpoint likely
compounds that served as intermediate steps in
building organic molecules as well as likely
conditions in which they formed. Proof of this is the Miller-Urey experiment in 1953.
The Miller-Urey experiment tested an earlier hypothesis that stated early conditions on Earth were
favorable for the production of organic compounds from pre-existing organic precursors. This theory that
life was able to originate from non-living precursor compounds is called abiogenesis. Stanley Miller and
Harold Urey were successfully able to, through an interesting lab set-up, produce amino acids artificially.
Amino acids as you should remember are the building blocks of protein and are theorized to be the
original organic molecules. The question is, how did the scientists know they produced those molecules?
How did they detect them?
In the first part of this activity, you will be working with spectral data to identify functional groups and
eventually full amino acids. If you remember, spectroscopy is the study of detecting emission and
absorption of specific electromagnetic wavelengths, aka light.
Part 1: Identifying Functional Groups and Amino Acids
One type of spectroscopy particularly useful in identifying organic compounds is infrared spectroscopy. In
this type of spectroscopy, infrared light is passed through a compound and particular wavelengths are
absorbed in this range based on what types of functional groups the compound contains. The resulting
spectra can usually be broken down into two regions, the functional group region along with the
“fingerprint” region. The functional group region is going to be similar to all compounds containing the
same groups while the fingerprint region will be unique to each and every compound. Because of this,
the functional group region is usually the first place you look when identifying a compound as each
functional group contained will have a characteristic band and shape.
Assignment: Refer to Handout A and use that information to identify the functional groups present in
each spectra provided in numbers 1 - 4. In numbers 5-8, use Handouts A and B to identify which amino
acid that spectra identifies overall. For numbers 5-8, there will likely be more than one answer.
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1.)
Functional groups present:
_____________________
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2.)
Functional groups present:
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_______________________
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3.)
Functional groups present:
_____________________
____________________
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4.)
Functional groups present:
_____________________
____________________
_______________________
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5.)
Functional groups present:
_____________________
____________________
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Which amino acids could this represent? Explain.
6.)
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Functional groups present:
_____________________
____________________
_______________________
Which amino acids could this represent? Explain.
7.)
Functional groups present:
_____________________
____________________
_______________________
Which amino acids could this represent? Explain.
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8.)
Functional groups present:
_____________________
____________________
_______________________
Which amino acids could this represent? Explain.
Part 2: Take Home
In 2007, scientists looked back at the vials that were sealed from the Miller-Urey experiment.
They re-tested these vials and confirmed that well over twenty different amino acids were
artificially produced by recreating what was thought to be early Earth atmospheric conditions.
Since then, our view of what early Earth conditions were has changed but despite this, scientists
argue that the updated version would be even more favorable to forming early organic
compounds. There is only one problem with all of this, we can’t actually see early Earth. So
how do you prove definitively that these early organic compounds can form? The answer is to
look elsewhere: space!
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There is one small issue here though, the IR portion of the EM spectrum that we use here on
Earth to identify molecules cannot penetrate our atmosphere. So how do we see and prove that
certain molecules exist elsewhere? The answer simply lies in another part of the spectrum.
Just as the absorption and emission of specific frequencies in the IR spectrum can be used for
identity, so can the same in other parts of the spectrum. In particular, radio waves.
Detection via radio waves differs slightly from using IR. In infrared spectroscopy, molecules
absorb and emit wavelengths based upon the stretching, bending, and rocking of atoms around
their chemical bonds. Radio spectroscopy relies on the slight energy differences between two
of more energy states in a compound. The best example of this is neutral hydrogen. Neutral
hydrogen has hyperfine energy structure based upon the spin states of its one electron in the 1s
orbital. When a hydrogen undergoes a ‘spin-flip’ between the two levels, it gives off a specific
packet of energy with a wavelength of 21-cm (frequency of 1420 MHz). Therefore, if a radio
astronomer points a radio telescope out in space and observes that wavelength, then a source
containing neutral hydrogen has been found.
Since hydrogen’s detection, many more compounds have been detected based on their unique
radio signatures. A list of common ones can be found in the accompanying handout titled “List
of Chemicals in Space.” Of extra interest though is a newly discovered molecule in space,
cyanomethanimine.
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Your assignment: Read the following excerpts and answer the accompanying discussion
questions.
Excerpt 1:
https://public.nrao.edu/news/pressreleases/icy-cosmic-start-for-amino-acids-and-dna
Discussion questions:
1.) What is a precursor molecule?
2.) What is significant about the finding of cyanomethanimine and ethanamine?
3.) What kinds of implications does this have for the origination of life?
4.) Does this finding support or go against there possibly being life outside of Earth? Why?
Excerpt 2:
http://helix.northwestern.edu/article/origin-life-panspermia-theory
Discussion questions:
1.) Briefly, in your own words, explain what the panspermia theory states.
2.) Provide at least four examples of evidence used to support this theory. You may look at and
use other sources for your information.
3.) What kinds of implications does this have for the origination of life?
4.) Does this finding support or go against there possibly being life outside of Earth? Why?
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Handout A: Functional Groups and their Accompanying Spectral Bands
First it needs to be stated that identifying molecules or even functional groups is no easy task. Hidden within the
infrared absorption bands is a lot of information and it isn’t easily deciphered. Usually, this area of study is reserved
for students in their second semester in Organic Chemistry or in Analytical Chemistry as an undergraduate student.
Because of this, these spectra have been greatly simplified to show general shapes and regions where each
functional group can be identified.
Functional Groups: C-H, O-H, C=C
Functional Groups: C-H, O-H (by C=O), C=O
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Functional Groups: C-H, NH2, C=N, Benzene ring
Functional Groups: C-H, S
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Handout B: Amino Acids and their Functional Groups
Alanine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
Arginine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH / NH2
C=N
Asparagine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
Aspartic Acid
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
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Cysteine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
S
Glutamic Acid
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
O-H
NH2
Glutamine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
Glycine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
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Histidine
Functional Groups Contained:
C-H
C=C
C=O
O-H (by C=O)
NH / NH2
C=N
Isoleucine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
Leucine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
Lysine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
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Methionine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2
S
Phenylalanine
Functional Groups Contained:
C-H
C=C
C=O
O-H (by C=O)
NH2
Benzene ring
Proline
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH
Serine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
O-H
NH2
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Threonine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
O-H
NH2
Tryptophan
Functional Groups Contained:
C-H
C=C
C=O
O-H (by C=O)
NH / NH2
Benzene ring
Tyrosine
Functional Groups Contained:
C-H
C=C
C=O
O-H (by C=O)
O-H
NH2
Benzene ring
Valine
Functional Groups Contained:
C-H
C=O
O-H (by C=O)
NH2