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ASTR/GEOL-2040: Search for life
in the Universe: Lecture 3
•Building blocks (wrap up)
•Biomarkers
•Carbon in Universe
What we did last time
• The 4 different building blocks
– Lipids, carbohydrates, proteins, nucleic acids
– Their usefulness
• How chemists drop C & H
– Applied to sugars
• Nucleotides: backbone + bases (A,G,C,T)
– Genetic code (word of 3  1 amino acid)
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What kind of molecule?
A. Lipid
B. Carbohydrate
C. Hydrocarbon
D. Amino acid
E. Nucleotide
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What kind of molecule?
A. Lipid
B. Carbohydrate
C. Hydrocarbon
D. Amino acid
E. Nucleotide
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Examples of amino acids
R=H: Glycine
R=CH3: Alanine
R=C3H4: Proline
R=C4H10N2: Arginine
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How many carbon atoms?
A. None
B. 3
C. 6
D. 12
E. 24
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How many carbon atoms?
C
C
C
C
C
C
A. None
B. 3
C. 6
D. 12
E. 24
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How many H should be drawn?
C is tetravalent
Hint: what do double bars mean?
 Ask your neighbor
C
C
C
C
C
C
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Tetravalent
only 3 bonds drawn
so 1 H missing on each C
CH
CH
CH
CH
CH
CH
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Which molecule is this then?
A. Lipid
B. Carbohydrate
C. Hydrocarbon
D. Amino acid
E. Nucleotide
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Which one is this then?
A. Lipid
B. Carbohydrate
C. Hydrocarbon
D. Amino acid
E. Nucleotide
In fact: this one “aromatic hydrocarbon”
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An enzyme consists of a chain of
A. Carbohydrates
B. Amino acids
C. nucleotides
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An enzyme consists of a chain of
A. Carbohydrates
B. Amino acids
C. nucleotides
Because proteins act as enzymes (=catalysts)
and proteins are made of amino acids
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What kind of molecule?
A. Lipid
B. Carbohydrate
C. Hydrocarbon
D. Amino acid
E. Nucleotide
Hint: find the answer by elimination
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Use of nucleobases
• The sequence contains genetic information
• The sequence can be copied
– TAA CAG
– ATT GTC
• One word (codon)  one amino acid
– TAA  stop (also nonsence or junk DNA)
– CAG  Gln (=Glutamine)
thymine
• In RNA, base U (=uracil)  base T
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What we did last time
• The
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What we did last time
• The
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Mutations
• Example of adding one letter
– the cat ate the rat
– the aca tat eth era t
• One word (codon)  one amino acid
– TAA  stop (also nonsence or junk DNA)
– CAG  Gln (=Glutamine)
thymine
• In RNA, base U (=uracil)  base T
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Which of the following mutations
has the greatest effect?
A. One that changes a single base in a
region of non-coding DNA;
B. one that changes the third letter;
C. one that deletes one base in the
middle of a gene?
Check with your neighbors
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Greatest effect?
A. One that changes a single base in a
region of non-coding DNA;
 Has a chance in not doing much damage
B. one that changes the third letter;
 has no effect in many cases
C. one that deletes one base in the middle
of a gene?
 see example with the cat!
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Was most of this on
DNA familiar?
A. Yes
B. Yes, mostly
C. Some of it
D. Not much
E. No
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Quiz #1 will be on
• Thursday, February 9
• Not Tuesday, February 7 (as announced earlier)
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For the rest of today
• Approaches to origin & remains of life
• Biomarkers: extinct & extant
• Further reading:
– RGS pp. 13-17
– Lon pp. 370-375, 40-43
– BS pp. 233-238 (artificial life), 69-74
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How to study origins & remains of life?
• Top-down versus bottom-up
– Bottom-up: how nonliving
matter combines to make living
matter
– Top-down: extrapolate biology
toward simplest living organism
• Biomarkers/biomarkers
– Extinct life (no longer alive)
– Extant life (currently living)
Biomarkers
• Petroleum, fossil fuel
– Molecular fossils
– Organic-rich rocks
• Astrobiology
–
–
–
–
–
–
Cellular remains
Textual fabrics in sediments: structure & function
Biogenic (biologially produced) org. Matter
Minerals deposition affected by biological processes
Stable isotopes reflecting biological activity
Atmospheric constituents: concentrations  biol source
Subjectivity
• Textual fabrics or organics
– Difficult to tell whether biogenic or not
– Giant stars produce carbon compounds
• Martian meteorite
– controversial
– abiogenic
•
13C
also not
unchallenged
• Contamination
(for meteorites)
Biosignatures from space
Spectral lines
• Emission spectrum
• Absorption lines
Spectrum of air
900 nm = 0.9 mm
Biosignatures from space
Think about other
non-equilibrium processes
•
•
•
•
....
........
..........
.............
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What is the energy source?
Example
Energy source Resulting activity
mountains
geothermal heat
Keeps rock rolling
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What is the energy source?
Example
Energy source Resulting activity
mountains
Atmosphere
El circuit
living cell
geothermal heat
Solar heating
Electric energy
Carbon supply
CO2+hn
or CH2O
Keeps rock rolling
Keeps rain coming
Keeps motor running
ADP  ATP
adenosine
triphosphate
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What we talked about
• DNS, Effect of mutations
• Biomarkers: Textual, cellular remains,
isotropic, atmospheric  specta
• Disequilibria: feature of life,
 different examples of disequilibria
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Next time
• Organic matter in the Universe
• Synthesis of organics on early Earth
– Miller/Urey experiment, Murchison
– Chirality
• Biomolecule delivery from space
• Reading:
– RGS pp. 18-29, Lon pp. 214-218
– BS pp. 204-212
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