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AGA 0316 Aula 11
Sigam o Carbono -1
RÁPIDO BALANÇO DA MATÉRIA ATÉ AQUI
1)O que é a Astrobiologia?
2)O que é vida? Quaestão Bio
3)O Universo – condições Astro
4)Complexidade
5)Complexidade & Princípio Antrópico
6)Evolução da vida na Terra:em 4 milhões de anos, cérebro
humano passa de 0,5 a 1,4 kg!
7)O satélite CoRoT: busca por exoplanetas (Brasil)
8)Buscando a vida: a) busque a água! Planetas...
9)b) Busque a água: a atmosfera terrestre
10)c) Busque o carbono + astroquímica-astrobio
FOLLOW THE LIFE
•
 •
•
•
•
•
Follow the water
Follow the carbon
Follow the nitrogen
Follow the energy
Follow the entropy
Follow the information
Universo Orgânico!
• 0.5 % da matéria bariônica “visível” está na forma molecular.
(Fraser, McCoustra & Willians, 2002, A&G, 43, 2.11).
• > 150 Moléculas detectadas no espaço
(~50% orgânicas: CHON).
Como as biomoléculas são encontradas?
IR-Telescopes (vibrational lines)
Radiotelescopes (rotational lines)
VLA
Itapetinga, SP
Onde são encontradas as biomoléculas?
Key hole Nebula
Gaseous Pillars – Eagle Nebula
Titan
Hale-Bopp
Murchinson
151 interstellar and circumstellar molecules
H2
C6H6
NH3
CO
Carbon in human body
Element
Percent by mass
Oxygen
65
Carbon
18
Hydrogen
10
Nitrogen
3
Calcium
1.5
Phosphorus
1.2
Potassium
0.2
Sulfur
0.2
Chlorine
0.2
Sodium
0.1
Magnesium
0.05
Iron, Cobalt, Copper, Zinc, Iodine
<0.05 each
Selenium, Fluorine
<0.01 each
Carbon in the Universe
Element
Parts per million
Hydrogen
739,000
Helium
240,000
Oxygen
10,700
Carbon
4,600
Neon
1,340
Iron
1,090
Nitrogen
950
Silicon
650
Magnesium 580
Sulfur
440
All Others
650
2.3
Why Carbon?
• Carbon atom can form up to 4 chemical
bonds with many other atoms – can form
long and complex molecules
• Carbon can form compounds that readily
dissolve in water.
Hydrogen
Outer shell/orbits
Typically only electrons
from the outer shell (valent
electrons) engage in
chemical bonds
Carbon
There is an “optimal”
number of electrons per
shell.
S-shell = 2 electrons
P-shell = 8 electrons
P-shell
S-shell
Helium
Chemical bonds
• Covalent
• Ionic
• Hydrogen
Carbon has 4 valent
electrons – can
form up to 4 bonds
Methane
Ethane
ethene
benzene
ethanol
fullerene
diamond
Polymerization
• A polymer is a substance composed of
molecules with large molecular mass
composed of repeating structural units, or
monomers, connected by covalent
chemical bonds. Well known examples of
polymers include plastics and DNA.
2º TRABALHO DE AGA 0316
Fazer resenha sobre o artigos:
“Finding a second sample of life on Earth”,
de Davies & Lineweaver
www.astro.iag.usp.br/~janot/
Silicon life?
• Si is abundant and also can form four
bonds at once (like C). But!
• Si bonds are much weaker – complex
molecules based on Si will be fragile
• Si does not form double bonds – less
variety
Organic and Inorganic Carbon
C can be in reduced or oxidized forms.
Organic carbon
(reduced)
‘CH2O’
Inorganic carbon
(oxidized)
CO2
carbon dioxide
H2CO3 carbonic acid
Example:
HCO3 bicarbonate ion
Glucose -- C6H12O6
CO3= carbonate ion
Organic carbon
(has C-H and C-C bonds)
Inorganic carbon
(C-O bonds only)
Coal
Oil
JENNY HAGER/ THE IMAGE WORKS
http://www.nationalfuelgas.com
Organic
carbon
http://www.upl.cs.wisc.edu/~stroker/jungle.jpg
Inorganic
carbon
Seashells
http://www.cmas-md.org/Images/Sanjay/UnivTop4.jpg
Coral
http://www.summerclouds.com/Vero/Sea%20Shells.jpg
http://educate.si.edu/lessons/currkits/ocean/
Four types of organic
macromolecules
in living systems.
Most of the molecules in the living systems are
water (H2O) and large organic
macromolecules:
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
Carbohydrates (sugars, starches)
• Representatives:
Glucose, Fructose
• Many hydroxyl
groups (-OH)
• Soluble in water
• Form Polysaccharides
• Good energy source
• Structural support for
organisms (cellulose
- the main constituent of wood)
Glucose
Fructose
Table sugar
Glucose polymerization
H2O
Polysaccharides
Linked by dehydration reaction
In starch molecule (potato) there can be 100s thousands of glucose units
Lipids (fats and oils)
• Representatives: fatty acids and
cholesterol
• Poorly soluble
• Good (concentrated)
energy source
• Flexible
(cell membrane material)
Proteins
• “Proteios” – primary
• Long “trains” of amino acids
• Different proteins have different sequence
of amino acids
• 20 amino acids used in any organism
• Some provide structure (fingernails, hair)
• Some serve as catalysts
• Enzymes – proteins with catalitic
properties
L-Alanine
Glycine
Linked by dehydration reaction
Catalysts in Chemistry
• Suppose chemical reaction:
A + B  AB is a slow reaction
• The same reaction can be accelerated
with catalyst (D):
A + D  AD fast step
B + AD  AB + D fast step
The net result is still:
A + B  AB but it is much faster
Proteins (continued)
• Even though there are ~70 amino acids
any known life uses only 20
• Amino acids derived abiotically are a mix
of both “left-handed” and “right-handed”
ones. Biological amino acids are only lefthanded.
Chirality
• Was there a common ancestor for all life?
Biology uses only
left-handed Alanine
Qual a Origem do Carbono?
Credit: Y.Pendleton
Nebulosas Planetárias
• O Sol vai morrer assim
• Estrelas com massas
menores que 8 vezes a
massa do Sol
• Núcleo anã branca
• Camadas exteriores
nebulosa planetária
• C, N
• Tempos: até varios
Ganos
• Promovem as
condições pré-bióticas.
Large carbonaceous molecules in space
Diamond <<
Fullerenes ~ 0.5 %
PAHs ~ 15 %
> 50% ??
Graphite ?
C-chains ~ 0.1%
C-onions
Soot
Nanotubes
Ehrenfreund & Charnley 2000
Meteorites
• A meteorite is a natural object originating
in outer space that survives an impact with
the Earth's surface without being
destroyed.
• Chondrites – 86%
(5% Carbonaceous Chondrites)
• Achondrites – 8%
• Iron meteorites – 5%
Meteorites represent the only extraterrestrial
material which can be studied on Earth !
Insoluble C-fraction:
60-80 % aromatic carbon
highly substituted small
aromatic moieties branched
by aliphatic chains
Murchison (1969, Australia)
Volatile fraction:
Abundances of soluble organic compounds in
the Murchison meteorite (Botta & Bada 2002, Sephton 2002, 2004)
Compound Class
Amino Acids CM
Concentration(ppm)
17-60
CI
~5
Aliphatic hydrocarbons
>35
Aromatic hydrocarbons
3.3
Fullerenes
>1
Carboxylic acids
> 300
Hydroxycarboxylic acids
15
Dicarboxylic acids &
Hydroxydicarboxylic acids
14
Purines & Pyrimidines
1.3
Basic N-heterocycles
7
Amines
8
Amides linear
> 70
cyclic
>2
Alcohols
11
Aldehydes & Ketones
27
Sulphonic acids
68
Phosphonic acids
2
2º TRABALHO DE AGA 0316
Fazer resenha sobre o artigo:
“Finding a second sample of life on Earth”,
de Davies & Lineweaver
www.astro.iag.usp.br/~janot/
QUESTÕES SOBRE A AULA 11
1) Onde há Carbono no Universo?
2) Porque o C e um elemento-chave para a vida?
3) Dê exemplos de compostos de C que encontramos
habitualmente.
4) Porque a quiralidade é um elemento-chave para a
descoberta de vida extraterrestre?