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 Bio3)O Universo – condições Astro4)Complexidade5)Complexidade & Princípio Antrópico6)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 terrestre10)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 > 150 Moléculas detectadas no espaço (~50% orgânicas: CHON).(~50% orgânicas: CHON).

Como as biomoléculas são encontradas?

Radiotelescopes (rotational lines)

IR-Telescopes (vibrational lines)

Itapetinga, SPItapetinga, SP

VLAVLA

Hale-BoppHale-Bopp MurchinsonMurchinson

Gaseous Pillars – Eagle NebulaGaseous Pillars – Eagle Nebula Key hole NebulaKey hole Nebula

TitanTitan

Onde são encontradas as biomoléculas?

151 interstellar and circumstellar molecules

H2

CO

C6H6

NH3

Carbon in human bodyElement 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

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

Carbon in the Universe

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.

Typically only electrons from the outer shell (valent electrons) engage in chemical bonds

Hydrogen

Helium

Carbon

Outer shell/orbits

There is an “optimal” number of electrons per shell. S-shell = 2 electronsP-shell = 8 electrons

P-shell S-shell

Chemical bonds

• Covalent

• Ionic

• Hydrogen

Carbon has 4 valent electrons – can

form up to 4 bonds

Methane Ethane

ethanol

diamond

ethene

benzene

fullerene

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 Inorganic carbon (reduced) (oxidized)

‘CH2O’ CO2 carbon dioxideH2CO3 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)

http://www.nationalfuelgas.com

                                              

http://www.upl.cs.wisc.edu/~stroker/jungle.jpg

JENNY HAGER/ THE IMAGE WORKS

Organiccarbon

Coal

Oil

http://www.summerclouds.com/Vero/Sea%20Shells.jpg http://educate.si.edu/lessons/currkits/ocean/

http://www.cmas-md.org/Images/Sanjay/UnivTop4.jpg

Inorganiccarbon

Seashells

Coral

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

FructoseTable sugar

Glucose polymerization

In starch molecule (potato) there can be 100s thousands of glucose units

H2O

Linked by dehydration reactionPolysaccharides

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 stepB + AD AB + D fast stepThe 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 left-handed.

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

Ehrenfreund & Charnley 2000

PAHs ~ 15 %

Diamond << Graphite ?Fullerenes ~ 0.5 %

C-chains ~ 0.1%

Nanotubes

C-onions> 50% ??Soot

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 !

Volatile fraction:

Insoluble C-fraction:60-80 % aromatic carbonhighly substituted smallaromatic moieties branchedby aliphatic chains

Murchison (1969, Australia)

Abundances of soluble organic compounds in the Murchison meteorite (Botta & Bada 2002, Sephton 2002, 2004) Compound Class Concentration(ppm)

Amino Acids CM 17-60CI ~5

Aliphatic hydrocarbons >35Aromatic hydrocarbons 3.3Fullerenes > 1Carboxylic acids > 300Hydroxycarboxylic acids 15Dicarboxylic acids & Hydroxydicarboxylic acids 14Purines & Pyrimidines 1.3Basic N-heterocycles 7Amines 8Amides linear > 70

cyclic > 2Alcohols 11Aldehydes & Ketones 27Sulphonic acids 68Phosphonic 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?