Unit 2: Origins of Life: Intro Flashcards
(17 cards)
Earth forms
4.6 BYA
Prokaryotes form
3.5 BYA
Early earth atmosphere
H20, CO2, CH4, NH3
N2, CO2, H2S, CH4, CO, H2, NH3 H2O, HCN
Early earth environment
- Meteor impacts, lots of lighting, no fire(no O), hot, volcanic eruptions, radiation from sun
- Destructive, but lots of ENERGY
Early earth began with
No organic molecules
Chemical evolution hypothesis
Said organic molecules could have formed from the compounds of Early Earth Environment
Miller-Urey experiment
- Water is heated Water vapor forms
- Mix of NH3, CH4, H20, H2 added to atmosphere
- Circulating gases are bombarded by sparks of electricity
- Cold water cools chamber causing droplets to form
- After a week liquid is collected containing amino acids, sugars, lipids, and other organic compounds.
1
- abiotic synthesis of organic monomers, such as amino acids, and nitrogenous bases
- The synthesis could have occurred in the early oceans, using energy from lightning or radiation.
2 - Polymerization
- these monomers spontaneously joined into polymers, in particular, nucleic acids and amino acid polymers.
- Could have happened in hydrothermal vents, edge of ocean, volcanoes
- Researchers have been able to reenact this step by dripping amino acid solutions onto hot sand, clay, or rock, which act as catalysts
3 - Protocells/Coacervate
- Phospholipid membrane bubbles with some molecules trapped inside
- Inside different from outside
- Phospholipids do this spontaneously in water - hydrophilic heads/hydrophobic tails
4 - Heredity
- Nucleotides assembled
- Some form of self replication
- RNA
Why RNA not DNA
- DNA is more structurally complex
- Requires more enzymes for replication + function
- These specific proteins may have existed, but more likely that RNA came first
- Deoxyribose + thymine probably appeared after ribose + uracil
Prokaryotes
- Small
- No membrane bound organelles or nuclear envelope
- Small ribosomes
- Circular chromosomes
- Cell walls made of peptidoglycan
Heterotroph/Autotroph
Heterotroph - Cannot make its own organic molecules
Autotroph - Can synthesize own organic molecules
Earth had a reducing atmosphere
- Lacks free oxygen
- may contain such reactive gases as hydrogen or carbon monoxide that oxidize in the presence of oxygen, such as hydrogen sulfide.
Reduction/Oxidation
Reduction - Addition of electrons, H, and energy
Oxidation - Reverse
Oxygen
As life forms developed, autotrophs such as cyanobacteria or types of algae appeared, and produced oxygen through photosynthesis
