Unit 2: Origins of Life: Intro Flashcards
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
