ORIGIN OF LIFE L4 Flashcards
I. Process of abiogenesis - CC requirements for life - CC abiotic synthesis hypothesis - SEQ abiogenesis II. History of life - SEQ timeline of life on earth
1
Q
process of abiogenesis
A
- abiotic synthesis of monomers
- formation of organic macromolecules
- formation of protocells
- appearance of self replication
2
Q
abiotic synthesis
A
- first life developed from non living organic molecules
- those molecules had to form spontaneously
3
Q
requirements for abiotic synthesis
A
- low O2
- oxygen is reactive - breaks bonds
- only forms 2 bonds - not conducive to building - energy source
- forming biological molecules - making bonds
- making bonds = storing energy - chemical building blocks
- liquid water
- dissolved inorganic molecules - ions
- atmospheric CO2, H2O, CO, H2, N2
- maybe NH3, H2S, CH4 - time
- spontaneous chemical reactions are slow
4
Q
Opain-Haldane hypothesis
A
- life formed near earths surface - shallow water
- tested using Miller-Urey experiment: found amino acids and other organic compounds, and more recently they found there were many molecules produced like DNA/RNA nucleic acid bases, all amino acids, several lipids and sugars, and ATP if phosphate is added
5
Q
iron-sulfer world hypothesis
A
- organic molecules at hydrothermal vents
- hot H2O, CO, iron and nickel sulfides released
- hot springs produce precursors to biological molecules
6
Q
formation of organic macromolecules
A
- can form on clay or rock surfaces
- negative ions bind monomers
- Zn, Fe catalyze polymerization
- experimentally: polypeptides, polynucleotides, vesicles
7
Q
formation of protocells
A
- vesicle: fluid filled compartment surrounded by membrane like structure
- forms from lipids in water
8
Q
protocells
A
- aggregates of abiotically produced organic macromolecules
- exhibit attributes of living cells
- electrical potential across surface
- absorb materials leads to osmotic swelling
- unique internal chemical environment
- divide if sufficiently large
- no mechanism of heredity
9
Q
self replication
A
- in living cells: genetic info stored in DNA, transmitted via mRNA, translated into protein
- DNA then RNA then protein
- thought that RNA was the first nucleic acid in living things
10
Q
RNA world hypothesis
A
- the first cells used RNA to store and copy genetic info
- DNA and proteins incorporated later
11
Q
ribozymes
A
- RNA molecules with enzymatic properties
- cleave RNA, catalyze RNA polymerization
12
Q
protocells and self-replicating RNA
A
- RNA polymers within vesicle leads to higher osmotic pressure which makes the vesicle grow
- growing vesicles take up lipids, RNA from environment/other vesicles
- RNA inside gets rewritten then vesicle continues to grow and eventually splits
13
Q
DNA
A
- thought that RNA came first - single stranded (ss)
- became double stranded (ds) - more stable, better for storage
- replaced by DNA - even more stable, better for storing over time
14
Q
geological time scale
A
- established via fossils, radiometric dating
- based on major geologic climate and biological events
- ex. mass extinctions often delineate periods
15
Q
first cells
A
- prokaryotes: no nucleus
- anaerobic
- heterotrophic
- obtained organic molecules from environment
- fermentation (how they got energy): no O2 required, relatively low yield
