Origins of Life Flashcards
Describe Earth during the Hadean time period.
Earth spinning rapidly Smoggy toxic environment Dust/ ash in atmosphere Anaerobic Surface mostly water Violent 30m+ tides Acidic sea, boiling and churning Some landed peaks above sea
What are the 7 basic chemical characteristics of life on Earth?
- Carbon based
- Use energy
- Use oxidative gradients
- Contain proteins, lipids and carbs
- Use nucleic acids for heredity
- Use ATP
- Same basic metabolic reactions
Where do membranes originate from?
Froth of iron sulphide bubbles around alkaline vents, simple organic molecules formed through catalysis of iron-nickel sulphides. Diffused from sources and collided, eventually accumulating and coating inside surface of bubbles with more robust protein synthesis
How many divergences were there post- LUCA?
2
When did Eukarya split off?
1.8bya
Describe what the oceans on Venus and Mars are like, to our knowledge.
Can’t tell for Venus, no way to survey
Mars= barren and dry
Why are there no oceans on Venus or Mars?
No ozone layer so UV splits water and the H2 is lost to space as it isn’t very dense and the O2 gets incorporated
Why did Earth have a massive increase in oxygen?
Due to the emergence of photosynthetic life
What was the Great Oxygenation Event? (come on, you have to get this right. It is legit in the name)
Massive increase in O2 levels on Earth
What were the causes of the Great Oxygenation Event?
Late appearance of the oxygen producing life forms
Reduction in reactive gases
Oxygen from photosynthesis
What were some possible impacts of increased oxygen levels?
Extinction of anaerobes?
Ice age 2.45-2.2 bya
What are the benefits of photosynthesis for an organism?
Free carbon source
Free living and protection
What is needed for photosynthesis?
Reducing power
Energy
Catalyst
Precursor to add carbon dioxide to
What would primitive photosynthesis have? e.g. What do all photosynthetic organisms have in common?
Photosystem Pigments RuBISCO Manganese cluster ATP Synthase, or equivalent
What does photosystem I do?
Uses light energy to drive the production of a strong reducing agent
What does photosystem II do?
Uses light energy to drive the import of protons to make a redox gradient to drive ATP production
What are the two common features of all electron transport methods?
Absorb light
Allow for protons to move
Why is there variation in certain common structures?
Selective loss: structures removed by mutation or deletion
Selective fusion: structures combined by duplication/ rearrangement
Why did photosystems probably evolve?
As an independent proton gradient
What are the two semi-autonomous organelles?
Mitochondria and chloroplasts
What are the defining features of semi-autonomous organelles?
Specific, distinct metabolic functions and structures
Circular DNA genomes with unique organelle genes
Transcription/ translation machinery
Distinct biogenesis with specific pathway, regulated by the cell
Self replicating by binary fission
What is the Endosymbiosis theory?
Has been argued semi-autonomous organelles were originally independent prokaryotes that got engulfed by a primitive eukaryote and incorporated into the cell
What is the shopping bag model?
The contents of a shopping bag don’t all have to come from the same shop
There may have been multiple endosymbiosis events with each one transferring more info
What is the circumstantial evidence for the endosymbiosis theory?
Approximate size No. of membranes Circular genome Prokaryotic enzymes and complexes Prokaryotic codon usage Examples of multiple endosymbioses
