Topic 1.4 - Origin of cells Flashcards
What four key processes are involved in the formation of living cell from non living materials ?
Non-living synthesis of simple organic molecules
Assembly of organic molecules into complex polymers
Formation of polymers that can self-replicate
Packaging of molecules into membranes to create an
internal chemistry different from the surroundings
What experiment replicated the conditions of a
pre-biotic Earth in order to synthesise organic molecules ?
The Miller-Urey experiment
Who demonstrated the law of biogenesis with his swan flask experiment ?
Louis Pasteur
Describe the swan flask experiment
Broths were stored in sealed vessels that were sterilised
Bacterial growth occurred if vessel was unsealed, but
did not occur if vessel stayed sealed (no contamination)
What was the conclusion of the swan flask experiment ?
Cell can only arise form pre-existing cells
What is biogenesis and how does it occur ?
It is the theory that all living things that come from other living things. Biogenesis requires specific conditions in order to proceed :
* Including a reducing atmosphere (no oxygen) and either high temperatures (>100oC) or electrical discharges
What is endosymbiosis ?
Eukaryotic cells are believed to have evolved from aerobic prokaryotes that were engulfed by endocytosis
The engulfed cell remained undigested and contributed new functionality to the engulfing cell (i.e. it became an organelle)
How can we show that chloroplasts arose via endosymbiosis ?
Membranes (have a double membrane)
Antibiotics (show susceptibility)
DNA (have naked and circular DNA)
Division (occurs via a fission-like process)
Ribosomes (have 70S ribosomes)
What lead to the rapidly increasing oxygenation of the Earth’s environment ?
The appearance of photosynthetic organisms
What did oceans originally consist of ?
Originally, Earth’s oceans had high levels of dissolved
iron (released from crust by underwater volcanic vents)
Oxygen chemically reacted with the iron to form an
insoluble precipitate (iron oxide)
How had oxygen started accumulating in the anoxic atmosphere ?
When dissolved iron was completely consumed
