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Lecture 9

BIOL107 Lecture 9: Origin of Cells

Biology (Biological Sciences)
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Biol107-Lecture 9: Origin of Cells
Biol107-Lecture 9: Origin of Cells
Origin of Cells
The Earth is 4.5 billion years old and the oldest life is 4 billion years old
Event 1 that took place is Protocells Hypothesis: life may have begun with the
enclosure of self-replicating molecules inside the lipidic membranes
Evidence: Some amphipathic molecules self-assemble into spheres following
the second law of thermodynamics
Event 2 was the origin of some organelles Hypothesis: infoldings of the
plasma membrane became permanent internal structures.
Evidence: some prokaryotes have in folds of their plasma membranes taking on
specific functions.
Event 3 is the origin of the mitochondria Hypothesis: an early eukaryote
ancestor engulfed an aerobic bacterium, but kept it alive instead of digesting it
Evidence: phagocytosis of bacteria by eukaryotes is common thing (ex:
neutrophil). Some present-day prokaryotes can live inside cells that the infect
Mitochondria divide independently and they contain their own DNA an ribosomes
They make some of their own protein from their DNA and have their own
Humans have 2 sets of chromosomes and the mitochondrial DNA are passed
exclusively from the mother to the offspring through the egg cell.
Event #2 and #3There can be an alternative swap of both of these events; first
came the mitochondrion, then the nucleus, and the engulfer was archaea
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