Topic 1.5: Origin of Cells Flashcards
Abiogenesis
Living cells arose from non-living matter.
Stages of Abiogenesis
a) Production of carbon compounds
b) Assembly of carbon compounds
c) Formation of membranes
d) Development of self-replication
Production of carbon compounds
Non-living synthesis of simple organic molecules (from primordial inorganic molecules)
Assembly of carbon compounds
Carbon molecules assembled into more complex polymers
Formation of membranes
Molecules became packaged into membranes with an internal chemistry different from their surroundings
Development of self-inheritance
Certain polymers formed the capacity to self-replicate (RNA)
Miller-Urey Experiment
a) Recreation of the conditions of pre-biotic Earth’s atmosphere by passing steam through a mixture of methane, hydrogen, ammonia, and electrical discharges.
b) The condensed mixture was found to contain traces of simple organic molecules such as sugars and amino acids.
Biogenesis
Cells can only be formed by the division of pre-existing cells
Louis Pasteur’s Experiment
a) Placed samples of broth in flasks with long necks and melted the glass of the necks and bent it into a variety of shapes.
b) Boiled the broth to kill pre-existing microorganisms.
c) Snapped the necks of some flasks to leave a shorter vertical neck.
d) Fungi and bacteria appeared in the flasks with shorter vertical neck but not in the no snapped.
Evidence against spontaneous generation of cells in Louis Pasteur’s experiment
a) Showing that bacteria could not grow in a sealed, sterilized container of chicken broth.
b) Organisms didn’t appear in the no snapped flasks in contact with air
c) Therefore, cells can only arise from pre-existing cells.
Endosymbiosis
Eukaryotic cells have evolved from early prokaryotes that were engulfed by endocytosis.
Process of endosymbiosis
a) Larger prokaryotes that could respire anaerobically took smaller cells in by endocytosis.
b) These engulfed prokaryotic cells remained undigested since they divided as fast as the larger ones and could persist
indefinitely inside the larger cells.
c) Then, both cells developed a mutualistic relationship.
Origin of mitochondria
a) Free-living prokaryote that developed aerobic cell respiration.
b) Engulfed by a larger prokaryotic cell, which provided the mitochondria with food as the it supplied ATP.
Chloroplasts
a) Free-living prokaryote that developed photosyntesis.
b) Engulfed by a larger prokaryotic cell, which provided the mitochondria with food as the it supplied energy.
Chloroplast and Mitochondrial Evidence
a) Membranes
b) Antibiotics
c) Division
d) DNA
e) Ribosomes
