Origin of Cells

Origin of Cells Synthesis of Life Describe the four processes needed for the spontaneous origin of life on Earth There was non-living synthesis of simple organic molecules (from primordial inorganic molecules) 1. …………………………………………………………………………………………………………………………………………………... These simple organic molecules became assembled into more complex polymers 2. …………………………………………………………………………………………………………………………………………………... Certain polymers formed the capacity to self-replicate (enabling inheritance) 3. …………………………………………………………………………………………………………………………………………………... These molecules became packaged into membranes with a distinct internal chemistry (protobionts) 4. …………………………………………………………………………………………………………………………………………………... Outline, with the aid of the diagram, the Miller-Urey experiment into the origins of organic compounds Water was boiled to vapour to reflect the high temperatures common to Earth’s original conditions ………………………………………………………………………………………………………………………………………………….......... The vapour was mixed with a variety of gases to create a reducing atmosphere (no oxygen) ………………………………………………………………………………………………………………………………………………….......... This mixture was then exposed to an electrical discharge (simulating effects of lightning as energy source) ………………………………………………………………………………………………………………………………………………….......... The mixture was then allowed to cool (concentrating components) and left for a period of ~1 week ………………………………………………………………………………………………………………………………………………….......... Later, the condensed mixture was analysed and found to contain traces of simple organic molecules ………………………………………………………………………………………………………………………………………………….......... Identify the conditions needed for the non-living synthesis of organic matter (and potential locations) Conditions: Reducing atmosphere (no oxygen), high temperatures (>100ºC) or electrical discharges ………………………………………………………………………………………………………………………………………………….......... Locations: Volcanoes, hydrothermal vents, meteors (panspermia) ………………………………………………………………………………………………………………………………………………….......... Outline the evidence from Pasteur’s experiments that demonstrates that abiogenesis no longer occurs Broths stored in vessels with long tubings (swan neck ducts) that can prevent passage of dust particles ………………………………………………………………………………………………………………………………………………….......... The broths were boiled to kill any micro-organisms present in the growth medium (sterilisation) ………………………………………………………………………………………………………………………………………………….......... Growth only occurred in the broth if the flask was broken open, exposing the contents to contaminants ………………………………………………………………………………………………………………………………………………….......... From this it was concluded that bacterial growth came from contaminants and did not spontaneously occur ………………………………………………………………………………………………………………………………………………….......... Outline two properties of RNA that would have allowed it to play a role in the formation of life Can self-replicate (although superseded by DNA due to double strands increasing stability) 1. …………………………………………………………………………………………………………………………………………………... Can act as catalyst (although superseded by proteins due to greater variability in subunits 2. …………………………………………………………………………………………………………………………………………………... Endosymbiosis Describe the process of endosymbiosis and how it led to the evolution of eukaryotic cells An endosymbiont is a cell which lives inside another cell with mutual benefit ………………………………………………………………………………………………………………………………………………….......... Eukaryotic cells are believed to have evolved from early prokaryotes that were engulfed by phagocytosis ………………………………………………………………………………………………………………………………………………….......... The engulfed cell remained undigested as it contributed new functionality to the engulfing cell ………………………………………………………………………………………………………………………………………………….......... Over generations, the engulfed cell lost its independent utility and became a supplemental organelle ………………………………………………………………………………………………………………………………………………….......... Outline the evidence supporting the theory of endosymbiosis Component Membranes Antibiotics Division DNA Ribosomes Evidence Chloroplasts / mitochondria have double membranes Chloroplasts / mitochondria susceptible to certain antibiotics Chloroplasts / mitochondria divide by a fission-like process Chloroplasts / mitochondria have own circular DNA Chloroplasts / mitochondria have 70S ribosomes