MIMG 100L #5 - metabolism growth differentiation...

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•metabolism, growth, differentiation, communication, movement, and evolutionFirst living entity much simpler than modern cells• a single molecule of RNA (or pre-RNA) was able to replicate itself and metabolize chemicals (RNA world). Membrane formed around RNA (protein synthesis with RNA templated translation). RNA gave rise to more stable DNA so able to store genetic info. Early cells had higher rates of HGT. Bacteria/ Archaea split. Cellular metabolism: At the beginning, oxygen was not present on planet Earthsome microorganisms, such as Archaea, are remnants of a primordial metabolism in very harsh conditions.~ 2.7 bya Cyanobacteria developed a photosystem that could use H2O instead ofH2S, generating O2~ 2.4 bya the Great Oxidation Event occurred and O2 level continued to riseEndosymbiotic theory: Organelles, such as mitochondria and chloroplasts, originated from a relationship of endosymbiosis. A smaller ancestral bacterium was engulfed by an ancestral prokaryote that lost its cell wall, lost its ability of living independently, and evolved into a mitochondrion or chloroplastOrigin of eukaryotes from prokaryotes Symbiotic relationship in which the host nucleoplasm supplied nutrients and the endosymbiotic bacterium produced energy that could be used by the nucleoplasm. Evidence for the endosymbiotic theory:• Mitochondrial and chloroplast ribosomes resemble those of prokaryotes, and their mechanism of protein synthesis is more similar to that found in bacteria thaneukaryotes• The same antibiotics that inhibit protein synthesis on ribosomes in bacteriaalso inhibit protein synthesis on ribosomes in mitochondria and chloroplasts.

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