📚 node [[the great oxygenation]]

The Great Oxygenation

  • The diverity of [[bacteria]] exploded during the [[Archaean]], leading to the evolution of [[Cyanobacteria]]
    • This does not mean that [[Spirulina]] existed during the [[Archaean]]: it is a modern organism
  • There was almost no O₂ in the atmosphere before the [[Archaean]]-[[Proterozoic]] break
    • No O₂ means no formation of peroxides
    • Peroxides are dangerous to many cells as they rob electrons from proteins, fatally altering them
  • Cells had to develop anti-oxidation defenses, including [[catalase]]
  • Cells had two ways to adapt to O₂
    1. Become a strict anaerobe, and avoid oxygen-containing habitats
    2. Tolerate O₂
      • O₂ toleration can easily lead to aerobic metabolism
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