2.11 - Origins of Cell Compartmentalization

Origin of Compartmentalization (Endosymbiont Theory):

• Endosymbiosis: This theory proposes that an early ancestor of eukaryotic cells engulfed an oxygen-using, non-photosynthetic prokaryotic cell.

• Development into Organelles: The engulfed cell, initially a separate organism, gradually became an integral part of the host cell, eventually evolving into organelles like mitochondria and chloroplasts.

• Evidence Supporting Endosymbiosis:

  • Dual Membranes: Mitochondria and chloroplasts are surrounded by two membranes.

  • Genetic Autonomy: They contain their own ribosomes and multiple circular DNA molecules, which is characteristic of prokaryotic cells.

  • Reproductive Independence: Both mitochondria and chloroplasts can reproduce independently within the cell, supporting their prokaryotic origins.