> See also: > - [[Microbiology]] > - [[Symbiosis]] # The Endosymbiotic Theory > [!info] Bacteria vs Mitochondria/Chloroplasts > Mitochondria and chloroplasts share many characteristics that are similar to bacterial cells (prokaryotes): > 1. Double membranes > 2. Contains free ribosomes and its own set of DNA separate from that found in the nucleus > 3. Grow and reproduce somewhat independently from the rest of the cell > > ![[Pasted image 20220802171821.png]] --- The **endosymbiotic theory** (sometimes called *symbiogenesis*) suggests that originally only prokaryotic cells existed. Over time, several independent species of prokaryotes would be incorporated into larger cells through a process called "**endosymbiosis**": ![[Pasted image 20220731123230.png]] 1. Because the smaller cells (mitochondria and chloroplasts) **produce high amounts of energy**, the larger cell benefits from keeping them around rather than consuming them for nutrients. 2. The smaller cell benefits by getting **shelter** thanks to the larger cell's membrane. > **Taxonomy of Endosymbiosis** > - $\alpha$ purple (proteobacterium) -> mitochondria > - cyanobacteria -> chloroplasts Because the *most recent ancestors* for both mitochondria and chloroplasts *are bacteria*, the *DNA* found within them is *drastically different* than the DNA found within the nucleus of the parent organism's cells When the smaller cell was taken up, it likely underwent **genome reduction** where its genetic information was removed and it evolved to become more dependent on the host cell - Inner mitochondrial membrane (IMM) and outer mitochondrial membrane (OMM) have parallels to the two-layered membrane found within prokaryotic cells