LIFESCI 7B Chapter Notes - Chapter 7: Proteobacteria, Chloroplast, Archaea
4 Sep 2018
School
Department
Course
Professor
Document Summary
Symbiont: an organism that lives in closely evolved association with another species. In this context--chloroplasts started as symbiotic cyanobacteria that became permanently incorporated into their hosts. Two membranes provides evidence for this: inner membrane is the cell membrane of the cyanobacterium, and the outer membrane is the engul ng cell"s membrane system. Chloroplasts have their own dna in a single circular chromosome, like bacteria. Nucleotides in chloroplast are similar to those in cyanobacterial genes, but very diff from those in genes in the nuclei of photosynthetic eukaryotes. Cyanobacteria have way more genes that chloroplast genes. This is prob bc some genes were lost if similar nuclear genes were enough. Or the genes were transported to the nucleus. It was found that chloroplasts in p. chromatophora seem to have originated in a branch of cyanobacteria diff from the one that gave rise to chloroplasts in other photosynthetic eukaryotes. There are some eukaryotes in no oxygen environments that don"t have mitochondria.
